greenplumn buf 源码
greenplumn buf 代码
文件路径：/src/include/storage/buf.h
/*-------------------------------------------------------------------------
*
* buf.h
* Basic buffer manager data types.
*
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/storage/buf.h
*
*-------------------------------------------------------------------------
*/
#ifndef BUF_H
#define BUF_H
/*
* Buffer identifiers.
*
* Zero is invalid, positive is the index of a shared buffer (1..NBuffers),
* negative is the index of a local buffer (-1 .. -NLocBuffer).
*/
typedef int Buffer;
#define InvalidBuffer 0
/*
* BufferIsInvalid
* True iff the buffer is invalid.
*/
#define BufferIsInvalid(buffer) ((buffer) == InvalidBuffer)
/*
* BufferIsLocal
* True iff the buffer is local (not visible to other backends).
*/
#define BufferIsLocal(buffer) ((buffer) < 0)
/*
* Buffer access strategy objects.
*
* BufferAccessStrategyData is private to freelist.c
*/
typedef struct BufferAccessStrategyData *BufferAccessStrategy;
#endif /* BUF_H */
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