The comments atop of this function describes behaviour in case of a
transactional WAL message only, but it accepts both transactional and
non-transactional WAL messages. Update the comments to describe
behaviour in case of non-transactional WAL message as well.

Ashutosh Bapat, rephrased by Amit Kapila
Discussion: https://postgr.es/m/CAGEoWWTTzNzHOi8bj0wfAo1siGi-YEh6wqH1oaz4DrkTJ6HbTQ@mail.gmail.com

Any subdirectory that's ignoring /output_iso/ should also
ignore /tmp_check_iso/, which could be left behind by a
failed pg_isolation_regress_check run.

I think these have been wrong for awhile, but it doesn't
seem important to fix in back branches.

A narrow reading of the C standard says that memcpy(x,x,n) is undefined,
although it's hard to envision an implementation that would really
misbehave.  However, analysis tools such as valgrind might whine about
this; accordingly, let's band-aid relmapper.c to not do it.

See also 5b630501, d3f4e8a8, ad7b48ea, and other similar fixes.
Apparently, none of those folk tried valgrinding initdb?  This has been
like this for long enough that I'm surprised it hasn't been reported
before.

Back-patch, just in case anybody wants to use a back branch on a platform
that complains about this; we back-patched those earlier fixes too.

Discussion: https://postgr.es/m/161790.1608310142@sss.pgh.pa.us

This commit adds "stats_reset" column into the pg_stat_statements_info
view. This column indicates the time at which all statistics in the
pg_stat_statements view were last reset.

Per discussion, this commit also changes pg_stat_statements_info code
so that "dealloc" column is reset at the same time as "stats_reset" is reset,
i.e., whenever all pg_stat_statements entries are removed, for the sake
of consistency. Previously "dealloc" was reset only when
pg_stat_statements_reset(0, 0, 0) is called and was not reset when
pg_stat_statements_reset() with non-zero value argument discards all
entries. This was confusing.

Author: Naoki Nakamichi, Yuki Seino
Reviewed-by: Yuki Seino, Kyotaro Horiguchi, Li Japin, Fujii Masao
Discussion: https://postgr.es/m/c102cf3180d0ee73c1c5a0f7f8558322@oss.nttdata.com

Revert ac22929a, as well as the followup fix 113d3591. Because it broke
the assumption that the startup process waiting for the recovery conflict
on buffer pin should be waken up only by buffer unpin or the timeout enabled
in ResolveRecoveryConflictWithBufferPin(). It caused, for example,
SIGHUP signal handler or walreceiver process to wake that startup process
up unnecessarily frequently.

Additionally, add the comments about why that dedicated latch that
the reverted patch tried to get rid of should not be removed.

Thanks to Kyotaro Horiguchi for the discussion.

Author: Fujii Masao
Discussion: https://postgr.es/m/d8c0c608-021b-3c73-fffd-3240829ee986@oss.nttdata.com

Seems to be a copy-and-pasteo in c06d6aa4.  Per buildfarm.

Offsets are shown as NULL only for anonymous allocations.

Author: Benoit Lobréau
Reviewed-by: Kyotaro Horiguchi
Discussion: https://postgr.es/m/CAPE8EZ5Lnoyqoz7aZpvQM0E8sW+hw+k6G2NULe+m4arFRrA1aA@mail.gmail.com
Backpatch-through: 13

It was not clear how COPY TO behaved with partitioning/inheritance
because the paragraphs were so far apart.  Also reword to simplify.

Discussion: https://postgr.es/m/20201203211723.GR24052@telsasoft.com

Author: Justin Pryzby

Backpatch-through: 10

"Ordering stuff" refered to a _bt_first() call to _bt_orderkeys().
However, the _bt_orderkeys() function was renamed to
_bt_preprocess_keys() by commit fa5c8a05.

_bt_preprocess_keys() is directly referenced just after the removed
comment already, which seems sufficient.

Mistakenly introduced in 4cbe3ac3; bug repaired in 148e632c but
the stores were accidentally.

To build Gather Merge path, the input needs to be sufficiently sorted.
Ensuring this is the responsibility of the code constructing the paths,
but create_gather_merge_plan tried to handle unsorted paths by adding
an explicit Sort. In light of the recent issues related to Incremental
Sort, this is rather fragile. Some of the expressions may be volatile
or parallel unsafe, in which case we can't add the Sort here.

We could do more checks and add the Sort in at least some cases, but
it seems cleaner to just error out and make it clear this is a bug in
code constructing those paths.

Author: James Coleman
Reviewed-by: Tomas Vondra
Discussion: https://postgr.es/m/CAAaqYe8cK3g5CfLC4w7bs%3DhC0mSksZC%3DH5M8LSchj5e5OxpTAg%40mail.gmail.com
Discussion: https://postgr.es/m/CAJGNTeNaxpXgBVcRhJX%2B2vSbq%2BF2kJqGBcvompmpvXb7pq%2BoFA%40mail.gmail.com

Many older tests where written in a style like

    SELECT '' AS two, i.* FROM INT2_TBL

where the first column indicated the number of expected result rows.
This has gotten increasingly out of date, as the test data fixtures
have expanded, so a lot of these were wrong and misleading.  Moreover,
this style isn't really necessary, since the psql output already shows
the number of result rows.

To clean this up, remove all those extra columns.

Discussion: https://www.postgresql.org/message-id/flat/1a25312b-2686-380d-3c67-7a69094a999f%40enterprisedb.com

Invent a new flag bit HASH_STRINGS to specify C-string hashing, which
was formerly the default; and add assertions insisting that exactly
one of the bits HASH_STRINGS, HASH_BLOBS, and HASH_FUNCTION be set.
This is in hopes of preventing recurrences of the type of oversight
fixed in commit a1b8aa1e (i.e., mistakenly omitting HASH_BLOBS).

Also, when HASH_STRINGS is specified, insist that the keysize be
more than 8 bytes.  This is a heuristic, but it should catch
accidental use of HASH_STRINGS for integer or pointer keys.
(Nearly all existing use-cases set the keysize to NAMEDATALEN or
more, so there's little reason to think this restriction should
be problematic.)

Tweak hash_create() to insist that the HASH_ELEM flag be set, and
remove the defaults it had for keysize and entrysize.  Since those
defaults were undocumented and basically useless, no callers
omitted HASH_ELEM anyway.

Also, remove memset's zeroing the HASHCTL parameter struct from
those callers that had one.  This has never been really necessary,
and while it wasn't a bad coding convention it was confusing that
some callers did it and some did not.  We might as well save a few
cycles by standardizing on "not".

Also improve the documentation for hash_create().

In passing, improve reinit.c's usage of a hash table by storing
the key as a binary Oid rather than a string; and, since that's
a temporary hash table, allocate it in CurrentMemoryContext for
neatness.

Discussion: https://postgr.es/m/590625.1607878171@sss.pgh.pa.us

This reverts commit 3a9e64aa.

Commit 4bad60e3 fixed the root of the problem that 3a9e64aa worked
around.

This enables proper pipelining of commands after terminating
replication, eliminating an undocumented limitation.

Discussion: https://postgr.es/m/3d57bc29-4459-578b-79cb-7641baf53c57%40iki.fi
Backpatch-through: 9.5

This adjusts some code related to recent changes for cryptohash
functions:
- Add a variable in md5.h to track down the size of a computed result,
moved from pgcrypto.  Note that pg_md5_hash() assumed a result of this
size already.
- Call explicit_bzero() on the hashed data when freeing the context for
fallback implementations.  For MD5, particularly, it would be annoying
to leave some non-zeroed data around.
- Clean up some code related to recent changes of uuid-ossp.  .gitignore
still included md5.c and a comment was incorrect.

Discussion: https://postgr.es/m/X9HXKTgrvJvYO7Oh@paquier.xyz

This is done for end-of-recovery and shutdown checkpoints/restartpoints
(end-of-recovery restartpoints don't exist) rather than all types of
checkpoints, in cases where it may not be possible to rely on
pg_stat_activity to get a status from the startup or checkpointer
processes.

For example, at the end of a crash recovery, this is useful to know if a
checkpoint is running in the startup process, while previously the ps
display may only show some information about "recovering" something,
that can be confusing while a checkpoint runs.

Author: Justin Pryzby
Reviewed-by: Nathan Bossart, Kirk Jamison, Fujii Masao, Michael Paquier
Discussion: https://postgr.es/m/20200818225238.GP17022@telsasoft.com

This caused BufFile errors on buildfarm member sungazer, and SIGSEGV was
possible.  Conditions for reaching those symptoms were more frequent on
big-endian systems.

Discussion: https://postgr.es/m/20201129214441.GA691200@rfd.leadboat.com

Backpatch-through: 9.5

Backpatch-through: 9.5

This is basically a finger exercise to prove that it's possible for
an extension module to add subscripting ability.  Subscripted fetch
from an hstore is not different from the existing "hstore -> text"
operator.  Subscripted update does seem to be a little easier to
use than the traditional update method using hstore concatenation,
but it's not a fundamentally new ability.

However, there may be some value in the code as sample code, since
it shows what's basically the minimum-complexity way to implement
subscripting when one needn't consider nested container objects.

Discussion: https://postgr.es/m/3724341.1607551174@sss.pgh.pa.us

This is essential if we'd like to allow existing extension data types
to support subscripting in future, since dropping and recreating the
type isn't a practical thing for an extension upgrade script, and
direct manipulation of pg_type isn't a great answer either.

There was some discussion about also allowing alteration of typelem,
but it's less clear whether that's a good idea or not, so for now
I forebore.

Discussion: https://postgr.es/m/3724341.1607551174@sss.pgh.pa.us

Commit c7aba7c1 didn't add this, but after more fooling with the
feature I feel that it'd be useful.  To make this possible, refactor
getSubscriptingRoutines() so that the caller is responsible for
throwing any error.  (In clauses.c, I just chose to make the
most conservative assumption rather than throwing an error.  We don't
expect failures there anyway really, so the code space for an error
message would be a poor investment.)

This usage would mean that values of the enum type are potentially not
one of the enum values.  Use macros instead, like everywhere else.

Discussion: https://www.postgresql.org/message-id/14dde730-1d34-260e-fa9d-7664df2d6313@enterprisedb.com

This module had a dependency on pgcrypto's md5.c that got removed by
b67b57a9.  Instead of the code from pgcrypto, this code can just use the
new cryptohash routines for MD5 as a drop-in replacement, so let's just
do this switch.  This has also the merit to simplify a bit the
compilation of uuid-ossp.

This requires --with-uuid to be reproduced, and I have used e2fs as a
way to reproduce the failure, then test this commit.

Per reports from buildfarm members longfin, florican and sifaka.

Discussion: https://postgr.es/m/X9GToVd3QmWeNvj8@paquier.xyz

This commit heavily reorganizes the MD5 implementations that exist in
the tree in various aspects.

First, MD5 is added to the list of options available in cryptohash.c and
cryptohash_openssl.c.  This means that if building with OpenSSL, EVP is
used for MD5 instead of the fallback implementation that Postgres had
for ages.  With the recent refactoring work for cryptohash functions,
this change is straight-forward.  If not building with OpenSSL, a
fallback implementation internal to src/common/ is used.

Second, this reduces the number of MD5 implementations present in the
tree from two to one, by moving the KAME implementation from pgcrypto to
src/common/, and by removing the implementation that existed in
src/common/.  KAME was already structured with an init/update/final set
of routines by pgcrypto (see original pgcrypto/md5.h) for compatibility
with OpenSSL, so moving it to src/common/ has proved to be a
straight-forward move, requiring no actual manipulation of the internals
of each routine.  Some benchmarking has not shown any performance gap
between both implementations.

Similarly to the fallback implementation used for SHA2, the fallback
implementation of MD5 is moved to src/common/md5.c with an internal
header called md5_int.h for the init, update and final routines.  This
gets then consumed by cryptohash.c.

The original routines used for MD5-hashed passwords are moved to a
separate file called md5_common.c, also in src/common/, aimed at being
shared between all MD5 implementations as utility routines to keep
compatibility with any code relying on them.

Like the SHA2 changes, this commit had its round of tests on both Linux
and Windows, across all versions of OpenSSL supported on HEAD, with and
even without OpenSSL.

Author: Michael Paquier
Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/20201106073434.GA4961@paquier.xyz

This patch generalizes the subscripting infrastructure so that any
data type can be subscripted, if it provides a handler function to
define what that means.  Traditional variable-length (varlena) arrays
all use array_subscript_handler(), while the existing fixed-length
types that support subscripting use raw_array_subscript_handler().
It's expected that other types that want to use subscripting notation
will define their own handlers.  (This patch provides no such new
features, though; it only lays the foundation for them.)

To do this, move the parser's semantic processing of subscripts
(including coercion to whatever data type is required) into a
method callback supplied by the handler.  On the execution side,
replace the ExecEvalSubscriptingRef* layer of functions with direct
calls to callback-supplied execution routines.  (Thus, essentially
no new run-time overhead should be caused by this patch.  Indeed,
there is room to remove some overhead by supplying specialized
execution routines.  This patch does a little bit in that line,
but more could be done.)

Additional work is required here and there to remove formerly
hard-wired assumptions about the result type, collation, etc
of a SubscriptingRef expression node; and to remove assumptions
that the subscript values must be integers.

One useful side-effect of this is that we now have a less squishy
mechanism for identifying whether a data type is a "true" array:
instead of wiring in weird rules about typlen, we can look to see
if pg_type.typsubscript == F_ARRAY_SUBSCRIPT_HANDLER.  For this
to be bulletproof, we have to forbid user-defined types from using
that handler directly; but there seems no good reason for them to
do so.

This patch also removes assumptions that the number of subscripts
is limited to MAXDIM (6), or indeed has any hard-wired limit.
That limit still applies to types handled by array_subscript_handler
or raw_array_subscript_handler, but to discourage other dependencies
on this constant, I've moved it from c.h to utils/array.h.

Dmitry Dolgov, reviewed at various times by Tom Lane, Arthur Zakirov,
Peter Eisentraut, Pavel Stehule

Discussion: https://postgr.es/m/CA+q6zcVDuGBv=M0FqBYX8DPebS3F_0KQ6OVFobGJPM507_SZ_w@mail.gmail.com
Discussion: https://postgr.es/m/CA+q6zcVovR+XY4mfk-7oNk-rF91gH0PebnNfuUjuuDsyHjOcVA@mail.gmail.com

It was still using a scan of pg_depend instead of using the conindid
column that has been added since.

Since it is now just a catalog lookup wrapper and not related to
pg_depend, move from pg_depend.c to lsyscache.c.
Reviewed-by: Matthias van de Meent <boekewurm+postgres@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://www.postgresql.org/message-id/flat/4688d55c-9a2e-9a5a-d166-5f24fe0bf8db%40enterprisedb.com

Three places of unicode_norm.c use a similar logic for getting the
combining class from a codepoint.  Commit 2991ac5f has added the function
get_canonical_class() for this purpose, but it was only called by the
backend.  This commit refactors the code to use this function in all
the places where the combining class is retrieved from a given
codepoint.

Author: John Naylor
Discussion: https://postgr.es/m/CAFBsxsHUV7s7YrOm6hFz-Jq8Sc7K_yxTkfNZxsDV-DuM-k-gwg@mail.gmail.com

It is error prone (see 5da871bf) and verbose to manually create function
types. Add a helper that can reference a function pointer type via
llvmjit_types.c and and convert existing instances of manual creation.

Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/20201207212142.wz5tnbk2jsaqzogb@alap3.anarazel.de

array_get_element and array_get_slice qualify as leakproof, since
they will silently return NULL for bogus subscripts.  But
array_set_element and array_set_slice throw errors for such cases,
making them clearly not leakproof.  contain_leaked_vars was evidently
written with only the former case in mind, as it gave the wrong answer
for assignment SubscriptingRefs (nee ArrayRefs).

This would be a live security bug, were it not that assignment
SubscriptingRefs can only occur in INSERT and UPDATE target lists,
while we only care about leakproofness for qual expressions; so the
wrong answer can't occur in practice.  Still, that's a rather shaky
answer for a security-related question; and maybe in future somebody
will want to ask about leakproofness of a tlist.  So it seems wise to
fix and even back-patch this correction.

(We would need some change here anyway for the upcoming
generic-subscripting patch, since extensions might make different
tradeoffs about whether to throw errors.  Commit 558d77f2 attempted
to lay groundwork for that by asking check_functions_in_node whether a
SubscriptingRef contains leaky functions; but that idea fails now that
the implementation methods of a SubscriptingRef are not SQL-visible
functions that could be marked leakproof or not.)

Back-patch to 9.6.  While 9.5 has the same issue, the code's a bit
different.  It seems quite unlikely that we'd introduce any actual bug
in the short time 9.5 has left to live, so the work/risk/reward balance
isn't attractive for changing 9.5.

Discussion: https://postgr.es/m/3143742.1607368115@sss.pgh.pa.us

This GUC was always intended as a temporary solution to help with
finding 9.4-to-9.5 migration issues.  Now that all pre-9.5 branches
are out of support, and 9.5 will be too before v14 is released,
it seems like it's okay to drop it.  Doing so allows removal of
several hundred lines of poorly-tested code in parse_expr.c,
which have been a fertile source of bugs when people did use this.

Discussion: https://postgr.es/m/2234320.1607117945@sss.pgh.pa.us

Formerly, extended statistics only handled clauses that were
RestrictInfos. However, the restrictinfo machinery doesn't create
sub-AND RestrictInfos for AND clauses underneath OR clauses.
Therefore teach extended statistics to handle bare AND clauses,
looking for compatible RestrictInfo clauses underneath them.

Dean Rasheed, reviewed by Tomas Vondra.

Discussion: https://postgr.es/m/CAEZATCW=J65GUFm50RcPv-iASnS2mTXQbr=CfBvWRVhFLJ_fWA@mail.gmail.com

When estimating an OR clause using multiple extended statistics
objects, treat the estimates for each set of clauses for each
statistics object as independent of one another. The overlap estimates
produced for each statistics object do not apply to clauses covered by
other statistics objects.

Dean Rasheed, reviewed by Tomas Vondra.

Discussion: https://postgr.es/m/CAEZATCW=J65GUFm50RcPv-iASnS2mTXQbr=CfBvWRVhFLJ_fWA@mail.gmail.com

The SQL standard says that redundant unique constraints are disallowed,
but we long ago decided that throwing an error would be too
user-unfriendly, so we just drop redundant ones.  The docs weren't very
clear about that though, as this behavior was only explained for PRIMARY
KEY vs UNIQUE, not UNIQUE vs UNIQUE.

While here, I couldn't resist doing some copy-editing and markup-fixing
on the adjacent text about INCLUDE options.

Per bug #16767 from Matthias vd Meent.

Discussion: https://postgr.es/m/16767-1714a2056ca516d0@postgresql.org

This restriction was mentioned in connection with string literals,
but it wasn't made clear that it's a general restriction not just
a syntactic limitation in query strings.

Per unsigned documentation comment.

Discussion: https://postgr.es/m/160720552914.710.16625261471128631268@wrigleys.postgresql.org

After autovacuum collects the relations to vacuum or analyze, it rechecks
whether each relation still needs to be vacuumed or analyzed before actually
doing that. Previously this recheck could be a significant overhead
especially when there were a very large number of relations. This was
because each recheck forced the statistics to be refreshed, and the refresh
of the statistics for a very large number of relations could cause heavy
overhead. There was the report that this issue caused autovacuum workers
to have gotten “stuck” in a tight loop of table_recheck_autovac() that
rechecks whether a relation needs to be vacuumed or analyzed.

This commit speeds up the recheck by making autovacuum worker reuse
the previously-read statistics for the recheck if possible. Then if that
"stale" statistics says that a relation still needs to be vacuumed or analyzed,
autovacuum refreshes the statistics and does the recheck again.

The benchmark shows that the more relations exist and autovacuum workers
are running concurrently, the more this change reduces the autovacuum
execution time. For example, when there are 20,000 tables and 10 autovacuum
workers are running, the benchmark showed that the change improved
the performance of autovacuum more than three times. On the other hand,
even when there are only 1000 tables and only a single autovacuum worker
is running, the benchmark didn't show any big performance regression by
the change.

Firstly POC patch was proposed by Jim Nasby. As the result of discussion,
we used Tatsuhito Kasahara's version of the patch using the approach
suggested by Tom Lane.

Reported-by: Jim Nasby
Author: Tatsuhito Kasahara
Reviewed-by: Masahiko Sawada, Fujii Masao
Discussion: https://postgr.es/m/3FC6C2F2-8A47-44C0-B997-28830B5716D0@amazon.com

Oversight in 01469241.

Reported-by: Andres Freund
Discussion: https://postgr.es/m/20201207185614.zzf63vggm5r4sozg@alap3.anarazel.de

The following routines are called within pgcrypto when handling digests
but there were no checks for failures:
- EVP_MD_CTX_size (can fail with -1 as of 3.0.0)
- EVP_MD_CTX_block_size (can fail with -1 as of 3.0.0)
- EVP_DigestInit_ex
- EVP_DigestUpdate
- EVP_DigestFinal_ex

A set of elog(ERROR) is added by this commit to detect such failures,
that should never happen except in the event of a processing failure
internal to OpenSSL.

Note that it would be possible to use ERR_reason_error_string() to get
more context about such errors, but these refer mainly to the internals
of OpenSSL, so it is not really obvious how useful that would be.  This
is left out for simplicity.

Per report from Coverity.  Thanks to Tom Lane for the discussion.

Backpatch-through: 9.5

clang only uses the 'i1' type for scalar booleans, not for pointers to
booleans (as the pointer might be pointing into a larger memory
allocation). Therefore a pointer-to-bool needs to the "storage" boolean.

There's no known case of wrong code generation due to this, but it seems quite
possible that it could cause problems (see e.g. 72559438).

Author: Andres Freund
Discussion: https://postgr.es/m/20201207212142.wz5tnbk2jsaqzogb@alap3.anarazel.de
Backpatch: 11-, where jit support was added