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Make some minor improvements in memory-context infrastructure.

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We lack a version of repalloc() that supports MCXT_ALLOC_NO_OOM
semantics, so invent repalloc_extended() with the usual set of
flags.  repalloc_huge() becomes a legacy wrapper for that.

Also, fix dynahash.c so that it can support HASH_ENTER_NULL
requests when using the default palloc-based allocator.
The only reason it didn't do that already was the lack of the
MCXT_ALLOC_NO_OOM option when that code was written, ages ago.

While here, simplify a few overcomplicated tests in mcxt.c.

Discussion: https://postgr.es/m/2982579.1662416866@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2022-10-14 11:55:56 -04:00
parent 1b11561cc1
commit 9c911ec065
3 changed files with 56 additions and 42 deletions
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13
src/backend/utils/hash/dynahash.c
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@@ -289,7 +289,8 @@ static void *
DynaHashAlloc(Size size)
{
Assert(MemoryContextIsValid(CurrentDynaHashCxt));
return MemoryContextAlloc(CurrentDynaHashCxt, size);
return MemoryContextAllocExtended(CurrentDynaHashCxt, size,
MCXT_ALLOC_NO_OOM);
}
@@ -939,9 +940,7 @@ calc_bucket(HASHHDR *hctl, uint32 hash_val)
*
* HASH_ENTER will normally ereport a generic "out of memory" error if
* it is unable to create a new entry. The HASH_ENTER_NULL operation is
* the same except it will return NULL if out of memory. Note that
* HASH_ENTER_NULL cannot be used with the default palloc-based allocator,
* since palloc internally ereports on out-of-memory.
* the same except it will return NULL if out of memory.
*
* If foundPtr isn't NULL, then *foundPtr is set true if we found an
* existing entry in the table, false otherwise. This is needed in the
@@ -1084,12 +1083,8 @@ hash_search_with_hash_value(HTAB *hashp,
}
return NULL;
case HASH_ENTER_NULL:
/* ENTER_NULL does not work with palloc-based allocator */
Assert(hashp->alloc != DynaHashAlloc);
/* FALL THRU */
case HASH_ENTER:
case HASH_ENTER_NULL:
/* Return existing element if found, else create one */
if (currBucket != NULL)
return (void *) ELEMENTKEY(currBucket);