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| 1 /* | |
| 2 ** 2004 April 6 | |
| 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 file implements an external (disk-based) database using BTrees. | |
| 13 ** For a detailed discussion of BTrees, refer to | |
| 14 ** | |
| 15 ** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3: | |
| 16 ** "Sorting And Searching", pages 473-480. Addison-Wesley | |
| 17 ** Publishing Company, Reading, Massachusetts. | |
| 18 ** | |
| 19 ** The basic idea is that each page of the file contains N database | |
| 20 ** entries and N+1 pointers to subpages. | |
| 21 ** | |
| 22 ** ---------------------------------------------------------------- | |
| 23 ** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) | | |
| 24 ** ---------------------------------------------------------------- | |
| 25 ** | |
| 26 ** All of the keys on the page that Ptr(0) points to have values less | |
| 27 ** than Key(0). All of the keys on page Ptr(1) and its subpages have | |
| 28 ** values greater than Key(0) and less than Key(1). All of the keys | |
| 29 ** on Ptr(N) and its subpages have values greater than Key(N-1). And | |
| 30 ** so forth. | |
| 31 ** | |
| 32 ** Finding a particular key requires reading O(log(M)) pages from the | |
| 33 ** disk where M is the number of entries in the tree. | |
| 34 ** | |
| 35 ** In this implementation, a single file can hold one or more separate | |
| 36 ** BTrees. Each BTree is identified by the index of its root page. The | |
| 37 ** key and data for any entry are combined to form the "payload". A | |
| 38 ** fixed amount of payload can be carried directly on the database | |
| 39 ** page. If the payload is larger than the preset amount then surplus | |
| 40 ** bytes are stored on overflow pages. The payload for an entry | |
| 41 ** and the preceding pointer are combined to form a "Cell". Each | |
| 42 ** page has a small header which contains the Ptr(N) pointer and other | |
| 43 ** information such as the size of key and data. | |
| 44 ** | |
| 45 ** FORMAT DETAILS | |
| 46 ** | |
| 47 ** The file is divided into pages. The first page is called page 1, | |
| 48 ** the second is page 2, and so forth. A page number of zero indicates | |
| 49 ** "no such page". The page size can be any power of 2 between 512 and 65536. | |
| 50 ** Each page can be either a btree page, a freelist page, an overflow | |
| 51 ** page, or a pointer-map page. | |
| 52 ** | |
| 53 ** The first page is always a btree page. The first 100 bytes of the first | |
| 54 ** page contain a special header (the "file header") that describes the file. | |
| 55 ** The format of the file header is as follows: | |
| 56 ** | |
| 57 ** OFFSET SIZE DESCRIPTION | |
| 58 ** 0 16 Header string: "SQLite format 3\000" | |
| 59 ** 16 2 Page size in bytes. (1 means 65536) | |
| 60 ** 18 1 File format write version | |
| 61 ** 19 1 File format read version | |
| 62 ** 20 1 Bytes of unused space at the end of each page | |
| 63 ** 21 1 Max embedded payload fraction (must be 64) | |
| 64 ** 22 1 Min embedded payload fraction (must be 32) | |
| 65 ** 23 1 Min leaf payload fraction (must be 32) | |
| 66 ** 24 4 File change counter | |
| 67 ** 28 4 Reserved for future use | |
| 68 ** 32 4 First freelist page | |
| 69 ** 36 4 Number of freelist pages in the file | |
| 70 ** 40 60 15 4-byte meta values passed to higher layers | |
| 71 ** | |
| 72 ** 40 4 Schema cookie | |
| 73 ** 44 4 File format of schema layer | |
| 74 ** 48 4 Size of page cache | |
| 75 ** 52 4 Largest root-page (auto/incr_vacuum) | |
| 76 ** 56 4 1=UTF-8 2=UTF16le 3=UTF16be | |
| 77 ** 60 4 User version | |
| 78 ** 64 4 Incremental vacuum mode | |
| 79 ** 68 4 Application-ID | |
| 80 ** 72 20 unused | |
| 81 ** 92 4 The version-valid-for number | |
| 82 ** 96 4 SQLITE_VERSION_NUMBER | |
| 83 ** | |
| 84 ** All of the integer values are big-endian (most significant byte first). | |
| 85 ** | |
| 86 ** The file change counter is incremented when the database is changed | |
| 87 ** This counter allows other processes to know when the file has changed | |
| 88 ** and thus when they need to flush their cache. | |
| 89 ** | |
| 90 ** The max embedded payload fraction is the amount of the total usable | |
| 91 ** space in a page that can be consumed by a single cell for standard | |
| 92 ** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default | |
| 93 ** is to limit the maximum cell size so that at least 4 cells will fit | |
| 94 ** on one page. Thus the default max embedded payload fraction is 64. | |
| 95 ** | |
| 96 ** If the payload for a cell is larger than the max payload, then extra | |
| 97 ** payload is spilled to overflow pages. Once an overflow page is allocated, | |
| 98 ** as many bytes as possible are moved into the overflow pages without letting | |
| 99 ** the cell size drop below the min embedded payload fraction. | |
| 100 ** | |
| 101 ** The min leaf payload fraction is like the min embedded payload fraction | |
| 102 ** except that it applies to leaf nodes in a LEAFDATA tree. The maximum | |
| 103 ** payload fraction for a LEAFDATA tree is always 100% (or 255) and it | |
| 104 ** not specified in the header. | |
| 105 ** | |
| 106 ** Each btree pages is divided into three sections: The header, the | |
| 107 ** cell pointer array, and the cell content area. Page 1 also has a 100-byte | |
| 108 ** file header that occurs before the page header. | |
| 109 ** | |
| 110 ** |----------------| | |
| 111 ** | file header | 100 bytes. Page 1 only. | |
| 112 ** |----------------| | |
| 113 ** | page header | 8 bytes for leaves. 12 bytes for interior nodes | |
| 114 ** |----------------| | |
| 115 ** | cell pointer | | 2 bytes per cell. Sorted order. | |
| 116 ** | array | | Grows downward | |
| 117 ** | | v | |
| 118 ** |----------------| | |
| 119 ** | unallocated | | |
| 120 ** | space | | |
| 121 ** |----------------| ^ Grows upwards | |
| 122 ** | cell content | | Arbitrary order interspersed with freeblocks. | |
| 123 ** | area | | and free space fragments. | |
| 124 ** |----------------| | |
| 125 ** | |
| 126 ** The page headers looks like this: | |
| 127 ** | |
| 128 ** OFFSET SIZE DESCRIPTION | |
| 129 ** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf | |
| 130 ** 1 2 byte offset to the first freeblock | |
| 131 ** 3 2 number of cells on this page | |
| 132 ** 5 2 first byte of the cell content area | |
| 133 ** 7 1 number of fragmented free bytes | |
| 134 ** 8 4 Right child (the Ptr(N) value). Omitted on leaves. | |
| 135 ** | |
| 136 ** The flags define the format of this btree page. The leaf flag means that | |
| 137 ** this page has no children. The zerodata flag means that this page carries | |
| 138 ** only keys and no data. The intkey flag means that the key is an integer | |
| 139 ** which is stored in the key size entry of the cell header rather than in | |
| 140 ** the payload area. | |
| 141 ** | |
| 142 ** The cell pointer array begins on the first byte after the page header. | |
| 143 ** The cell pointer array contains zero or more 2-byte numbers which are | |
| 144 ** offsets from the beginning of the page to the cell content in the cell | |
| 145 ** content area. The cell pointers occur in sorted order. The system strives | |
| 146 ** to keep free space after the last cell pointer so that new cells can | |
| 147 ** be easily added without having to defragment the page. | |
| 148 ** | |
| 149 ** Cell content is stored at the very end of the page and grows toward the | |
| 150 ** beginning of the page. | |
| 151 ** | |
| 152 ** Unused space within the cell content area is collected into a linked list of | |
| 153 ** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset | |
| 154 ** to the first freeblock is given in the header. Freeblocks occur in | |
| 155 ** increasing order. Because a freeblock must be at least 4 bytes in size, | |
| 156 ** any group of 3 or fewer unused bytes in the cell content area cannot | |
| 157 ** exist on the freeblock chain. A group of 3 or fewer free bytes is called | |
| 158 ** a fragment. The total number of bytes in all fragments is recorded. | |
| 159 ** in the page header at offset 7. | |
| 160 ** | |
| 161 ** SIZE DESCRIPTION | |
| 162 ** 2 Byte offset of the next freeblock | |
| 163 ** 2 Bytes in this freeblock | |
| 164 ** | |
| 165 ** Cells are of variable length. Cells are stored in the cell content area at | |
| 166 ** the end of the page. Pointers to the cells are in the cell pointer array | |
| 167 ** that immediately follows the page header. Cells is not necessarily | |
| 168 ** contiguous or in order, but cell pointers are contiguous and in order. | |
| 169 ** | |
| 170 ** Cell content makes use of variable length integers. A variable | |
| 171 ** length integer is 1 to 9 bytes where the lower 7 bits of each | |
| 172 ** byte are used. The integer consists of all bytes that have bit 8 set and | |
| 173 ** the first byte with bit 8 clear. The most significant byte of the integer | |
| 174 ** appears first. A variable-length integer may not be more than 9 bytes long. | |
| 175 ** As a special case, all 8 bytes of the 9th byte are used as data. This | |
| 176 ** allows a 64-bit integer to be encoded in 9 bytes. | |
| 177 ** | |
| 178 ** 0x00 becomes 0x00000000 | |
| 179 ** 0x7f becomes 0x0000007f | |
| 180 ** 0x81 0x00 becomes 0x00000080 | |
| 181 ** 0x82 0x00 becomes 0x00000100 | |
| 182 ** 0x80 0x7f becomes 0x0000007f | |
| 183 ** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678 | |
| 184 ** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081 | |
| 185 ** | |
| 186 ** Variable length integers are used for rowids and to hold the number of | |
| 187 ** bytes of key and data in a btree cell. | |
| 188 ** | |
| 189 ** The content of a cell looks like this: | |
| 190 ** | |
| 191 ** SIZE DESCRIPTION | |
| 192 ** 4 Page number of the left child. Omitted if leaf flag is set. | |
| 193 ** var Number of bytes of data. Omitted if the zerodata flag is set. | |
| 194 ** var Number of bytes of key. Or the key itself if intkey flag is set. | |
| 195 ** * Payload | |
| 196 ** 4 First page of the overflow chain. Omitted if no overflow | |
| 197 ** | |
| 198 ** Overflow pages form a linked list. Each page except the last is completely | |
| 199 ** filled with data (pagesize - 4 bytes). The last page can have as little | |
| 200 ** as 1 byte of data. | |
| 201 ** | |
| 202 ** SIZE DESCRIPTION | |
| 203 ** 4 Page number of next overflow page | |
| 204 ** * Data | |
| 205 ** | |
| 206 ** Freelist pages come in two subtypes: trunk pages and leaf pages. The | |
| 207 ** file header points to the first in a linked list of trunk page. Each trunk | |
| 208 ** page points to multiple leaf pages. The content of a leaf page is | |
| 209 ** unspecified. A trunk page looks like this: | |
| 210 ** | |
| 211 ** SIZE DESCRIPTION | |
| 212 ** 4 Page number of next trunk page | |
| 213 ** 4 Number of leaf pointers on this page | |
| 214 ** * zero or more pages numbers of leaves | |
| 215 */ | |
| 216 #include "sqliteInt.h" | |
| 217 | |
| 218 | |
| 219 /* The following value is the maximum cell size assuming a maximum page | |
| 220 ** size give above. | |
| 221 */ | |
| 222 #define MX_CELL_SIZE(pBt) ((int)(pBt->pageSize-8)) | |
| 223 | |
| 224 /* The maximum number of cells on a single page of the database. This | |
| 225 ** assumes a minimum cell size of 6 bytes (4 bytes for the cell itself | |
| 226 ** plus 2 bytes for the index to the cell in the page header). Such | |
| 227 ** small cells will be rare, but they are possible. | |
| 228 */ | |
| 229 #define MX_CELL(pBt) ((pBt->pageSize-8)/6) | |
| 230 | |
| 231 /* Forward declarations */ | |
| 232 typedef struct MemPage MemPage; | |
| 233 typedef struct BtLock BtLock; | |
| 234 | |
| 235 /* | |
| 236 ** This is a magic string that appears at the beginning of every | |
| 237 ** SQLite database in order to identify the file as a real database. | |
| 238 ** | |
| 239 ** You can change this value at compile-time by specifying a | |
| 240 ** -DSQLITE_FILE_HEADER="..." on the compiler command-line. The | |
| 241 ** header must be exactly 16 bytes including the zero-terminator so | |
| 242 ** the string itself should be 15 characters long. If you change | |
| 243 ** the header, then your custom library will not be able to read | |
| 244 ** databases generated by the standard tools and the standard tools | |
| 245 ** will not be able to read databases created by your custom library. | |
| 246 */ | |
| 247 #ifndef SQLITE_FILE_HEADER /* 123456789 123456 */ | |
| 248 # define SQLITE_FILE_HEADER "SQLite format 3" | |
| 249 #endif | |
| 250 | |
| 251 /* | |
| 252 ** Page type flags. An ORed combination of these flags appear as the | |
| 253 ** first byte of on-disk image of every BTree page. | |
| 254 */ | |
| 255 #define PTF_INTKEY 0x01 | |
| 256 #define PTF_ZERODATA 0x02 | |
| 257 #define PTF_LEAFDATA 0x04 | |
| 258 #define PTF_LEAF 0x08 | |
| 259 | |
| 260 /* | |
| 261 ** As each page of the file is loaded into memory, an instance of the following | |
| 262 ** structure is appended and initialized to zero. This structure stores | |
| 263 ** information about the page that is decoded from the raw file page. | |
| 264 ** | |
| 265 ** The pParent field points back to the parent page. This allows us to | |
| 266 ** walk up the BTree from any leaf to the root. Care must be taken to | |
| 267 ** unref() the parent page pointer when this page is no longer referenced. | |
| 268 ** The pageDestructor() routine handles that chore. | |
| 269 ** | |
| 270 ** Access to all fields of this structure is controlled by the mutex | |
| 271 ** stored in MemPage.pBt->mutex. | |
| 272 */ | |
| 273 struct MemPage { | |
| 274 u8 isInit; /* True if previously initialized. MUST BE FIRST! */ | |
| 275 u8 nOverflow; /* Number of overflow cell bodies in aCell[] */ | |
| 276 u8 intKey; /* True if table b-trees. False for index b-trees */ | |
| 277 u8 intKeyLeaf; /* True if the leaf of an intKey table */ | |
| 278 u8 noPayload; /* True if internal intKey page (thus w/o data) */ | |
| 279 u8 leaf; /* True if a leaf page */ | |
| 280 u8 hdrOffset; /* 100 for page 1. 0 otherwise */ | |
| 281 u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */ | |
| 282 u8 max1bytePayload; /* min(maxLocal,127) */ | |
| 283 u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */ | |
| 284 u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */ | |
| 285 u16 cellOffset; /* Index in aData of first cell pointer */ | |
| 286 u16 nFree; /* Number of free bytes on the page */ | |
| 287 u16 nCell; /* Number of cells on this page, local and ovfl */ | |
| 288 u16 maskPage; /* Mask for page offset */ | |
| 289 u16 aiOvfl[5]; /* Insert the i-th overflow cell before the aiOvfl-th | |
| 290 ** non-overflow cell */ | |
| 291 u8 *apOvfl[5]; /* Pointers to the body of overflow cells */ | |
| 292 BtShared *pBt; /* Pointer to BtShared that this page is part of */ | |
| 293 u8 *aData; /* Pointer to disk image of the page data */ | |
| 294 u8 *aDataEnd; /* One byte past the end of usable data */ | |
| 295 u8 *aCellIdx; /* The cell index area */ | |
| 296 DbPage *pDbPage; /* Pager page handle */ | |
| 297 Pgno pgno; /* Page number for this page */ | |
| 298 }; | |
| 299 | |
| 300 /* | |
| 301 ** The in-memory image of a disk page has the auxiliary information appended | |
| 302 ** to the end. EXTRA_SIZE is the number of bytes of space needed to hold | |
| 303 ** that extra information. | |
| 304 */ | |
| 305 #define EXTRA_SIZE sizeof(MemPage) | |
| 306 | |
| 307 /* | |
| 308 ** A linked list of the following structures is stored at BtShared.pLock. | |
| 309 ** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor | |
| 310 ** is opened on the table with root page BtShared.iTable. Locks are removed | |
| 311 ** from this list when a transaction is committed or rolled back, or when | |
| 312 ** a btree handle is closed. | |
| 313 */ | |
| 314 struct BtLock { | |
| 315 Btree *pBtree; /* Btree handle holding this lock */ | |
| 316 Pgno iTable; /* Root page of table */ | |
| 317 u8 eLock; /* READ_LOCK or WRITE_LOCK */ | |
| 318 BtLock *pNext; /* Next in BtShared.pLock list */ | |
| 319 }; | |
| 320 | |
| 321 /* Candidate values for BtLock.eLock */ | |
| 322 #define READ_LOCK 1 | |
| 323 #define WRITE_LOCK 2 | |
| 324 | |
| 325 /* A Btree handle | |
| 326 ** | |
| 327 ** A database connection contains a pointer to an instance of | |
| 328 ** this object for every database file that it has open. This structure | |
| 329 ** is opaque to the database connection. The database connection cannot | |
| 330 ** see the internals of this structure and only deals with pointers to | |
| 331 ** this structure. | |
| 332 ** | |
| 333 ** For some database files, the same underlying database cache might be | |
| 334 ** shared between multiple connections. In that case, each connection | |
| 335 ** has it own instance of this object. But each instance of this object | |
| 336 ** points to the same BtShared object. The database cache and the | |
| 337 ** schema associated with the database file are all contained within | |
| 338 ** the BtShared object. | |
| 339 ** | |
| 340 ** All fields in this structure are accessed under sqlite3.mutex. | |
| 341 ** The pBt pointer itself may not be changed while there exists cursors | |
| 342 ** in the referenced BtShared that point back to this Btree since those | |
| 343 ** cursors have to go through this Btree to find their BtShared and | |
| 344 ** they often do so without holding sqlite3.mutex. | |
| 345 */ | |
| 346 struct Btree { | |
| 347 sqlite3 *db; /* The database connection holding this btree */ | |
| 348 BtShared *pBt; /* Sharable content of this btree */ | |
| 349 u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */ | |
| 350 u8 sharable; /* True if we can share pBt with another db */ | |
| 351 u8 locked; /* True if db currently has pBt locked */ | |
| 352 int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */ | |
| 353 int nBackup; /* Number of backup operations reading this btree */ | |
| 354 Btree *pNext; /* List of other sharable Btrees from the same db */ | |
| 355 Btree *pPrev; /* Back pointer of the same list */ | |
| 356 #ifndef SQLITE_OMIT_SHARED_CACHE | |
| 357 BtLock lock; /* Object used to lock page 1 */ | |
| 358 #endif | |
| 359 }; | |
| 360 | |
| 361 /* | |
| 362 ** Btree.inTrans may take one of the following values. | |
| 363 ** | |
| 364 ** If the shared-data extension is enabled, there may be multiple users | |
| 365 ** of the Btree structure. At most one of these may open a write transaction, | |
| 366 ** but any number may have active read transactions. | |
| 367 */ | |
| 368 #define TRANS_NONE 0 | |
| 369 #define TRANS_READ 1 | |
| 370 #define TRANS_WRITE 2 | |
| 371 | |
| 372 /* | |
| 373 ** An instance of this object represents a single database file. | |
| 374 ** | |
| 375 ** A single database file can be in use at the same time by two | |
| 376 ** or more database connections. When two or more connections are | |
| 377 ** sharing the same database file, each connection has it own | |
| 378 ** private Btree object for the file and each of those Btrees points | |
| 379 ** to this one BtShared object. BtShared.nRef is the number of | |
| 380 ** connections currently sharing this database file. | |
| 381 ** | |
| 382 ** Fields in this structure are accessed under the BtShared.mutex | |
| 383 ** mutex, except for nRef and pNext which are accessed under the | |
| 384 ** global SQLITE_MUTEX_STATIC_MASTER mutex. The pPager field | |
| 385 ** may not be modified once it is initially set as long as nRef>0. | |
| 386 ** The pSchema field may be set once under BtShared.mutex and | |
| 387 ** thereafter is unchanged as long as nRef>0. | |
| 388 ** | |
| 389 ** isPending: | |
| 390 ** | |
| 391 ** If a BtShared client fails to obtain a write-lock on a database | |
| 392 ** table (because there exists one or more read-locks on the table), | |
| 393 ** the shared-cache enters 'pending-lock' state and isPending is | |
| 394 ** set to true. | |
| 395 ** | |
| 396 ** The shared-cache leaves the 'pending lock' state when either of | |
| 397 ** the following occur: | |
| 398 ** | |
| 399 ** 1) The current writer (BtShared.pWriter) concludes its transaction, OR | |
| 400 ** 2) The number of locks held by other connections drops to zero. | |
| 401 ** | |
| 402 ** while in the 'pending-lock' state, no connection may start a new | |
| 403 ** transaction. | |
| 404 ** | |
| 405 ** This feature is included to help prevent writer-starvation. | |
| 406 */ | |
| 407 struct BtShared { | |
| 408 Pager *pPager; /* The page cache */ | |
| 409 sqlite3 *db; /* Database connection currently using this Btree */ | |
| 410 BtCursor *pCursor; /* A list of all open cursors */ | |
| 411 MemPage *pPage1; /* First page of the database */ | |
| 412 u8 openFlags; /* Flags to sqlite3BtreeOpen() */ | |
| 413 #ifndef SQLITE_OMIT_AUTOVACUUM | |
| 414 u8 autoVacuum; /* True if auto-vacuum is enabled */ | |
| 415 u8 incrVacuum; /* True if incr-vacuum is enabled */ | |
| 416 u8 bDoTruncate; /* True to truncate db on commit */ | |
| 417 #endif | |
| 418 u8 inTransaction; /* Transaction state */ | |
| 419 u8 max1bytePayload; /* Maximum first byte of cell for a 1-byte payload */ | |
| 420 u16 btsFlags; /* Boolean parameters. See BTS_* macros below */ | |
| 421 u16 maxLocal; /* Maximum local payload in non-LEAFDATA tables */ | |
| 422 u16 minLocal; /* Minimum local payload in non-LEAFDATA tables */ | |
| 423 u16 maxLeaf; /* Maximum local payload in a LEAFDATA table */ | |
| 424 u16 minLeaf; /* Minimum local payload in a LEAFDATA table */ | |
| 425 u32 pageSize; /* Total number of bytes on a page */ | |
| 426 u32 usableSize; /* Number of usable bytes on each page */ | |
| 427 int nTransaction; /* Number of open transactions (read + write) */ | |
| 428 u32 nPage; /* Number of pages in the database */ | |
| 429 void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */ | |
| 430 void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */ | |
| 431 sqlite3_mutex *mutex; /* Non-recursive mutex required to access this object */ | |
| 432 Bitvec *pHasContent; /* Set of pages moved to free-list this transaction */ | |
| 433 #ifndef SQLITE_OMIT_SHARED_CACHE | |
| 434 int nRef; /* Number of references to this structure */ | |
| 435 BtShared *pNext; /* Next on a list of sharable BtShared structs */ | |
| 436 BtLock *pLock; /* List of locks held on this shared-btree struct */ | |
| 437 Btree *pWriter; /* Btree with currently open write transaction */ | |
| 438 #endif | |
| 439 u8 *pTmpSpace; /* Temp space sufficient to hold a single cell */ | |
| 440 }; | |
| 441 | |
| 442 /* | |
| 443 ** Allowed values for BtShared.btsFlags | |
| 444 */ | |
| 445 #define BTS_READ_ONLY 0x0001 /* Underlying file is readonly */ | |
| 446 #define BTS_PAGESIZE_FIXED 0x0002 /* Page size can no longer be changed */ | |
| 447 #define BTS_SECURE_DELETE 0x0004 /* PRAGMA secure_delete is enabled */ | |
| 448 #define BTS_INITIALLY_EMPTY 0x0008 /* Database was empty at trans start */ | |
| 449 #define BTS_NO_WAL 0x0010 /* Do not open write-ahead-log files */ | |
| 450 #define BTS_EXCLUSIVE 0x0020 /* pWriter has an exclusive lock */ | |
| 451 #define BTS_PENDING 0x0040 /* Waiting for read-locks to clear */ | |
| 452 | |
| 453 /* | |
| 454 ** An instance of the following structure is used to hold information | |
| 455 ** about a cell. The parseCellPtr() function fills in this structure | |
| 456 ** based on information extract from the raw disk page. | |
| 457 */ | |
| 458 typedef struct CellInfo CellInfo; | |
| 459 struct CellInfo { | |
| 460 i64 nKey; /* The key for INTKEY tables, or nPayload otherwise */ | |
| 461 u8 *pPayload; /* Pointer to the start of payload */ | |
| 462 u32 nPayload; /* Bytes of payload */ | |
| 463 u16 nLocal; /* Amount of payload held locally, not on overflow */ | |
| 464 u16 iOverflow; /* Offset to overflow page number. Zero if no overflow */ | |
| 465 u16 nSize; /* Size of the cell content on the main b-tree page */ | |
| 466 }; | |
| 467 | |
| 468 /* | |
| 469 ** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than | |
| 470 ** this will be declared corrupt. This value is calculated based on a | |
| 471 ** maximum database size of 2^31 pages a minimum fanout of 2 for a | |
| 472 ** root-node and 3 for all other internal nodes. | |
| 473 ** | |
| 474 ** If a tree that appears to be taller than this is encountered, it is | |
| 475 ** assumed that the database is corrupt. | |
| 476 */ | |
| 477 #define BTCURSOR_MAX_DEPTH 20 | |
| 478 | |
| 479 /* | |
| 480 ** A cursor is a pointer to a particular entry within a particular | |
| 481 ** b-tree within a database file. | |
| 482 ** | |
| 483 ** The entry is identified by its MemPage and the index in | |
| 484 ** MemPage.aCell[] of the entry. | |
| 485 ** | |
| 486 ** A single database file can be shared by two more database connections, | |
| 487 ** but cursors cannot be shared. Each cursor is associated with a | |
| 488 ** particular database connection identified BtCursor.pBtree.db. | |
| 489 ** | |
| 490 ** Fields in this structure are accessed under the BtShared.mutex | |
| 491 ** found at self->pBt->mutex. | |
| 492 ** | |
| 493 ** skipNext meaning: | |
| 494 ** eState==SKIPNEXT && skipNext>0: Next sqlite3BtreeNext() is no-op. | |
| 495 ** eState==SKIPNEXT && skipNext<0: Next sqlite3BtreePrevious() is no-op. | |
| 496 ** eState==FAULT: Cursor fault with skipNext as error code. | |
| 497 */ | |
| 498 struct BtCursor { | |
| 499 Btree *pBtree; /* The Btree to which this cursor belongs */ | |
| 500 BtShared *pBt; /* The BtShared this cursor points to */ | |
| 501 BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */ | |
| 502 struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */ | |
| 503 Pgno *aOverflow; /* Cache of overflow page locations */ | |
| 504 CellInfo info; /* A parse of the cell we are pointing at */ | |
| 505 i64 nKey; /* Size of pKey, or last integer key */ | |
| 506 void *pKey; /* Saved key that was cursor last known position */ | |
| 507 Pgno pgnoRoot; /* The root page of this tree */ | |
| 508 int nOvflAlloc; /* Allocated size of aOverflow[] array */ | |
| 509 int skipNext; /* Prev() is noop if negative. Next() is noop if positive. | |
| 510 ** Error code if eState==CURSOR_FAULT */ | |
| 511 u8 curFlags; /* zero or more BTCF_* flags defined below */ | |
| 512 u8 eState; /* One of the CURSOR_XXX constants (see below) */ | |
| 513 u8 hints; /* As configured by CursorSetHints() */ | |
| 514 i16 iPage; /* Index of current page in apPage */ | |
| 515 u16 aiIdx[BTCURSOR_MAX_DEPTH]; /* Current index in apPage[i] */ | |
| 516 MemPage *apPage[BTCURSOR_MAX_DEPTH]; /* Pages from root to current page */ | |
| 517 }; | |
| 518 | |
| 519 /* | |
| 520 ** Legal values for BtCursor.curFlags | |
| 521 */ | |
| 522 #define BTCF_WriteFlag 0x01 /* True if a write cursor */ | |
| 523 #define BTCF_ValidNKey 0x02 /* True if info.nKey is valid */ | |
| 524 #define BTCF_ValidOvfl 0x04 /* True if aOverflow is valid */ | |
| 525 #define BTCF_AtLast 0x08 /* Cursor is pointing ot the last entry */ | |
| 526 #define BTCF_Incrblob 0x10 /* True if an incremental I/O handle */ | |
| 527 | |
| 528 /* | |
| 529 ** Potential values for BtCursor.eState. | |
| 530 ** | |
| 531 ** CURSOR_INVALID: | |
| 532 ** Cursor does not point to a valid entry. This can happen (for example) | |
| 533 ** because the table is empty or because BtreeCursorFirst() has not been | |
| 534 ** called. | |
| 535 ** | |
| 536 ** CURSOR_VALID: | |
| 537 ** Cursor points to a valid entry. getPayload() etc. may be called. | |
| 538 ** | |
| 539 ** CURSOR_SKIPNEXT: | |
| 540 ** Cursor is valid except that the Cursor.skipNext field is non-zero | |
| 541 ** indicating that the next sqlite3BtreeNext() or sqlite3BtreePrevious() | |
| 542 ** operation should be a no-op. | |
| 543 ** | |
| 544 ** CURSOR_REQUIRESEEK: | |
| 545 ** The table that this cursor was opened on still exists, but has been | |
| 546 ** modified since the cursor was last used. The cursor position is saved | |
| 547 ** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in | |
| 548 ** this state, restoreCursorPosition() can be called to attempt to | |
| 549 ** seek the cursor to the saved position. | |
| 550 ** | |
| 551 ** CURSOR_FAULT: | |
| 552 ** An unrecoverable error (an I/O error or a malloc failure) has occurred | |
| 553 ** on a different connection that shares the BtShared cache with this | |
| 554 ** cursor. The error has left the cache in an inconsistent state. | |
| 555 ** Do nothing else with this cursor. Any attempt to use the cursor | |
| 556 ** should return the error code stored in BtCursor.skipNext | |
| 557 */ | |
| 558 #define CURSOR_INVALID 0 | |
| 559 #define CURSOR_VALID 1 | |
| 560 #define CURSOR_SKIPNEXT 2 | |
| 561 #define CURSOR_REQUIRESEEK 3 | |
| 562 #define CURSOR_FAULT 4 | |
| 563 | |
| 564 /* | |
| 565 ** The database page the PENDING_BYTE occupies. This page is never used. | |
| 566 */ | |
| 567 # define PENDING_BYTE_PAGE(pBt) PAGER_MJ_PGNO(pBt) | |
| 568 | |
| 569 /* | |
| 570 ** These macros define the location of the pointer-map entry for a | |
| 571 ** database page. The first argument to each is the number of usable | |
| 572 ** bytes on each page of the database (often 1024). The second is the | |
| 573 ** page number to look up in the pointer map. | |
| 574 ** | |
| 575 ** PTRMAP_PAGENO returns the database page number of the pointer-map | |
| 576 ** page that stores the required pointer. PTRMAP_PTROFFSET returns | |
| 577 ** the offset of the requested map entry. | |
| 578 ** | |
| 579 ** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page, | |
| 580 ** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be | |
| 581 ** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements | |
| 582 ** this test. | |
| 583 */ | |
| 584 #define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno) | |
| 585 #define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1)) | |
| 586 #define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno)) | |
| 587 | |
| 588 /* | |
| 589 ** The pointer map is a lookup table that identifies the parent page for | |
| 590 ** each child page in the database file. The parent page is the page that | |
| 591 ** contains a pointer to the child. Every page in the database contains | |
| 592 ** 0 or 1 parent pages. (In this context 'database page' refers | |
| 593 ** to any page that is not part of the pointer map itself.) Each pointer map | |
| 594 ** entry consists of a single byte 'type' and a 4 byte parent page number. | |
| 595 ** The PTRMAP_XXX identifiers below are the valid types. | |
| 596 ** | |
| 597 ** The purpose of the pointer map is to facility moving pages from one | |
| 598 ** position in the file to another as part of autovacuum. When a page | |
| 599 ** is moved, the pointer in its parent must be updated to point to the | |
| 600 ** new location. The pointer map is used to locate the parent page quickly. | |
| 601 ** | |
| 602 ** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not | |
| 603 ** used in this case. | |
| 604 ** | |
| 605 ** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number | |
| 606 ** is not used in this case. | |
| 607 ** | |
| 608 ** PTRMAP_OVERFLOW1: The database page is the first page in a list of | |
| 609 ** overflow pages. The page number identifies the page that | |
| 610 ** contains the cell with a pointer to this overflow page. | |
| 611 ** | |
| 612 ** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of | |
| 613 ** overflow pages. The page-number identifies the previous | |
| 614 ** page in the overflow page list. | |
| 615 ** | |
| 616 ** PTRMAP_BTREE: The database page is a non-root btree page. The page number | |
| 617 ** identifies the parent page in the btree. | |
| 618 */ | |
| 619 #define PTRMAP_ROOTPAGE 1 | |
| 620 #define PTRMAP_FREEPAGE 2 | |
| 621 #define PTRMAP_OVERFLOW1 3 | |
| 622 #define PTRMAP_OVERFLOW2 4 | |
| 623 #define PTRMAP_BTREE 5 | |
| 624 | |
| 625 /* A bunch of assert() statements to check the transaction state variables | |
| 626 ** of handle p (type Btree*) are internally consistent. | |
| 627 */ | |
| 628 #define btreeIntegrity(p) \ | |
| 629 assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \ | |
| 630 assert( p->pBt->inTransaction>=p->inTrans ); | |
| 631 | |
| 632 | |
| 633 /* | |
| 634 ** The ISAUTOVACUUM macro is used within balance_nonroot() to determine | |
| 635 ** if the database supports auto-vacuum or not. Because it is used | |
| 636 ** within an expression that is an argument to another macro | |
| 637 ** (sqliteMallocRaw), it is not possible to use conditional compilation. | |
| 638 ** So, this macro is defined instead. | |
| 639 */ | |
| 640 #ifndef SQLITE_OMIT_AUTOVACUUM | |
| 641 #define ISAUTOVACUUM (pBt->autoVacuum) | |
| 642 #else | |
| 643 #define ISAUTOVACUUM 0 | |
| 644 #endif | |
| 645 | |
| 646 | |
| 647 /* | |
| 648 ** This structure is passed around through all the sanity checking routines | |
| 649 ** in order to keep track of some global state information. | |
| 650 ** | |
| 651 ** The aRef[] array is allocated so that there is 1 bit for each page in | |
| 652 ** the database. As the integrity-check proceeds, for each page used in | |
| 653 ** the database the corresponding bit is set. This allows integrity-check to | |
| 654 ** detect pages that are used twice and orphaned pages (both of which | |
| 655 ** indicate corruption). | |
| 656 */ | |
| 657 typedef struct IntegrityCk IntegrityCk; | |
| 658 struct IntegrityCk { | |
| 659 BtShared *pBt; /* The tree being checked out */ | |
| 660 Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */ | |
| 661 u8 *aPgRef; /* 1 bit per page in the db (see above) */ | |
| 662 Pgno nPage; /* Number of pages in the database */ | |
| 663 int mxErr; /* Stop accumulating errors when this reaches zero */ | |
| 664 int nErr; /* Number of messages written to zErrMsg so far */ | |
| 665 int mallocFailed; /* A memory allocation error has occurred */ | |
| 666 const char *zPfx; /* Error message prefix */ | |
| 667 int v1, v2; /* Values for up to two %d fields in zPfx */ | |
| 668 StrAccum errMsg; /* Accumulate the error message text here */ | |
| 669 }; | |
| 670 | |
| 671 /* | |
| 672 ** Routines to read or write a two- and four-byte big-endian integer values. | |
| 673 */ | |
| 674 #define get2byte(x) ((x)[0]<<8 | (x)[1]) | |
| 675 #define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v)) | |
| 676 #define get4byte sqlite3Get4byte | |
| 677 #define put4byte sqlite3Put4byte | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2363173002:
[sqlite] Remove obsolete reference version 3.8.7.4. (Closed)
