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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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4
src/include/utils/palloc.h
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@ -51,6 +51,10 @@ extern void *MemoryContextAlloc(MemoryContext context, Size size);
extern void *MemoryContextAllocZero(MemoryContext context, Size size);
extern void *MemoryContextAllocZeroAligned(MemoryContext context, Size size);
/* Higher-limit allocators. */
extern void *MemoryContextAllocHuge(MemoryContext context, Size size);
extern void *repalloc_huge(void *pointer, Size size);
/*
* The result of palloc() is always word-aligned, so we can skip testing
* alignment of the pointer when deciding which MemSet variant to use.