1
0
mirror of https://github.com/postgres/postgres.git synced 2025-12-18 05:01:01 +03:00
Files
postgres/src/backend/utils
Noah Misch 27e4fad980 Assert lack of hazardous buffer locks before possible catalog read.
Commit 0bada39c83 fixed a bug of this kind,
which existed in all branches for six days before detection.  While the
probability of reaching the trouble was low, the disruption was extreme.  No
new backends could start, and service restoration needed an immediate
shutdown.  Hence, add this to catch the next bug like it.

The new check in RelationIdGetRelation() suffices to make autovacuum detect
the bug in commit 243e9b40f1 that led to commit
0bada39.  This also checks in a number of similar places.  It replaces each
Assert(IsTransactionState()) that pertained to a conditional catalog read.

Back-patch to v14 - v17.  This a back-patch of commit
f4ece891fc (from before v18 branched) to
all supported branches, to accompany the back-patch of commits 243e9b4
and 0bada39.  For catalog indexes, the bttextcmp() behavior that
motivated IsCatalogTextUniqueIndexOid() was v18-specific.  Hence, this
back-patch doesn't need that or its correction from commit
4a4ee0c2c1.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/20250410191830.0e.nmisch@google.com
Discussion: https://postgr.es/m/10ec0bc3-5933-1189-6bb8-5dec4114558e@gmail.com
Backpatch-through: 14-17
2025-12-16 16:13:55 -08:00
..
2023-01-02 15:00:37 -05:00
2023-01-02 15:00:37 -05:00
2024-04-27 11:38:41 +07:00
2023-01-02 15:00:37 -05:00

# Generating dummy probes

If Postgres isn't configured with dtrace enabled, we need to generate
dummy probes for the entries in probes.d, that do nothing.

This is accomplished in Unix via the sed script `Gen_dummy_probes.sed`. We
used to use this in MSVC builds using the perl utility `psed`, which mimicked
sed. However, that utility disappeared from Windows perl distributions and so
we converted the sed script to a perl script to be used in MSVC builds.

We still keep the sed script as the authoritative source for generating
these dummy probes because except on Windows perl is not a hard requirement
when building from a tarball.

So, if you need to change the way dummy probes are generated, first change
the sed script, and when it's working generate the perl script. This can
be accomplished by using the perl utility s2p.

s2p is no longer part of the perl core, so it might not be on your system,
but it is available on CPAN and also in many package systems. e.g.
on Fedora it can be installed using `cpan App::s2p` or
`dnf install perl-App-s2p`.

The Makefile contains a recipe for regenerating Gen_dummy_probes.pl, so all
you need to do is once you have s2p installed is `make Gen_dummy_probes.pl`
Note that in a VPATH build this will generate the file in the vpath tree,
not the source tree.