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8396447cdb
libpgcommon is a new static library to allow sharing code among the various frontend programs and backend; this lets us eliminate duplicate implementations of common routines. We avoid libpgport, because that's intended as a place for porting issues; per discussion, it seems better to keep them separate. The first use case, and the only implemented by this patch, is pg_malloc and friends, which many frontend programs were already using. At the same time, we can use this to provide palloc emulation functions for the frontend; this way, some palloc-using files in the backend can also be used by the frontend cleanly. To do this, we change palloc() in the backend to be a function instead of a macro on top of MemoryContextAlloc(). This was previously believed to cause loss of performance, but this implementation has been tweaked by Tom and Andres so that on modern compilers it provides a slight improvement over the previous one. This lets us clean up some places that were already with localized hacks. Most of the pg_malloc/palloc changes in this patch were authored by Andres Freund. Zoltán Böszörményi also independently provided a form of that. libpgcommon infrastructure was authored by Álvaro.
102 lines
3.6 KiB
C
102 lines
3.6 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) 1996-2013, 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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* src/include/utils/palloc.h
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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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#ifndef FRONTEND
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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 PGDLLIMPORT 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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/*
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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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/*
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* MemoryContextSwitchTo can't be a macro in standard C compilers.
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* But we can make it an inline function if the compiler supports it.
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* See STATIC_IF_INLINE in c.h.
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*/
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#ifndef PG_USE_INLINE
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extern MemoryContext MemoryContextSwitchTo(MemoryContext context);
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#endif /* !PG_USE_INLINE */
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#if defined(PG_USE_INLINE) || defined(MCXT_INCLUDE_DEFINITIONS)
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STATIC_IF_INLINE MemoryContext
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MemoryContextSwitchTo(MemoryContext context)
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{
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MemoryContext old = CurrentMemoryContext;
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CurrentMemoryContext = context;
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return old;
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}
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#endif /* PG_USE_INLINE || MCXT_INCLUDE_DEFINITIONS */
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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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#endif /* !FRONTEND */
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extern char *pstrdup(const char *in);
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extern char *pnstrdup(const char *in, Size len);
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extern void *palloc(Size size);
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extern void *palloc0(Size size);
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extern void pfree(void *pointer);
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extern void *repalloc(void *pointer, Size size);
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#endif /* PALLOC_H */
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