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e6faf910d7
Rewrite plancache.c so that a "cached plan" (which is rather a misnomer at this point) can support generation of custom, parameter-value-dependent plans, and can make an intelligent choice between using custom plans and the traditional generic-plan approach. The specific choice algorithm implemented here can probably be improved in future, but this commit is all about getting the mechanism in place, not the policy. In addition, restructure the API to greatly reduce the amount of extraneous data copying needed. The main compromise needed to make that possible was to split the initial creation of a CachedPlanSource into two steps. It's worth noting in particular that SPI_saveplan is now deprecated in favor of SPI_keepplan, which accomplishes the same end result with zero data copying, and no need to then spend even more cycles throwing away the original SPIPlan. The risk of long-term memory leaks while manipulating SPIPlans has also been greatly reduced. Most of this improvement is based on use of the recently-added MemoryContextSetParent primitive.
145 lines
4.9 KiB
C
145 lines
4.9 KiB
C
/*-------------------------------------------------------------------------
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*
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* memutils.h
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* This file contains declarations for memory allocation utility
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* functions. These are functions that are not quite widely used
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* enough to justify going in utils/palloc.h, but are still part
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* of the API of the memory management subsystem.
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*
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*
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* Portions Copyright (c) 1996-2011, 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/memutils.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef MEMUTILS_H
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#define MEMUTILS_H
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#include "nodes/memnodes.h"
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/*
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* MaxAllocSize
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* Quasi-arbitrary limit on size of allocations.
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*
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* Note:
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* There is no guarantee that allocations smaller than MaxAllocSize
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* will succeed. Allocation requests larger than MaxAllocSize will
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* be summarily denied.
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*
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* XXX This is deliberately chosen to correspond to the limiting size
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* of varlena objects under TOAST. See VARSIZE_4B() and related macros
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* in postgres.h. Many datatypes assume that any allocatable size can
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* be represented in a varlena header.
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*
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* XXX Also, various places in aset.c assume they can compute twice an
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* allocation's size without overflow, so beware of raising this.
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*/
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#define MaxAllocSize ((Size) 0x3fffffff) /* 1 gigabyte - 1 */
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#define AllocSizeIsValid(size) ((Size) (size) <= MaxAllocSize)
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/*
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* All chunks allocated by any memory context manager are required to be
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* preceded by a StandardChunkHeader at a spacing of STANDARDCHUNKHEADERSIZE.
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* A currently-allocated chunk must contain a backpointer to its owning
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* context as well as the allocated size of the chunk. The backpointer is
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* used by pfree() and repalloc() to find the context to call. The allocated
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* size is not absolutely essential, but it's expected to be needed by any
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* reasonable implementation.
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*/
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typedef struct StandardChunkHeader
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{
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MemoryContext context; /* owning context */
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Size size; /* size of data space allocated in chunk */
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#ifdef MEMORY_CONTEXT_CHECKING
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/* when debugging memory usage, also store actual requested size */
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Size requested_size;
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#endif
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} StandardChunkHeader;
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#define STANDARDCHUNKHEADERSIZE MAXALIGN(sizeof(StandardChunkHeader))
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/*
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* Standard top-level memory contexts.
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*
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* Only TopMemoryContext and ErrorContext are initialized by
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* MemoryContextInit() itself.
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*/
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extern PGDLLIMPORT MemoryContext TopMemoryContext;
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extern PGDLLIMPORT MemoryContext ErrorContext;
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extern PGDLLIMPORT MemoryContext PostmasterContext;
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extern PGDLLIMPORT MemoryContext CacheMemoryContext;
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extern PGDLLIMPORT MemoryContext MessageContext;
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extern PGDLLIMPORT MemoryContext TopTransactionContext;
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extern PGDLLIMPORT MemoryContext CurTransactionContext;
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/* This is a transient link to the active portal's memory context: */
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extern PGDLLIMPORT MemoryContext PortalContext;
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/*
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* Memory-context-type-independent functions in mcxt.c
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*/
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extern void MemoryContextInit(void);
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extern void MemoryContextReset(MemoryContext context);
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extern void MemoryContextDelete(MemoryContext context);
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extern void MemoryContextResetChildren(MemoryContext context);
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extern void MemoryContextDeleteChildren(MemoryContext context);
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extern void MemoryContextResetAndDeleteChildren(MemoryContext context);
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extern void MemoryContextSetParent(MemoryContext context,
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MemoryContext new_parent);
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extern Size GetMemoryChunkSpace(void *pointer);
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extern MemoryContext GetMemoryChunkContext(void *pointer);
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extern MemoryContext MemoryContextGetParent(MemoryContext context);
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extern bool MemoryContextIsEmpty(MemoryContext context);
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extern void MemoryContextStats(MemoryContext context);
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#ifdef MEMORY_CONTEXT_CHECKING
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extern void MemoryContextCheck(MemoryContext context);
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#endif
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extern bool MemoryContextContains(MemoryContext context, void *pointer);
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/*
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* This routine handles the context-type-independent part of memory
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* context creation. It's intended to be called from context-type-
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* specific creation routines, and noplace else.
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*/
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extern MemoryContext MemoryContextCreate(NodeTag tag, Size size,
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MemoryContextMethods *methods,
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MemoryContext parent,
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const char *name);
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/*
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* Memory-context-type-specific functions
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*/
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/* aset.c */
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extern MemoryContext AllocSetContextCreate(MemoryContext parent,
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const char *name,
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Size minContextSize,
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Size initBlockSize,
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Size maxBlockSize);
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/*
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* Recommended default alloc parameters, suitable for "ordinary" contexts
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* that might hold quite a lot of data.
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*/
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#define ALLOCSET_DEFAULT_MINSIZE 0
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#define ALLOCSET_DEFAULT_INITSIZE (8 * 1024)
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#define ALLOCSET_DEFAULT_MAXSIZE (8 * 1024 * 1024)
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/*
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* Recommended alloc parameters for "small" contexts that are not expected
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* to contain much data (for example, a context to contain a query plan).
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*/
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#define ALLOCSET_SMALL_MINSIZE 0
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#define ALLOCSET_SMALL_INITSIZE (1 * 1024)
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#define ALLOCSET_SMALL_MAXSIZE (8 * 1024)
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#endif /* MEMUTILS_H */
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