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* memnodes.h
* POSTGRES memory context node definitions.
* Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
* src/include/nodes/memnodes.h
#ifndef MEMNODES_H
#define MEMNODES_H
#include "nodes/nodes.h"
* MemoryContextCounters
* Summarization state for MemoryContextStats collection.
* The set of counters in this struct is biased towards AllocSet; if we ever
* add any context types that are based on fundamentally different approaches,
* we might need more or different counters here. A possible API spec then
* would be to print only nonzero counters, but for now we just summarize in
* the format historically used by AllocSet.
typedef struct MemoryContextCounters
Size nblocks; /* Total number of malloc blocks */
Size freechunks; /* Total number of free chunks */
Size totalspace; /* Total bytes requested from malloc */
Size freespace; /* The unused portion of totalspace */
} MemoryContextCounters;
* MemoryContext
* A logical context in which memory allocations occur.
* MemoryContext itself is an abstract type that can have multiple
* implementations.
* The function pointers in MemoryContextMethods define one specific
* implementation of MemoryContext --- they are a virtual function table
* in C++ terms.
* Node types that are actual implementations of memory contexts must
* begin with the same fields as MemoryContextData.
* Note: for largely historical reasons, typedef MemoryContext is a pointer
* to the context struct rather than the struct type itself.
typedef void (*MemoryStatsPrintFunc) (MemoryContext context, void *passthru,
const char *stats_string);
typedef struct MemoryContextMethods
void *(*alloc) (MemoryContext context, Size size);
/* call this free_p in case someone #define's free() */
void (*free_p) (MemoryContext context, void *pointer);
void *(*realloc) (MemoryContext context, void *pointer, Size size);
void (*reset) (MemoryContext context);
void (*delete_context) (MemoryContext context);
Size (*get_chunk_space) (MemoryContext context, void *pointer);
bool (*is_empty) (MemoryContext context);
void (*stats) (MemoryContext context,
MemoryStatsPrintFunc printfunc, void *passthru,
MemoryContextCounters *totals);
void (*check) (MemoryContext context);
} MemoryContextMethods;
typedef struct MemoryContextData
NodeTag type; /* identifies exact kind of context */
/* these two fields are placed here to minimize alignment wastage: */
bool isReset; /* T = no space alloced since last reset */
bool allowInCritSection; /* allow palloc in critical section */
Size mem_allocated; /* track memory allocated for this context */
const MemoryContextMethods *methods; /* virtual function table */
MemoryContext parent; /* NULL if no parent (toplevel context) */
MemoryContext firstchild; /* head of linked list of children */
MemoryContext prevchild; /* previous child of same parent */
MemoryContext nextchild; /* next child of same parent */
const char *name; /* context name (just for debugging) */
const char *ident; /* context ID if any (just for debugging) */
MemoryContextCallback *reset_cbs; /* list of reset/delete callbacks */
} MemoryContextData;
/* utils/palloc.h contains typedef struct MemoryContextData *MemoryContext */
* MemoryContextIsValid
* True iff memory context is valid.
* Add new context types to the set accepted by this macro.
#define MemoryContextIsValid(context) \
((context) != NULL && \
(IsA((context), AllocSetContext) || \
IsA((context), SlabContext) || \
IsA((context), GenerationContext)))
#endif /* MEMNODES_H */
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