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| 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 file implements that page cache. | |
| 13 */ | |
| 14 #include "sqliteInt.h" | |
| 15 | |
| 16 /* | |
| 17 ** A complete page cache is an instance of this structure. | |
| 18 */ | |
| 19 struct PCache { | |
| 20 PgHdr *pDirty, *pDirtyTail; /* List of dirty pages in LRU order */ | |
| 21 PgHdr *pSynced; /* Last synced page in dirty page list */ | |
| 22 int nRef; /* Number of referenced pages */ | |
| 23 int szCache; /* Configured cache size */ | |
| 24 int szPage; /* Size of every page in this cache */ | |
| 25 int szExtra; /* Size of extra space for each page */ | |
| 26 u8 bPurgeable; /* True if pages are on backing store */ | |
| 27 u8 eCreate; /* eCreate value for for xFetch() */ | |
| 28 int (*xStress)(void*,PgHdr*); /* Call to try make a page clean */ | |
| 29 void *pStress; /* Argument to xStress */ | |
| 30 sqlite3_pcache *pCache; /* Pluggable cache module */ | |
| 31 PgHdr *pPage1; /* Reference to page 1 */ | |
| 32 }; | |
| 33 | |
| 34 /* | |
| 35 ** Some of the assert() macros in this code are too expensive to run | |
| 36 ** even during normal debugging. Use them only rarely on long-running | |
| 37 ** tests. Enable the expensive asserts using the | |
| 38 ** -DSQLITE_ENABLE_EXPENSIVE_ASSERT=1 compile-time option. | |
| 39 */ | |
| 40 #ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT | |
| 41 # define expensive_assert(X) assert(X) | |
| 42 #else | |
| 43 # define expensive_assert(X) | |
| 44 #endif | |
| 45 | |
| 46 /********************************** Linked List Management ********************/ | |
| 47 | |
| 48 /* Allowed values for second argument to pcacheManageDirtyList() */ | |
| 49 #define PCACHE_DIRTYLIST_REMOVE 1 /* Remove pPage from dirty list */ | |
| 50 #define PCACHE_DIRTYLIST_ADD 2 /* Add pPage to the dirty list */ | |
| 51 #define PCACHE_DIRTYLIST_FRONT 3 /* Move pPage to the front of the list */ | |
| 52 | |
| 53 /* | |
| 54 ** Manage pPage's participation on the dirty list. Bits of the addRemove | |
| 55 ** argument determines what operation to do. The 0x01 bit means first | |
| 56 ** remove pPage from the dirty list. The 0x02 means add pPage back to | |
| 57 ** the dirty list. Doing both moves pPage to the front of the dirty list. | |
| 58 */ | |
| 59 static void pcacheManageDirtyList(PgHdr *pPage, u8 addRemove){ | |
| 60 PCache *p = pPage->pCache; | |
| 61 | |
| 62 if( addRemove & PCACHE_DIRTYLIST_REMOVE ){ | |
| 63 assert( pPage->pDirtyNext || pPage==p->pDirtyTail ); | |
| 64 assert( pPage->pDirtyPrev || pPage==p->pDirty ); | |
| 65 | |
| 66 /* Update the PCache1.pSynced variable if necessary. */ | |
| 67 if( p->pSynced==pPage ){ | |
| 68 PgHdr *pSynced = pPage->pDirtyPrev; | |
| 69 while( pSynced && (pSynced->flags&PGHDR_NEED_SYNC) ){ | |
| 70 pSynced = pSynced->pDirtyPrev; | |
| 71 } | |
| 72 p->pSynced = pSynced; | |
| 73 } | |
| 74 | |
| 75 if( pPage->pDirtyNext ){ | |
| 76 pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev; | |
| 77 }else{ | |
| 78 assert( pPage==p->pDirtyTail ); | |
| 79 p->pDirtyTail = pPage->pDirtyPrev; | |
| 80 } | |
| 81 if( pPage->pDirtyPrev ){ | |
| 82 pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext; | |
| 83 }else{ | |
| 84 assert( pPage==p->pDirty ); | |
| 85 p->pDirty = pPage->pDirtyNext; | |
| 86 if( p->pDirty==0 && p->bPurgeable ){ | |
| 87 assert( p->eCreate==1 ); | |
| 88 p->eCreate = 2; | |
| 89 } | |
| 90 } | |
| 91 pPage->pDirtyNext = 0; | |
| 92 pPage->pDirtyPrev = 0; | |
| 93 } | |
| 94 if( addRemove & PCACHE_DIRTYLIST_ADD ){ | |
| 95 assert( pPage->pDirtyNext==0 && pPage->pDirtyPrev==0 && p->pDirty!=pPage ); | |
| 96 | |
| 97 pPage->pDirtyNext = p->pDirty; | |
| 98 if( pPage->pDirtyNext ){ | |
| 99 assert( pPage->pDirtyNext->pDirtyPrev==0 ); | |
| 100 pPage->pDirtyNext->pDirtyPrev = pPage; | |
| 101 }else{ | |
| 102 p->pDirtyTail = pPage; | |
| 103 if( p->bPurgeable ){ | |
| 104 assert( p->eCreate==2 ); | |
| 105 p->eCreate = 1; | |
| 106 } | |
| 107 } | |
| 108 p->pDirty = pPage; | |
| 109 if( !p->pSynced && 0==(pPage->flags&PGHDR_NEED_SYNC) ){ | |
| 110 p->pSynced = pPage; | |
| 111 } | |
| 112 } | |
| 113 } | |
| 114 | |
| 115 /* | |
| 116 ** Wrapper around the pluggable caches xUnpin method. If the cache is | |
| 117 ** being used for an in-memory database, this function is a no-op. | |
| 118 */ | |
| 119 static void pcacheUnpin(PgHdr *p){ | |
| 120 if( p->pCache->bPurgeable ){ | |
| 121 if( p->pgno==1 ){ | |
| 122 p->pCache->pPage1 = 0; | |
| 123 } | |
| 124 sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 0); | |
| 125 } | |
| 126 } | |
| 127 | |
| 128 /* | |
| 129 ** Compute the number of pages of cache requested. | |
| 130 */ | |
| 131 static int numberOfCachePages(PCache *p){ | |
| 132 if( p->szCache>=0 ){ | |
| 133 return p->szCache; | |
| 134 }else{ | |
| 135 return (int)((-1024*(i64)p->szCache)/(p->szPage+p->szExtra)); | |
| 136 } | |
| 137 } | |
| 138 | |
| 139 /*************************************************** General Interfaces ****** | |
| 140 ** | |
| 141 ** Initialize and shutdown the page cache subsystem. Neither of these | |
| 142 ** functions are threadsafe. | |
| 143 */ | |
| 144 int sqlite3PcacheInitialize(void){ | |
| 145 if( sqlite3GlobalConfig.pcache2.xInit==0 ){ | |
| 146 /* IMPLEMENTATION-OF: R-26801-64137 If the xInit() method is NULL, then the | |
| 147 ** built-in default page cache is used instead of the application defined | |
| 148 ** page cache. */ | |
| 149 sqlite3PCacheSetDefault(); | |
| 150 } | |
| 151 return sqlite3GlobalConfig.pcache2.xInit(sqlite3GlobalConfig.pcache2.pArg); | |
| 152 } | |
| 153 void sqlite3PcacheShutdown(void){ | |
| 154 if( sqlite3GlobalConfig.pcache2.xShutdown ){ | |
| 155 /* IMPLEMENTATION-OF: R-26000-56589 The xShutdown() method may be NULL. */ | |
| 156 sqlite3GlobalConfig.pcache2.xShutdown(sqlite3GlobalConfig.pcache2.pArg); | |
| 157 } | |
| 158 } | |
| 159 | |
| 160 /* | |
| 161 ** Return the size in bytes of a PCache object. | |
| 162 */ | |
| 163 int sqlite3PcacheSize(void){ return sizeof(PCache); } | |
| 164 | |
| 165 /* | |
| 166 ** Create a new PCache object. Storage space to hold the object | |
| 167 ** has already been allocated and is passed in as the p pointer. | |
| 168 ** The caller discovers how much space needs to be allocated by | |
| 169 ** calling sqlite3PcacheSize(). | |
| 170 */ | |
| 171 int sqlite3PcacheOpen( | |
| 172 int szPage, /* Size of every page */ | |
| 173 int szExtra, /* Extra space associated with each page */ | |
| 174 int bPurgeable, /* True if pages are on backing store */ | |
| 175 int (*xStress)(void*,PgHdr*),/* Call to try to make pages clean */ | |
| 176 void *pStress, /* Argument to xStress */ | |
| 177 PCache *p /* Preallocated space for the PCache */ | |
| 178 ){ | |
| 179 memset(p, 0, sizeof(PCache)); | |
| 180 p->szPage = 1; | |
| 181 p->szExtra = szExtra; | |
| 182 p->bPurgeable = bPurgeable; | |
| 183 p->eCreate = 2; | |
| 184 p->xStress = xStress; | |
| 185 p->pStress = pStress; | |
| 186 p->szCache = 100; | |
| 187 return sqlite3PcacheSetPageSize(p, szPage); | |
| 188 } | |
| 189 | |
| 190 /* | |
| 191 ** Change the page size for PCache object. The caller must ensure that there | |
| 192 ** are no outstanding page references when this function is called. | |
| 193 */ | |
| 194 int sqlite3PcacheSetPageSize(PCache *pCache, int szPage){ | |
| 195 assert( pCache->nRef==0 && pCache->pDirty==0 ); | |
| 196 if( pCache->szPage ){ | |
| 197 sqlite3_pcache *pNew; | |
| 198 pNew = sqlite3GlobalConfig.pcache2.xCreate( | |
| 199 szPage, pCache->szExtra + sizeof(PgHdr), pCache->bPurgeable | |
| 200 ); | |
| 201 if( pNew==0 ) return SQLITE_NOMEM; | |
| 202 sqlite3GlobalConfig.pcache2.xCachesize(pNew, numberOfCachePages(pCache)); | |
| 203 if( pCache->pCache ){ | |
| 204 sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache); | |
| 205 } | |
| 206 pCache->pCache = pNew; | |
| 207 pCache->pPage1 = 0; | |
| 208 pCache->szPage = szPage; | |
| 209 } | |
| 210 return SQLITE_OK; | |
| 211 } | |
| 212 | |
| 213 /* | |
| 214 ** Try to obtain a page from the cache. | |
| 215 ** | |
| 216 ** This routine returns a pointer to an sqlite3_pcache_page object if | |
| 217 ** such an object is already in cache, or if a new one is created. | |
| 218 ** This routine returns a NULL pointer if the object was not in cache | |
| 219 ** and could not be created. | |
| 220 ** | |
| 221 ** The createFlags should be 0 to check for existing pages and should | |
| 222 ** be 3 (not 1, but 3) to try to create a new page. | |
| 223 ** | |
| 224 ** If the createFlag is 0, then NULL is always returned if the page | |
| 225 ** is not already in the cache. If createFlag is 1, then a new page | |
| 226 ** is created only if that can be done without spilling dirty pages | |
| 227 ** and without exceeding the cache size limit. | |
| 228 ** | |
| 229 ** The caller needs to invoke sqlite3PcacheFetchFinish() to properly | |
| 230 ** initialize the sqlite3_pcache_page object and convert it into a | |
| 231 ** PgHdr object. The sqlite3PcacheFetch() and sqlite3PcacheFetchFinish() | |
| 232 ** routines are split this way for performance reasons. When separated | |
| 233 ** they can both (usually) operate without having to push values to | |
| 234 ** the stack on entry and pop them back off on exit, which saves a | |
| 235 ** lot of pushing and popping. | |
| 236 */ | |
| 237 sqlite3_pcache_page *sqlite3PcacheFetch( | |
| 238 PCache *pCache, /* Obtain the page from this cache */ | |
| 239 Pgno pgno, /* Page number to obtain */ | |
| 240 int createFlag /* If true, create page if it does not exist already */ | |
| 241 ){ | |
| 242 int eCreate; | |
| 243 | |
| 244 assert( pCache!=0 ); | |
| 245 assert( pCache->pCache!=0 ); | |
| 246 assert( createFlag==3 || createFlag==0 ); | |
| 247 assert( pgno>0 ); | |
| 248 | |
| 249 /* eCreate defines what to do if the page does not exist. | |
| 250 ** 0 Do not allocate a new page. (createFlag==0) | |
| 251 ** 1 Allocate a new page if doing so is inexpensive. | |
| 252 ** (createFlag==1 AND bPurgeable AND pDirty) | |
| 253 ** 2 Allocate a new page even it doing so is difficult. | |
| 254 ** (createFlag==1 AND !(bPurgeable AND pDirty) | |
| 255 */ | |
| 256 eCreate = createFlag & pCache->eCreate; | |
| 257 assert( eCreate==0 || eCreate==1 || eCreate==2 ); | |
| 258 assert( createFlag==0 || pCache->eCreate==eCreate ); | |
| 259 assert( createFlag==0 || eCreate==1+(!pCache->bPurgeable||!pCache->pDirty) ); | |
| 260 return sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate); | |
| 261 } | |
| 262 | |
| 263 /* | |
| 264 ** If the sqlite3PcacheFetch() routine is unable to allocate a new | |
| 265 ** page because new clean pages are available for reuse and the cache | |
| 266 ** size limit has been reached, then this routine can be invoked to | |
| 267 ** try harder to allocate a page. This routine might invoke the stress | |
| 268 ** callback to spill dirty pages to the journal. It will then try to | |
| 269 ** allocate the new page and will only fail to allocate a new page on | |
| 270 ** an OOM error. | |
| 271 ** | |
| 272 ** This routine should be invoked only after sqlite3PcacheFetch() fails. | |
| 273 */ | |
| 274 int sqlite3PcacheFetchStress( | |
| 275 PCache *pCache, /* Obtain the page from this cache */ | |
| 276 Pgno pgno, /* Page number to obtain */ | |
| 277 sqlite3_pcache_page **ppPage /* Write result here */ | |
| 278 ){ | |
| 279 PgHdr *pPg; | |
| 280 if( pCache->eCreate==2 ) return 0; | |
| 281 | |
| 282 | |
| 283 /* Find a dirty page to write-out and recycle. First try to find a | |
| 284 ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC | |
| 285 ** cleared), but if that is not possible settle for any other | |
| 286 ** unreferenced dirty page. | |
| 287 */ | |
| 288 for(pPg=pCache->pSynced; | |
| 289 pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); | |
| 290 pPg=pPg->pDirtyPrev | |
| 291 ); | |
| 292 pCache->pSynced = pPg; | |
| 293 if( !pPg ){ | |
| 294 for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev); | |
| 295 } | |
| 296 if( pPg ){ | |
| 297 int rc; | |
| 298 #ifdef SQLITE_LOG_CACHE_SPILL | |
| 299 sqlite3_log(SQLITE_FULL, | |
| 300 "spill page %d making room for %d - cache used: %d/%d", | |
| 301 pPg->pgno, pgno, | |
| 302 sqlite3GlobalConfig.pcache.xPagecount(pCache->pCache), | |
| 303 numberOfCachePages(pCache)); | |
| 304 #endif | |
| 305 rc = pCache->xStress(pCache->pStress, pPg); | |
| 306 if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){ | |
| 307 return rc; | |
| 308 } | |
| 309 } | |
| 310 *ppPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, 2); | |
| 311 return *ppPage==0 ? SQLITE_NOMEM : SQLITE_OK; | |
| 312 } | |
| 313 | |
| 314 /* | |
| 315 ** This is a helper routine for sqlite3PcacheFetchFinish() | |
| 316 ** | |
| 317 ** In the uncommon case where the page being fetched has not been | |
| 318 ** initialized, this routine is invoked to do the initialization. | |
| 319 ** This routine is broken out into a separate function since it | |
| 320 ** requires extra stack manipulation that can be avoided in the common | |
| 321 ** case. | |
| 322 */ | |
| 323 static SQLITE_NOINLINE PgHdr *pcacheFetchFinishWithInit( | |
| 324 PCache *pCache, /* Obtain the page from this cache */ | |
| 325 Pgno pgno, /* Page number obtained */ | |
| 326 sqlite3_pcache_page *pPage /* Page obtained by prior PcacheFetch() call */ | |
| 327 ){ | |
| 328 PgHdr *pPgHdr; | |
| 329 assert( pPage!=0 ); | |
| 330 pPgHdr = (PgHdr*)pPage->pExtra; | |
| 331 assert( pPgHdr->pPage==0 ); | |
| 332 memset(pPgHdr, 0, sizeof(PgHdr)); | |
| 333 pPgHdr->pPage = pPage; | |
| 334 pPgHdr->pData = pPage->pBuf; | |
| 335 pPgHdr->pExtra = (void *)&pPgHdr[1]; | |
| 336 memset(pPgHdr->pExtra, 0, pCache->szExtra); | |
| 337 pPgHdr->pCache = pCache; | |
| 338 pPgHdr->pgno = pgno; | |
| 339 return sqlite3PcacheFetchFinish(pCache,pgno,pPage); | |
| 340 } | |
| 341 | |
| 342 /* | |
| 343 ** This routine converts the sqlite3_pcache_page object returned by | |
| 344 ** sqlite3PcacheFetch() into an initialized PgHdr object. This routine | |
| 345 ** must be called after sqlite3PcacheFetch() in order to get a usable | |
| 346 ** result. | |
| 347 */ | |
| 348 PgHdr *sqlite3PcacheFetchFinish( | |
| 349 PCache *pCache, /* Obtain the page from this cache */ | |
| 350 Pgno pgno, /* Page number obtained */ | |
| 351 sqlite3_pcache_page *pPage /* Page obtained by prior PcacheFetch() call */ | |
| 352 ){ | |
| 353 PgHdr *pPgHdr; | |
| 354 | |
| 355 if( pPage==0 ) return 0; | |
| 356 pPgHdr = (PgHdr *)pPage->pExtra; | |
| 357 | |
| 358 if( !pPgHdr->pPage ){ | |
| 359 return pcacheFetchFinishWithInit(pCache, pgno, pPage); | |
| 360 } | |
| 361 if( 0==pPgHdr->nRef ){ | |
| 362 pCache->nRef++; | |
| 363 } | |
| 364 pPgHdr->nRef++; | |
| 365 if( pgno==1 ){ | |
| 366 pCache->pPage1 = pPgHdr; | |
| 367 } | |
| 368 return pPgHdr; | |
| 369 } | |
| 370 | |
| 371 /* | |
| 372 ** Decrement the reference count on a page. If the page is clean and the | |
| 373 ** reference count drops to 0, then it is made eligible for recycling. | |
| 374 */ | |
| 375 void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){ | |
| 376 assert( p->nRef>0 ); | |
| 377 p->nRef--; | |
| 378 if( p->nRef==0 ){ | |
| 379 p->pCache->nRef--; | |
| 380 if( (p->flags&PGHDR_DIRTY)==0 ){ | |
| 381 pcacheUnpin(p); | |
| 382 }else if( p->pDirtyPrev!=0 ){ | |
| 383 /* Move the page to the head of the dirty list. */ | |
| 384 pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT); | |
| 385 } | |
| 386 } | |
| 387 } | |
| 388 | |
| 389 /* | |
| 390 ** Increase the reference count of a supplied page by 1. | |
| 391 */ | |
| 392 void sqlite3PcacheRef(PgHdr *p){ | |
| 393 assert(p->nRef>0); | |
| 394 p->nRef++; | |
| 395 } | |
| 396 | |
| 397 /* | |
| 398 ** Drop a page from the cache. There must be exactly one reference to the | |
| 399 ** page. This function deletes that reference, so after it returns the | |
| 400 ** page pointed to by p is invalid. | |
| 401 */ | |
| 402 void sqlite3PcacheDrop(PgHdr *p){ | |
| 403 assert( p->nRef==1 ); | |
| 404 if( p->flags&PGHDR_DIRTY ){ | |
| 405 pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE); | |
| 406 } | |
| 407 p->pCache->nRef--; | |
| 408 if( p->pgno==1 ){ | |
| 409 p->pCache->pPage1 = 0; | |
| 410 } | |
| 411 sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 1); | |
| 412 } | |
| 413 | |
| 414 /* | |
| 415 ** Make sure the page is marked as dirty. If it isn't dirty already, | |
| 416 ** make it so. | |
| 417 */ | |
| 418 void sqlite3PcacheMakeDirty(PgHdr *p){ | |
| 419 p->flags &= ~PGHDR_DONT_WRITE; | |
| 420 assert( p->nRef>0 ); | |
| 421 if( 0==(p->flags & PGHDR_DIRTY) ){ | |
| 422 p->flags |= PGHDR_DIRTY; | |
| 423 pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD); | |
| 424 } | |
| 425 } | |
| 426 | |
| 427 /* | |
| 428 ** Make sure the page is marked as clean. If it isn't clean already, | |
| 429 ** make it so. | |
| 430 */ | |
| 431 void sqlite3PcacheMakeClean(PgHdr *p){ | |
| 432 if( (p->flags & PGHDR_DIRTY) ){ | |
| 433 pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE); | |
| 434 p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC); | |
| 435 if( p->nRef==0 ){ | |
| 436 pcacheUnpin(p); | |
| 437 } | |
| 438 } | |
| 439 } | |
| 440 | |
| 441 /* | |
| 442 ** Make every page in the cache clean. | |
| 443 */ | |
| 444 void sqlite3PcacheCleanAll(PCache *pCache){ | |
| 445 PgHdr *p; | |
| 446 while( (p = pCache->pDirty)!=0 ){ | |
| 447 sqlite3PcacheMakeClean(p); | |
| 448 } | |
| 449 } | |
| 450 | |
| 451 /* | |
| 452 ** Clear the PGHDR_NEED_SYNC flag from all dirty pages. | |
| 453 */ | |
| 454 void sqlite3PcacheClearSyncFlags(PCache *pCache){ | |
| 455 PgHdr *p; | |
| 456 for(p=pCache->pDirty; p; p=p->pDirtyNext){ | |
| 457 p->flags &= ~PGHDR_NEED_SYNC; | |
| 458 } | |
| 459 pCache->pSynced = pCache->pDirtyTail; | |
| 460 } | |
| 461 | |
| 462 /* | |
| 463 ** Change the page number of page p to newPgno. | |
| 464 */ | |
| 465 void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){ | |
| 466 PCache *pCache = p->pCache; | |
| 467 assert( p->nRef>0 ); | |
| 468 assert( newPgno>0 ); | |
| 469 sqlite3GlobalConfig.pcache2.xRekey(pCache->pCache, p->pPage, p->pgno,newPgno); | |
| 470 p->pgno = newPgno; | |
| 471 if( (p->flags&PGHDR_DIRTY) && (p->flags&PGHDR_NEED_SYNC) ){ | |
| 472 pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT); | |
| 473 } | |
| 474 } | |
| 475 | |
| 476 /* | |
| 477 ** Drop every cache entry whose page number is greater than "pgno". The | |
| 478 ** caller must ensure that there are no outstanding references to any pages | |
| 479 ** other than page 1 with a page number greater than pgno. | |
| 480 ** | |
| 481 ** If there is a reference to page 1 and the pgno parameter passed to this | |
| 482 ** function is 0, then the data area associated with page 1 is zeroed, but | |
| 483 ** the page object is not dropped. | |
| 484 */ | |
| 485 void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){ | |
| 486 if( pCache->pCache ){ | |
| 487 PgHdr *p; | |
| 488 PgHdr *pNext; | |
| 489 for(p=pCache->pDirty; p; p=pNext){ | |
| 490 pNext = p->pDirtyNext; | |
| 491 /* This routine never gets call with a positive pgno except right | |
| 492 ** after sqlite3PcacheCleanAll(). So if there are dirty pages, | |
| 493 ** it must be that pgno==0. | |
| 494 */ | |
| 495 assert( p->pgno>0 ); | |
| 496 if( ALWAYS(p->pgno>pgno) ){ | |
| 497 assert( p->flags&PGHDR_DIRTY ); | |
| 498 sqlite3PcacheMakeClean(p); | |
| 499 } | |
| 500 } | |
| 501 if( pgno==0 && pCache->pPage1 ){ | |
| 502 memset(pCache->pPage1->pData, 0, pCache->szPage); | |
| 503 pgno = 1; | |
| 504 } | |
| 505 sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1); | |
| 506 } | |
| 507 } | |
| 508 | |
| 509 /* | |
| 510 ** Close a cache. | |
| 511 */ | |
| 512 void sqlite3PcacheClose(PCache *pCache){ | |
| 513 assert( pCache->pCache!=0 ); | |
| 514 sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache); | |
| 515 } | |
| 516 | |
| 517 /* | |
| 518 ** Discard the contents of the cache. | |
| 519 */ | |
| 520 void sqlite3PcacheClear(PCache *pCache){ | |
| 521 sqlite3PcacheTruncate(pCache, 0); | |
| 522 } | |
| 523 | |
| 524 /* | |
| 525 ** Merge two lists of pages connected by pDirty and in pgno order. | |
| 526 ** Do not both fixing the pDirtyPrev pointers. | |
| 527 */ | |
| 528 static PgHdr *pcacheMergeDirtyList(PgHdr *pA, PgHdr *pB){ | |
| 529 PgHdr result, *pTail; | |
| 530 pTail = &result; | |
| 531 while( pA && pB ){ | |
| 532 if( pA->pgno<pB->pgno ){ | |
| 533 pTail->pDirty = pA; | |
| 534 pTail = pA; | |
| 535 pA = pA->pDirty; | |
| 536 }else{ | |
| 537 pTail->pDirty = pB; | |
| 538 pTail = pB; | |
| 539 pB = pB->pDirty; | |
| 540 } | |
| 541 } | |
| 542 if( pA ){ | |
| 543 pTail->pDirty = pA; | |
| 544 }else if( pB ){ | |
| 545 pTail->pDirty = pB; | |
| 546 }else{ | |
| 547 pTail->pDirty = 0; | |
| 548 } | |
| 549 return result.pDirty; | |
| 550 } | |
| 551 | |
| 552 /* | |
| 553 ** Sort the list of pages in accending order by pgno. Pages are | |
| 554 ** connected by pDirty pointers. The pDirtyPrev pointers are | |
| 555 ** corrupted by this sort. | |
| 556 ** | |
| 557 ** Since there cannot be more than 2^31 distinct pages in a database, | |
| 558 ** there cannot be more than 31 buckets required by the merge sorter. | |
| 559 ** One extra bucket is added to catch overflow in case something | |
| 560 ** ever changes to make the previous sentence incorrect. | |
| 561 */ | |
| 562 #define N_SORT_BUCKET 32 | |
| 563 static PgHdr *pcacheSortDirtyList(PgHdr *pIn){ | |
| 564 PgHdr *a[N_SORT_BUCKET], *p; | |
| 565 int i; | |
| 566 memset(a, 0, sizeof(a)); | |
| 567 while( pIn ){ | |
| 568 p = pIn; | |
| 569 pIn = p->pDirty; | |
| 570 p->pDirty = 0; | |
| 571 for(i=0; ALWAYS(i<N_SORT_BUCKET-1); i++){ | |
| 572 if( a[i]==0 ){ | |
| 573 a[i] = p; | |
| 574 break; | |
| 575 }else{ | |
| 576 p = pcacheMergeDirtyList(a[i], p); | |
| 577 a[i] = 0; | |
| 578 } | |
| 579 } | |
| 580 if( NEVER(i==N_SORT_BUCKET-1) ){ | |
| 581 /* To get here, there need to be 2^(N_SORT_BUCKET) elements in | |
| 582 ** the input list. But that is impossible. | |
| 583 */ | |
| 584 a[i] = pcacheMergeDirtyList(a[i], p); | |
| 585 } | |
| 586 } | |
| 587 p = a[0]; | |
| 588 for(i=1; i<N_SORT_BUCKET; i++){ | |
| 589 p = pcacheMergeDirtyList(p, a[i]); | |
| 590 } | |
| 591 return p; | |
| 592 } | |
| 593 | |
| 594 /* | |
| 595 ** Return a list of all dirty pages in the cache, sorted by page number. | |
| 596 */ | |
| 597 PgHdr *sqlite3PcacheDirtyList(PCache *pCache){ | |
| 598 PgHdr *p; | |
| 599 for(p=pCache->pDirty; p; p=p->pDirtyNext){ | |
| 600 p->pDirty = p->pDirtyNext; | |
| 601 } | |
| 602 return pcacheSortDirtyList(pCache->pDirty); | |
| 603 } | |
| 604 | |
| 605 /* | |
| 606 ** Return the total number of referenced pages held by the cache. | |
| 607 */ | |
| 608 int sqlite3PcacheRefCount(PCache *pCache){ | |
| 609 return pCache->nRef; | |
| 610 } | |
| 611 | |
| 612 /* | |
| 613 ** Return the number of references to the page supplied as an argument. | |
| 614 */ | |
| 615 int sqlite3PcachePageRefcount(PgHdr *p){ | |
| 616 return p->nRef; | |
| 617 } | |
| 618 | |
| 619 /* | |
| 620 ** Return the total number of pages in the cache. | |
| 621 */ | |
| 622 int sqlite3PcachePagecount(PCache *pCache){ | |
| 623 assert( pCache->pCache!=0 ); | |
| 624 return sqlite3GlobalConfig.pcache2.xPagecount(pCache->pCache); | |
| 625 } | |
| 626 | |
| 627 #ifdef SQLITE_TEST | |
| 628 /* | |
| 629 ** Get the suggested cache-size value. | |
| 630 */ | |
| 631 int sqlite3PcacheGetCachesize(PCache *pCache){ | |
| 632 return numberOfCachePages(pCache); | |
| 633 } | |
| 634 #endif | |
| 635 | |
| 636 /* | |
| 637 ** Set the suggested cache-size value. | |
| 638 */ | |
| 639 void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){ | |
| 640 assert( pCache->pCache!=0 ); | |
| 641 pCache->szCache = mxPage; | |
| 642 sqlite3GlobalConfig.pcache2.xCachesize(pCache->pCache, | |
| 643 numberOfCachePages(pCache)); | |
| 644 } | |
| 645 | |
| 646 /* | |
| 647 ** Free up as much memory as possible from the page cache. | |
| 648 */ | |
| 649 void sqlite3PcacheShrink(PCache *pCache){ | |
| 650 assert( pCache->pCache!=0 ); | |
| 651 sqlite3GlobalConfig.pcache2.xShrink(pCache->pCache); | |
| 652 } | |
| 653 | |
| 654 #if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG) | |
| 655 /* | |
| 656 ** For all dirty pages currently in the cache, invoke the specified | |
| 657 ** callback. This is only used if the SQLITE_CHECK_PAGES macro is | |
| 658 ** defined. | |
| 659 */ | |
| 660 void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)){ | |
| 661 PgHdr *pDirty; | |
| 662 for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext){ | |
| 663 xIter(pDirty); | |
| 664 } | |
| 665 } | |
| 666 #endif | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2363173002:
[sqlite] Remove obsolete reference version 3.8.7.4. (Closed)
