bc59ac0e26
which are significantly faster overall and about 100 bytes smaller in size as well. FossilOrigin-Name: bdb6e4978d1a26d5f795262172605184264ede9c
164 lines
5.7 KiB
C
164 lines
5.7 KiB
C
/*
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** 2008 August 05
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This header file defines the interface that the sqlite page cache
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** subsystem.
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*/
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#ifndef _PCACHE_H_
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typedef struct PgHdr PgHdr;
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typedef struct PCache PCache;
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/*
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** Every page in the cache is controlled by an instance of the following
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** structure.
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*/
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struct PgHdr {
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sqlite3_pcache_page *pPage; /* Pcache object page handle */
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void *pData; /* Page data */
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void *pExtra; /* Extra content */
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PgHdr *pDirty; /* Transient list of dirty pages */
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Pager *pPager; /* The pager this page is part of */
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Pgno pgno; /* Page number for this page */
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#ifdef SQLITE_CHECK_PAGES
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u32 pageHash; /* Hash of page content */
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#endif
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u16 flags; /* PGHDR flags defined below */
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/**********************************************************************
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** Elements above are public. All that follows is private to pcache.c
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** and should not be accessed by other modules.
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*/
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i16 nRef; /* Number of users of this page */
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PCache *pCache; /* Cache that owns this page */
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PgHdr *pDirtyNext; /* Next element in list of dirty pages */
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PgHdr *pDirtyPrev; /* Previous element in list of dirty pages */
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};
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/* Bit values for PgHdr.flags */
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#define PGHDR_DIRTY 0x002 /* Page has changed */
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#define PGHDR_NEED_SYNC 0x004 /* Fsync the rollback journal before
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** writing this page to the database */
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#define PGHDR_NEED_READ 0x008 /* Content is unread */
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#define PGHDR_REUSE_UNLIKELY 0x010 /* A hint that reuse is unlikely */
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#define PGHDR_DONT_WRITE 0x020 /* Do not write content to disk */
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#define PGHDR_MMAP 0x040 /* This is an mmap page object */
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/* Initialize and shutdown the page cache subsystem */
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int sqlite3PcacheInitialize(void);
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void sqlite3PcacheShutdown(void);
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/* Page cache buffer management:
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** These routines implement SQLITE_CONFIG_PAGECACHE.
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*/
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void sqlite3PCacheBufferSetup(void *, int sz, int n);
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/* Create a new pager cache.
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** Under memory stress, invoke xStress to try to make pages clean.
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** Only clean and unpinned pages can be reclaimed.
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*/
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int sqlite3PcacheOpen(
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int szPage, /* Size of every page */
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int szExtra, /* Extra space associated with each page */
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int bPurgeable, /* True if pages are on backing store */
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int (*xStress)(void*, PgHdr*), /* Call to try to make pages clean */
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void *pStress, /* Argument to xStress */
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PCache *pToInit /* Preallocated space for the PCache */
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);
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/* Modify the page-size after the cache has been created. */
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int sqlite3PcacheSetPageSize(PCache *, int);
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/* Return the size in bytes of a PCache object. Used to preallocate
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** storage space.
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*/
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int sqlite3PcacheSize(void);
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/* One release per successful fetch. Page is pinned until released.
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** Reference counted.
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*/
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sqlite3_pcache_page *sqlite3PcacheFetch(PCache*, Pgno, int createFlag);
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int sqlite3PcacheFetchStress(PCache*, Pgno, sqlite3_pcache_page**);
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PgHdr *sqlite3PcacheFetchFinish(PCache*, Pgno, sqlite3_pcache_page *pPage);
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void sqlite3PcacheRelease(PgHdr*);
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void sqlite3PcacheDrop(PgHdr*); /* Remove page from cache */
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void sqlite3PcacheMakeDirty(PgHdr*); /* Make sure page is marked dirty */
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void sqlite3PcacheMakeClean(PgHdr*); /* Mark a single page as clean */
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void sqlite3PcacheCleanAll(PCache*); /* Mark all dirty list pages as clean */
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/* Change a page number. Used by incr-vacuum. */
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void sqlite3PcacheMove(PgHdr*, Pgno);
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/* Remove all pages with pgno>x. Reset the cache if x==0 */
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void sqlite3PcacheTruncate(PCache*, Pgno x);
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/* Get a list of all dirty pages in the cache, sorted by page number */
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PgHdr *sqlite3PcacheDirtyList(PCache*);
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/* Reset and close the cache object */
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void sqlite3PcacheClose(PCache*);
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/* Clear flags from pages of the page cache */
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void sqlite3PcacheClearSyncFlags(PCache *);
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/* Discard the contents of the cache */
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void sqlite3PcacheClear(PCache*);
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/* Return the total number of outstanding page references */
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int sqlite3PcacheRefCount(PCache*);
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/* Increment the reference count of an existing page */
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void sqlite3PcacheRef(PgHdr*);
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int sqlite3PcachePageRefcount(PgHdr*);
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/* Return the total number of pages stored in the cache */
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int sqlite3PcachePagecount(PCache*);
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#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)
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/* Iterate through all dirty pages currently stored in the cache. This
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** interface is only available if SQLITE_CHECK_PAGES is defined when the
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** library is built.
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*/
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void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *));
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#endif
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/* Set and get the suggested cache-size for the specified pager-cache.
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**
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** If no global maximum is configured, then the system attempts to limit
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** the total number of pages cached by purgeable pager-caches to the sum
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** of the suggested cache-sizes.
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*/
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void sqlite3PcacheSetCachesize(PCache *, int);
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#ifdef SQLITE_TEST
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int sqlite3PcacheGetCachesize(PCache *);
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#endif
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/* Free up as much memory as possible from the page cache */
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void sqlite3PcacheShrink(PCache*);
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#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
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/* Try to return memory used by the pcache module to the main memory heap */
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int sqlite3PcacheReleaseMemory(int);
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#endif
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#ifdef SQLITE_TEST
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void sqlite3PcacheStats(int*,int*,int*,int*);
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#endif
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void sqlite3PCacheSetDefault(void);
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#endif /* _PCACHE_H_ */
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