pgsql: Allow memory contexts to have both fixed and variable identstri - Mailing list pgsql-committers
From | Tom Lane |
---|---|
Subject | pgsql: Allow memory contexts to have both fixed and variable identstri |
Date | |
Msg-id | E1f0vV0-000169-Hk@gemulon.postgresql.org Whole thread Raw |
List | pgsql-committers |
Allow memory contexts to have both fixed and variable ident strings. Originally, we treated memory context names as potentially variable in all cases, and therefore always copied them into the context header. Commit 9fa6f00b1 rethought this a little bit and invented a distinction between fixed and variable names, skipping the copy step for the former. But we can make things both simpler and more useful by instead allowing there to be two parts to a context's identification, a fixed "name" and an optional, variable "ident". The name supplied in the context create call is now required to be a compile-time-constant string in all cases, as it is never copied but just pointed to. The "ident" string, if wanted, is supplied later. This is needed because typically we want the ident to be stored inside the context so that it's cleaned up automatically on context deletion; that means it has to be copied into the context before we can set the pointer. The cost of this approach is basically just an additional pointer field in struct MemoryContextData, which isn't much overhead, and is bought back entirely in the AllocSet case by not needing a headerSize field anymore, since we no longer have to cope with variable header length. In addition, we can simplify the internal interfaces for memory context creation still further, saving a few cycles there. And it's no longer true that a custom identifier disqualifies a context from participating in aset.c's freelist scheme, so possibly there's some win on that end. All the places that were using non-compile-time-constant context names are adjusted to put the variable info into the "ident" instead. This allows more effective identification of those contexts in many cases; for example, subsidary contexts of relcache entries are now identified by both type (e.g. "index info") and relname, where before you got only one or the other. Contexts associated with PL function cache entries are now identified more fully and uniformly, too. I also arranged for plancache contexts to use the query source string as their identifier. This is basically free for CachedPlanSources, as they contained a copy of that string already. We pay an extra pstrdup to do it for CachedPlans. That could perhaps be avoided, but it would make things more fragile (since the CachedPlanSource is sometimes destroyed first). I suspect future improvements in error reporting will require CachedPlans to have a copy of that string anyway, so it's not clear that it's worth moving mountains to avoid it now. This also changes the APIs for context statistics routines so that the context-specific routines no longer assume that output goes straight to stderr, nor do they know all details of the output format. This is useful immediately to reduce code duplication, and it also allows for external code to do something with stats output that's different from printing to stderr. The reason for pushing this now rather than waiting for v12 is that it rethinks some of the API changes made by commit 9fa6f00b1. Seems better for extension authors to endure just one round of API changes not two. Discussion: https://postgr.es/m/CAB=Je-FdtmFZ9y9REHD7VsSrnCkiBhsA4mdsLKSPauwXtQBeNA@mail.gmail.com Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/442accc3fe0cd556de40d9d6c776449e82254763 Modified Files -------------- src/backend/access/transam/xact.c | 1 - src/backend/catalog/partition.c | 9 +- src/backend/commands/policy.c | 3 + src/backend/executor/functions.c | 6 +- src/backend/replication/logical/reorderbuffer.c | 3 - src/backend/statistics/extended_stats.c | 3 +- src/backend/utils/cache/plancache.c | 3 + src/backend/utils/cache/relcache.c | 37 ++++--- src/backend/utils/cache/ts_cache.c | 13 ++- src/backend/utils/hash/dynahash.c | 12 ++- src/backend/utils/mmgr/aset.c | 72 +++++-------- src/backend/utils/mmgr/generation.c | 52 ++++----- src/backend/utils/mmgr/mcxt.c | 138 ++++++++++++++++++------ src/backend/utils/mmgr/slab.c | 47 ++++---- src/include/nodes/memnodes.h | 11 +- src/include/utils/memutils.h | 33 +++--- src/pl/plperl/plperl.c | 8 +- src/pl/plpgsql/src/pl_comp.c | 5 +- src/pl/plpython/plpy_procedure.c | 8 +- src/pl/tcl/pltcl.c | 9 +- 20 files changed, 263 insertions(+), 210 deletions(-)
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