SQLite

Check-in [03dceaea15]
Login

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Enhance sqlite3PcacheTruncate() to run faster in the common case where the cutoff is just a few pages less than the page number highwater mark.
Downloads: Tarball | ZIP archive
Timelines: family | ancestors | descendants | both | branch-3.14
Files: files | file ages | folders
SHA1: 03dceaea15aa357097a4615ef6044be36d505044
User & Date: drh 2016-08-11 13:03:51.493
Context
2016-08-11
13:08
Increase the version number to 3.14.1. (check-in: 34aed3a318 user: drh tags: branch-3.14)
13:03
Enhance sqlite3PcacheTruncate() to run faster in the common case where the cutoff is just a few pages less than the page number highwater mark. (check-in: 03dceaea15 user: drh tags: branch-3.14)
2016-08-10
15:02
Tweaks to pcache1TruncateUnsafe() to make it slightly smaller and faster and easier to test. (check-in: 059f4e2efe user: drh tags: trunk)
11:50
Fix pcache1TruncateUnsafe() run faster for the case where iLimit is very close to iMaxKey. (check-in: b07a26df06 user: drh tags: trunk)
2016-08-08
13:40
Version 3.14 (check-in: d5e9805702 user: drh tags: trunk, release, version-3.14.0)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/pcache1.c.
628
629
630
631
632
633
634
635
636
637













638



639
640


641
642
643
644
645
646
647
648
649
650
651


652
653
654
655
656
657
658
659
660
**
** The PCache mutex must be held when this function is called.
*/
static void pcache1TruncateUnsafe(
  PCache1 *pCache,             /* The cache to truncate */
  unsigned int iLimit          /* Drop pages with this pgno or larger */
){
  TESTONLY( unsigned int nPage = 0; )  /* To assert pCache->nPage is correct */
  unsigned int h;
  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );













  for(h=0; h<pCache->nHash; h++){



    PgHdr1 **pp = &pCache->apHash[h]; 
    PgHdr1 *pPage;


    while( (pPage = *pp)!=0 ){
      if( pPage->iKey>=iLimit ){
        pCache->nPage--;
        *pp = pPage->pNext;
        if( !pPage->isPinned ) pcache1PinPage(pPage);
        pcache1FreePage(pPage);
      }else{
        pp = &pPage->pNext;
        TESTONLY( nPage++; )
      }
    }


  }
  assert( pCache->nPage==nPage );
}

/******************************************************************************/
/******** sqlite3_pcache Methods **********************************************/

/*
** Implementation of the sqlite3_pcache.xInit method.







|
|

>
>
>
>
>
>
>
>
>
>
>
>
>
|
>
>
>
|

>
>








|


>
>

|







628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
**
** The PCache mutex must be held when this function is called.
*/
static void pcache1TruncateUnsafe(
  PCache1 *pCache,             /* The cache to truncate */
  unsigned int iLimit          /* Drop pages with this pgno or larger */
){
  TESTONLY( int nPage = 0; )  /* To assert pCache->nPage is correct */
  unsigned int h, iStop;
  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
  assert( pCache->iMaxKey >= iLimit );
  assert( pCache->nHash > 0 );
  if( pCache->iMaxKey - iLimit < pCache->nHash ){
    /* If we are just shaving the last few pages off the end of the
    ** cache, then there is no point in scanning the entire hash table.
    ** Only scan those hash slots that might contain pages that need to
    ** be removed. */
    h = iLimit % pCache->nHash;
    iStop = pCache->iMaxKey % pCache->nHash;
    TESTONLY( nPage = -10; )  /* Disable the pCache->nPage validity check */
  }else{
    /* This is the general case where many pages are being removed.
    ** It is necessary to scan the entire hash table */
    h = pCache->nHash/2;
    iStop = h - 1;
  }
  for(;;){
    PgHdr1 **pp;
    PgHdr1 *pPage;
    assert( h<pCache->nHash );
    pp = &pCache->apHash[h]; 
    while( (pPage = *pp)!=0 ){
      if( pPage->iKey>=iLimit ){
        pCache->nPage--;
        *pp = pPage->pNext;
        if( !pPage->isPinned ) pcache1PinPage(pPage);
        pcache1FreePage(pPage);
      }else{
        pp = &pPage->pNext;
        TESTONLY( if( nPage>=0 ) nPage++; )
      }
    }
    if( h==iStop ) break;
    h = (h+1) % pCache->nHash;
  }
  assert( nPage<0 || pCache->nPage==(unsigned)nPage );
}

/******************************************************************************/
/******** sqlite3_pcache Methods **********************************************/

/*
** Implementation of the sqlite3_pcache.xInit method.
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
** Destroy a cache allocated using pcache1Create().
*/
static void pcache1Destroy(sqlite3_pcache *p){
  PCache1 *pCache = (PCache1 *)p;
  PGroup *pGroup = pCache->pGroup;
  assert( pCache->bPurgeable || (pCache->nMax==0 && pCache->nMin==0) );
  pcache1EnterMutex(pGroup);
  pcache1TruncateUnsafe(pCache, 0);
  assert( pGroup->nMaxPage >= pCache->nMax );
  pGroup->nMaxPage -= pCache->nMax;
  assert( pGroup->nMinPage >= pCache->nMin );
  pGroup->nMinPage -= pCache->nMin;
  pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
  pcache1EnforceMaxPage(pCache);
  pcache1LeaveMutex(pGroup);







|







1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
** Destroy a cache allocated using pcache1Create().
*/
static void pcache1Destroy(sqlite3_pcache *p){
  PCache1 *pCache = (PCache1 *)p;
  PGroup *pGroup = pCache->pGroup;
  assert( pCache->bPurgeable || (pCache->nMax==0 && pCache->nMin==0) );
  pcache1EnterMutex(pGroup);
  if( pCache->nPage ) pcache1TruncateUnsafe(pCache, 0);
  assert( pGroup->nMaxPage >= pCache->nMax );
  pGroup->nMaxPage -= pCache->nMax;
  assert( pGroup->nMinPage >= pCache->nMin );
  pGroup->nMinPage -= pCache->nMin;
  pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
  pcache1EnforceMaxPage(pCache);
  pcache1LeaveMutex(pGroup);