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/*-------------------------------------------------------------------------
*
* xlogprefetch.h
* Declarations for the recovery prefetching module.
*
* Portions Copyright (c) 2021, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/include/access/xlogprefetch.h
*-------------------------------------------------------------------------
*/
#ifndef XLOGPREFETCH_H
#define XLOGPREFETCH_H
#include "access/xlogreader.h"
/* GUCs */
extern bool recovery_prefetch;
extern bool recovery_prefetch_fpw;
struct XLogPrefetcher;
typedef struct XLogPrefetcher XLogPrefetcher;
extern int XLogPrefetchReconfigureCount;
typedef struct XLogPrefetchState
{
XLogReaderState *reader;
XLogPrefetcher *prefetcher;
int reconfigure_count;
} XLogPrefetchState;
extern size_t XLogPrefetchShmemSize(void);
extern void XLogPrefetchShmemInit(void);
extern void XLogPrefetchReconfigure(void);
extern void XLogPrefetchRequestResetStats(void);
extern void XLogPrefetchBegin(XLogPrefetchState *state, XLogReaderState *reader);
extern void XLogPrefetchEnd(XLogPrefetchState *state);
/* Functions exposed only for the use of XLogPrefetch(). */
extern XLogPrefetcher *XLogPrefetcherAllocate(XLogReaderState *reader);
extern void XLogPrefetcherFree(XLogPrefetcher *prefetcher);
extern bool XLogPrefetcherReadAhead(XLogPrefetcher *prefetch,
XLogRecPtr replaying_lsn);
/*
* Tell the prefetching module that we are now replaying a given LSN, so that
* it can decide how far ahead to read in the WAL, if configured. Return
* true if more data is needed by the reader.
*/
static inline bool
XLogPrefetch(XLogPrefetchState *state, XLogRecPtr replaying_lsn)
{
/*
* Handle any configuration changes. Rather than trying to deal with
* various parameter changes, we just tear down and set up a new
* prefetcher if anything we depend on changes.
*/
if (unlikely(state->reconfigure_count != XLogPrefetchReconfigureCount))
{
/* If we had a prefetcher, tear it down. */
if (state->prefetcher)
{
XLogPrefetcherFree(state->prefetcher);
state->prefetcher = NULL;
}
/* If we want a prefetcher, set it up. */
if (recovery_prefetch)
state->prefetcher = XLogPrefetcherAllocate(state->reader);
state->reconfigure_count = XLogPrefetchReconfigureCount;
}
if (state->prefetcher)
return XLogPrefetcherReadAhead(state->prefetcher, replaying_lsn);
return false;
}
#endif
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