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88177f77b1
practice of evaluating MemSet's arguments multiple times, except for the special case of newNode(), where we can assume the argument is a constant sizeof() operator. Also, add GetMemoryChunkContext() to mcxt.c's API, in preparation for fixing recent GEQO breakage.
84 lines
3.2 KiB
C
84 lines
3.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* palloc.h
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* POSTGRES memory allocator definitions.
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*
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* This file contains the basic memory allocation interface that is
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* needed by almost every backend module. It is included directly by
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* postgres.h, so the definitions here are automatically available
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* everywhere. Keep it lean!
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*
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* Memory allocation occurs within "contexts". Every chunk obtained from
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* palloc()/MemoryContextAlloc() is allocated within a specific context.
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* The entire contents of a context can be freed easily and quickly by
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* resetting or deleting the context --- this is both faster and less
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* prone to memory-leakage bugs than releasing chunks individually.
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* We organize contexts into context trees to allow fine-grain control
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* over chunk lifetime while preserving the certainty that we will free
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* everything that should be freed. See utils/mmgr/README for more info.
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*
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*
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* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: palloc.h,v 1.24 2002/12/16 16:22:46 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PALLOC_H
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#define PALLOC_H
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/*
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* Type MemoryContextData is declared in nodes/memnodes.h. Most users
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* of memory allocation should just treat it as an abstract type, so we
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* do not provide the struct contents here.
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*/
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typedef struct MemoryContextData *MemoryContext;
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/*
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* CurrentMemoryContext is the default allocation context for palloc().
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* We declare it here so that palloc() can be a macro. Avoid accessing it
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* directly! Instead, use MemoryContextSwitchTo() to change the setting.
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*/
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extern DLLIMPORT MemoryContext CurrentMemoryContext;
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/*
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* Fundamental memory-allocation operations (more are in utils/memutils.h)
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*/
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extern void *MemoryContextAlloc(MemoryContext context, Size size);
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extern void *MemoryContextAllocZero(MemoryContext context, Size size);
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extern void *MemoryContextAllocZeroAligned(MemoryContext context, Size size);
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#define palloc(sz) MemoryContextAlloc(CurrentMemoryContext, (sz))
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#define palloc0(sz) MemoryContextAllocZero(CurrentMemoryContext, (sz))
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/*
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* The result of palloc() is always word-aligned, so we can skip testing
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* alignment of the pointer when deciding which MemSet variant to use.
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* Note that this variant does not offer any advantage, and should not be
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* used, unless its "sz" argument is a compile-time constant; therefore, the
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* issue that it evaluates the argument multiple times isn't a problem in
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* practice.
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*/
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#define palloc0fast(sz) \
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( MemSetTest(0, sz) ? \
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MemoryContextAllocZeroAligned(CurrentMemoryContext, sz) : \
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MemoryContextAllocZero(CurrentMemoryContext, sz) )
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extern void pfree(void *pointer);
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extern void *repalloc(void *pointer, Size size);
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extern MemoryContext MemoryContextSwitchTo(MemoryContext context);
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/*
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* These are like standard strdup() except the copied string is
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* allocated in a context, not with malloc().
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*/
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extern char *MemoryContextStrdup(MemoryContext context, const char *string);
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#define pstrdup(str) MemoryContextStrdup(CurrentMemoryContext, (str))
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#endif /* PALLOC_H */
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