1 /* 2 ** 2008 August 05 3 ** 4 ** The author disclaims copyright to this source code. In place of 5 ** a legal notice, here is a blessing: 6 ** 7 ** May you do good and not evil. 8 ** May you find forgiveness for yourself and forgive others. 9 ** May you share freely, never taking more than you give. 10 ** 11 ************************************************************************* 12 ** This header file defines the interface that the sqlite page cache 13 ** subsystem. 14 */ 15 16 #ifndef _PCACHE_H_ 17 18 typedef struct PgHdr PgHdr; 19 typedef struct PCache PCache; 20 21 /* 22 ** Every page in the cache is controlled by an instance of the following 23 ** structure. 24 */ 25 struct PgHdr { 26 sqlite3_pcache_page *pPage; /* Pcache object page handle */ 27 void *pData; /* Page data */ 28 void *pExtra; /* Extra content */ 29 PgHdr *pDirty; /* Transient list of dirty pages */ 30 Pager *pPager; /* The pager this page is part of */ 31 Pgno pgno; /* Page number for this page */ 32 #ifdef SQLITE_CHECK_PAGES 33 u32 pageHash; /* Hash of page content */ 34 #endif 35 u16 flags; /* PGHDR flags defined below */ 36 37 /********************************************************************** 38 ** Elements above are public. All that follows is private to pcache.c 39 ** and should not be accessed by other modules. 40 */ 41 i16 nRef; /* Number of users of this page */ 42 PCache *pCache; /* Cache that owns this page */ 43 44 PgHdr *pDirtyNext; /* Next element in list of dirty pages */ 45 PgHdr *pDirtyPrev; /* Previous element in list of dirty pages */ 46 }; 47 48 /* Bit values for PgHdr.flags */ 49 #define PGHDR_CLEAN 0x001 /* Page not on the PCache.pDirty list */ 50 #define PGHDR_DIRTY 0x002 /* Page is on the PCache.pDirty list */ 51 #define PGHDR_WRITEABLE 0x004 /* Journaled and ready to modify */ 52 #define PGHDR_NEED_SYNC 0x008 /* Fsync the rollback journal before 53 ** writing this page to the database */ 54 #define PGHDR_NEED_READ 0x010 /* Content is unread */ 55 #define PGHDR_DONT_WRITE 0x020 /* Do not write content to disk */ 56 #define PGHDR_MMAP 0x040 /* This is an mmap page object */ 57 58 #define PGHDR_WAL_APPEND 0x080 /* Appended to wal file */ 59 60 /* Initialize and shutdown the page cache subsystem */ 61 int sqlite3PcacheInitialize(void); 62 void sqlite3PcacheShutdown(void); 63 64 /* Page cache buffer management: 65 ** These routines implement SQLITE_CONFIG_PAGECACHE. 66 */ 67 void sqlite3PCacheBufferSetup(void *, int sz, int n); 68 69 /* Create a new pager cache. 70 ** Under memory stress, invoke xStress to try to make pages clean. 71 ** Only clean and unpinned pages can be reclaimed. 72 */ 73 int sqlite3PcacheOpen( 74 int szPage, /* Size of every page */ 75 int szExtra, /* Extra space associated with each page */ 76 int bPurgeable, /* True if pages are on backing store */ 77 int (*xStress)(void*, PgHdr*), /* Call to try to make pages clean */ 78 void *pStress, /* Argument to xStress */ 79 PCache *pToInit /* Preallocated space for the PCache */ 80 ); 81 82 /* Modify the page-size after the cache has been created. */ 83 int sqlite3PcacheSetPageSize(PCache *, int); 84 85 /* Return the size in bytes of a PCache object. Used to preallocate 86 ** storage space. 87 */ 88 int sqlite3PcacheSize(void); 89 90 /* One release per successful fetch. Page is pinned until released. 91 ** Reference counted. 92 */ 93 sqlite3_pcache_page *sqlite3PcacheFetch(PCache*, Pgno, int createFlag); 94 int sqlite3PcacheFetchStress(PCache*, Pgno, sqlite3_pcache_page**); 95 PgHdr *sqlite3PcacheFetchFinish(PCache*, Pgno, sqlite3_pcache_page *pPage); 96 void sqlite3PcacheRelease(PgHdr*); 97 98 void sqlite3PcacheDrop(PgHdr*); /* Remove page from cache */ 99 void sqlite3PcacheMakeDirty(PgHdr*); /* Make sure page is marked dirty */ 100 void sqlite3PcacheMakeClean(PgHdr*); /* Mark a single page as clean */ 101 void sqlite3PcacheCleanAll(PCache*); /* Mark all dirty list pages as clean */ 102 103 /* Change a page number. Used by incr-vacuum. */ 104 void sqlite3PcacheMove(PgHdr*, Pgno); 105 106 /* Remove all pages with pgno>x. Reset the cache if x==0 */ 107 void sqlite3PcacheTruncate(PCache*, Pgno x); 108 109 /* Get a list of all dirty pages in the cache, sorted by page number */ 110 PgHdr *sqlite3PcacheDirtyList(PCache*); 111 112 /* Reset and close the cache object */ 113 void sqlite3PcacheClose(PCache*); 114 115 /* Clear flags from pages of the page cache */ 116 void sqlite3PcacheClearSyncFlags(PCache *); 117 118 /* Discard the contents of the cache */ 119 void sqlite3PcacheClear(PCache*); 120 121 /* Return the total number of outstanding page references */ 122 int sqlite3PcacheRefCount(PCache*); 123 124 /* Increment the reference count of an existing page */ 125 void sqlite3PcacheRef(PgHdr*); 126 127 int sqlite3PcachePageRefcount(PgHdr*); 128 129 /* Return the total number of pages stored in the cache */ 130 int sqlite3PcachePagecount(PCache*); 131 132 #if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG) 133 /* Iterate through all dirty pages currently stored in the cache. This 134 ** interface is only available if SQLITE_CHECK_PAGES is defined when the 135 ** library is built. 136 */ 137 void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)); 138 #endif 139 140 /* Set and get the suggested cache-size for the specified pager-cache. 141 ** 142 ** If no global maximum is configured, then the system attempts to limit 143 ** the total number of pages cached by purgeable pager-caches to the sum 144 ** of the suggested cache-sizes. 145 */ 146 void sqlite3PcacheSetCachesize(PCache *, int); 147 #ifdef SQLITE_TEST 148 int sqlite3PcacheGetCachesize(PCache *); 149 #endif 150 151 /* Set or get the suggested spill-size for the specified pager-cache. 152 ** 153 ** The spill-size is the minimum number of pages in cache before the cache 154 ** will attempt to spill dirty pages by calling xStress. 155 */ 156 int sqlite3PcacheSetSpillsize(PCache *, int); 157 158 /* Free up as much memory as possible from the page cache */ 159 void sqlite3PcacheShrink(PCache*); 160 161 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT 162 /* Try to return memory used by the pcache module to the main memory heap */ 163 int sqlite3PcacheReleaseMemory(int); 164 #endif 165 166 #ifdef SQLITE_TEST 167 void sqlite3PcacheStats(int*,int*,int*,int*); 168 #endif 169 170 void sqlite3PCacheSetDefault(void); 171 172 /* Return the header size */ 173 int sqlite3HeaderSizePcache(void); 174 int sqlite3HeaderSizePcache1(void); 175 176 #endif /* _PCACHE_H_ */ 177