PostgreSQL 12.7 commit log

commit   : 4bf0bce161097869be5a56706b31388ba15e0113    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 10 May 2021 16:43:52 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 10 May 2021 16:43:52 -0400    

commit   : a9c718bd2d35586da8ebdefa0b72fe7e0d1a725b    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 10 May 2021 13:10:29 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 10 May 2021 13:10:29 -0400    

Security: CVE-2021-32027, CVE-2021-32028, CVE-2021-32029  

commit   : a5fa3e0671474411ad81600a8f2b4800a4464afc    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 10 May 2021 11:02:29 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 10 May 2021 11:02:29 -0400    

It's unusual to have any resjunk columns in an ON CONFLICT ... UPDATE  
list, but it can happen when MULTIEXPR_SUBLINK SubPlans are present.  
If it happens, the ON CONFLICT UPDATE code path would end up storing  
tuples that include the values of the extra resjunk columns.  That's  
fairly harmless in the short run, but if new columns are added to  
the table then the values would become accessible, possibly leading  
to malfunctions if they don't match the datatypes of the new columns.  
  
This had escaped notice through a confluence of missing sanity checks,  
including  
  
* There's no cross-check that a tuple presented to heap_insert or  
heap_update matches the table rowtype.  While it's difficult to  
check that fully at reasonable cost, we can easily add assertions  
that there aren't too many columns.  
  
* The output-column-assignment cases in execExprInterp.c lacked  
any sanity checks on the output column numbers, which seems like  
an oversight considering there are plenty of assertion checks on  
input column numbers.  Add assertions there too.  
  
* We failed to apply nodeModifyTable's ExecCheckPlanOutput() to  
the ON CONFLICT UPDATE tlist.  That wouldn't have caught this  
specific error, since that function is chartered to ignore resjunk  
columns; but it sure seems like a bad omission now that we've seen  
this bug.  
  
In HEAD, the right way to fix this is to make the processing of  
ON CONFLICT UPDATE tlists work the same as regular UPDATE tlists  
now do, that is don't add "SET x = x" entries, and use  
ExecBuildUpdateProjection to evaluate the tlist and combine it with  
old values of the not-set columns.  This adds a little complication  
to ExecBuildUpdateProjection, but allows removal of a comparable  
amount of now-dead code from the planner.  
  
In the back branches, the most expedient solution seems to be to  
(a) use an output slot for the ON CONFLICT UPDATE projection that  
actually matches the target table, and then (b) invent a variant of  
ExecBuildProjectionInfo that can be told to not store values resulting  
from resjunk columns, so it doesn't try to store into nonexistent  
columns of the output slot.  (We can't simply ignore the resjunk columns  
altogether; they have to be evaluated for MULTIEXPR_SUBLINK to work.)  
This works back to v10.  In 9.6, projections work much differently and  
we can't cheaply give them such an option.  The 9.6 version of this  
patch works by inserting a JunkFilter when it's necessary to get rid  
of resjunk columns.  
  
In addition, v11 and up have the reverse problem when trying to  
perform ON CONFLICT UPDATE on a partitioned table.  Through a  
further oversight, adjust_partition_tlist() discarded resjunk columns  
when re-ordering the ON CONFLICT UPDATE tlist to match a partition.  
This accidentally prevented the storing-bogus-tuples problem, but  
at the cost that MULTIEXPR_SUBLINK cases didn't work, typically  
crashing if more than one row has to be updated.  Fix by preserving  
resjunk columns in that routine.  (I failed to resist the temptation  
to add more assertions there too, and to do some minor code  
beautification.)  
  
Per report from Andres Freund.  Back-patch to all supported branches.  
  
Security: CVE-2021-32028  

commit   : 3b0f6a7ae5d812d9a70fc854d2e54d3657467e25    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 10 May 2021 10:44:38 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 10 May 2021 10:44:38 -0400    

While we were (mostly) careful about ensuring that the dimensions of  
arrays aren't large enough to cause integer overflow, the lower bound  
values were generally not checked.  This allows situations where  
lower_bound + dimension overflows an integer.  It seems that that's  
harmless so far as array reading is concerned, except that array  
elements with subscripts notionally exceeding INT_MAX are inaccessible.  
However, it confuses various array-assignment logic, resulting in a  
potential for memory stomps.  
  
Fix by adding checks that array lower bounds aren't large enough to  
cause lower_bound + dimension to overflow.  (Note: this results in  
disallowing cases where the last subscript position would be exactly  
INT_MAX.  In principle we could probably allow that, but there's a lot  
of code that computes lower_bound + dimension and would need adjustment.  
It seems doubtful that it's worth the trouble/risk to allow it.)  
  
Somewhat independently of that, array_set_element() was careless  
about possible overflow when checking the subscript of a fixed-length  
array, creating a different route to memory stomps.  Fix that too.  
  
Security: CVE-2021-32027  

commit   : c5edbfeb172722eb5a0ef50aa8c449545de9b321    
  
author   : Peter Eisentraut <peter@eisentraut.org>    
date     : Mon, 10 May 2021 14:30:04 +0200    
  
committer: Peter Eisentraut <peter@eisentraut.org>    
date     : Mon, 10 May 2021 14:30:04 +0200    

Source-Git-URL: git://git.postgresql.org/git/pgtranslation/messages.git  
Source-Git-Hash: 7221ef1e0bfee1318f195b8faca683c0ffbee895  

commit   : dc7816eb845f6686cac2b42303cb82de1c30f265    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Sun, 9 May 2021 13:31:40 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Sun, 9 May 2021 13:31:40 -0400    

commit   : cfebc7080c990d60183cc486861d07db9dd8808b    
  
author   : Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Fri, 7 May 2021 11:46:37 -0400    
  
committer: Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Fri, 7 May 2021 11:46:37 -0400    

This patch replaces use of the global "wrconn" variable in  
AlterSubscription_refresh with a local variable of the same name, making  
it consistent with other functions in subscriptioncmds.c (e.g.  
DropSubscription).  
  
The global wrconn is only meant to be used for logical apply/tablesync worker.  
Abusing it this way is known to cause trouble if an apply worker  
manages to do a subscription refresh, such as reported by Jeremy Finzel  
and diagnosed by Andres Freund back in November 2020, at  
https://www.postgresql.org/message-id/20201111215820.qihhrz7fayu6myfi@alap3.anarazel.de  
  
Backpatch to 10.  In branch master, also move the connection establishment  
to occur outside the PG_TRY block; this way we can remove a test for NULL in  
PG_FINALLY, and it also makes the code more consistent with similar code in  
the same file.  
  
Author: Peter Smith <peter.b.smith@fujitsu.com>  
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>  
Reviewed-by: Japin Li <japinli@hotmail.com>  
Discussion: https://postgr.es/m/CAHut+Pu7Jv9L2BOEx_Z0UtJxfDevQSAUW2mJqWU+CtmDrEZVAg@mail.gmail.com  

commit   : b075e08d869b3f73ad1221098c331ddb01005a89    
  
author   : Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Thu, 6 May 2021 17:17:56 -0400    
  
committer: Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Thu, 6 May 2021 17:17:56 -0400    

Backpatch all the way back to 9.6.  
  
Author: Simon Riggs <simon.riggs@enterprisedb.com>  
Discussion: https://postgr.es/m/CANbhV-EwxvdhHuOLdfG2ciYrHOHXV=mm6=fD5aMhqcH09Li3Tg@mail.gmail.com  

commit   : abce26c9eb95698c5bd07ae21ce4df5d45e3c02b    
  
author   : Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Wed, 5 May 2021 12:14:21 -0400    
  
committer: Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Wed, 5 May 2021 12:14:21 -0400    

When ALTER TABLE .. ALTER CONSTRAINT changes deferrability properties  
changed in a partitioned table, we failed to propagate those changes  
correctly to partitions and to triggers.  Repair by adding a recursion  
mechanism to affect all derived constraints and all derived triggers.  
(In particular, recurse to partitions even if their respective parents  
are already in the desired state: it is possible for the partitions to  
have been altered individually.)  Because foreign keys involve tables in  
two sides, we cannot use the standard ALTER TABLE recursion mechanism,  
so we invent our own by following pg_constraint.conparentid down.  
  
When ALTER TABLE .. ALTER CONSTRAINT is invoked on the derived  
pg_constraint object that's automaticaly created in a partition as a  
result of a constraint added to its parent, raise an error instead of  
pretending to work and then failing to modify all the affected triggers.  
Before this commit such a command would be allowed but failed to affect  
all triggers, so it would silently misbehave.  (Restoring dumps of  
existing databases is not affected, because pg_dump does not produce  
anything for such a derived constraint anyway.)  
  
Add some tests for the case.  
  
Backpatch to 11, where foreign key support was added to partitioned  
tables by commit 3de241dba86f.  (A related change is commit f56f8f8da6af  
in pg12 which added support for FKs *referencing* partitioned tables;  
this is what forces us to use an ad-hoc recursion mechanism for this.)  
  
Diagnosed by Tom Lane from bug report from Ron L Johnson.  As of this  
writing, no reviews were offered.  
  
Discussion: https://postgr.es/m/75fe0761-a291-86a9-c8d8-4906da077469@gmail.com  
Discussion: https://postgr.es/m/3144850.1607369633@sss.pgh.pa.us  

commit   : 72fabd4bfb5a8189591933cf244eabcaf83d4b8b    
  
author   : Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Tue, 4 May 2021 10:09:11 -0400    
  
committer: Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Tue, 4 May 2021 10:09:11 -0400    

The OID of the constraint is used instead of the OID of the trigger --  
an easy mistake to make.  Apparently the object-alter hooks are not very  
well tested :-(  
  
Backpatch to 12, where this typo was introduced by 578b229718e8  
  
Discussion: https://postgr.es/m/20210503231633.GA6994@alvherre.pgsql  

commit   : bdaa0d2d726911e31b19ed3a02ecb33dfc6d3673    
  
author   : Peter Eisentraut <peter@eisentraut.org>    
date     : Tue, 4 May 2021 14:03:54 +0200    
  
committer: Peter Eisentraut <peter@eisentraut.org>    
date     : Tue, 4 May 2021 14:03:54 +0200    

The previous fix for dumping of inherited generated columns  
(0bf83648a52df96f7c8677edbbdf141bfa0cf32b) must not be applied to  
partitions, since, unlike normal inherited tables, they are always  
dumped separately and reattached.  
  
Reported-by: Santosh Udupi <email@hitha.net>  
Discussion: https://www.postgresql.org/message-id/flat/CACLRvHZ4a-%2BSM_159%2BtcrHdEqxFrG%3DW4gwTRnwf7Oj0UNj5R2A%40mail.gmail.com  

commit   : 13ff139a238480cd3221c51c269d5ccdd429594f    
  
author   : Peter Eisentraut <peter@eisentraut.org>    
date     : Tue, 4 May 2021 11:45:37 +0200    
  
committer: Peter Eisentraut <peter@eisentraut.org>    
date     : Tue, 4 May 2021 11:45:37 +0200    

When running ALTER TABLE t2 INHERIT t1, we must check that columns in  
t2 that correspond to a generated column in t1 are also generated and  
have the same generation expression.  Otherwise, this would allow  
creating setups that a normal CREATE TABLE sequence would not allow.  
  
Discussion: https://www.postgresql.org/message-id/22de27f6-7096-8d96-4619-7b882932ca25@2ndquadrant.com  

commit   : bd9e46a1a4acafa170e9dbf35299518a216ffa41    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 30 Apr 2021 15:37:56 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 30 Apr 2021 15:37:56 -0400    

While we've always allowed such cases, the documentation didn't  
say you could do it.  
  
Discussion: https://postgr.es/m/161969805833.690.13680986983883602407@wrigleys.postgresql.org  

commit   : 8e9b7c63877094bee343283d00b4e29bd9bb4ffa    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 30 Apr 2021 15:10:06 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 30 Apr 2021 15:10:06 -0400    

Mention specifically that you can't call aggregates, window functions,  
or procedures this way (the inability to call SRFs was already  
mentioned).  
  
Also, the claim that PQfn doesn't support NULL arguments or results  
has been a lie since we invented protocol 3.0.  Not sure why this  
text was never updated for that, but do it now.  
  
Discussion: https://postgr.es/m/2039442.1615317309@sss.pgh.pa.us  

commit   : 89768ee696bfe1dd77dcd3f84cb10817aa379874    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 30 Apr 2021 14:10:26 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 30 Apr 2021 14:10:26 -0400    

Reject aggregates, window functions, and procedures.  Aggregates  
failed anyway, though with a somewhat obscure error message.  
Window functions would hit an Assert or null-pointer dereference.  
Procedures seemed to work as long as you didn't try to do  
transaction control, but (a) transaction control is sort of the  
point of a procedure, and (b) it's not entirely clear that no  
bugs lurk in that path.  Given the lack of testing of this area,  
it seems safest to be conservative in what we support.  
  
Also reject proretset functions, as the fastpath protocol can't  
support returning a set.  
  
Also remove an easily-triggered assertion that the given OID  
isn't 0; the subsequent lookups can handle that case themselves.  
  
Per report from Theodor-Arsenij Larionov-Trichkin.  
Back-patch to all supported branches.  (The procedure angle  
only applies in v11+, of course.)  
  
Discussion: https://postgr.es/m/2039442.1615317309@sss.pgh.pa.us  

commit   : ba86371b9ca048eeffc5f26530b78f64f2884ed5    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 29 Apr 2021 15:24:37 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 29 Apr 2021 15:24:37 -0400    

Commits 29aeda6e4 et al closed up some oversights involving not checking  
for non-upgradable types within container types, such as arrays and  
ranges.  However, I only looked at version.c, failing to notice that  
there were substantially-equivalent tests in check.c.  (The division  
of responsibility between those files is less than clear...)  
  
In addition, because genbki.pl does not guarantee that auto-generated  
rowtype OIDs will hold still across versions, we need to consider that  
the composite type associated with a system catalog or view is  
non-upgradable.  It seems unlikely that someone would have a user  
column declared that way, but if they did, trying to read it in another  
PG version would likely draw "no such pg_type OID" failures, thanks  
to the type OID embedded in composite Datums.  
  
To support the composite and reg*-type cases, extend the recursive  
query that does the search to allow any base query that returns  
a column of pg_type OIDs, rather than limiting it to exactly one  
starting type.  
  
As before, back-patch to all supported branches.  
  
Discussion: https://postgr.es/m/2798740.1619622555@sss.pgh.pa.us  

commit   : adbcd3e6634aa37c86bd8d5463dab552c22510f9    
  
author   : Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Thu, 29 Apr 2021 11:31:24 -0400    
  
committer: Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Thu, 29 Apr 2021 11:31:24 -0400    

Backpatch to 12, where 87259588d0ab introduced the current behavior.  
  
Per note from Justin Pryzby.  
  
Co-authored-by: Justin Pryzby <pryzby@telsasoft.com>  
Discussion: https://postgr.es/m/20210416143135.GI3315@telsasoft.com  

commit   : 824df1cccb74f5f634439ecf6c9828fea6ecc3ef    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Wed, 28 Apr 2021 10:03:28 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Wed, 28 Apr 2021 10:03:28 -0400    

Somehow I'd convinced myself that rotating to UTC-12 was the way  
to do this, but upon further review, it's definitely UTC+12.  
  
Discussion: https://postgr.es/m/1197050.1619123213@sss.pgh.pa.us  

commit   : 85a3e0be1e94b4e0e94d1480f43fe47ce7f68b62    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Wed, 28 Apr 2021 11:58:46 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Wed, 28 Apr 2021 11:58:46 +0900    

Spotted by buildfarm member prion, with -DRELCACHE_FORCE_RELEASE.  
  
Introduced in f7aab36.  
  
Discussion: https://postgr.es/m/2759018.1619577848@sss.pgh.pa.us  
Backpatch-through: 9.6  

commit   : 7e76cb1d82bcc2d39a3d70930822c247d6a034d8    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Wed, 28 Apr 2021 11:18:20 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Wed, 28 Apr 2021 11:18:20 +0900    

Attempting to use this function with event triggers failed, as, since  
its introduction in a676201, this code has never associated an object  
name with event triggers.  This addresses the failure by adding the  
event trigger name to the set defining its object address.  
  
Note that regression tests are added within event_trigger and not  
object_address to avoid issues with concurrent connections in parallel  
schedules.  
  
Author: Joel Jacobson  
Discussion: https://postgr.es/m/3c905e77-a026-46ae-8835-c3f6cd1d24c8@www.fastmail.com  
Backpatch-through: 9.6  

commit   : b230618ce8759147e838c3a08709685cddca2468    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 26 Apr 2021 11:50:35 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 26 Apr 2021 11:50:35 -0400    

For some reason, the "julian" option for extract()/date_part() has  
never gotten listed in the manual.  Also, while Appendix B mentioned  
in passing that we don't conform to the usual astronomical definition  
that a Julian date starts at noon UTC, it was kind of vague about what  
we do instead.  Clarify that, and add an example showing how to get  
the astronomical definition if you want it.  
  
It's been like this for ages, so back-patch to all supported branches.  
  
Discussion: https://postgr.es/m/1197050.1619123213@sss.pgh.pa.us  

commit   : 0ecc88076ed2eb52b36261ee82c5c5fc93c10b6c    
  
author   : Fujii Masao <fujii@postgresql.org>    
date     : Fri, 23 Apr 2021 15:45:46 +0900    
  
committer: Fujii Masao <fujii@postgresql.org>    
date     : Fri, 23 Apr 2021 15:45:46 +0900    

Previously it was documented that if using "-X none" option there was  
no guarantee that all required WAL files were archived at the end of  
pg_basebackup when taking a backup from the standby. But this limitation  
was removed by commit 52f8a59dd9. Now, even when taking a backup  
from the standby, pg_basebackup can wait for all required WAL files  
to be archived. Therefore this commit removes such obsolete  
description from the docs.  
  
Also this commit adds new description about the limitation when  
taking a backup from the standby, into the docs. The limitation is that  
pg_basebackup cannot force the standbfy to switch to a new WAL file  
at the end of backup, which may cause pg_basebackup to wait a long  
time for the last required WAL file to be switched and archived,  
especially when write activity on the primary is low.  
  
Back-patch to v10 where the issue was introduced.  
  
Reported-by: Kyotaro Horiguchi  
Author: Kyotaro Horiguchi, Fujii Masao  
Reviewed-by: Kyotaro Horiguchi, Fujii Masao  
Discussion: https://postgr.es/m/20210420.133235.1342729068750553399.horikyota.ntt@gmail.com  

commit   : 05ce4bf8b1d45cc55762fab627ea91d1ffbbdc03    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 22 Apr 2021 17:30:42 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 22 Apr 2021 17:30:42 -0400    

Adopt a more consistent policy about what slot-type-specific  
getsysattr functions should do when system attributes are not  
available.  To wit, they should all throw the same user-oriented  
error, rather than variously crashing or emitting developer-oriented  
messages.  
  
This closes a identifiable problem in commits a71cfc56b and  
3fb93103a (in v13 and v12), so back-patch into those branches,  
along with a test case to try to ensure we don't break it again.  
It is not known that any of the former crash cases are reachable  
in HEAD, but this seems like a good safety improvement in any case.  
  
Discussion: https://postgr.es/m/141051591267657@mail.yandex.ru  

commit   : 3fb93103a9fd5182f4f75d6da87dadcb3b36d7b1    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 22 Apr 2021 11:46:41 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 22 Apr 2021 11:46:41 -0400    

If the source and destination partitions don't have identical  
rowtypes (for example, one has dropped columns the other lacks),  
then the planSlot contents will be different because of that.  
If the query has a RETURNING list that tries to return resjunk  
columns out of the planSlot, that is columns from tables that  
were joined to the target table, we'd get errors or wrong answers.  
That's because we used the RETURNING list generated for the  
destination partition, which expects a planSlot matching that  
partition's subplan.  
  
The most practical fix seems to be to convert the updated destination  
tuple back to the source partition's rowtype, and then apply the  
RETURNING list generated for the source partition.  This avoids making  
fragile assumptions about whether the per-subpartition subplans  
generated all the resjunk columns in the same order.  
  
This has been broken since v11 introduced cross-partition UPDATE.  
The lack of field complaints shows that non-identical partitions  
aren't a common case; therefore, don't stress too hard about  
making the conversion efficient.  
  
There's no such bug in HEAD, because commit 86dc90056 got rid of  
per-target-relation variance in the contents of the planSlot.  
Hence, patch v11-v13 only.  
  
Amit Langote and Etsuro Fujita, small changes by me  
  
Discussion: https://postgr.es/m/CA+HiwqE_UK1jTSNrjb8mpTdivzd3dum6mK--xqKq0Y9VmfwWQA@mail.gmail.com  

commit   : f7ac005c70588b8bedbe5f1a91848e0d1c9b258d    
  
author   : Andrew Dunstan <andrew@dunslane.net>    
date     : Wed, 21 Apr 2021 11:12:04 -0400    
  
committer: Andrew Dunstan <andrew@dunslane.net>    
date     : Wed, 21 Apr 2021 11:12:04 -0400    

commit   : b931304506064b7890c712e4c6d925da59f389d5    
  
author   : Andrew Dunstan <andrew@dunslane.net>    
date     : Wed, 21 Apr 2021 10:21:22 -0400    
  
committer: Andrew Dunstan <andrew@dunslane.net>    
date     : Wed, 21 Apr 2021 10:21:22 -0400    

This has been found to cause hangs where tcp usage is forced.  
  
Alexey Kodratov  
  
Discussion: https://postgr.es/m/82e271a9a11928337fcb5b5e57b423c0@postgrespro.ru  
  
Backpatch to all live branches  

commit   : e4fbd11a1d5c291fe719b0bc833882e0baad1f8e    
  
author   : Magnus Hagander <magnus@hagander.net>    
date     : Tue, 20 Apr 2021 14:35:16 +0200    
  
committer: Magnus Hagander <magnus@hagander.net>    
date     : Tue, 20 Apr 2021 14:35:16 +0200    

Author: Julien Rouhaud  
Backpatch-through: 11  
Discussion: https://postgr.es/m/20210420121659.odjueyd4rpilorn5@nol  

commit   : d380ec9891db13d8a4fc8a40adc68880a88ecb31    
  
author   : Andrew Dunstan <andrew@dunslane.net>    
date     : Fri, 16 Apr 2021 16:54:04 -0400    
  
committer: Andrew Dunstan <andrew@dunslane.net>    
date     : Fri, 16 Apr 2021 16:54:04 -0400    

In order to avoid getting old logfile contents certain functions in  
PostgresNode were doing one of two things. On Windows it rotated the  
logfile and restarted the server, while elsewhere it truncated the log  
file. Both of these are unnecessary. We borrow from the buildfarm which  
does this instead: note the size of the logfile before we start, and  
then when fetching the logfile skip to that position before accumulating  
contents. This is spelled differently on Windows but the effect is the  
same. This is largely centralized in TestLib's slurp_file function,  
which has a new optional parameter, the offset to skip to before  
starting to reading the file. Code in the client becomes much neater.  
  
Backpatch to all live branches.  
  
Michael Paquier, slightly modified by me.  
  
Discussion: https://postgr.es/m/YHajnhcMAI3++pJL@paquier.xyz  

commit   : 26cf32455c501f01d3b73dcf680072169749c980    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Fri, 16 Apr 2021 16:56:29 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Fri, 16 Apr 2021 16:56:29 +0900    

Author: Erik Rijkers  
Discussion: https://postgr.es/m/1219476687.20432.1617452918468@webmailclassic.xs4all.nl  
Backpatch-through: 12  

commit   : a7fcb62852dcf886ef7632ff6b490558c11fca2c    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Tue, 13 Apr 2021 15:10:18 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Tue, 13 Apr 2021 15:10:18 -0400    

Most GUC check hooks that inspect database state have special checks  
that prevent them from throwing hard errors for state-dependent issues  
when source == PGC_S_TEST.  This allows, for example,  
"ALTER DATABASE d SET default_text_search_config = foo" when the "foo"  
configuration hasn't been created yet.  Without this, we have problems  
during dump/reload or pg_upgrade, because pg_dump has no idea about  
possible dependencies of GUC values and can't ensure a safe restore  
ordering.  
  
However, check_role() and check_session_authorization() hadn't gotten  
the memo about that, and would throw hard errors anyway.  It's not  
entirely clear what is the use-case for "ALTER ROLE x SET role = y",  
but we've now heard two independent complaints about that bollixing  
an upgrade, so apparently some people are doing it.  
  
Hence, fix these two functions to act more like other check hooks  
with similar needs.  (But I did not change their insistence on  
being inside a transaction, as it's still not apparent that setting  
either GUC from the configuration file would be wise.)  
  
Also fix check_temp_buffers, which had a different form of the disease  
of making state-dependent checks without any exception for PGC_S_TEST.  
A cursory survey of other GUC check hooks did not find any more issues  
of this ilk.  (There are a lot of interdependencies among  
PGC_POSTMASTER and PGC_SIGHUP GUCs, which may be a bad idea, but  
they're not relevant to the immediate concern because they can't be  
set via ALTER ROLE/DATABASE.)  
  
Per reports from Charlie Hornsby and Nathan Bossart.  Back-patch  
to all supported branches.  
  
Discussion: https://postgr.es/m/HE1P189MB0523B31598B0C772C908088DB7709@HE1P189MB0523.EURP189.PROD.OUTLOOK.COM  
Discussion: https://postgr.es/m/20160711223641.1426.86096@wrigleys.postgresql.org  

commit   : 6530df6c294c3f3b2dba6a1703574f6bbcde0886    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Tue, 13 Apr 2021 13:37:07 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Tue, 13 Apr 2021 13:37:07 -0400    

Previously, get_cached_rowtype() cached a pointer to a reference-counted  
tuple descriptor from the typcache, relying on the ExprContextCallback  
mechanism to release the tupdesc refcount when the expression tree  
using the tupdesc was destroyed.  This worked fine when it was designed,  
but the introduction of within-DO-block COMMITs broke it.  The refcount  
is logged in a transaction-lifespan resource owner, but plpgsql won't  
destroy simple expressions made within the DO block (before its first  
commit) until the DO block is exited.  That results in a warning about  
a leaked tupdesc refcount when the COMMIT destroys the original resource  
owner, and then an error about the active resource owner not holding a  
matching refcount when the expression is destroyed.  
  
To fix, get rid of the need to have a shutdown callback at all, by  
instead caching a pointer to the relevant typcache entry.  Those  
survive for the life of the backend, so we needn't worry about the  
pointer becoming stale.  (For registered RECORD types, we can still  
cache a pointer to the tupdesc, knowing that it won't change for the  
life of the backend.)  This mechanism has been in use in plpgsql  
and expandedrecord.c since commit 4b93f5799, and seems to work well.  
  
This change requires modifying the ExprEvalStep structs used by the  
relevant expression step types, which is slightly worrisome for  
back-patching.  However, there seems no good reason for extensions  
to be familiar with the details of these particular sub-structs.  
  
Per report from Rohit Bhogate.  Back-patch to v11 where within-DO-block  
COMMITs became a thing.  
  
Discussion: https://postgr.es/m/CAAV6ZkQRCVBh8qAY+SZiHnz+U+FqAGBBDaDTjF2yiKa2nJSLKg@mail.gmail.com  

commit   : 5f12bc94dcc60403bdfec6ea3d97aa616a512d9e    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Tue, 13 Apr 2021 12:17:24 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Tue, 13 Apr 2021 12:17:24 -0400    

heap_update needs to clear any existing "all visible" flag on  
the old tuple's page (and on the new page too, if different).  
Per coding rules, to do this it must acquire pin on the appropriate  
visibility-map page while not holding exclusive buffer lock;  
which creates a race condition since someone else could set the  
flag whenever we're not holding the buffer lock.  The code is  
supposed to handle that by re-checking the flag after acquiring  
buffer lock and retrying if it became set.  However, one code  
path through heap_update itself, as well as one in its subroutine  
RelationGetBufferForTuple, failed to do this.  The end result,  
in the unlikely event that a concurrent VACUUM did set the flag  
while we're transiently not holding lock, is a non-recurring  
"PANIC: wrong buffer passed to visibilitymap_clear" failure.  
  
This has been seen a few times in the buildfarm since recent VACUUM  
changes that added code paths that could set the all-visible flag  
while holding only exclusive buffer lock.  Previously, the flag  
was (usually?) set only after doing LockBufferForCleanup, which  
would insist on buffer pin count zero, thus preventing the flag  
from becoming set partway through heap_update.  However, it's  
clear that it's heap_update not VACUUM that's at fault here.  
  
What's less clear is whether there is any hazard from these bugs  
in released branches.  heap_update is certainly violating API  
expectations, but if there is no code path that can set all-visible  
without a cleanup lock then it's only a latent bug.  That's not  
100% certain though, besides which we should worry about extensions  
or future back-patch fixes that could introduce such code paths.  
  
I chose to back-patch to v12.  Fixing RelationGetBufferForTuple  
before that would require also back-patching portions of older  
fixes (notably 0d1fe9f74), which is more code churn than seems  
prudent to fix a hypothetical issue.  
  
Discussion: https://postgr.es/m/2247102.1618008027@sss.pgh.pa.us  

commit   : 4749c7ff4932ca593fcde9928904155642c0b496    
  
author   : Noah Misch <noah@leadboat.com>    
date     : Mon, 12 Apr 2021 19:24:41 -0700    
  
committer: Noah Misch <noah@leadboat.com>    
date     : Mon, 12 Apr 2021 19:24:41 -0700    

With the Oracle Developer Studio 12.6 compiler, #line directives alter  
the current source file location for purposes of #include "..."  
directives.  Hence, a VPATH build failed with 'cannot find include file:  
"specscanner.c"'.  With two exceptions, parser-containing directories  
already add "-I. -I$(srcdir)"; eliminate the exceptions.  Back-patch to  
9.6 (all supported versions).  

commit   : e3ac7d17616b6baea12d21e3a0b32c683b81f9a6    
  
author   : Noah Misch <noah@leadboat.com>    
date     : Mon, 12 Apr 2021 19:24:21 -0700    
  
committer: Noah Misch <noah@leadboat.com>    
date     : Mon, 12 Apr 2021 19:24:21 -0700    

It doesn't support "\(foo\)*" like a POSIX "sed" implementation does;  
see the Autoconf manual.  Back-patch to 9.6 (all supported versions).  

commit   : 27011bcffa74a5113c9b5408c678315e74fb9a70    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 12 Apr 2021 14:37:22 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 12 Apr 2021 14:37:22 -0400    

There are hacks in parse_coerce.c to push down a requested coercion  
to below any CollateExpr that may appear.  However, we did that even  
if the requested data type is non-collatable, leading to an invalid  
expression tree in which CollateExpr is applied to a non-collatable  
type.  The fix is just to drop the CollateExpr altogether, reasoning  
that it's useless.  
  
This bug is ten years old, dating to the original addition of  
COLLATE support.  The lack of field complaints suggests that there  
aren't a lot of user-visible consequences.  We noticed the problem  
because it would trigger an assertion in DefineVirtualRelation if  
the invalid structure appears as an output column of a view; however,  
in a non-assert build, you don't see a crash just a (subtly incorrect)  
complaint about applying collation to a non-collatable type.  I found  
that by putting the incorrect structure further down in a view, I could  
make a view definition that would fail dump/reload, per the added  
regression test case.  But CollateExpr doesn't do anything at run-time,  
so this likely doesn't lead to any really exciting consequences.  
  
Per report from Yulin Pei.  Back-patch to all supported branches.  
  
Discussion: https://postgr.es/m/HK0PR01MB22744393C474D503E16C8509F4709@HK0PR01MB2274.apcprd01.prod.exchangelabs.com  

commit   : 82dd5706ee5a5fc4db962fe1a672b4f71ab51612    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Mon, 12 Apr 2021 11:31:30 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Mon, 12 Apr 2021 11:31:30 +0900    

Using Roman numbers (via "RM" or "rm") for a conversion to calculate a  
number of months has never considered the case of negative numbers,  
where a conversion could easily cause out-of-bound memory accesses.  The  
conversions in themselves were not completely consistent either, as  
specifying 12 would result in NULL, but it should mean XII.  
  
This commit reworks the conversion calculation to have a more  
consistent behavior:  
- If the number of months and years is 0, return NULL.  
- If the number of months is positive, return the exact month number.  
- If the number of months is negative, do a backward calculation, with  
-1 meaning December, -2 November, etc.  
  
Reported-by: Theodor Arsenij Larionov-Trichkin  
Author: Julien Rouhaud  
Discussion: https://postgr.es/m/16953-f255a18f8c51f1d5@postgresql.org  
backpatch-through: 9.6  

commit   : 2bf44fbe271dae3f4bd458e19e32d51996b988b4    
  
author   : Magnus Hagander <magnus@hagander.net>    
date     : Fri, 9 Apr 2021 12:40:14 +0200    
  
committer: Magnus Hagander <magnus@hagander.net>    
date     : Fri, 9 Apr 2021 12:40:14 +0200    

Author: Daniel Westermann  
Backpatch-through: 9.6  
Discussion: https://postgr.es/m/GV0P278MB0483A7AA85BAFCC06D90F453D2739@GV0P278MB0483.CHEP278.PROD.OUTLOOK.COM  

commit   : d42978c67afa930b1208caa9555024da10550cdb    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Fri, 9 Apr 2021 13:53:22 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Fri, 9 Apr 2021 13:53:22 +0900    

Comment fixes are applied on HEAD, and documentation improvements are  
applied on back-branches where needed.  
  
Author: Justin Pryzby  
Discussion: https://postgr.es/m/20210408164008.GJ6592@telsasoft.com  
Backpatch-through: 9.6  

commit   : 847612fda6f6da88441f4c823ebcbf8474bfe0b7    
  
author   : Tomas Vondra <tomas.vondra@postgresql.org>    
date     : Wed, 7 Apr 2021 15:58:35 +0200    
  
committer: Tomas Vondra <tomas.vondra@postgresql.org>    
date     : Wed, 7 Apr 2021 15:58:35 +0200    

The code in bringetbitmap() simply added the whole matching page range  
to the TID bitmap, as determined by pages_per_range, even if some of the  
pages were beyond the end of the heap. The query then might fail with  
an error like this:  
  
  ERROR:  could not open file "base/20176/20228.2" (target block  
          262144): previous segment is only 131021 blocks  
  
In this case, the relation has 262093 pages (131072 and 131021 pages),  
but we're trying to acess block 262144, i.e. first block of the 3rd  
segment. At that point _mdfd_getseg() notices the preceding segment is  
incomplete, and fails.  
  
Hitting this in practice is rather unlikely, because:  
  
* Most indexes use power-of-two ranges, so segments and page ranges  
  align perfectly (segment end is also a page range end).  
  
* The table size has to be just right, with the last segment being  
  almost full - less than one page range from full segment, so that the  
  last page range actually crosses the segment boundary.  
  
* Prefetch has to be enabled. The regular page access checks that  
  pages are not beyond heap end, but prefetch does not. On older  
  releases (before 12) the execution stops after hitting the first  
  non-existent page, so the prefetch distance has to be sufficient  
  to reach the first page in the next segment to trigger the issue.  
  Since 12 it's enough to just have prefetch enabled, the prefetch  
  distance does not matter.  
  
Fixed by not adding non-existent pages to the TID bitmap. Backpatch  
all the way back to 9.6 (BRIN indexes were introduced in 9.5, but that  
release is EOL).  
  
Backpatch-through: 9.6  

commit   : 92273d48771a76fdd8e8d8f7fd7b7f6dcfb86d92    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Wed, 7 Apr 2021 19:59:27 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Wed, 7 Apr 2021 19:59:27 +0900    

Instead of writing a query to psql's stdin, which can cause a failure  
where psql exits before writing, reporting a write failure with a broken  
pipe, this changes the logic to use -c.  This was not seen in the  
buildfarm as no animals with a sensitive environment are running the  
kerberos tests, but let's be safe.  
  
HEAD is able to handle the situation as of 6d41dd0 for all the test  
suites doing connection checks.  f44b9b6 has fixed the same problem for  
the LDAP tests.  
  
Discussion: https://postgr.es/m/YGu7ceWAiSNQDgH5@paquier.xyz  
Backpatch-through: 11  

commit   : dd5b7e486a4f90b54db62e57b84b81003c0d032d    
  
author   : Fujii Masao <fujii@postgresql.org>    
date     : Tue, 6 Apr 2021 02:25:37 +0900    
  
committer: Fujii Masao <fujii@postgresql.org>    
date     : Tue, 6 Apr 2021 02:25:37 +0900    

Maxim Orlov reported that the shutdown of standby server could result in  
the following assertion failure. The cause of this issue was that,  
when the shutdown caused the startup process to exit, recovery-time  
transaction tracking was not shut down even if it's already initialized,  
and some locks the tracked transactions were holding could not be released.  
At this situation, if other process was invoked and the PGPROC entry that  
the startup process used was assigned to it, it found such unreleased locks  
and caused the assertion failure, during the initialization of it.  
  
    TRAP: FailedAssertion("SHMQueueEmpty(&(MyProc->myProcLocks[i]))"  
  
This commit fixes this issue by making the startup process shut down  
transaction tracking and release all locks, at the exit of it.  
  
Back-patch to all supported branches.  
  
Reported-by: Maxim Orlov  
Author: Fujii Masao  
Reviewed-by: Maxim Orlov  
Discussion: https://postgr.es/m/ad4ce692cc1d89a093b471ab1d969b0b@postgrespro.ru  

commit   : 48b319e87636aebcce05f06b02c7feb7ceb9e9a1    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Sun, 4 Apr 2021 17:57:07 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Sun, 4 Apr 2021 17:57:07 -0400    

spg_box_quad_leaf_consistent unconditionally returned the leaf  
datum as leafValue, even though in its usage for poly_ops that  
value is of completely the wrong type.  
  
In versions before 12, that was harmless because the core code did  
nothing with leafValue in non-index-only scans ... but since commit  
2a6368343, if we were doing a KNN-style scan, spgNewHeapItem would  
unconditionally try to copy the value using the wrong datatype  
parameters.  Said copying is a waste of time and space if we're not  
going to return the data, but it accidentally failed to fail until  
I fixed the datatype confusion in ac9099fc1.  
  
Hence, change spgNewHeapItem to not copy the datum unless we're  
actually going to return it later.  This saves cycles and dodges  
the question of whether lossy opclasses are returning the right  
type.  Also change spg_box_quad_leaf_consistent to not return  
data that might be of the wrong type, as insurance against  
somebody introducing a similar bug into the core code in future.  
  
It seems like a good idea to back-patch these two changes into  
v12 and v13, although I'm afraid to change spgNewHeapItem's  
mistaken idea of which datatype to use in those branches.  
  
Per buildfarm results from ac9099fc1.  
  
Discussion: https://postgr.es/m/3728741.1617381471@sss.pgh.pa.us  

commit   : 6972d9104b6c54bae2fd63d8e02e9c014d162ca3    
  
author   : Bruce Momjian <bruce@momjian.us>    
date     : Fri, 2 Apr 2021 16:42:29 -0400    
  
committer: Bruce Momjian <bruce@momjian.us>    
date     : Fri, 2 Apr 2021 16:42:29 -0400    

All other places already use MONTHS_PER_YEAR appropriately.  
  
Backpatch-through: 9.6  

commit   : 53f5c2df05368bade3523d440f5c10cfae6ad5ef    
  
author   : Joe Conway <mail@joeconway.com>    
date     : Fri, 2 Apr 2021 13:48:48 -0400    
  
committer: Joe Conway <mail@joeconway.com>    
date     : Fri, 2 Apr 2021 13:48:48 -0400    

Command-line options, or previous "ALTER (ROLE|DATABASE) ...  
SET ROLE ..." commands, can change the value of the default role  
for a session. In the presence of one of these, RESET ROLE will  
change the current user identifier to the default role rather  
than the session user identifier. Fix the documentation to  
reflect this reality. Backpatch to all supported versions.  
  
Author: Nathan Bossart  
Reviewed-By: Laurenz Albe, David G. Johnston, Joe Conway  
Reported by: Nathan Bossart  
Discussion: https://postgr.es/m/flat/925134DB-8212-4F60-8AB1-B1231D750CB4%40amazon.com  
Backpatch-through: 9.6  

commit   : 24bcce3bd6b458d0d2b064c2ab2ed2837c1211a3    
  
author   : Fujii Masao <fujii@postgresql.org>    
date     : Sat, 3 Apr 2021 00:07:00 +0900    
  
committer: Fujii Masao <fujii@postgresql.org>    
date     : Sat, 3 Apr 2021 00:07:00 +0900    

pg_checksums uses two counters, total size and current size,  
to calculate the progress. Previously the progress that  
pg_checksums reported could not reach 100% at the end.  
The cause of this issue was that the sizes of only pages excluding  
new ones in each file were counted as the current size  
while the size of each file is counted as the total size.  
That is, the total size of all new pages could be reported  
as the difference between the total size and current size.  
  
This commit fixes this issue by making pg_checksums count  
the sizes of all pages including new ones in each file as  
the current size.  
  
Back-patch to v12 where progress reporting was added to pg_checksums.  
  
Reported-by: Shinya Kato  
Author: Shinya Kato  
Reviewed-by: Fujii Masao  
Discussion: https://postgr.es/m/TYAPR01MB289656B1ACA0A5E7CAD07BE3C47A9@TYAPR01MB2896.jpnprd01.prod.outlook.com  

commit   : 677357047b9c920e351b73d9670a813fcdc6801b    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Fri, 2 Apr 2021 16:37:11 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Fri, 2 Apr 2021 16:37:11 +0900    

The current instructions describing how to write the backup_label and  
tablespace_map files are confusing.  For example, opening a file in text  
mode on Windows and copy-pasting the file's contents would result in a  
failure at recovery because of the extra CRLF characters generated.  The  
documentation was not stating that clearly, and per discussion this is  
not considered as a supported scenario.  
  
This commit extends a bit the documentation to mention that it may be  
required to open the file in binary mode before writing its data.  
  
Reported-by: Wang Shenhao  
Author: David Steele  
Reviewed-by: Andrew Dunstan, Magnus Hagander  
Discussion: https://postgr.es/m/8373f61426074f2cb6be92e02f838389@G08CNEXMBPEKD06.g08.fujitsu.local  
Backpatch-through: 9.6  

commit   : d6ca789dde70f2c323b79559b8ce0746ddf7a48d    
  
author   : Bruce Momjian <bruce@momjian.us>    
date     : Thu, 1 Apr 2021 21:17:24 -0400    
  
committer: Bruce Momjian <bruce@momjian.us>    
date     : Thu, 1 Apr 2021 21:17:24 -0400    

Also mention that you should read the intervening major releases notes.  
This change was also applied to the website.  
  
Discussion: https://postgr.es/m/20210330144949.GA8259@momjian.us  
  
Backpatch-through: 9.6  

commit   : bada6280f0b98765ecad8d85063cddf6ce82b3b0    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Fri, 2 Apr 2021 09:44:54 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Fri, 2 Apr 2021 09:44:54 +0900    

This test has been using a simple VACUUM with pg_relation_size() to  
check if a relation gets physically truncated or not, but forgot the  
fact that some concurrent activity, like checkpoint buffer writes, could  
cause some pages to be skipped.  The second test enabling  
vacuum_truncate could fail, seeing a non-empty relation.  The first test  
would not have failed, but could finish by testing a behavior different  
than the one aimed for.  Both tests gain a FREEZE option, to make the  
vacuums more aggressive and prevent page skips.  
  
This is similar to the issues fixed in c2dc1a7.  
  
Author: Arseny Sher  
Reviewed-by: Masahiko Sawada  
Discussion: https://postgr.es/m/87tuotr2hh.fsf@ars-thinkpad  
backpatch-through: 12  

commit   : 84c5e0dd2e7344d36d5c3a32228b35a284ef1a1a    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 1 Apr 2021 13:34:16 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 1 Apr 2021 13:34:16 -0400    

Despite the clear comments pointing out that the duplicative code  
segments in ReadHead() and _discoverArchiveFormat() needed to be  
in sync, they were not: the latter did not bother to apply any of  
the sanity checks in the former.  We'd missed noticing this partly  
because none of those checks would fail in scenarios we customarily  
test, and partly because the oversight would be masked if both  
segments execute, which they would in cases other than needing to  
autodetect the format of a non-seekable stdin source.  However,  
in a case meeting all these requirements --- for example, trying  
to read a newer-than-supported archive format from non-seekable  
stdin --- pg_restore missed applying the version check and would  
likely dump core or otherwise misbehave.  
  
The whole thing is silly anyway, because there seems little reason  
to duplicate the logic beyond the one-line verification that the  
file starts with "PGDMP".  There seems to have been an undocumented  
assumption that multiple major formats (major enough to require  
separate reader modules) would nonetheless share the first half-dozen  
fields of the custom-format header.  This seems unlikely, so let's  
fix it by just nuking the duplicate logic in _discoverArchiveFormat().  
  
Also get rid of the pointless attempt to seek back to the start of  
the file after successful autodetection.  That wastes cycles and  
it means we have four behaviors to verify not two.  
  
Per bug #16951 from Sergey Koposov.  This has been broken for  
decades, so back-patch to all supported versions.  
  
Discussion: https://postgr.es/m/16951-a4dd68cf0de23048@postgresql.org  

commit   : a126a9510def33fedcddf6288ae431f8d6f2f85c    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Thu, 1 Apr 2021 15:28:56 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Thu, 1 Apr 2021 15:28:56 +0900    

Some sections of the documentation used "exclusive lock" to describe  
that an ACCESS EXCLUSIVE lock is taken during a given operation.  This  
can be confusing to the reader as ACCESS SHARE is allowed with an  
EXCLUSIVE lock is used, but that would not be the case with what is  
described on those parts of the documentation.  
  
Author: Greg Rychlewski  
Discussion: https://postgr.es/m/CAKemG7VptD=7fNWckFMsMVZL_zzvgDO6v2yVmQ+ZiBfc_06kCQ@mail.gmail.com  
Backpatch-through: 9.6  

commit   : 448e86c3345bb41d3e530ab204b8f59301cdfb36    
  
author   : Stephen Frost <sfrost@snowman.net>    
date     : Wed, 31 Mar 2021 16:23:13 -0400    
  
committer: Stephen Frost <sfrost@snowman.net>    
date     : Wed, 31 Mar 2021 16:23:13 -0400    

The new appendix groups information on renamed or removed settings,  
commands, etc into an out-of-the-way part of the docs.  
  
The original id elements are retained in each subsection to ensure that  
the same filenames are produced for HTML docs. This prevents /current/  
links on the web from breaking, and allows users of the web docs  
to follow links from old version pages to info on the changes in the  
new version. Prior to this change, a link to /current/ for renamed  
sections like the recovery.conf docs would just 404. Similarly if  
someone searched for recovery.conf they would find the pg11 docs,  
but there would be no /12/ or /current/ link, so they couldn't easily  
find out that it was removed in pg12 or how to adapt.  
  
Index entries are also added so that there's a breadcrumb trail for  
users to follow when they know the old name, but not what we changed it  
to. So a user who is trying to find out how to set standby_mode in  
PostgreSQL 12+, or where pg_resetxlog went, now has more chance of  
finding that information.  
  
Craig Ringer and Stephen Frost  
Reviewed-by: Euler Taveira  
Discussion: https://postgr.es/m/CAGRY4nzPNOyYQ_1-pWYToUVqQ0ThqP5jdURnJMZPm539fdizOg%40mail.gmail.com  
Backpatch-through: 10  

commit   : cf8384ac8333dea9742b754d998491a321269704    
  
author   : Etsuro Fujita <efujita@postgresql.org>    
date     : Tue, 30 Mar 2021 13:00:03 +0900    
  
committer: Etsuro Fujita <efujita@postgresql.org>    
date     : Tue, 30 Mar 2021 13:00:03 +0900    

Back-patch to all supported branches.  
  
Author: Etsuro Fujita  
Discussion: https://postgr.es/m/CAPmGK17DwzaSf%2BB71dhL2apXdtG-OmD6u2AL9Cq2ZmAR0%2BzapQ%40mail.gmail.com  

commit   : 3c3221a138413bf04d86a815733c321849792bd8    
  
author   : Stephen Frost <sfrost@snowman.net>    
date     : Sun, 28 Mar 2021 11:28:15 -0400    
  
committer: Stephen Frost <sfrost@snowman.net>    
date     : Sun, 28 Mar 2021 11:28:15 -0400    

Commit c6763156589 added an acronym reference for "TLS" but the definition  
was never added.  
  
Author: Daniel Gustafsson  
Reviewed-by: Michael Paquier  
Backpatch-through: 9.6  
Discussion: https://postgr.es/m/27109504-82DB-41A8-8E63-C0498314F5B0@yesql.se  

commit   : 88acb0135720076599308e6fd58b659c81d1beba    
  
author   : Tomas Vondra <tomas.vondra@postgresql.org>    
date     : Fri, 26 Mar 2021 22:34:53 +0100    
  
committer: Tomas Vondra <tomas.vondra@postgresql.org>    
date     : Fri, 26 Mar 2021 22:34:53 +0100    

When estimating the number of groups using extended statistics, the code  
was discarding information about system attributes. This led to strange  
situation that  
  
    SELECT 1 FROM t GROUP BY ctid;  
  
could have produced higher estimate (equal to pg_class.reltuples) than  
  
    SELECT 1 FROM t GROUP BY a, b, ctid;  
  
with extended statistics on (a,b). Fixed by retaining information about  
the system attribute.  
  
Backpatch all the way to 10, where extended statistics were introduced.  
  
Author: Tomas Vondra  
Backpatch-through: 10  

commit   : 366aa374b315667fe44480ec8934cb1034ba0930    
  
author   : Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Thu, 25 Mar 2021 16:30:22 -0300    
  
committer: Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Thu, 25 Mar 2021 16:30:22 -0300    

On partition detach, we acquire a SHARE lock on all tables that  
reference the partitioned table that we're detaching a partition from,  
but failed to document this fact.  My oversight in commit f56f8f8da6af.  
Repair.  Backpatch to 12.  
  
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>  
Discussion: https://postgr.es/m/20210325180244.GA12738@alvherre.pgsql  

commit   : 292b7d9ffa18dfdf2c90efd4f14bbd196ebad76f    
  
author   : Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Thu, 25 Mar 2021 10:47:38 -0300    
  
committer: Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Thu, 25 Mar 2021 10:47:38 -0300    

I introduced this duplicate code in commit 8b08f7d4820f for no good  
reason.  Remove it, and backpatch to 11 where it was introduced.  
  
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>  

commit   : 73cce168ffcb1a0343cfa6fafe237f49b1449734    
  
author   : Fujii Masao <fujii@postgresql.org>    
date     : Thu, 25 Mar 2021 11:23:30 +0900    
  
committer: Fujii Masao <fujii@postgresql.org>    
date     : Thu, 25 Mar 2021 11:23:30 +0900    

Previously the WAL replay of COMMIT_TS_SETTS record called  
TransactionTreeSetCommitTsData() with the argument write_xlog=true,  
which generated and wrote new COMMIT_TS_SETTS record.  
This should not be acceptable because it's during recovery.  
  
This commit fixes the WAL replay of COMMIT_TS_SETTS record  
so that it calls TransactionTreeSetCommitTsData() with write_xlog=false  
and doesn't generate new WAL during recovery.  
  
Back-patch to all supported branches.  
  
Reported-by: lx zou <zoulx1982@163.com>  
Author: Fujii Masao  
Reviewed-by: Alvaro Herrera  
Discussion: https://postgr.es/m/16931-620d0f2fdc6108f1@postgresql.org  

commit   : beac4bd65dcf02a86013120c660498e50f3f88dd    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Tue, 23 Mar 2021 14:27:50 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Tue, 23 Mar 2021 14:27:50 -0400    

Jasen Betts reported yet another unintended side effect of commit  
85c54287a: reconnecting with "\c service=whatever" did not have the  
expected results.  The reason is that starting from the output of  
PQconndefaults() effectively allows environment variables (such  
as PGPORT) to override entries in the service file, whereas the  
normal priority is the other way around.  
  
Not using PQconndefaults at all would require yet a third main code  
path in do_connect's parameter setup, so I don't really want to fix  
it that way.  But we can have the logic effectively ignore all the  
default values for just a couple more lines of code.  
  
This patch doesn't change the behavior for "\c -reuse-previous=on  
service=whatever".  That remains significantly different from before  
85c54287a, because many more parameters will be re-used, and thus  
not be possible for service entries to replace.  But I think this  
is (mostly?) intentional.  In any case, since libpq does not report  
where it got parameter values from, it's hard to do differently.  
  
Per bug #16936 from Jasen Betts.  As with the previous patches,  
back-patch to all supported branches.  (9.5 is unfortunately now  
out of support, so this won't get fixed there.)  
  
Discussion: https://postgr.es/m/16936-3f524322a53a29f0@postgresql.org  

commit   : 1c457b8b5194bb838b61b02c883ddac4a212ea7e    
  
author   : Tomas Vondra <tomas.vondra@postgresql.org>    
date     : Tue, 23 Mar 2021 04:51:53 +0100    
  
committer: Tomas Vondra <tomas.vondra@postgresql.org>    
date     : Tue, 23 Mar 2021 04:51:53 +0100    

A couple error messages and comments used 'statistic kind', not the  
correct 'statistics kind'. Fix and backpatch all the way back to 10,  
where extended statistics were introduced.  
  
Backpatch-through: 10  

commit   : 4220e06f4c0c597c77e0170b4032c3cd10fb9555    
  
author   : Fujii Masao <fujii@postgresql.org>    
date     : Tue, 23 Mar 2021 09:53:08 +0900    
  
committer: Fujii Masao <fujii@postgresql.org>    
date     : Tue, 23 Mar 2021 09:53:08 +0900    

pg_waldump --stats=record identifies a record by a combination  
of the RmgrId and the four bits of the xl_info field of the record.  
But XACT records use the first bit of those four bits for an optional  
flag variable, and the following three bits for the opcode to  
identify a record. So previously the same type of XACT record  
could have different four bits (three bits are the same but the  
first one bit is different), and which could cause  
pg_waldump --stats=record to show two lines of per-record statistics  
for the same XACT record. This is a bug.  
  
This commit changes pg_waldump --stats=record so that it processes  
only XACT record differently, i.e., filters the opcode out of xl_info  
and uses a combination of the RmgrId and those three bits as  
the identifier of a record, only for XACT record. For other records,  
the four bits of the xl_info field are still used.  
  
Back-patch to all supported branches.  
  
Author: Kyotaro Horiguchi  
Reviewed-by: Shinya Kato, Fujii Masao  
Discussion: https://postgr.es/m/2020100913412132258847@highgo.ca  

commit   : c0849e41322d4e791e78a3990f8f3ccc437c8006    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Mon, 22 Mar 2021 09:51:19 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Mon, 22 Mar 2021 09:51:19 +0900    

The test added by 595b9cb forgot that on Windows it is necessary to set  
up pg_hba.conf (see PostgresNode::set_replication_conf) with a specific  
entry or base backups fail.  Any node that requires to support  
replication just needs to pass down allows_streaming at initialization.  
This updates the test to do so.  Simplify things a bit while on it.  
  
Per buildfarm member fairywren.  Any Windows hosts running this test  
would have failed, and I have reproduced the problem as well.  
  
Backpatch-through: 10  

commit   : 4b1dd9b1ea75bc57d00f691f0dcf80e4eca91dc0    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Mon, 22 Mar 2021 08:31:05 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Mon, 22 Mar 2021 08:31:05 +0900    

Any transactions found as still prepared by a checkpoint have their  
state data read from the WAL records generated by PREPARE TRANSACTION  
before being moved into their new location within pg_twophase/.  While  
reading such records, the WAL reader uses the callback  
read_local_xlog_page() to read a page, that is shared across various  
parts of the system.  This callback, since 1148e22a, has introduced an  
update of ThisTimeLineID when reading a record while in recovery, which  
is potentially helpful in the context of cascading WAL senders.  
  
This update of ThisTimeLineID interacts badly with the checkpointer if a  
promotion happens while some 2PC data is read from its record, as, by  
changing ThisTimeLineID, any follow-up WAL records would be written to  
an timeline older than the promoted one.  This results in consistency  
issues.  For instance, a subsequent server restart would cause a failure  
in finding a valid checkpoint record, resulting in a PANIC, for  
instance.  
  
This commit changes the code reading the 2PC data to reset the timeline  
once the 2PC record has been read, to prevent messing up with the static  
state of the checkpointer.  It would be tempting to do the same thing  
directly in read_local_xlog_page().  However, based on the discussion  
that has led to 1148e22a, users may rely on the updates of  
ThisTimeLineID when a WAL record page is read in recovery, so changing  
this callback could break some cases that are working currently.  
  
A TAP test reproducing the issue is added, relying on a PITR to  
precisely trigger a promotion with a prepared transaction still  
tracked.  
  
Per discussion with Heikki Linnakangas, Kyotaro Horiguchi, Fujii Masao  
and myself.  
  
Author: Soumyadeep Chakraborty, Jimmy Yih, Kevin Yeap  
Discussion: https://postgr.es/m/CAE-ML+_EjH_fzfq1F3RJ1=XaaNG=-Jz-i3JqkNhXiLAsM3z-Ew@mail.gmail.com  
Backpatch-through: 10  

commit   : 2f31414f4322876b34674eedc6e7d19c29ebe0d0    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Sat, 20 Mar 2021 12:47:21 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Sat, 20 Mar 2021 12:47:21 -0400    

While back-patching e0e569e1d, I noted that there were some other  
places where we ought to be applying DH_free(); namely, where we  
load some DH parameters from a file and then reject them as not  
being sufficiently secure.  While it seems really unlikely that  
anybody would hit these code paths in production, let alone do  
so repeatedly, let's fix it for consistency.  
  
Back-patch to v10 where this code was introduced.  
  
Discussion: https://postgr.es/m/16160-18367e56e9a28264@postgresql.org  

commit   : 992cba94d38ef20765e4c54e4dff00ae8a58a6c5    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Sat, 20 Mar 2021 12:38:22 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Sat, 20 Mar 2021 12:38:22 -0400    

When loading DH parameters used for the generation of ephemeral DH keys  
in the backend, the code has never bothered releasing the memory used  
for the DH information loaded from a file or from libpq's default.  This  
commit makes sure that the information is properly free()'d.  
  
Back-patch of e0e569e1d.  We originally thought the leak was minor and  
not worth back-patching, but Jelte Fennema pointed out that repeated  
SIGHUP's can result in very serious bloat of the postmaster, which is  
then multiplied by being duplicated into eadh forked child.  
  
Back-patch to v10; the code looked different before c0a15e07c,  
and didn't have a leak in the actually-live code paths.  
  
Michael Paquier  
  
Discussion: https://postgr.es/m/16160-18367e56e9a28264@postgresql.org  

commit   : 4eca51d4464133e6f4cd923355c6dd971d9c27d3    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Mar 2021 22:21:58 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Mar 2021 22:21:58 -0400    

We leaked the error report from PQconninfoParse, when there was  
one.  It seems unlikely that real usage patterns would repeat  
the failure often enough to create serious bloat, but let's  
back-patch anyway to keep the code similar in all branches.  
  
Found via valgrind testing.  
Back-patch to v10 where this code was added.  
  
Discussion: https://postgr.es/m/3816764.1616104288@sss.pgh.pa.us  

commit   : fc552f8680a79d602beae230615ffe8ed236cc43    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Mar 2021 22:09:41 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Mar 2021 22:09:41 -0400    

Because guc.c prefers to keep all its string values in malloc'd  
not palloc'd storage, it has to be more careful than usual to  
avoid leaks.  Error exits out of string GUC hook checks failed  
to clear the proposed value string, and error exits out of  
ProcessGUCArray() failed to clear the malloc'd results of  
ParseLongOption().  
  
Found via valgrind testing.  
This problem is ancient, so back-patch to all supported branches.  
  
Discussion: https://postgr.es/m/3816764.1616104288@sss.pgh.pa.us  

commit   : 92bc14a1027d9da079264c71329b87e137878845    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Mar 2021 21:44:43 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Mar 2021 21:44:43 -0400    

The text search cache mechanisms assume that we can clean up  
an invalidated dictionary cache entry simply by resetting the  
associated long-lived memory context.  However, that does not work  
for ispell affixes that make use of regular expressions, because  
the regex library deals in plain old malloc.  Hence, we leaked  
compiled regex(es) any time we dropped such a cache entry.  That  
could quickly add up, since even a fairly trivial regex can use up  
tens of kB, and a large one can eat megabytes.  Add a memory context  
callback to ensure that a regex gets freed when its owning cache  
entry is cleared.  
  
Found via valgrind testing.  
This problem is ancient, so back-patch to all supported branches.  
  
Discussion: https://postgr.es/m/3816764.1616104288@sss.pgh.pa.us  

commit   : 1452a0bb87c78812372f103de14cb6492a932ac6    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Mar 2021 20:50:56 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Mar 2021 20:50:56 -0400    

Some code paths in this function perform syscache lookups, which  
can lead to table accesses and possibly leakage of cruft into  
the caller's context.  If said context is CacheMemoryContext,  
we eventually will have visible bloat.  But fixing this is no  
harder than moving one memory context switch step.  (The other  
callers don't have a problem.)  
  
Andres Freund and I independently found this via valgrind testing.  
Back-patch to v12 where this code was added.  
  
Discussion: https://postgr.es/m/20210317023101.anvejcfotwka6gaa@alap3.anarazel.de  
Discussion: https://postgr.es/m/3816764.1616104288@sss.pgh.pa.us  

commit   : fbcc9fe33c43a3fb79812b72960df4909a4551e5    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Mar 2021 20:37:09 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Mar 2021 20:37:09 -0400    

Although these lists are usually NIL, and even when not empty  
are unlikely to be large, constant relcache update traffic could  
eventually result in visible bloat of CacheMemoryContext.  
  
Found via valgrind testing.  
Back-patch to v10 where this field was added.  
  
Discussion: https://postgr.es/m/3816764.1616104288@sss.pgh.pa.us  

commit   : a5eb70cfca5bc252d7913eb6bb0ff304c4b7d7ae    
  
author   : Magnus Hagander <magnus@hagander.net>    
date     : Thu, 18 Mar 2021 11:23:48 +0100    
  
committer: Magnus Hagander <magnus@hagander.net>    
date     : Thu, 18 Mar 2021 11:23:48 +0100    

pg_read_file() is the function that's in core, pg_file_read() is in  
adminpack. But when using pg_file_read() in adminpack it calls the *C*  
level function pg_read_file() in core, which probably threw the original  
author off. But the error hint should be about the SQL function.  
  
Reported-By: Sergei Kornilov  
Backpatch-through: 11  
Discussion: https://postgr.es/m/373021616060475@mail.yandex.ru  

commit   : 2111b409879eee6900aaa3107987f932524064ca    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Wed, 17 Mar 2021 16:10:38 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Wed, 17 Mar 2021 16:10:38 -0400    

Robert Foggia of Trustwave reported that read_tablespace_map()  
fails to prevent an overrun of its on-stack input buffer.  
Since the tablespace map file is presumed trustworthy, this does  
not seem like an interesting security vulnerability, but still  
we should fix it just in the name of robustness.  
  
While here, document that pg_basebackup's --tablespace-mapping option  
doesn't work with tar-format output, because it doesn't.  To make it  
work, we'd have to modify the tablespace_map file within the tarball  
sent by the server, which might be possible but I'm not volunteering.  
(Less-painful solutions would require changing the basebackup protocol  
so that the source server could adjust the map.  That's not very  
appetizing either.)  

commit   : b9ed85698f3e101bc84eb9b1adf77f5d04ebe7eb    
  
author   : Thomas Munro <tmunro@postgresql.org>    
date     : Thu, 18 Mar 2021 01:06:01 +1300    
  
committer: Thomas Munro <tmunro@postgresql.org>    
date     : Thu, 18 Mar 2021 01:06:01 +1300    

This reverts commit 8fa2478b407ef867d501fafcdea45fd827f70799.  
  
Discussion: https://postgr.es/m/CA%2BhUKGJmcqAE3MZeDCLLXa62cWM0AJbKmp2JrJYaJ86bz36LFA%40mail.gmail.com  

commit   : 8fa2478b407ef867d501fafcdea45fd827f70799    
  
author   : Thomas Munro <tmunro@postgresql.org>    
date     : Wed, 17 Mar 2021 17:46:39 +1300    
  
committer: Thomas Munro <tmunro@postgresql.org>    
date     : Wed, 17 Mar 2021 17:46:39 +1300    

With very unlucky timing and parallel_leader_participation off, PHJ  
could attempt to access per-batch state just as it was being freed.  
There was code intended to prevent that by checking for a cleared  
pointer, but it was buggy.  
  
Fix, by introducing an extra barrier phase.  The new phase  
PHJ_BUILD_RUNNING means that it's safe to access the per-batch state to  
find a batch to help with, and PHJ_BUILD_DONE means that it is too late.  
The last to detach will free the array of per-batch state as before, but  
now it will also atomically advance the phase at the same time, so that  
late attachers can avoid the hazard, without the data race.  This  
mirrors the way per-batch hash tables are freed (see phases  
PHJ_BATCH_PROBING and PHJ_BATCH_DONE).  
  
Revealed by a one-off build farm failure, where BarrierAttach() failed a  
sanity check assertion, because the memory had been clobbered by  
dsa_free().  
  
Back-patch to 11, where the code arrived.  
  
Reported-by: Michael Paquier <michael@paquier.xyz>  
Discussion: https://postgr.es/m/20200929061142.GA29096%40paquier.xyz  

commit   : 6e34755560aa1bf241b498968f7ac26ea11ec15c    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Tue, 16 Mar 2021 16:02:49 -0400    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Tue, 16 Mar 2021 16:02:49 -0400    

After reading the root cert list from the ssl_ca_file, immediately  
install it as client CA list of the new SSL context.  That gives the  
SSL context ownership of the list, so that SSL_CTX_free will free it.  
This avoids a permanent memory leak if we fail further down in  
be_tls_init(), which could happen if bogus CRL data is offered.  
  
The leak could only amount to something if the CRL parameters get  
broken after server start (else we'd just quit) and then the server  
is SIGHUP'd many times without fixing the CRL data.  That's rather  
unlikely perhaps, but it seems worth fixing, if only because the  
code is clearer this way.  
  
While we're here, add some comments about the memory management  
aspects of this logic.  
  
Noted by Jelte Fennema and independently by Andres Freund.  
Back-patch to v10; before commit de41869b6 it doesn't matter,  
since we'd not re-execute this code during SIGHUP.  
  
Discussion: https://postgr.es/m/16160-18367e56e9a28264@postgresql.org  

commit   : 60e5c2b143a4bba698992d65cbab363550d5c863    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 12 Mar 2021 12:20:15 -0500    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 12 Mar 2021 12:20:15 -0500    

psql's editing commands decide whether the user has edited the file  
by checking for change of modification timestamp.  This is probably  
fine for a pre-existing file, but with a temporary file that is  
created within the command, it's possible for a fast typist to  
save-and-exit in less than the one-second granularity of stat(2)  
timestamps.  On Windows FAT filesystems the granularity is even  
worse, 2 seconds, making the race a bit easier to hit.  
  
To fix, try to set the temp file's mod time to be two seconds ago.  
It's unlikely this would fail, but then again the race condition  
itself is unlikely, so just ignore any error.  
  
Also, we might as well check the file size as well as its mod time.  
  
While this is a difficult bug to hit, it still seems worth  
back-patching, to ensure that users' edits aren't lost.  
  
Laurenz Albe, per gripe from Jacob Champion; based on fix suggestions  
from Jacob and myself  
  
Discussion: https://postgr.es/m/0ba3f2a658bac6546d9934ab6ba63a805d46a49b.camel@cybertec.at  

commit   : e7f7950f6741a799bdf1dc3d2dbcb85e1b0a3c8c    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 12 Mar 2021 11:08:42 -0500    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 12 Mar 2021 11:08:42 -0500    

GENERATED ALWAYS AS IDENTITY implies NOT NULL, but the code failed  
to complain if you overrode that with "GENERATED ALWAYS AS IDENTITY  
NULL".  One might think the old behavior was a feature, but it was  
inconsistent because the outcome varied depending on the order of  
the clauses, so it seems to have been just an oversight.  
  
Per bug #16913 from Pavel Boev.  Back-patch to v10 where identity  
columns were introduced.  
  
Vik Fearing (minor tweaks by me)  
  
Discussion: https://postgr.es/m/16913-3b5198410f67d8c6@postgresql.org  

commit   : ce54c024d9bf3022690dc84a17f1207aceec430a    
  
author   : Peter Geoghegan <pg@bowt.ie>    
date     : Thu, 11 Mar 2021 12:52:37 -0800    
  
committer: Peter Geoghegan <pg@bowt.ie>    
date     : Thu, 11 Mar 2021 12:52:37 -0800    

Revert two recent commits that had btree_index.sql drop regression test  
indexes rather than leave them behind for pg_dump testing.  
  
This is intended to restore pg_upgrade coverage of indexes with the  
vacuum_cleanup_index_scale_factor storage parameter set on buildfarm  
member crake.  
  
Backpatch: 11-12 only  

commit   : 56defbdd0f4e152545c50619385902ed060dca61    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 11 Mar 2021 14:43:45 -0500    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 11 Mar 2021 14:43:45 -0500    

Commit 92785dac2 copied some logic related to advancement of inStart  
from pqParseInput3 into getRowDescriptions and getAnotherTuple,  
because it wanted to allow user-defined row processor callbacks to  
potentially longjmp out of the library, and inStart would have to be  
updated before that happened to avoid an infinite loop.  We later  
decided that that API was impossibly fragile and reverted it, but  
we didn't undo all of the related code changes, and this bit of  
messiness survived.  Undo it now so that there's just one place in  
pqParseInput3's processing where inStart is advanced; this will  
simplify addition of better tracing support.  
  
getParamDescriptions had grown similar processing somewhere along  
the way (not in 92785dac2; I didn't track down just when), but it's  
actually buggy because its handling of corrupt-message cases seems to  
have been copied from the v2 logic where we lacked a known message  
length.  The cases where we "goto not_enough_data" should not simply  
return EOF, because then we won't consume the message, potentially  
creating an infinite loop.  That situation now represents a  
definitively corrupt message, and we should report it as such.  
  
Although no field reports of getParamDescriptions getting stuck in  
a loop have been seen, it seems appropriate to back-patch that fix.  
I chose to back-patch all of this to keep the logic looking more alike  
in supported branches.  
  
Discussion: https://postgr.es/m/2217283.1615411989@sss.pgh.pa.us  

commit   : 1cc33ab95ccea0e1e36651d57ca1c8088f9994c2    
  
author   : Peter Geoghegan <pg@bowt.ie>    
date     : Wed, 10 Mar 2021 23:32:58 -0800    
  
committer: Peter Geoghegan <pg@bowt.ie>    
date     : Wed, 10 Mar 2021 23:32:58 -0800    

Fix the test failure by dropping the index in question.  Missed by  
commit 57ae7885.  
  
Per buildfarm member crake.  
  
Backpatch: 11-12 only  

commit   : 57ae7885cfe7a6301e1fd4b59c2e525ecc35cd55    
  
author   : Peter Geoghegan <pg@bowt.ie>    
date     : Wed, 10 Mar 2021 19:00:48 -0800    
  
committer: Peter Geoghegan <pg@bowt.ie>    
date     : Wed, 10 Mar 2021 19:00:48 -0800    

The vacuum_cleanup_index_scale_factor storage parameter was set in a  
btree index that was previously left behind in the regression test  
database.  As a result, the index gets tested within pg_dump and  
pg_restore tests, as well as pg_upgrade testing.  This won't work when  
upgrading to Postgres 14, though, because the storage parameter was  
removed on that version by commit 9f3665fb.  
  
Fix the test failure by dropping the index in question.  
  
Per buildfarm member crake.  
  
Discussion: https://postgr.es/m/CAH2-WzmeXYBWdhF7BMhNjhq9exsk=E1ohqBFAwzPdXJZ1XDMUA@mail.gmail.com  
Backpatch: 11-12 only  

commit   : 5645a6af70adaaaa485b8568bad9bc7fc130d474    
  
author   : Bruce Momjian <bruce@momjian.us>    
date     : Wed, 10 Mar 2021 20:25:18 -0500    
  
committer: Bruce Momjian <bruce@momjian.us>    
date     : Wed, 10 Mar 2021 20:25:18 -0500    

This is a follow-on patch to 92c12e46d5.  In that patch, we renamed  
"altitude" to "elevation" in the docs, based on these details:  
  
   https://mapscaping.com/blogs/geo-candy/what-is-the-difference-between-elevation-relief-and-altitude  
  
This renames the tutorial SQL files to match the documentation.  
  
Reported-by: max1@inbox.ru  
  
Discussion: https://postgr.es/m/161512392887.1046.3137472627109459518@wrigleys.postgresql.org  
  
Backpatch-through: 9.6  

commit   : 74207b8fc5a03a902171460aa42f7d816f2c6597    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Wed, 10 Mar 2021 11:33:50 -0500    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Wed, 10 Mar 2021 11:33:50 -0500    

Clarify the discussion in "User-Defined Procedures", by laying out  
the key differences between functions and procedures in a bulleted  
list.  Notably, this avoids burying the lede about procedures being  
able to do transaction control.  Make the back-link in the CREATE  
FUNCTION reference page more prominent, and add one in CREATE  
PROCEDURE.  
  
Per gripe from Guyren Howe.  Thanks to David Johnston for discussion.  
  
Discussion: https://postgr.es/m/BYAPR03MB4903C53A8BB7EFF5EA289674A6949@BYAPR03MB4903.namprd03.prod.outlook.com  

commit   : 8fff8a87493a238b45ecf6635baf334c4051b9df    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 8 Mar 2021 18:21:51 -0500    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Mon, 8 Mar 2021 18:21:51 -0500    

"SELECT pg_import_system_collations(0)" caused an assertion failure.  
With a random nonzero argument --- or indeed with zero, in non-assert  
builds --- it would happily make pg_collation entries with garbage  
values of collnamespace.  These are harmless as far as I can tell  
(unless maybe the OID happens to become used for a schema, later on?).  
In any case this isn't a security issue, since the function is  
superuser-only.  But it seems like a gotcha for unwary DBAs, so let's  
add a check that the given OID belongs to some schema.  
  
Back-patch to v10 where this function was introduced.  

commit   : c267ca682803f8ca233076d216fba18b635238a6    
  
author   : Amit Kapila <akapila@postgresql.org>    
date     : Wed, 3 Mar 2021 10:30:27 +0530    
  
committer: Amit Kapila <akapila@postgresql.org>    
date     : Wed, 3 Mar 2021 10:30:27 +0530    

It was not clear in the docs that the max_replication_slots is also used  
to track replication origins on the subscriber side.  
  
Author: Paul Martinez  
Reviewed-by: Amit Kapila  
Backpatch-through: 10 where logical replication was introduced  
Discussion: https://postgr.es/m/CACqFVBZgwCN_pHnW6dMNCrOS7tiHCw6Retf_=U2Vvj3aUSeATw@mail.gmail.com  

commit   : f927767919e8d7079043d637d2177b554126ad6c    
  
author   : Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Tue, 2 Mar 2021 15:39:34 -0300    
  
committer: Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Tue, 2 Mar 2021 15:39:34 -0300    

On Windows, CMD.EXE allegedly does not run a command that uses forward slashes,  
so let's convert the path to use backslashes instead.  
  
Backpatch to 10.  
  
Author: Nitin Jadhav <nitinjadhavpostgres@gmail.com>  
Reviewed-by: Juan José Santamaría Flecha <juanjo.santamaria@gmail.com>  
Discussion: https://postgr.es/m/CAMm1aWaNDuaPYFYMAqDeJrZmPtNvLcJRS++CcZWY8LT6KcoBZw@mail.gmail.com  

commit   : 0f1b0c0b60ef7b56bbccacd4307fdda8afa1a59b    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Tue, 2 Mar 2021 13:19:11 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Tue, 2 Mar 2021 13:19:11 +0900    

The same test for REINDEX (VERBOSE) was done twice, while it is clear  
that the second test should use --concurrently.  Issue introduced in  
5dc92b8, for what looks like a copy-paste mistake.  
  
Reviewed-by: Mark Dilger  
Discussion: https://postgr.es/m/A7AE97EA-F4B0-4CAB-8FFF-3FECD31F9D63@enterprisedb.com  
Backpatch-through: 12  

commit   : 262eb990c72097bd804e5c747fe38bf9b3a1ded9    
  
author   : Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Sat, 27 Feb 2021 18:09:15 -0300    
  
committer: Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Sat, 27 Feb 2021 18:09:15 -0300    

AfterTriggerSaveEvent() wrongly allocates the slot in execution-span  
memory context, whereas the correct thing is to allocate it in  
a transaction-span context, because that's where the enclosing  
AfterTriggersTableData instance belongs into.  
  
Backpatch to 12 (the test back to 11, where it works well with no code  
changes, and it's good to have to confirm that the case was previously  
well supported); this bug seems introduced by commit ff11e7f4b9ae.  
  
Reported-by: Bertrand Drouvot <bdrouvot@amazon.com>  
Author: Amit Langote <amitlangote09@gmail.com>  
Discussion: https://postgr.es/m/39a71864-b120-5a5c-8cc5-c632b6f16761@amazon.com  

commit   : fb1e218cb07e9b78a26d52d1c7fc03f5ce8691eb    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 26 Feb 2021 15:24:01 -0500    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 26 Feb 2021 15:24:01 -0500    

Break the synopsis into named parts to make it less confusing.  
Make more than zero effort at applying SGML markup.  Do a bit  
of copy-editing of nearby text.  
  
The synopsis revision is by Alvaro Herrera and Paul Förster,  
the rest is my fault.  Back-patch to v10 where multi-host  
connection strings appeared.  
  
Discussion: https://postgr.es/m/6E752D6B-487C-463E-B6E2-C32E7FB007EA@gmail.com  

commit   : 9e9b5c05010d25e16e04c8c282a52626650ae233    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Thu, 25 Feb 2021 16:07:08 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Thu, 25 Feb 2021 16:07:08 +0900    

PGHOST, PGPORT and PGUSER were already mentioned, but not PGDATABASE.  
Like 5aaa584, backpatch down to 12.  
  
Reported-by: Christophe Courtois  
Discussion: https://postgr.es/m/161399398648.21711.15387267201764682579@wrigleys.postgresql.org  
Backpatch-through: 12  

commit   : 3b2af88788e1e136bcde78b74ff7387b0c58488a    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Wed, 24 Feb 2021 16:14:00 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Wed, 24 Feb 2021 16:14:00 +0900    

The portions fixing the documentation are backpatched where needed.  
  
Author: Justin Pryzby  
Discussion: https://postgr.es/m/20210210235557.GQ20012@telsasoft.com  
backpatch-through: 9.6  

commit   : 2796ae2ad25330e80e97e823aa72091a9374d87d    
  
author   : Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Tue, 23 Feb 2021 17:30:21 -0300    
  
committer: Alvaro Herrera <alvherre@alvh.no-ip.org>    
date     : Tue, 23 Feb 2021 17:30:21 -0300    

Commit 866e24d47db1 added an assert that HEAP_XMAX_LOCK_ONLY and  
HEAP_KEYS_UPDATED cannot appear together, on the faulty assumption that  
the latter necessarily referred to an update and not a tuple lock; but  
that's wrong, because SELECT FOR UPDATE can use precisely that  
combination, as evidenced by the amcheck test case added here.  
  
Remove the Assert(), and also patch amcheck's verify_heapam.c to not  
complain if the combination is found.  Also, out of overabundance of  
caution, update (across all branches) README.tuplock to be more explicit  
about this.  
  
Author: Julien Rouhaud <rjuju123@gmail.com>  
Reviewed-by: Mahendra Singh Thalor <mahi6run@gmail.com>  
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>  
Discussion: https://postgr.es/m/20210124061758.GA11756@nol  

commit   : 67b3ee292935352b4b12b7a1bce17c64f85ce32e    
  
author   : Fujii Masao <fujii@postgresql.org>    
date     : Fri, 19 Feb 2021 22:01:25 +0900    
  
committer: Fujii Masao <fujii@postgresql.org>    
date     : Fri, 19 Feb 2021 22:01:25 +0900    

When ON_ERROR_ROLLBACK is enabled, psql releases a temporary savepoint  
if it's idle in a valid transaction block after executing a query. But psql  
doesn't do that after RELEASE or ROLLBACK is executed because a temporary  
savepoint has already been destroyed in that case.  
  
This commit changes psql's ON_ERROR_ROLLBACK so that it doesn't release  
a temporary savepoint also when COMMIT AND CHAIN is executed. A temporary  
savepoint doesn't need to be released in that case because  
COMMIT AND CHAIN also destroys any savepoints defined within the transaction  
to commit. Otherwise psql tries to release the savepoint that  
COMMIT AND CHAIN has already destroyed and cause an error  
"ERROR:  savepoint "pg_psql_temporary_savepoint" does not exist".  
  
Back-patch to v12 where transaction chaining was added.  
  
Reported-by: Arthur Nascimento  
Author: Arthur Nascimento  
Reviewed-by: Fujii Masao, Vik Fearing  
Discussion: https://postgr.es/m/16867-3475744069228158@postgresql.org  

commit   : fadcc4e81bd99e6032ae042cae53be0c6eea7580    
  
author   : Fujii Masao <fujii@postgresql.org>    
date     : Fri, 19 Feb 2021 21:57:52 +0900    
  
committer: Fujii Masao <fujii@postgresql.org>    
date     : Fri, 19 Feb 2021 21:57:52 +0900    

This commit fixes COMMIT AND CHAIN command so that it starts new transaction  
immediately even if savepoints are defined within the transaction to commit.  
Previously COMMIT AND CHAIN command did not in that case because  
commit 280a408b48 forgot to make CommitTransactionCommand() handle  
a transaction chaining when the transaction state was TBLOCK_SUBCOMMIT.  
  
Also this commit adds the regression test for COMMIT AND CHAIN command  
when savepoints are defined.  
  
Back-patch to v12 where transaction chaining was added.  
  
Reported-by: Arthur Nascimento  
Author: Fujii Masao  
Reviewed-by: Arthur Nascimento, Vik Fearing  
Discussion: https://postgr.es/m/16867-3475744069228158@postgresql.org  

commit   : e7cddb5f29171a536233acecb7ac9b9c5e1b4c77    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Feb 2021 22:38:55 -0500    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Thu, 18 Feb 2021 22:38:55 -0500    

While poking at the regex code, I happened to notice that the bug  
squashed in commit afcc8772e had a sibling: next() failed to return  
a specific value associated with the '}' token for a "\{m,n\}"  
quantifier when parsing in basic RE mode.  Again, this could result  
in treating the quantifier as non-greedy, which it never should be in  
basic mode.  For that to happen, the last character before "\}" that  
sets "nextvalue" would have to set it to zero, or it'd have to have  
accidentally been zero from the start.  The failure can be provoked  
repeatably with, for example, a bound ending in digit "0".  
  
Like the previous patch, back-patch all the way.  

commit   : 6a31b48ec88ae506c6f115948c86f61abb89a89a    
  
author   : Magnus Hagander <magnus@hagander.net>    
date     : Wed, 17 Feb 2021 13:53:26 +0100    
  
committer: Magnus Hagander <magnus@hagander.net>    
date     : Wed, 17 Feb 2021 13:53:26 +0100    

Author: Daniel Gustafsson <daniel@yesql.se>  
Discussion: https://postgr.es/m/0CF087FC-BEAD-4010-8BB9-3CDD74DC9060@yesql.se  

commit   : 2b81444a88cc499f5d3608c5943e9a6e4b489070    
  
author   : Heikki Linnakangas <heikki.linnakangas@iki.fi>    
date     : Mon, 15 Feb 2021 09:28:08 +0200    
  
committer: Heikki Linnakangas <heikki.linnakangas@iki.fi>    
date     : Mon, 15 Feb 2021 09:28:08 +0200    

If ExecGetInsertedCols(), ExecGetUpdatedCols() or ExecGetExtraUpdatedCols()  
were called with a ResultRelInfo that's not in the range table and isn't a  
partition routing target, the functions would dereference a NULL pointer,  
relinfo->ri_RootResultRelInfo. Such ResultRelInfos are created when firing  
RI triggers in tables that are not modified directly. None of the current  
callers of these functions pass such relations, so this isn't a live bug,  
but let's make them more robust.  
  
Also update comment in ResultRelInfo; after commit 6214e2b228,  
ri_RangeTableIndex is zero for ResultRelInfos created for partition tuple  
routing.  
  
Noted by Coverity. Backpatch down to v11, like commit 6214e2b228.  
  
Reviewed-by: Tom Lane, Amit Langote  

commit   : a27f3a7f4159c5afaf33932df16ca4fed6689c06    
  
author   : Thomas Munro <tmunro@postgresql.org>    
date     : Mon, 15 Feb 2021 15:43:39 +1300    
  
committer: Thomas Munro <tmunro@postgresql.org>    
date     : Mon, 15 Feb 2021 15:43:39 +1300    

FreeBSD 13 gained O_DSYNC, which would normally cause wal_sync_method to  
choose open_datasync as its default value.  That may not be a good  
choice for all systems, and performs worse than fdatasync in some  
scenarios.  Let's preserve the existing default behavior for now.  
  
Like commit 576477e73c4, which did the same for Linux, back-patch to all  
supported releases.  
  
Discussion: https://postgr.es/m/CA%2BhUKGLsAMXBQrCxCXoW-JsUYmdOL8ALYvaX%3DCrHqWxm-nWbGA%40mail.gmail.com  

commit   : 840eda04ebc99ce211ffd11946a59ad43c42bfa6    
  
author   : Thomas Munro <tmunro@postgresql.org>    
date     : Mon, 15 Feb 2021 13:32:58 +1300    
  
committer: Thomas Munro <tmunro@postgresql.org>    
date     : Mon, 15 Feb 2021 13:32:58 +1300    

While cleaning up after a parallel query or parallel index creation that  
created temporary files, we could be interrupted by a statement timeout.  
The error handling path would then fail to clean up the files when it  
ran dsm_detach() again, because the callback was already popped off the  
list.  Prevent this hazard by holding interrupts while the cleanup code  
runs.  
  
Thanks to Heikki Linnakangas for this suggestion, and also to Kyotaro  
Horiguchi, Masahiko Sawada, Justin Pryzby and Tom Lane for discussion of  
this and earlier ideas on how to fix the problem.  
  
Back-patch to all supported releases.  
  
Reported-by: Justin Pryzby <pryzby@telsasoft.com>  
Discussion: https://postgr.es/m/20191212180506.GR2082@telsasoft.com  

commit   : c3dc311ffd6417b15a467c6ea53e642577e9f00e    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Sat, 13 Feb 2021 17:49:08 -0500    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Sat, 13 Feb 2021 17:49:08 -0500    

Modern gcc and clang compilers offer alignment sanitizers, which help to detect  
pointer misalignment.  However, our codebase already contains x86-specific  
crc32 computation code, which uses unalignment access.  Thankfully, those  
compilers also support the attribute, which disables alignment sanitizers at  
the function level.  This commit adds pg_attribute_no_sanitize_alignment(),  
which wraps this attribute, and applies it to pg_comp_crc32c_sse42() function.  
  
Back-patch of commits 993bdb9f9 and ad2ad698a, to enable doing  
alignment testing in all supported branches.  
  
Discussion: https://postgr.es/m/CAPpHfdsne3%3DT%3DfMNU45PtxdhSL_J2PjLTeS8rwKnJzUR4YNd4w%40mail.gmail.com  
Discussion: https://postgr.es/m/475514.1612745257%40sss.pgh.pa.us  
Author: Alexander Korotkov, revised by Tom Lane  
Reviewed-by: Tom Lane  

commit   : 0347470b31c139aa4f1d366fbdb85f32b7f82ad0    
  
author   : Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 12 Feb 2021 16:26:47 -0500    
  
committer: Tom Lane <tgl@sss.pgh.pa.us>    
date     : Fri, 12 Feb 2021 16:26:47 -0500    

Given a regex pattern with a very long fixed prefix (approaching 500  
characters), the result of pow(FIXED_CHAR_SEL, fixed_prefix_len) can  
underflow to zero.  Typically the preceding selectivity calculation  
would have underflowed as well, so that we compute 0/0 and get NaN.  
In released branches this leads to an assertion failure later on.  
That doesn't happen in HEAD, for reasons I've not explored yet,  
but it's surely still a bug.  
  
To fix, just skip the division when the pow() result is zero, so  
that we'll (most likely) return a zero selectivity estimate.  In  
the edge cases where "sel" didn't yet underflow, perhaps this  
isn't desirable, but I'm not sure that the case is worth spending  
a lot of effort on.  The results of regex_selectivity_sub() are  
barely worth the electrons they're written on anyway :-(  
  
Per report from Alexander Lakhin.  Back-patch to all supported versions.  
  
Discussion: https://postgr.es/m/6de0a0c3-ada9-cd0c-3e4e-2fa9964b41e3@gmail.com  

commit   : 5b2945ec0a39959962072c39d1817d0fdf23d486    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Wed, 10 Feb 2021 16:59:04 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Wed, 10 Feb 2021 16:59:04 +0900    

Oversight in bd12080.  
  
Reported-by: Justin Pryzby  
Discussion: https://postgr.es/m/20210210065805.GG20012@telsasoft.com  
Backpatch-through: 12  

commit   : 85edb1f2615d48bdc2420b00c55286eef3a3244c    
  
author   : Michael Paquier <michael@paquier.xyz>    
date     : Wed, 10 Feb 2021 13:09:12 +0900    
  
committer: Michael Paquier <michael@paquier.xyz>    
date     : Wed, 10 Feb 2021 13:09:12 +0900    

For an index, attstattarget can be updated using ALTER INDEX SET  
STATISTICS.  This data was lost on the new index after REINDEX  
CONCURRENTLY.  
  
The update of this field is done when the old and new indexes are  
swapped to make the fix back-patchable.  Another approach we could look  
after in the long-term is to change index_create() to pass the wanted  
values of attstattarget when creating the new relation, but, as this  
would cause an ABI breakage this can be done only on HEAD.  
  
Reported-by: Ronan Dunklau  
Author: Michael Paquier  
Reviewed-by: Ronan Dunklau, Tomas Vondra  
Discussion: https://postgr.es/m/16628084.uLZWGnKmhe@laptop-ronand  
Backpatch-through: 12