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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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67
src/backend/utils/cache/relcache.c vendored
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@ -91,15 +91,15 @@
#define RELCACHE_INIT_FILEMAGIC 0x573266 /* version ID value */
/*
* Default policy for whether to apply RECOVER_RELATION_BUILD_MEMORY:
* do so in clobber-cache builds but not otherwise. This choice can be
* overridden at compile time with -DRECOVER_RELATION_BUILD_MEMORY=1 or =0.
* Whether to bother checking if relation cache memory needs to be freed
* eagerly. See also RelationBuildDesc() and pg_config_manual.h.
*/
#ifndef RECOVER_RELATION_BUILD_MEMORY
#if defined(CLOBBER_CACHE_ALWAYS) || defined(CLOBBER_CACHE_RECURSIVELY)
#define RECOVER_RELATION_BUILD_MEMORY 1
#if defined(RECOVER_RELATION_BUILD_MEMORY) && (RECOVER_RELATION_BUILD_MEMORY != 0)
#define MAYBE_RECOVER_RELATION_BUILD_MEMORY 1
#else
#define RECOVER_RELATION_BUILD_MEMORY 0
#ifdef CLOBBER_CACHE_ENABLED
#define MAYBE_RECOVER_RELATION_BUILD_MEMORY 1
#endif
#endif
@ -1040,19 +1040,25 @@ RelationBuildDesc(Oid targetRelId, bool insertIt)
* scope, and relcache loads shouldn't happen so often that it's essential
* to recover transient data before end of statement/transaction. However
* that's definitely not true in clobber-cache test builds, and perhaps
* it's not true in other cases. If RECOVER_RELATION_BUILD_MEMORY is not
* zero, arrange to allocate the junk in a temporary context that we'll
* free before returning. Make it a child of caller's context so that it
* will get cleaned up appropriately if we error out partway through.
* it's not true in other cases.
*
* When cache clobbering is enabled or when forced to by
* RECOVER_RELATION_BUILD_MEMORY=1, arrange to allocate the junk in a
* temporary context that we'll free before returning. Make it a child
* of caller's context so that it will get cleaned up appropriately if
* we error out partway through.
*/
#if RECOVER_RELATION_BUILD_MEMORY
MemoryContext tmpcxt;
MemoryContext oldcxt;
#ifdef MAYBE_RECOVER_RELATION_BUILD_MEMORY
MemoryContext tmpcxt = NULL;
MemoryContext oldcxt = NULL;
tmpcxt = AllocSetContextCreate(CurrentMemoryContext,
"RelationBuildDesc workspace",
ALLOCSET_DEFAULT_SIZES);
oldcxt = MemoryContextSwitchTo(tmpcxt);
if (RECOVER_RELATION_BUILD_MEMORY || debug_invalidate_system_caches_always > 0)
{
tmpcxt = AllocSetContextCreate(CurrentMemoryContext,
"RelationBuildDesc workspace",
ALLOCSET_DEFAULT_SIZES);
oldcxt = MemoryContextSwitchTo(tmpcxt);
}
#endif
/*
@ -1065,10 +1071,13 @@ RelationBuildDesc(Oid targetRelId, bool insertIt)
*/
if (!HeapTupleIsValid(pg_class_tuple))
{
#if RECOVER_RELATION_BUILD_MEMORY
/* Return to caller's context, and blow away the temporary context */
MemoryContextSwitchTo(oldcxt);
MemoryContextDelete(tmpcxt);
#ifdef MAYBE_RECOVER_RELATION_BUILD_MEMORY
if (tmpcxt)
{
/* Return to caller's context, and blow away the temporary context */
MemoryContextSwitchTo(oldcxt);
MemoryContextDelete(tmpcxt);
}
#endif
return NULL;
}
@ -1247,10 +1256,13 @@ RelationBuildDesc(Oid targetRelId, bool insertIt)
/* It's fully valid */
relation->rd_isvalid = true;
#if RECOVER_RELATION_BUILD_MEMORY
/* Return to caller's context, and blow away the temporary context */
MemoryContextSwitchTo(oldcxt);
MemoryContextDelete(tmpcxt);
#ifdef MAYBE_RECOVER_RELATION_BUILD_MEMORY
if (tmpcxt)
{
/* Return to caller's context, and blow away the temporary context */
MemoryContextSwitchTo(oldcxt);
MemoryContextDelete(tmpcxt);
}
#endif
return relation;
@ -1646,8 +1658,9 @@ LookupOpclassInfo(Oid operatorClassOid,
* while we are loading the info, and it's very hard to provoke that if
* this happens only once per opclass per backend.
*/
#if defined(CLOBBER_CACHE_ALWAYS)
opcentry->valid = false;
#ifdef CLOBBER_CACHE_ENABLED
if (debug_invalidate_system_caches_always > 0)
opcentry->valid = false;
#endif
if (opcentry->valid)