A few more

When a row is updated, and the new tuple version is put on the same page as
the old one, only WAL-log the part of the new tuple that's not identical to
the old. This saves significantly on the amount of WAL that needs to be
written, in the common case that most fields are not modified.

Amit Kapila, with a lot of back and forth with me, Robert Haas, and others.

Also improve the comments a bit.

Christian Kruse, reviewed by Kumar Rajeev Rastogi.

Andres Freund

Also fix some nearby comments.

Andres Freund

Andres Freund, per complaints by Peter Eisentraut.

With the GIN "fast scan" feature, GIN can skip items without fetching all
the keys for them, if it can prove that they don't match regardless of
those keys. So far, it has done the proving by calling the boolean
consistent function with all combinations of TRUE/FALSE for the unfetched
keys, but since that's O(n^2), it becomes unfeasible with more than a few
keys. We can avoid calling consistent with all the combinations, if we can
tell the operator class implementation directly which keys are unknown.

This commit includes a triConsistent function for the built-in array and
tsvector opclasses.

Alexander Korotkov, with some changes by me.

We don't take a full-page image of the GIN metapage; instead, the WAL record
contains all the information required to reconstruct it from scratch. But
to avoid torn page hazards, we must re-initialize it from the WAL record
every time, even if it already has a greater LSN, similar to how normal full
page images are restored.

This was highly unlikely to cause any problems in practice, because the GIN
metapage is small. We rely on an update smaller than a 512 byte disk sector
to be atomic elsewhere, at least in pg_control. But better safe than sorry,
and this would be easy to overlook if more fields are added to the metapage
so that it's no longer small.

Reported by Noah Misch. Backpatch to all supported versions.

Commit 08146775 changed do_copy() to
temporarily scribble on pset.cur_cmd_source.  That was a mighty ugly bit of
code in any case, but in particular it broke handleCopyIn's ability to tell
whether it was reading from the current script source file (in which case
pset.lineno should be incremented for each line of COPY data), or from
someplace else (in which case it shouldn't).  The former case still worked,
the latter not so much.  The visible effect was that line numbers reported
for errors in a script file would be wrong if there were an earlier \copy
that was reading anything other than inline-in-the-script-file data.

To fix, introduce another pset field that holds the file do_copy wants the
COPY code to use.  This is a little bit ugly, but less so than passing the
file down explicitly through several layers that aren't COPY-specific.

Extracted from a larger patch by Kumar Rajeev Rastogi; that patch also
changes printing of COPY command tags, which is not a bug fix and shouldn't
get back-patched.  This particular idea was from a suggestion by Amit
Khandekar, if I'm reading the thread correctly.

Back-patch to 9.2 where the faulty code was introduced.

Amit Kapila, reviewed by Kyotaro Horiguchi, with some further
changes by me.

In order for this to work, walsenders need the optional ability to
connect to a database, so the "replication" keyword now allows true
or false, for backward-compatibility, and the new value "database"
(which causes the "dbname" parameter to be respected).

walsender needs to loop not only when idle but also when sending
decoded data to the user and when waiting for more xlog data to decode.
This means that there are now three separate loops inside walsender.c;
although some refactoring has been done here, this is still a bit ugly.

Andres Freund, with contributions from Álvaro Herrera, and further
review by me.

If a postmaster child invokes fork() and then calls on_exit_reset, that
should be sufficient to let it exit() without breaking anything, but
dynamic shared memory broke that by not updating on_exit_reset() to
discard callbacks registered with dynamic shared memory segments.

Per investigation of a complaint from Tom Lane.

Report by Antonin Houska

Return '4' and report a meaningful error message when a non-existent or
invalid data directory is passed.  Previously, pg_ctl would just report
the server was not running.

Patch by me and Amit Kapila
Report from Peter Eisentraut

Per report by Marc Mamin

Use superior libpq keepalive description for the server-level
parameters.

Per report by Tatsuo Ishii and Marko Tiikkaja

Initial patch by Colin 't Hart

In b89e1510 I had assumed it was ok to use anonymous unions as
struct members, but while a longstanding extension in many compilers,
it's only been standardized in C11.

To fix, remove one of the anonymous unions which tried to hide some
implementation specific enum values and give the other a name. The
latter unfortunately requires changes in output plugins, but since the
feature has only been added a few days ago...

Andres Freund

The previous coding supposed that it could consider just a single join
condition in any one parameterized path for the foreign table.  But in
reality, the parameterized-path machinery forces all join clauses that are
"movable to" the foreign table to be evaluated at that node; including
clauses that we might not consider safe to send across.  Such cases would
result in an Assert failure in an assert-enabled build, and otherwise in
sending an unsafe clause to the foreign server, which might result in
errors or silently-wrong answers.  A lesser problem was that the
cost/rowcount estimates generated for the parameterized path failed to
account for any additional join quals that get assigned to the scan.

To fix, rewrite postgresGetForeignPaths so that it correctly collects all
the movable quals for any one outer relation when generating parameterized
paths; we'll now generate just one path per outer relation not one per join
qual.  Also fix bogus assumptions in postgresGetForeignPlan and
estimate_path_cost_size that only safe-to-send join quals will be
presented.

Based on complaint from Etsuro Fujita that the path costs were being
miscalculated, though this is significantly different from his proposed
patch.

Item is "Prevent errors in WAL replay due to references to uninitialized
empty pages".

Report and text by Andres Freund

Backpatch through 9.2.

YAMAMOTO Takashi

A fake relcache entry can "own" a SmgrRelation object, like a regular
relcache entry. But when it was free'd, the owner field in SmgrRelation
was not cleared, so it was left pointing to free'd memory.

Amazingly this apparently hasn't caused crashes in practice, or we would've
heard about it earlier. Andres found this with Valgrind.

Report and fix by Andres Freund, with minor modifications by me. Backpatch
to all supported versions.

The behavior of that is undefined, although unlikely to lead to problems in
practice.

Found by running regression tests with Valgrind.

Michael Paquier

In make_ruledef and get_query_def, we have long used AcquireRewriteLocks
to ensure that the querytree we are about to deparse is up-to-date and
the schemas of the underlying relations aren't changing.  Howwever, that
function thinks the query is about to be executed, so it acquires locks
that are stronger than necessary for the purpose of deparsing.  Thus for
example, if pg_dump asks to deparse a rule that includes "INSERT INTO t",
we'd acquire RowExclusiveLock on t.  That results in interference with
concurrent transactions that might for example ask for ShareLock on t.
Since pg_dump is documented as being purely read-only, this is unexpected.
(Worse, it used to actually be read-only; this behavior dates back only
to 8.1, cf commit ba420024.)

Fix this by adding a parameter to AcquireRewriteLocks to tell it whether
we want the "real" execution locks or only AccessShareLock.

Report, diagnosis, and patch by Dean Rasheed.  Back-patch to all supported
branches.

Per the C standard, the routine should be passed an int, with a value that's
representable as an unsigned char or EOF. Passing a signed char is wrong,
because a negative value is not representable as an unsigned char.
Unfortunately no compiler warns about that.

If walsender doesn't hear from the client for the time specified by
wal_sender_timeout, it will conclude the connection or client is dead, and
disconnect. When half of wal_sender_timeout has elapsed, it sends a ping
to the client, leaving it the remainig half of wal_sender_timeout to
respond. However, it only checked if half of wal_sender_timeout had elapsed
when it was about to sleep, so if it was busy sending WAL to the client for
long enough, it would not send the ping request in time. Then the client
would not know it needs to send a reply, and the walsender will disconnect
even though the client is still alive. Fix that.

Andres Freund, reviewed by Robert Haas, and some further changes by me.
Backpatch to 9.3. Earlier versions relied on the client to send the
keepalives on its own, and hence didn't have this problem.

We should allow this so that matviews can be referenced in UPDATE/DELETE
statements in READ COMMITTED isolation level.  The requirement for that
is that a re-fetch by TID will see the same row version the query saw
earlier, which is true of matviews, so there's no reason for the
restriction.  Per bug #9398.

Michael Paquier, after a suggestion by me

Report from Antonin Houska

Initial patch from Steve Crawford

Per report from Pavel Golub

Explicitly reject infinity/NaN inputs, rather than just assuming that
something else will do it for us.  Per buildfarm.

While at it, make some over-parenthesized and under-legible code
more readable.

This was already documented a few lines further down, but the comment
just beside the field declaration could be misleading.  Per gripe
from Kyotaro Horiguchi.

Erik Rijkers

Commit 6f37c080 removed whitespace
from the SQL file but not the expected-output file, and commit
7e8db2dc changed the error message
without updating the expected outputs.