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Permit super-MaxAllocSize allocations with MemoryContextAllocHuge().

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The MaxAllocSize guard is convenient for most callers, because it
reduces the need for careful attention to overflow, data type selection,
and the SET_VARSIZE() limit.  A handful of callers are happy to navigate
those hazards in exchange for the ability to allocate a larger chunk.
Introduce MemoryContextAllocHuge() and repalloc_huge().  Use this in
tuplesort.c and tuplestore.c, enabling internal sorts of up to INT_MAX
tuples, a factor-of-48 increase.  In particular, B-tree index builds can
now benefit from much-larger maintenance_work_mem settings.

Reviewed by Stephen Frost, Simon Riggs and Jeff Janes.
This commit is contained in:
Noah Misch
2013-06-27 14:53:57 -04:00
parent 9ef86cd994
commit 263865a489
7 changed files with 183 additions and 98 deletions
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5
src/backend/utils/mmgr/aset.c
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@@ -458,6 +458,7 @@ AllocSetContextCreate(MemoryContext parent,
maxBlockSize = MAXALIGN(maxBlockSize);
if (maxBlockSize < initBlockSize)
maxBlockSize = initBlockSize;
Assert(AllocHugeSizeIsValid(maxBlockSize)); /* must be safe to double */
context->initBlockSize = initBlockSize;
context->maxBlockSize = maxBlockSize;
context->nextBlockSize = initBlockSize;
@@ -643,6 +644,10 @@ AllocSetDelete(MemoryContext context)
* AllocSetAlloc
* Returns pointer to allocated memory of given size; memory is added
* to the set.
*
* No request may exceed:
* MAXALIGN_DOWN(SIZE_MAX) - ALLOC_BLOCKHDRSZ - ALLOC_CHUNKHDRSZ
* All callers use a much-lower limit.
*/
static void *
AllocSetAlloc(MemoryContext context, Size size)