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Replace CLOBBER_CACHE_ALWAYS with run-time GUC

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Forced cache invalidation (CLOBBER_CACHE_ALWAYS) has been impractical
to use for testing in PostgreSQL because it's so slow and because it's
toggled on/off only at build time.  It is helpful when hunting bugs in
any code that uses the sycache/relcache because causes cache
invalidations to be injected whenever it would be possible for an
invalidation to occur, whether or not one was really pending.

Address this by providing run-time control over cache clobber
behaviour using the new debug_invalidate_system_caches_always GUC.
Support is not compiled in at all unless assertions are enabled or
CLOBBER_CACHE_ENABLED is explicitly defined at compile time.  It
defaults to 0 if compiled in, so it has negligible effect on assert
build performance by default.

When support is compiled in, test code can now set
debug_invalidate_system_caches_always=1 locally to a backend to test
specific queries, functions, extensions, etc.  Or tests can toggle it
globally for a specific test case while retaining normal performance
during test setup and teardown.

For backwards compatibility with existing test harnesses and scripts,
debug_invalidate_system_caches_always defaults to 1 if
CLOBBER_CACHE_ALWAYS is defined, and to 3 if CLOBBER_CACHE_RECURSIVE
is defined.

CLOBBER_CACHE_ENABLED is now visible in pg_config_manual.h, as is the
related RECOVER_RELATION_BUILD_MEMORY setting for the relcache.

Author: Craig Ringer <craig.ringer@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/CAMsr+YF=+ctXBZj3ywmvKNUjWpxmuTuUKuv-rgbHGX5i5pLstQ@mail.gmail.com
This commit is contained in:
Peter Eisentraut
2021-01-06 10:15:19 +01:00
parent 8900b5a9d5
commit 4656e3d668
9 changed files with 169 additions and 54 deletions
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24
src/backend/utils/misc/guc.c
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@ -99,6 +99,7 @@
#include "utils/rls.h"
#include "utils/snapmgr.h"
#include "utils/tzparser.h"
#include "utils/inval.h"
#include "utils/varlena.h"
#include "utils/xml.h"
@ -3402,6 +3403,29 @@ static struct config_int ConfigureNamesInt[] =
check_huge_page_size, NULL, NULL
},
{
{"debug_invalidate_system_caches_always", PGC_SUSET, DEVELOPER_OPTIONS,
gettext_noop("Aggressively invalidate system caches for debugging purposes."),
NULL,
GUC_NOT_IN_SAMPLE
},
&debug_invalidate_system_caches_always,
#ifdef CLOBBER_CACHE_ENABLED
/* Set default based on older compile-time-only cache clobber macros */
#if defined(CLOBBER_CACHE_RECURSIVELY)
3,
#elif defined(CLOBBER_CACHE_ALWAYS)
1,
#else
0,
#endif
0, 5,
#else /* not CLOBBER_CACHE_ENABLED */
0, 0, 0,
#endif /* not CLOBBER_CACHE_ENABLED */
NULL, NULL, NULL
},
/* End-of-list marker */
{
{NULL, 0, 0, NULL, NULL}, NULL, 0, 0, 0, NULL, NULL, NULL