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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2025-07-25 10:56:55 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2025-07-25 10:56:55 -0400 |
| commit | 5457ea46d181f8b8dbe1ae482720b23bff4029de (patch) | |
| tree | 60612035a3b742b02c5cff108121bd5d63e54d00 /src | |
| parent | 1dfe3ef3f960d6924eb1f18facf4fbdae6e1cc1d (diff) | |
| download | postgresql-5457ea46d181f8b8dbe1ae482720b23bff4029de.tar.gz postgresql-5457ea46d181f8b8dbe1ae482720b23bff4029de.zip | |
Fix dynahash's HASH_FIXED_SIZE ("isfixed") option.
This flag was effectively a no-op in EXEC_BACKEND (ie, Windows)
builds, because it was kept in the process-local HTAB struct,
and it could only ever become set in the postmaster's copy.
The simplest fix is to move it to the shared HASHHDR struct.
We could keep a copy in HTAB as well, as we do with keysize
and some other fields, but the "too much contention" argument
doesn't seem to apply here: we only examine isfixed during
element_alloc(), which had better not get hit very often for
a shared hashtable.
This oversight dates to 7c797e719 which invented the option.
But back-patching doesn't seem appropriate given the lack of
field complaints. If there is anyone running an affected
workload on Windows, they might be unhappy about the behavior
changing in a minor release.
Author: Aidar Imamov <a.imamov@postgrespro.ru>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/4d0cb35ff01c5c74d2b9a582ecb73823@postgrespro.ru
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/utils/hash/dynahash.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/src/backend/utils/hash/dynahash.c b/src/backend/utils/hash/dynahash.c index 1ad155d446e..42e9be274fc 100644 --- a/src/backend/utils/hash/dynahash.c +++ b/src/backend/utils/hash/dynahash.c @@ -195,6 +195,7 @@ struct HASHHDR long ssize; /* segment size --- must be power of 2 */ int sshift; /* segment shift = log2(ssize) */ int nelem_alloc; /* number of entries to allocate at once */ + bool isfixed; /* if true, don't enlarge */ #ifdef HASH_STATISTICS @@ -227,7 +228,6 @@ struct HTAB MemoryContext hcxt; /* memory context if default allocator used */ char *tabname; /* table name (for error messages) */ bool isshared; /* true if table is in shared memory */ - bool isfixed; /* if true, don't enlarge */ /* freezing a shared table isn't allowed, so we can keep state here */ bool frozen; /* true = no more inserts allowed */ @@ -618,8 +618,10 @@ hash_create(const char *tabname, long nelem, const HASHCTL *info, int flags) } } + /* Set isfixed if requested, but not till after we build initial entries */ if (flags & HASH_FIXED_SIZE) - hashp->isfixed = true; + hctl->isfixed = true; + return hashp; } @@ -644,6 +646,8 @@ hdefault(HTAB *hashp) hctl->ssize = DEF_SEGSIZE; hctl->sshift = DEF_SEGSIZE_SHIFT; + hctl->isfixed = false; /* can be enlarged */ + #ifdef HASH_STATISTICS hctl->accesses = hctl->collisions = 0; #endif @@ -1713,7 +1717,7 @@ element_alloc(HTAB *hashp, int nelem, int freelist_idx) HASHELEMENT *prevElement; int i; - if (hashp->isfixed) + if (hctl->isfixed) return false; /* Each element has a HASHELEMENT header plus user data. */ |