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/*
* slru.h
*
* Simple LRU
*
* Portions Copyright (c) 2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/slru.h,v 1.5 2004/05/28 05:13:17 tgl Exp $
*/
#ifndef SLRU_H
#define SLRU_H
#include "access/xlog.h"
/* exported because lwlock.c needs it */
#define NUM_CLOG_BUFFERS 8
/*
* Note: the separation between SlruLockData and SlruSharedData is purely
* historical; the structs could be combined.
*/
typedef struct SlruLockData
{
LWLockId ControlLock;
LWLockId BufferLocks[NUM_CLOG_BUFFERS]; /* Per-buffer I/O locks */
} SlruLockData;
typedef SlruLockData *SlruLock;
/*
* SlruCtlData is an unshared structure that points to the active information
* in shared memory.
*/
typedef struct SlruCtlData
{
void *shared; /* pointer to SlruSharedData */
SlruLock locks;
/*
* Dir is set during SimpleLruShmemInit and does not change thereafter.
* The value is automatically inherited by backends via fork, and
* doesn't need to be in shared memory.
*/
char Dir[MAXPGPATH];
/*
* Decide which of two page numbers is "older" for truncation purposes.
* We need to use comparison of TransactionIds here in order to do the
* right thing with wraparound XID arithmetic.
*/
bool (*PagePrecedes) (int, int);
} SlruCtlData;
typedef SlruCtlData *SlruCtl;
extern int SimpleLruShmemSize(void);
extern void SimpleLruInit(SlruCtl ctl, const char *name, const char *subdir);
extern int SimpleLruZeroPage(SlruCtl ctl, int pageno);
extern char *SimpleLruReadPage(SlruCtl ctl, int pageno, TransactionId xid, bool forwrite);
extern void SimpleLruWritePage(SlruCtl ctl, int slotno);
extern void SimpleLruSetLatestPage(SlruCtl ctl, int pageno);
extern void SimpleLruFlush(SlruCtl ctl, bool checkpoint);
extern void SimpleLruTruncate(SlruCtl ctl, int cutoffPage);
#endif /* SLRU_H */
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