2004-08-24 01:22:45 +02:00
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/*-------------------------------------------------------------------------
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2003-06-12 00:37:46 +02:00
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*
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2004-08-24 01:22:45 +02:00
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* slru.h
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* Simple LRU buffering for transaction status logfiles
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2003-06-12 00:37:46 +02:00
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*
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2004-08-29 06:13:13 +02:00
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* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
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2003-06-12 00:37:46 +02:00
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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2004-08-29 06:13:13 +02:00
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* $PostgreSQL: pgsql/src/include/access/slru.h,v 1.9 2004/08/29 04:13:03 momjian Exp $
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2004-08-24 01:22:45 +02:00
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*
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*-------------------------------------------------------------------------
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2003-06-12 00:37:46 +02:00
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*/
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#ifndef SLRU_H
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#define SLRU_H
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2004-05-31 05:48:10 +02:00
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#include "storage/lwlock.h"
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2003-06-12 00:37:46 +02:00
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2004-08-24 01:22:45 +02:00
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/*
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* Number of page buffers. Ideally this could be different for CLOG and
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* SUBTRANS, but the benefit doesn't seem to be worth any additional
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* notational cruft.
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*/
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#define NUM_SLRU_BUFFERS 8
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/* Page status codes */
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typedef enum
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{
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SLRU_PAGE_EMPTY, /* buffer is not in use */
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SLRU_PAGE_READ_IN_PROGRESS, /* page is being read in */
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SLRU_PAGE_CLEAN, /* page is valid and not dirty */
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SLRU_PAGE_DIRTY, /* page is valid but needs write */
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SLRU_PAGE_WRITE_IN_PROGRESS /* page is being written out */
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} SlruPageStatus;
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/*
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* Shared-memory state
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*/
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typedef struct SlruSharedData
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{
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LWLockId ControlLock;
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/*
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* Info for each buffer slot. Page number is undefined when status is
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* EMPTY. lru_count is essentially the number of page switches since
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* last use of this page; the page with highest lru_count is the best
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* candidate to replace.
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*/
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char *page_buffer[NUM_SLRU_BUFFERS];
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SlruPageStatus page_status[NUM_SLRU_BUFFERS];
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int page_number[NUM_SLRU_BUFFERS];
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unsigned int page_lru_count[NUM_SLRU_BUFFERS];
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LWLockId buffer_locks[NUM_SLRU_BUFFERS];
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/*
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* latest_page_number is the page number of the current end of the
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* log; this is not critical data, since we use it only to avoid
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* swapping out the latest page.
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*/
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int latest_page_number;
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} SlruSharedData;
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typedef SlruSharedData *SlruShared;
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2003-06-12 00:37:46 +02:00
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2004-05-28 07:13:32 +02:00
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/*
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* SlruCtlData is an unshared structure that points to the active information
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* in shared memory.
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*/
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2003-06-12 00:37:46 +02:00
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typedef struct SlruCtlData
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{
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2004-05-31 05:48:10 +02:00
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SlruShared shared;
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2004-05-28 07:13:32 +02:00
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/*
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2004-08-24 01:22:45 +02:00
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* This flag tells whether to fsync writes (true for pg_clog,
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* false for pg_subtrans).
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2004-05-28 07:13:32 +02:00
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*/
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2004-08-24 01:22:45 +02:00
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bool do_fsync;
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2003-08-04 02:43:34 +02:00
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2004-05-28 07:13:32 +02:00
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/*
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* Decide which of two page numbers is "older" for truncation purposes.
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* We need to use comparison of TransactionIds here in order to do the
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* right thing with wraparound XID arithmetic.
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*/
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2003-08-04 02:43:34 +02:00
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bool (*PagePrecedes) (int, int);
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2003-06-12 00:37:46 +02:00
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2004-08-24 01:22:45 +02:00
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/*
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* Dir is set during SimpleLruInit and does not change thereafter.
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* Since it's always the same, it doesn't need to be in shared memory.
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*/
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char Dir[MAXPGPATH];
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2003-08-08 23:42:59 +02:00
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} SlruCtlData;
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2004-05-31 05:48:10 +02:00
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2003-06-12 00:37:46 +02:00
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typedef SlruCtlData *SlruCtl;
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2004-08-24 01:22:45 +02:00
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/* Opaque struct known only in slru.c */
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typedef struct SlruFlushData *SlruFlush;
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2004-05-31 05:48:10 +02:00
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2003-06-12 00:37:46 +02:00
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extern int SimpleLruShmemSize(void);
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2004-08-24 01:22:45 +02:00
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extern void SimpleLruInit(SlruCtl ctl, const char *name,
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LWLockId ctllock, const char *subdir);
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2003-06-12 00:37:46 +02:00
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extern int SimpleLruZeroPage(SlruCtl ctl, int pageno);
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2004-08-24 01:22:45 +02:00
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extern int SimpleLruReadPage(SlruCtl ctl, int pageno, TransactionId xid);
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2004-05-31 05:48:10 +02:00
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extern void SimpleLruWritePage(SlruCtl ctl, int slotno, SlruFlush fdata);
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2003-06-12 00:37:46 +02:00
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extern void SimpleLruFlush(SlruCtl ctl, bool checkpoint);
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extern void SimpleLruTruncate(SlruCtl ctl, int cutoffPage);
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2004-08-24 01:22:45 +02:00
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extern bool SlruScanDirectory(SlruCtl ctl, int cutoffPage, bool doDeletions);
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2004-07-01 02:52:04 +02:00
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2003-06-12 00:37:46 +02:00
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#endif /* SLRU_H */
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