mirror of
https://github.com/postgres/postgres.git
synced 2026-06-01 13:28:44 -04:00
Tom Lane
eaa5808e8e
That is, MemoryContextReset() now means what was formerly meant by MemoryContextResetAndDeleteChildren(), and the latter is now just a macro alias for the former. If you really want the functionality that was formerly provided by MemoryContextReset(), what you have to do is MemoryContextResetChildren() plus MemoryContextResetOnly() (which is a new API to reset *only* the named context and not touch its children). The reason for this change is that near fifteen years of experience has proven that there is noplace where old-style MemoryContextReset() is actually what you want. Making that the default behavior has led to lots of context-leakage bugs, while we've not found anyplace where it's actually necessary to keep the child contexts; at least the standard regression tests do not reveal anyplace where this change breaks anything. And there are upcoming patches that will introduce additional reasons why child contexts need to be removed. We could change existing calls of MemoryContextResetAndDeleteChildren to be just MemoryContextReset, but for the moment I'll leave them alone; they're not costing anything.
156 lines
5.5 KiB
C
156 lines
5.5 KiB
C
/*-------------------------------------------------------------------------
|
|
*
|
|
* memutils.h
|
|
* This file contains declarations for memory allocation utility
|
|
* functions. These are functions that are not quite widely used
|
|
* enough to justify going in utils/palloc.h, but are still part
|
|
* of the API of the memory management subsystem.
|
|
*
|
|
*
|
|
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
|
|
* Portions Copyright (c) 1994, Regents of the University of California
|
|
*
|
|
* src/include/utils/memutils.h
|
|
*
|
|
*-------------------------------------------------------------------------
|
|
*/
|
|
#ifndef MEMUTILS_H
|
|
#define MEMUTILS_H
|
|
|
|
#include "nodes/memnodes.h"
|
|
|
|
|
|
/*
|
|
* MaxAllocSize, MaxAllocHugeSize
|
|
* Quasi-arbitrary limits on size of allocations.
|
|
*
|
|
* Note:
|
|
* There is no guarantee that smaller allocations will succeed, but
|
|
* larger requests will be summarily denied.
|
|
*
|
|
* palloc() enforces MaxAllocSize, chosen to correspond to the limiting size
|
|
* of varlena objects under TOAST. See VARSIZE_4B() and related macros in
|
|
* postgres.h. Many datatypes assume that any allocatable size can be
|
|
* represented in a varlena header. This limit also permits a caller to use
|
|
* an "int" variable for an index into or length of an allocation. Callers
|
|
* careful to avoid these hazards can access the higher limit with
|
|
* MemoryContextAllocHuge(). Both limits permit code to assume that it may
|
|
* compute twice an allocation's size without overflow.
|
|
*/
|
|
#define MaxAllocSize ((Size) 0x3fffffff) /* 1 gigabyte - 1 */
|
|
|
|
#define AllocSizeIsValid(size) ((Size) (size) <= MaxAllocSize)
|
|
|
|
#define MaxAllocHugeSize ((Size) -1 >> 1) /* SIZE_MAX / 2 */
|
|
|
|
#define AllocHugeSizeIsValid(size) ((Size) (size) <= MaxAllocHugeSize)
|
|
|
|
/*
|
|
* All chunks allocated by any memory context manager are required to be
|
|
* preceded by a StandardChunkHeader at a spacing of STANDARDCHUNKHEADERSIZE.
|
|
* A currently-allocated chunk must contain a backpointer to its owning
|
|
* context as well as the allocated size of the chunk. The backpointer is
|
|
* used by pfree() and repalloc() to find the context to call. The allocated
|
|
* size is not absolutely essential, but it's expected to be needed by any
|
|
* reasonable implementation.
|
|
*/
|
|
typedef struct StandardChunkHeader
|
|
{
|
|
MemoryContext context; /* owning context */
|
|
Size size; /* size of data space allocated in chunk */
|
|
#ifdef MEMORY_CONTEXT_CHECKING
|
|
/* when debugging memory usage, also store actual requested size */
|
|
Size requested_size;
|
|
#endif
|
|
} StandardChunkHeader;
|
|
|
|
#define STANDARDCHUNKHEADERSIZE MAXALIGN(sizeof(StandardChunkHeader))
|
|
|
|
|
|
/*
|
|
* Standard top-level memory contexts.
|
|
*
|
|
* Only TopMemoryContext and ErrorContext are initialized by
|
|
* MemoryContextInit() itself.
|
|
*/
|
|
extern PGDLLIMPORT MemoryContext TopMemoryContext;
|
|
extern PGDLLIMPORT MemoryContext ErrorContext;
|
|
extern PGDLLIMPORT MemoryContext PostmasterContext;
|
|
extern PGDLLIMPORT MemoryContext CacheMemoryContext;
|
|
extern PGDLLIMPORT MemoryContext MessageContext;
|
|
extern PGDLLIMPORT MemoryContext TopTransactionContext;
|
|
extern PGDLLIMPORT MemoryContext CurTransactionContext;
|
|
|
|
/* This is a transient link to the active portal's memory context: */
|
|
extern PGDLLIMPORT MemoryContext PortalContext;
|
|
|
|
/* Backwards compatibility macro */
|
|
#define MemoryContextResetAndDeleteChildren(ctx) MemoryContextReset(ctx)
|
|
|
|
|
|
/*
|
|
* Memory-context-type-independent functions in mcxt.c
|
|
*/
|
|
extern void MemoryContextInit(void);
|
|
extern void MemoryContextReset(MemoryContext context);
|
|
extern void MemoryContextDelete(MemoryContext context);
|
|
extern void MemoryContextResetOnly(MemoryContext context);
|
|
extern void MemoryContextResetChildren(MemoryContext context);
|
|
extern void MemoryContextDeleteChildren(MemoryContext context);
|
|
extern void MemoryContextRegisterResetCallback(MemoryContext context,
|
|
MemoryContextCallback *cb);
|
|
extern void MemoryContextSetParent(MemoryContext context,
|
|
MemoryContext new_parent);
|
|
extern Size GetMemoryChunkSpace(void *pointer);
|
|
extern MemoryContext GetMemoryChunkContext(void *pointer);
|
|
extern MemoryContext MemoryContextGetParent(MemoryContext context);
|
|
extern bool MemoryContextIsEmpty(MemoryContext context);
|
|
extern void MemoryContextStats(MemoryContext context);
|
|
extern void MemoryContextAllowInCriticalSection(MemoryContext context,
|
|
bool allow);
|
|
|
|
#ifdef MEMORY_CONTEXT_CHECKING
|
|
extern void MemoryContextCheck(MemoryContext context);
|
|
#endif
|
|
extern bool MemoryContextContains(MemoryContext context, void *pointer);
|
|
|
|
/*
|
|
* This routine handles the context-type-independent part of memory
|
|
* context creation. It's intended to be called from context-type-
|
|
* specific creation routines, and noplace else.
|
|
*/
|
|
extern MemoryContext MemoryContextCreate(NodeTag tag, Size size,
|
|
MemoryContextMethods *methods,
|
|
MemoryContext parent,
|
|
const char *name);
|
|
|
|
|
|
/*
|
|
* Memory-context-type-specific functions
|
|
*/
|
|
|
|
/* aset.c */
|
|
extern MemoryContext AllocSetContextCreate(MemoryContext parent,
|
|
const char *name,
|
|
Size minContextSize,
|
|
Size initBlockSize,
|
|
Size maxBlockSize);
|
|
|
|
/*
|
|
* Recommended default alloc parameters, suitable for "ordinary" contexts
|
|
* that might hold quite a lot of data.
|
|
*/
|
|
#define ALLOCSET_DEFAULT_MINSIZE 0
|
|
#define ALLOCSET_DEFAULT_INITSIZE (8 * 1024)
|
|
#define ALLOCSET_DEFAULT_MAXSIZE (8 * 1024 * 1024)
|
|
|
|
/*
|
|
* Recommended alloc parameters for "small" contexts that are not expected
|
|
* to contain much data (for example, a context to contain a query plan).
|
|
*/
|
|
#define ALLOCSET_SMALL_MINSIZE 0
|
|
#define ALLOCSET_SMALL_INITSIZE (1 * 1024)
|
|
#define ALLOCSET_SMALL_MAXSIZE (8 * 1024)
|
|
|
|
#endif /* MEMUTILS_H */
|