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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 nRefSum; /* Sum of ref counts over all pages */ | |
| 23 int szCache; /* Configured cache size */ | |
| 24 int szSpill; /* Size before spilling occurs */ | |
| 25 int szPage; /* Size of every page in this cache */ | |
| 26 int szExtra; /* Size of extra space for each page */ | |
| 27 u8 bPurgeable; /* True if pages are on backing store */ | |
| 28 u8 eCreate; /* eCreate value for for xFetch() */ | |
| 29 int (*xStress)(void*,PgHdr*); /* Call to try make a page clean */ | |
| 30 void *pStress; /* Argument to xStress */ | |
| 31 sqlite3_pcache *pCache; /* Pluggable cache module */ | |
| 32 }; | |
| 33 | |
| 34 /********************************** Linked List Management ********************/ | |
| 35 | |
| 36 /* Allowed values for second argument to pcacheManageDirtyList() */ | |
| 37 #define PCACHE_DIRTYLIST_REMOVE 1 /* Remove pPage from dirty list */ | |
| 38 #define PCACHE_DIRTYLIST_ADD 2 /* Add pPage to the dirty list */ | |
| 39 #define PCACHE_DIRTYLIST_FRONT 3 /* Move pPage to the front of the list */ | |
| 40 | |
| 41 /* | |
| 42 ** Manage pPage's participation on the dirty list. Bits of the addRemove | |
| 43 ** argument determines what operation to do. The 0x01 bit means first | |
| 44 ** remove pPage from the dirty list. The 0x02 means add pPage back to | |
| 45 ** the dirty list. Doing both moves pPage to the front of the dirty list. | |
| 46 */ | |
| 47 static void pcacheManageDirtyList(PgHdr *pPage, u8 addRemove){ | |
| 48 PCache *p = pPage->pCache; | |
| 49 | |
| 50 if( addRemove & PCACHE_DIRTYLIST_REMOVE ){ | |
| 51 assert( pPage->pDirtyNext || pPage==p->pDirtyTail ); | |
| 52 assert( pPage->pDirtyPrev || pPage==p->pDirty ); | |
| 53 | |
| 54 /* Update the PCache1.pSynced variable if necessary. */ | |
| 55 if( p->pSynced==pPage ){ | |
| 56 PgHdr *pSynced = pPage->pDirtyPrev; | |
| 57 while( pSynced && (pSynced->flags&PGHDR_NEED_SYNC) ){ | |
| 58 pSynced = pSynced->pDirtyPrev; | |
| 59 } | |
| 60 p->pSynced = pSynced; | |
| 61 } | |
| 62 | |
| 63 if( pPage->pDirtyNext ){ | |
| 64 pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev; | |
| 65 }else{ | |
| 66 assert( pPage==p->pDirtyTail ); | |
| 67 p->pDirtyTail = pPage->pDirtyPrev; | |
| 68 } | |
| 69 if( pPage->pDirtyPrev ){ | |
| 70 pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext; | |
| 71 }else{ | |
| 72 assert( pPage==p->pDirty ); | |
| 73 p->pDirty = pPage->pDirtyNext; | |
| 74 if( p->pDirty==0 && p->bPurgeable ){ | |
| 75 assert( p->eCreate==1 ); | |
| 76 p->eCreate = 2; | |
| 77 } | |
| 78 } | |
| 79 pPage->pDirtyNext = 0; | |
| 80 pPage->pDirtyPrev = 0; | |
| 81 } | |
| 82 if( addRemove & PCACHE_DIRTYLIST_ADD ){ | |
| 83 assert( pPage->pDirtyNext==0 && pPage->pDirtyPrev==0 && p->pDirty!=pPage ); | |
| 84 | |
| 85 pPage->pDirtyNext = p->pDirty; | |
| 86 if( pPage->pDirtyNext ){ | |
| 87 assert( pPage->pDirtyNext->pDirtyPrev==0 ); | |
| 88 pPage->pDirtyNext->pDirtyPrev = pPage; | |
| 89 }else{ | |
| 90 p->pDirtyTail = pPage; | |
| 91 if( p->bPurgeable ){ | |
| 92 assert( p->eCreate==2 ); | |
| 93 p->eCreate = 1; | |
| 94 } | |
| 95 } | |
| 96 p->pDirty = pPage; | |
| 97 if( !p->pSynced && 0==(pPage->flags&PGHDR_NEED_SYNC) ){ | |
| 98 p->pSynced = pPage; | |
| 99 } | |
| 100 } | |
| 101 } | |
| 102 | |
| 103 /* | |
| 104 ** Wrapper around the pluggable caches xUnpin method. If the cache is | |
| 105 ** being used for an in-memory database, this function is a no-op. | |
| 106 */ | |
| 107 static void pcacheUnpin(PgHdr *p){ | |
| 108 if( p->pCache->bPurgeable ){ | |
| 109 sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 0); | |
| 110 } | |
| 111 } | |
| 112 | |
| 113 /* | |
| 114 ** Compute the number of pages of cache requested. p->szCache is the | |
| 115 ** cache size requested by the "PRAGMA cache_size" statement. | |
| 116 */ | |
| 117 static int numberOfCachePages(PCache *p){ | |
| 118 if( p->szCache>=0 ){ | |
| 119 /* IMPLEMENTATION-OF: R-42059-47211 If the argument N is positive then the | |
| 120 ** suggested cache size is set to N. */ | |
| 121 return p->szCache; | |
| 122 }else{ | |
| 123 /* IMPLEMENTATION-OF: R-61436-13639 If the argument N is negative, then | |
| 124 ** the number of cache pages is adjusted to use approximately abs(N*1024) | |
| 125 ** bytes of memory. */ | |
| 126 return (int)((-1024*(i64)p->szCache)/(p->szPage+p->szExtra)); | |
| 127 } | |
| 128 } | |
| 129 | |
| 130 /*************************************************** General Interfaces ****** | |
| 131 ** | |
| 132 ** Initialize and shutdown the page cache subsystem. Neither of these | |
| 133 ** functions are threadsafe. | |
| 134 */ | |
| 135 int sqlite3PcacheInitialize(void){ | |
| 136 if( sqlite3GlobalConfig.pcache2.xInit==0 ){ | |
| 137 /* IMPLEMENTATION-OF: R-26801-64137 If the xInit() method is NULL, then the | |
| 138 ** built-in default page cache is used instead of the application defined | |
| 139 ** page cache. */ | |
| 140 sqlite3PCacheSetDefault(); | |
| 141 } | |
| 142 return sqlite3GlobalConfig.pcache2.xInit(sqlite3GlobalConfig.pcache2.pArg); | |
| 143 } | |
| 144 void sqlite3PcacheShutdown(void){ | |
| 145 if( sqlite3GlobalConfig.pcache2.xShutdown ){ | |
| 146 /* IMPLEMENTATION-OF: R-26000-56589 The xShutdown() method may be NULL. */ | |
| 147 sqlite3GlobalConfig.pcache2.xShutdown(sqlite3GlobalConfig.pcache2.pArg); | |
| 148 } | |
| 149 } | |
| 150 | |
| 151 /* | |
| 152 ** Return the size in bytes of a PCache object. | |
| 153 */ | |
| 154 int sqlite3PcacheSize(void){ return sizeof(PCache); } | |
| 155 | |
| 156 /* | |
| 157 ** Create a new PCache object. Storage space to hold the object | |
| 158 ** has already been allocated and is passed in as the p pointer. | |
| 159 ** The caller discovers how much space needs to be allocated by | |
| 160 ** calling sqlite3PcacheSize(). | |
| 161 */ | |
| 162 int sqlite3PcacheOpen( | |
| 163 int szPage, /* Size of every page */ | |
| 164 int szExtra, /* Extra space associated with each page */ | |
| 165 int bPurgeable, /* True if pages are on backing store */ | |
| 166 int (*xStress)(void*,PgHdr*),/* Call to try to make pages clean */ | |
| 167 void *pStress, /* Argument to xStress */ | |
| 168 PCache *p /* Preallocated space for the PCache */ | |
| 169 ){ | |
| 170 memset(p, 0, sizeof(PCache)); | |
| 171 p->szPage = 1; | |
| 172 p->szExtra = szExtra; | |
| 173 p->bPurgeable = bPurgeable; | |
| 174 p->eCreate = 2; | |
| 175 p->xStress = xStress; | |
| 176 p->pStress = pStress; | |
| 177 p->szCache = 100; | |
| 178 p->szSpill = 1; | |
| 179 return sqlite3PcacheSetPageSize(p, szPage); | |
| 180 } | |
| 181 | |
| 182 /* | |
| 183 ** Change the page size for PCache object. The caller must ensure that there | |
| 184 ** are no outstanding page references when this function is called. | |
| 185 */ | |
| 186 int sqlite3PcacheSetPageSize(PCache *pCache, int szPage){ | |
| 187 assert( pCache->nRefSum==0 && pCache->pDirty==0 ); | |
| 188 if( pCache->szPage ){ | |
| 189 sqlite3_pcache *pNew; | |
| 190 pNew = sqlite3GlobalConfig.pcache2.xCreate( | |
| 191 szPage, pCache->szExtra + ROUND8(sizeof(PgHdr)), | |
| 192 pCache->bPurgeable | |
| 193 ); | |
| 194 if( pNew==0 ) return SQLITE_NOMEM; | |
| 195 sqlite3GlobalConfig.pcache2.xCachesize(pNew, numberOfCachePages(pCache)); | |
| 196 if( pCache->pCache ){ | |
| 197 sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache); | |
| 198 } | |
| 199 pCache->pCache = pNew; | |
| 200 pCache->szPage = szPage; | |
| 201 } | |
| 202 return SQLITE_OK; | |
| 203 } | |
| 204 | |
| 205 /* | |
| 206 ** Try to obtain a page from the cache. | |
| 207 ** | |
| 208 ** This routine returns a pointer to an sqlite3_pcache_page object if | |
| 209 ** such an object is already in cache, or if a new one is created. | |
| 210 ** This routine returns a NULL pointer if the object was not in cache | |
| 211 ** and could not be created. | |
| 212 ** | |
| 213 ** The createFlags should be 0 to check for existing pages and should | |
| 214 ** be 3 (not 1, but 3) to try to create a new page. | |
| 215 ** | |
| 216 ** If the createFlag is 0, then NULL is always returned if the page | |
| 217 ** is not already in the cache. If createFlag is 1, then a new page | |
| 218 ** is created only if that can be done without spilling dirty pages | |
| 219 ** and without exceeding the cache size limit. | |
| 220 ** | |
| 221 ** The caller needs to invoke sqlite3PcacheFetchFinish() to properly | |
| 222 ** initialize the sqlite3_pcache_page object and convert it into a | |
| 223 ** PgHdr object. The sqlite3PcacheFetch() and sqlite3PcacheFetchFinish() | |
| 224 ** routines are split this way for performance reasons. When separated | |
| 225 ** they can both (usually) operate without having to push values to | |
| 226 ** the stack on entry and pop them back off on exit, which saves a | |
| 227 ** lot of pushing and popping. | |
| 228 */ | |
| 229 sqlite3_pcache_page *sqlite3PcacheFetch( | |
| 230 PCache *pCache, /* Obtain the page from this cache */ | |
| 231 Pgno pgno, /* Page number to obtain */ | |
| 232 int createFlag /* If true, create page if it does not exist already */ | |
| 233 ){ | |
| 234 int eCreate; | |
| 235 | |
| 236 assert( pCache!=0 ); | |
| 237 assert( pCache->pCache!=0 ); | |
| 238 assert( createFlag==3 || createFlag==0 ); | |
| 239 assert( pgno>0 ); | |
| 240 | |
| 241 /* eCreate defines what to do if the page does not exist. | |
| 242 ** 0 Do not allocate a new page. (createFlag==0) | |
| 243 ** 1 Allocate a new page if doing so is inexpensive. | |
| 244 ** (createFlag==1 AND bPurgeable AND pDirty) | |
| 245 ** 2 Allocate a new page even it doing so is difficult. | |
| 246 ** (createFlag==1 AND !(bPurgeable AND pDirty) | |
| 247 */ | |
| 248 eCreate = createFlag & pCache->eCreate; | |
| 249 assert( eCreate==0 || eCreate==1 || eCreate==2 ); | |
| 250 assert( createFlag==0 || pCache->eCreate==eCreate ); | |
| 251 assert( createFlag==0 || eCreate==1+(!pCache->bPurgeable||!pCache->pDirty) ); | |
| 252 return sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate); | |
| 253 } | |
| 254 | |
| 255 /* | |
| 256 ** If the sqlite3PcacheFetch() routine is unable to allocate a new | |
| 257 ** page because new clean pages are available for reuse and the cache | |
| 258 ** size limit has been reached, then this routine can be invoked to | |
| 259 ** try harder to allocate a page. This routine might invoke the stress | |
| 260 ** callback to spill dirty pages to the journal. It will then try to | |
| 261 ** allocate the new page and will only fail to allocate a new page on | |
| 262 ** an OOM error. | |
| 263 ** | |
| 264 ** This routine should be invoked only after sqlite3PcacheFetch() fails. | |
| 265 */ | |
| 266 int sqlite3PcacheFetchStress( | |
| 267 PCache *pCache, /* Obtain the page from this cache */ | |
| 268 Pgno pgno, /* Page number to obtain */ | |
| 269 sqlite3_pcache_page **ppPage /* Write result here */ | |
| 270 ){ | |
| 271 PgHdr *pPg; | |
| 272 if( pCache->eCreate==2 ) return 0; | |
| 273 | |
| 274 if( sqlite3PcachePagecount(pCache)>pCache->szSpill ){ | |
| 275 /* Find a dirty page to write-out and recycle. First try to find a | |
| 276 ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC | |
| 277 ** cleared), but if that is not possible settle for any other | |
| 278 ** unreferenced dirty page. | |
| 279 */ | |
| 280 for(pPg=pCache->pSynced; | |
| 281 pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); | |
| 282 pPg=pPg->pDirtyPrev | |
| 283 ); | |
| 284 pCache->pSynced = pPg; | |
| 285 if( !pPg ){ | |
| 286 for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev); | |
| 287 } | |
| 288 if( pPg ){ | |
| 289 int rc; | |
| 290 #ifdef SQLITE_LOG_CACHE_SPILL | |
| 291 sqlite3_log(SQLITE_FULL, | |
| 292 "spill page %d making room for %d - cache used: %d/%d", | |
| 293 pPg->pgno, pgno, | |
| 294 sqlite3GlobalConfig.pcache.xPagecount(pCache->pCache), | |
| 295 numberOfCachePages(pCache)); | |
| 296 #endif | |
| 297 rc = pCache->xStress(pCache->pStress, pPg); | |
| 298 if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){ | |
| 299 return rc; | |
| 300 } | |
| 301 } | |
| 302 } | |
| 303 *ppPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, 2); | |
| 304 return *ppPage==0 ? SQLITE_NOMEM : SQLITE_OK; | |
| 305 } | |
| 306 | |
| 307 /* | |
| 308 ** This is a helper routine for sqlite3PcacheFetchFinish() | |
| 309 ** | |
| 310 ** In the uncommon case where the page being fetched has not been | |
| 311 ** initialized, this routine is invoked to do the initialization. | |
| 312 ** This routine is broken out into a separate function since it | |
| 313 ** requires extra stack manipulation that can be avoided in the common | |
| 314 ** case. | |
| 315 */ | |
| 316 static SQLITE_NOINLINE PgHdr *pcacheFetchFinishWithInit( | |
| 317 PCache *pCache, /* Obtain the page from this cache */ | |
| 318 Pgno pgno, /* Page number obtained */ | |
| 319 sqlite3_pcache_page *pPage /* Page obtained by prior PcacheFetch() call */ | |
| 320 ){ | |
| 321 PgHdr *pPgHdr; | |
| 322 assert( pPage!=0 ); | |
| 323 pPgHdr = (PgHdr*)pPage->pExtra; | |
| 324 assert( pPgHdr->pPage==0 ); | |
| 325 memset(pPgHdr, 0, sizeof(PgHdr)); | |
| 326 pPgHdr->pPage = pPage; | |
| 327 pPgHdr->pData = pPage->pBuf; | |
| 328 pPgHdr->pExtra = (void *)&pPgHdr[1]; | |
| 329 memset(pPgHdr->pExtra, 0, pCache->szExtra); | |
| 330 pPgHdr->pCache = pCache; | |
| 331 pPgHdr->pgno = pgno; | |
| 332 pPgHdr->flags = PGHDR_CLEAN; | |
| 333 return sqlite3PcacheFetchFinish(pCache,pgno,pPage); | |
| 334 } | |
| 335 | |
| 336 /* | |
| 337 ** This routine converts the sqlite3_pcache_page object returned by | |
| 338 ** sqlite3PcacheFetch() into an initialized PgHdr object. This routine | |
| 339 ** must be called after sqlite3PcacheFetch() in order to get a usable | |
| 340 ** result. | |
| 341 */ | |
| 342 PgHdr *sqlite3PcacheFetchFinish( | |
| 343 PCache *pCache, /* Obtain the page from this cache */ | |
| 344 Pgno pgno, /* Page number obtained */ | |
| 345 sqlite3_pcache_page *pPage /* Page obtained by prior PcacheFetch() call */ | |
| 346 ){ | |
| 347 PgHdr *pPgHdr; | |
| 348 | |
| 349 assert( pPage!=0 ); | |
| 350 pPgHdr = (PgHdr *)pPage->pExtra; | |
| 351 | |
| 352 if( !pPgHdr->pPage ){ | |
| 353 return pcacheFetchFinishWithInit(pCache, pgno, pPage); | |
| 354 } | |
| 355 pCache->nRefSum++; | |
| 356 pPgHdr->nRef++; | |
| 357 return pPgHdr; | |
| 358 } | |
| 359 | |
| 360 /* | |
| 361 ** Decrement the reference count on a page. If the page is clean and the | |
| 362 ** reference count drops to 0, then it is made eligible for recycling. | |
| 363 */ | |
| 364 void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){ | |
| 365 assert( p->nRef>0 ); | |
| 366 p->pCache->nRefSum--; | |
| 367 if( (--p->nRef)==0 ){ | |
| 368 if( p->flags&PGHDR_CLEAN ){ | |
| 369 pcacheUnpin(p); | |
| 370 }else if( p->pDirtyPrev!=0 ){ | |
| 371 /* Move the page to the head of the dirty list. */ | |
| 372 pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT); | |
| 373 } | |
| 374 } | |
| 375 } | |
| 376 | |
| 377 /* | |
| 378 ** Increase the reference count of a supplied page by 1. | |
| 379 */ | |
| 380 void sqlite3PcacheRef(PgHdr *p){ | |
| 381 assert(p->nRef>0); | |
| 382 p->nRef++; | |
| 383 p->pCache->nRefSum++; | |
| 384 } | |
| 385 | |
| 386 /* | |
| 387 ** Drop a page from the cache. There must be exactly one reference to the | |
| 388 ** page. This function deletes that reference, so after it returns the | |
| 389 ** page pointed to by p is invalid. | |
| 390 */ | |
| 391 void sqlite3PcacheDrop(PgHdr *p){ | |
| 392 assert( p->nRef==1 ); | |
| 393 if( p->flags&PGHDR_DIRTY ){ | |
| 394 pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE); | |
| 395 } | |
| 396 p->pCache->nRefSum--; | |
| 397 sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 1); | |
| 398 } | |
| 399 | |
| 400 /* | |
| 401 ** Make sure the page is marked as dirty. If it isn't dirty already, | |
| 402 ** make it so. | |
| 403 */ | |
| 404 void sqlite3PcacheMakeDirty(PgHdr *p){ | |
| 405 assert( p->nRef>0 ); | |
| 406 if( p->flags & (PGHDR_CLEAN|PGHDR_DONT_WRITE) ){ | |
| 407 p->flags &= ~PGHDR_DONT_WRITE; | |
| 408 if( p->flags & PGHDR_CLEAN ){ | |
| 409 p->flags ^= (PGHDR_DIRTY|PGHDR_CLEAN); | |
| 410 assert( (p->flags & (PGHDR_DIRTY|PGHDR_CLEAN))==PGHDR_DIRTY ); | |
| 411 pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD); | |
| 412 } | |
| 413 } | |
| 414 } | |
| 415 | |
| 416 /* | |
| 417 ** Make sure the page is marked as clean. If it isn't clean already, | |
| 418 ** make it so. | |
| 419 */ | |
| 420 void sqlite3PcacheMakeClean(PgHdr *p){ | |
| 421 if( (p->flags & PGHDR_DIRTY) ){ | |
| 422 assert( (p->flags & PGHDR_CLEAN)==0 ); | |
| 423 pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE); | |
| 424 p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC|PGHDR_WRITEABLE); | |
| 425 p->flags |= PGHDR_CLEAN; | |
| 426 if( p->nRef==0 ){ | |
| 427 pcacheUnpin(p); | |
| 428 } | |
| 429 } | |
| 430 } | |
| 431 | |
| 432 /* | |
| 433 ** Make every page in the cache clean. | |
| 434 */ | |
| 435 void sqlite3PcacheCleanAll(PCache *pCache){ | |
| 436 PgHdr *p; | |
| 437 while( (p = pCache->pDirty)!=0 ){ | |
| 438 sqlite3PcacheMakeClean(p); | |
| 439 } | |
| 440 } | |
| 441 | |
| 442 /* | |
| 443 ** Clear the PGHDR_NEED_SYNC flag from all dirty pages. | |
| 444 */ | |
| 445 void sqlite3PcacheClearSyncFlags(PCache *pCache){ | |
| 446 PgHdr *p; | |
| 447 for(p=pCache->pDirty; p; p=p->pDirtyNext){ | |
| 448 p->flags &= ~PGHDR_NEED_SYNC; | |
| 449 } | |
| 450 pCache->pSynced = pCache->pDirtyTail; | |
| 451 } | |
| 452 | |
| 453 /* | |
| 454 ** Change the page number of page p to newPgno. | |
| 455 */ | |
| 456 void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){ | |
| 457 PCache *pCache = p->pCache; | |
| 458 assert( p->nRef>0 ); | |
| 459 assert( newPgno>0 ); | |
| 460 sqlite3GlobalConfig.pcache2.xRekey(pCache->pCache, p->pPage, p->pgno,newPgno); | |
| 461 p->pgno = newPgno; | |
| 462 if( (p->flags&PGHDR_DIRTY) && (p->flags&PGHDR_NEED_SYNC) ){ | |
| 463 pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT); | |
| 464 } | |
| 465 } | |
| 466 | |
| 467 /* | |
| 468 ** Drop every cache entry whose page number is greater than "pgno". The | |
| 469 ** caller must ensure that there are no outstanding references to any pages | |
| 470 ** other than page 1 with a page number greater than pgno. | |
| 471 ** | |
| 472 ** If there is a reference to page 1 and the pgno parameter passed to this | |
| 473 ** function is 0, then the data area associated with page 1 is zeroed, but | |
| 474 ** the page object is not dropped. | |
| 475 */ | |
| 476 void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){ | |
| 477 if( pCache->pCache ){ | |
| 478 PgHdr *p; | |
| 479 PgHdr *pNext; | |
| 480 for(p=pCache->pDirty; p; p=pNext){ | |
| 481 pNext = p->pDirtyNext; | |
| 482 /* This routine never gets call with a positive pgno except right | |
| 483 ** after sqlite3PcacheCleanAll(). So if there are dirty pages, | |
| 484 ** it must be that pgno==0. | |
| 485 */ | |
| 486 assert( p->pgno>0 ); | |
| 487 if( ALWAYS(p->pgno>pgno) ){ | |
| 488 assert( p->flags&PGHDR_DIRTY ); | |
| 489 sqlite3PcacheMakeClean(p); | |
| 490 } | |
| 491 } | |
| 492 if( pgno==0 && pCache->nRefSum ){ | |
| 493 sqlite3_pcache_page *pPage1; | |
| 494 pPage1 = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache,1,0); | |
| 495 if( ALWAYS(pPage1) ){ /* Page 1 is always available in cache, because | |
| 496 ** pCache->nRefSum>0 */ | |
| 497 memset(pPage1->pBuf, 0, pCache->szPage); | |
| 498 pgno = 1; | |
| 499 } | |
| 500 } | |
| 501 sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1); | |
| 502 } | |
| 503 } | |
| 504 | |
| 505 /* | |
| 506 ** Close a cache. | |
| 507 */ | |
| 508 void sqlite3PcacheClose(PCache *pCache){ | |
| 509 assert( pCache->pCache!=0 ); | |
| 510 sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache); | |
| 511 } | |
| 512 | |
| 513 /* | |
| 514 ** Discard the contents of the cache. | |
| 515 */ | |
| 516 void sqlite3PcacheClear(PCache *pCache){ | |
| 517 sqlite3PcacheTruncate(pCache, 0); | |
| 518 } | |
| 519 | |
| 520 /* | |
| 521 ** Merge two lists of pages connected by pDirty and in pgno order. | |
| 522 ** Do not both fixing the pDirtyPrev pointers. | |
| 523 */ | |
| 524 static PgHdr *pcacheMergeDirtyList(PgHdr *pA, PgHdr *pB){ | |
| 525 PgHdr result, *pTail; | |
| 526 pTail = &result; | |
| 527 while( pA && pB ){ | |
| 528 if( pA->pgno<pB->pgno ){ | |
| 529 pTail->pDirty = pA; | |
| 530 pTail = pA; | |
| 531 pA = pA->pDirty; | |
| 532 }else{ | |
| 533 pTail->pDirty = pB; | |
| 534 pTail = pB; | |
| 535 pB = pB->pDirty; | |
| 536 } | |
| 537 } | |
| 538 if( pA ){ | |
| 539 pTail->pDirty = pA; | |
| 540 }else if( pB ){ | |
| 541 pTail->pDirty = pB; | |
| 542 }else{ | |
| 543 pTail->pDirty = 0; | |
| 544 } | |
| 545 return result.pDirty; | |
| 546 } | |
| 547 | |
| 548 /* | |
| 549 ** Sort the list of pages in accending order by pgno. Pages are | |
| 550 ** connected by pDirty pointers. The pDirtyPrev pointers are | |
| 551 ** corrupted by this sort. | |
| 552 ** | |
| 553 ** Since there cannot be more than 2^31 distinct pages in a database, | |
| 554 ** there cannot be more than 31 buckets required by the merge sorter. | |
| 555 ** One extra bucket is added to catch overflow in case something | |
| 556 ** ever changes to make the previous sentence incorrect. | |
| 557 */ | |
| 558 #define N_SORT_BUCKET 32 | |
| 559 static PgHdr *pcacheSortDirtyList(PgHdr *pIn){ | |
| 560 PgHdr *a[N_SORT_BUCKET], *p; | |
| 561 int i; | |
| 562 memset(a, 0, sizeof(a)); | |
| 563 while( pIn ){ | |
| 564 p = pIn; | |
| 565 pIn = p->pDirty; | |
| 566 p->pDirty = 0; | |
| 567 for(i=0; ALWAYS(i<N_SORT_BUCKET-1); i++){ | |
| 568 if( a[i]==0 ){ | |
| 569 a[i] = p; | |
| 570 break; | |
| 571 }else{ | |
| 572 p = pcacheMergeDirtyList(a[i], p); | |
| 573 a[i] = 0; | |
| 574 } | |
| 575 } | |
| 576 if( NEVER(i==N_SORT_BUCKET-1) ){ | |
| 577 /* To get here, there need to be 2^(N_SORT_BUCKET) elements in | |
| 578 ** the input list. But that is impossible. | |
| 579 */ | |
| 580 a[i] = pcacheMergeDirtyList(a[i], p); | |
| 581 } | |
| 582 } | |
| 583 p = a[0]; | |
| 584 for(i=1; i<N_SORT_BUCKET; i++){ | |
| 585 p = pcacheMergeDirtyList(p, a[i]); | |
| 586 } | |
| 587 return p; | |
| 588 } | |
| 589 | |
| 590 /* | |
| 591 ** Return a list of all dirty pages in the cache, sorted by page number. | |
| 592 */ | |
| 593 PgHdr *sqlite3PcacheDirtyList(PCache *pCache){ | |
| 594 PgHdr *p; | |
| 595 for(p=pCache->pDirty; p; p=p->pDirtyNext){ | |
| 596 p->pDirty = p->pDirtyNext; | |
| 597 } | |
| 598 return pcacheSortDirtyList(pCache->pDirty); | |
| 599 } | |
| 600 | |
| 601 /* | |
| 602 ** Return the total number of references to all pages held by the cache. | |
| 603 ** | |
| 604 ** This is not the total number of pages referenced, but the sum of the | |
| 605 ** reference count for all pages. | |
| 606 */ | |
| 607 int sqlite3PcacheRefCount(PCache *pCache){ | |
| 608 return pCache->nRefSum; | |
| 609 } | |
| 610 | |
| 611 /* | |
| 612 ** Return the number of references to the page supplied as an argument. | |
| 613 */ | |
| 614 int sqlite3PcachePageRefcount(PgHdr *p){ | |
| 615 return p->nRef; | |
| 616 } | |
| 617 | |
| 618 /* | |
| 619 ** Return the total number of pages in the cache. | |
| 620 */ | |
| 621 int sqlite3PcachePagecount(PCache *pCache){ | |
| 622 assert( pCache->pCache!=0 ); | |
| 623 return sqlite3GlobalConfig.pcache2.xPagecount(pCache->pCache); | |
| 624 } | |
| 625 | |
| 626 #ifdef SQLITE_TEST | |
| 627 /* | |
| 628 ** Get the suggested cache-size value. | |
| 629 */ | |
| 630 int sqlite3PcacheGetCachesize(PCache *pCache){ | |
| 631 return numberOfCachePages(pCache); | |
| 632 } | |
| 633 #endif | |
| 634 | |
| 635 /* | |
| 636 ** Set the suggested cache-size value. | |
| 637 */ | |
| 638 void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){ | |
| 639 assert( pCache->pCache!=0 ); | |
| 640 pCache->szCache = mxPage; | |
| 641 sqlite3GlobalConfig.pcache2.xCachesize(pCache->pCache, | |
| 642 numberOfCachePages(pCache)); | |
| 643 } | |
| 644 | |
| 645 /* | |
| 646 ** Set the suggested cache-spill value. Make no changes if if the | |
| 647 ** argument is zero. Return the effective cache-spill size, which will | |
| 648 ** be the larger of the szSpill and szCache. | |
| 649 */ | |
| 650 int sqlite3PcacheSetSpillsize(PCache *p, int mxPage){ | |
| 651 int res; | |
| 652 assert( p->pCache!=0 ); | |
| 653 if( mxPage ){ | |
| 654 if( mxPage<0 ){ | |
| 655 mxPage = (int)((-1024*(i64)mxPage)/(p->szPage+p->szExtra)); | |
| 656 } | |
| 657 p->szSpill = mxPage; | |
| 658 } | |
| 659 res = numberOfCachePages(p); | |
| 660 if( res<p->szSpill ) res = p->szSpill; | |
| 661 return res; | |
| 662 } | |
| 663 | |
| 664 /* | |
| 665 ** Free up as much memory as possible from the page cache. | |
| 666 */ | |
| 667 void sqlite3PcacheShrink(PCache *pCache){ | |
| 668 assert( pCache->pCache!=0 ); | |
| 669 sqlite3GlobalConfig.pcache2.xShrink(pCache->pCache); | |
| 670 } | |
| 671 | |
| 672 /* | |
| 673 ** Return the size of the header added by this middleware layer | |
| 674 ** in the page-cache hierarchy. | |
| 675 */ | |
| 676 int sqlite3HeaderSizePcache(void){ return ROUND8(sizeof(PgHdr)); } | |
| 677 | |
| 678 | |
| 679 #if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG) | |
| 680 /* | |
| 681 ** For all dirty pages currently in the cache, invoke the specified | |
| 682 ** callback. This is only used if the SQLITE_CHECK_PAGES macro is | |
| 683 ** defined. | |
| 684 */ | |
| 685 void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)){ | |
| 686 PgHdr *pDirty; | |
| 687 for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext){ | |
| 688 xIter(pDirty); | |
| 689 } | |
| 690 } | |
| 691 #endif | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2846743003:
[sql] Remove SQLite 3.10.2 reference directory. (Closed)
