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
18typedef struct PgHdr PgHdr;
19typedef struct PCache PCache;
20
21/*
22** Every page in the cache is controlled by an instance of the following
23** structure.
24*/
25struct PgHdr {
26 sqlite3_pcache_page *pPage; /* Pcache object page handle */
27 void *pData; /* Page data */
28 void *pExtra; /* Extra content */
29 PCache *pCache; /* PRIVATE: Cache that owns this page */
30 PgHdr *pDirty; /* Transient list of dirty sorted by pgno */
31 Pager *pPager; /* The pager this page is part of */
32 Pgno pgno; /* Page number for this page */
33#ifdef SQLITE_CHECK_PAGES
34 u32 pageHash; /* Hash of page content */
35#endif
36 u16 flags; /* PGHDR flags defined below */
37
38 /**********************************************************************
39 ** Elements above, except pCache, are public. All that follow are
40 ** private to pcache.c and should not be accessed by other modules.
41 ** pCache is grouped with the public elements for efficiency.
42 */
43 i16 nRef; /* Number of users of this page */
44 PgHdr *pDirtyNext; /* Next element in list of dirty pages */
45 PgHdr *pDirtyPrev; /* Previous element in list of dirty pages */
46 /* NB: pDirtyNext and pDirtyPrev are undefined if the
47 ** PgHdr object is not dirty */
48};
49
50/* Bit values for PgHdr.flags */
51#define PGHDR_CLEAN 0x001 /* Page not on the PCache.pDirty list */
52#define PGHDR_DIRTY 0x002 /* Page is on the PCache.pDirty list */
53#define PGHDR_WRITEABLE 0x004 /* Journaled and ready to modify */
54#define PGHDR_NEED_SYNC 0x008 /* Fsync the rollback journal before
55 ** writing this page to the database */
56#define PGHDR_DONT_WRITE 0x010 /* Do not write content to disk */
57#define PGHDR_MMAP 0x020 /* This is an mmap page object */
58
59#define PGHDR_WAL_APPEND 0x040 /* Appended to wal file */
60
61/* Initialize and shutdown the page cache subsystem */
62int sqlite3PcacheInitialize(void);
63void sqlite3PcacheShutdown(void);
64
65/* Page cache buffer management:
66** These routines implement SQLITE_CONFIG_PAGECACHE.
67*/
68void sqlite3PCacheBufferSetup(void *, int sz, int n);
69
70/* Create a new pager cache.
71** Under memory stress, invoke xStress to try to make pages clean.
72** Only clean and unpinned pages can be reclaimed.
73*/
74int sqlite3PcacheOpen(
75 int szPage, /* Size of every page */
76 int szExtra, /* Extra space associated with each page */
77 int bPurgeable, /* True if pages are on backing store */
78 int (*xStress)(void*, PgHdr*), /* Call to try to make pages clean */
79 void *pStress, /* Argument to xStress */
80 PCache *pToInit /* Preallocated space for the PCache */
81);
82
83/* Modify the page-size after the cache has been created. */
84int sqlite3PcacheSetPageSize(PCache *, int);
85
86/* Return the size in bytes of a PCache object. Used to preallocate
87** storage space.
88*/
89int sqlite3PcacheSize(void);
90
91/* One release per successful fetch. Page is pinned until released.
92** Reference counted.
93*/
94sqlite3_pcache_page *sqlite3PcacheFetch(PCache*, Pgno, int createFlag);
95int sqlite3PcacheFetchStress(PCache*, Pgno, sqlite3_pcache_page**);
96PgHdr *sqlite3PcacheFetchFinish(PCache*, Pgno, sqlite3_pcache_page *pPage);
97void sqlite3PcacheRelease(PgHdr*);
98
99void sqlite3PcacheDrop(PgHdr*); /* Remove page from cache */
100void sqlite3PcacheMakeDirty(PgHdr*); /* Make sure page is marked dirty */
101void sqlite3PcacheMakeClean(PgHdr*); /* Mark a single page as clean */
102void sqlite3PcacheCleanAll(PCache*); /* Mark all dirty list pages as clean */
103void sqlite3PcacheClearWritable(PCache*);
104
105/* Change a page number. Used by incr-vacuum. */
106void sqlite3PcacheMove(PgHdr*, Pgno);
107
108/* Remove all pages with pgno>x. Reset the cache if x==0 */
109void sqlite3PcacheTruncate(PCache*, Pgno x);
110
111/* Get a list of all dirty pages in the cache, sorted by page number */
112PgHdr *sqlite3PcacheDirtyList(PCache*);
113
114/* Reset and close the cache object */
115void sqlite3PcacheClose(PCache*);
116
117/* Clear flags from pages of the page cache */
118void sqlite3PcacheClearSyncFlags(PCache *);
119
120/* Discard the contents of the cache */
121void sqlite3PcacheClear(PCache*);
122
123/* Return the total number of outstanding page references */
124int sqlite3PcacheRefCount(PCache*);
125
126/* Increment the reference count of an existing page */
127void sqlite3PcacheRef(PgHdr*);
128
129int sqlite3PcachePageRefcount(PgHdr*);
130
131/* Return the total number of pages stored in the cache */
132int sqlite3PcachePagecount(PCache*);
133
134#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)
135/* Iterate through all dirty pages currently stored in the cache. This
136** interface is only available if SQLITE_CHECK_PAGES is defined when the
137** library is built.
138*/
139void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *));
140#endif
141
142#if defined(SQLITE_DEBUG)
143/* Check invariants on a PgHdr object */
144int sqlite3PcachePageSanity(PgHdr*);
145#endif
146
147/* Set and get the suggested cache-size for the specified pager-cache.
148**
149** If no global maximum is configured, then the system attempts to limit
150** the total number of pages cached by purgeable pager-caches to the sum
151** of the suggested cache-sizes.
152*/
153void sqlite3PcacheSetCachesize(PCache *, int);
154#ifdef SQLITE_TEST
155int sqlite3PcacheGetCachesize(PCache *);
156#endif
157
158/* Set or get the suggested spill-size for the specified pager-cache.
159**
160** The spill-size is the minimum number of pages in cache before the cache
161** will attempt to spill dirty pages by calling xStress.
162*/
163int sqlite3PcacheSetSpillsize(PCache *, int);
164
165/* Free up as much memory as possible from the page cache */
166void sqlite3PcacheShrink(PCache*);
167
168#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
169/* Try to return memory used by the pcache module to the main memory heap */
170int sqlite3PcacheReleaseMemory(int);
171#endif
172
173#ifdef SQLITE_TEST
174void sqlite3PcacheStats(int*,int*,int*,int*);
175#endif
176
177void sqlite3PCacheSetDefault(void);
178
179/* Return the header size */
180int sqlite3HeaderSizePcache(void);
181int sqlite3HeaderSizePcache1(void);
182
183/* Number of dirty pages as a percentage of the configured cache size */
184int sqlite3PCachePercentDirty(PCache*);
185
186#ifdef SQLITE_DIRECT_OVERFLOW_READ
187int sqlite3PCacheIsDirty(PCache *pCache);
188#endif
189
190#endif /* _PCACHE_H_ */
191