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Overview
Comment: | Remove some a small amount of redundant code related to PCache.pSynced from pcache.c. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
9cc8cad78fdfe044ad6726ebfe6909c1 |
User & Date: | dan 2016-05-11 15:41:15.317 |
Context
2016-05-11
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20:03 | Remove a redundant condition from pcache.c. Add an OPTIMIZATION-IF-TRUE comment to another condition that requires it. (check-in: 3bfd2621d1 user: dan tags: trunk) | |
18:20 | Remove a redundant condition from pcache.c. Add an OPTIMIZATION-IF-TRUE comment to another condition that requires it. (Closed-Leaf check-in: 4533ed352d user: dan tags: mistake) | |
15:41 | Remove some a small amount of redundant code related to PCache.pSynced from pcache.c. (check-in: 9cc8cad78f user: dan tags: trunk) | |
12:47 | Do not reset the page cache when a rollback journal truncate fails, as doing so can cause loss of information for an in-memory TEMP file. (check-in: 345ce1c9f6 user: drh tags: trunk) | |
Changes
Changes to src/pcache.c.
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11 12 13 14 15 16 17 18 19 20 21 22 23 24 | ************************************************************************* ** This file implements that page cache. */ #include "sqliteInt.h" /* ** A complete page cache is an instance of this structure. */ struct PCache { PgHdr *pDirty, *pDirtyTail; /* List of dirty pages in LRU order */ PgHdr *pSynced; /* Last synced page in dirty page list */ int nRefSum; /* Sum of ref counts over all pages */ int szCache; /* Configured cache size */ int szSpill; /* Size before spilling occurs */ | > > > > > > > > > > > > > > > > | 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | ************************************************************************* ** This file implements that page cache. */ #include "sqliteInt.h" /* ** A complete page cache is an instance of this structure. ** ** pDirty, pDirtyTail, pSynced: ** All dirty pages are linked into the doubly linked list using ** PgHdr.pDirtyNext and pDirtyPrev. The list is maintained in LRU order ** such that p was added to the list more recently than p->pDirtyNext. ** PCache.pDirty points to the first (newest) element in the list and ** pDirtyTail to the last (oldest). ** ** The PCache.pSynced variable is used to optimize searching for a dirty ** page to eject from the cache mid-transaction. It is better to eject ** a page that does not require a journal sync than one that does. ** Therefore, pSynced is maintained to that it *almost* always points ** to either the oldest page in the pDirty/pDirtyTail list that has a ** clear PGHDR_NEED_SYNC flag or to a page that is older than this one ** (so that the right page to eject can be found by following pDirtyPrev ** pointers). */ struct PCache { PgHdr *pDirty, *pDirtyTail; /* List of dirty pages in LRU order */ PgHdr *pSynced; /* Last synced page in dirty page list */ int nRefSum; /* Sum of ref counts over all pages */ int szCache; /* Configured cache size */ int szSpill; /* Size before spilling occurs */ |
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62 63 64 65 66 67 68 | pPage->pgno)); if( addRemove & PCACHE_DIRTYLIST_REMOVE ){ assert( pPage->pDirtyNext || pPage==p->pDirtyTail ); assert( pPage->pDirtyPrev || pPage==p->pDirty ); /* Update the PCache1.pSynced variable if necessary. */ if( p->pSynced==pPage ){ | | < < < < | 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 | pPage->pgno)); if( addRemove & PCACHE_DIRTYLIST_REMOVE ){ assert( pPage->pDirtyNext || pPage==p->pDirtyTail ); assert( pPage->pDirtyPrev || pPage==p->pDirty ); /* Update the PCache1.pSynced variable if necessary. */ if( p->pSynced==pPage ){ p->pSynced = pPage->pDirtyPrev; } if( pPage->pDirtyNext ){ pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev; }else{ assert( pPage==p->pDirtyTail ); p->pDirtyTail = pPage->pDirtyPrev; |
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292 293 294 295 296 297 298 | if( pCache->eCreate==2 ) return 0; if( sqlite3PcachePagecount(pCache)>pCache->szSpill ){ /* Find a dirty page to write-out and recycle. First try to find a ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC ** cleared), but if that is not possible settle for any other ** unreferenced dirty page. | | > > > > | 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 | if( pCache->eCreate==2 ) return 0; if( sqlite3PcachePagecount(pCache)>pCache->szSpill ){ /* Find a dirty page to write-out and recycle. First try to find a ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC ** cleared), but if that is not possible settle for any other ** unreferenced dirty page. ** ** If the LRU page in the dirty list that has a clear PGHDR_NEED_SYNC ** flag is currently referenced, then the following may leave pSynced ** set incorrectly (pointing to other than the LRU page with NEED_SYNC ** cleared). This is Ok, as pSynced is just an optimization. */ for(pPg=pCache->pSynced; pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); pPg=pPg->pDirtyPrev ); pCache->pSynced = pPg; if( !pPg ){ for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev); |
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