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When doing an UPDATE or DELETE using a multi-column index where only a few

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of the earlier columns of the index are useful for the index lookup,
postpone doing the main table seek until after all WHERE clause constraints
have been evaluated, in case those constraints can be covered by unused
later terms of the index, thus avoiding unnecessary main table seeks.

FossilOrigin-Name: 7fee0b1075d622835dc6828c061be516102da9e2809f52d9ab7c4bbef7dfb871
This commit is contained in:
drh 2020-08-14 21:51:02 +00:00
commit 861889e4f8
8 changed files with 51 additions and 45 deletions
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23
manifest
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@ -1,5 +1,5 @@
C Update\sthe\sversion\snumber\sto\s3.34.0\sfor\sthe\snext\sdevelopment\scycle.
D 2020-08-14T21:37:32.306
C When\sdoing\san\sUPDATE\sor\sDELETE\susing\sa\smulti-column\sindex\swhere\sonly\sa\sfew\nof\sthe\searlier\scolumns\sof\sthe\sindex\sare\suseful\sfor\sthe\sindex\slookup,\npostpone\sdoing\sthe\smain\stable\sseek\suntil\safter\sall\sWHERE\sclause\sconstraints\nhave\sbeen\sevaluated,\sin\scase\sthose\sconstraints\scan\sbe\scovered\sby\sunused\nlater\sterms\sof\sthe\sindex,\sthus\savoiding\sunnecessary\smain\stable\sseeks.
D 2020-08-14T21:51:02.627
F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@ -486,7 +486,7 @@ F src/ctime.c e98518d2d3d4029a13c805e07313fb60c877be56db76e90dd5f3af73085d0ce6
F src/date.c dace306a10d9b02ee553d454c8e1cf8d3c9b932e137738a6b15b90253a9bfc10
F src/dbpage.c 8a01e865bf8bc6d7b1844b4314443a6436c07c3efe1d488ed89e81719047833a
F src/dbstat.c 3aa79fc3aed7ce906e4ea6c10e85d657299e304f6049861fe300053ac57de36c
F src/delete.c 410c771c25afc113c273d9efad6ab6881bda28c75a1838b9d2c52ba20d1dc704
F src/delete.c a2a603ab07cced8560065b0e2c4c9c842f2c5a2fd43d87355f95eb53bae7fe21
F src/expr.c 58c06940d964c2cf455b979cf66a648499d294a5ee6dadcaeaed447257c1dc75
F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
F src/fkey.c 83372403298e6a7dd989a47aaacdbaa5b4307b5199dbd56e07d4896066b3de72
@ -540,7 +540,7 @@ F src/shell.c.in b9b819feede7b85585ab0826490a352e04e2ee46e8132c92597d29972b2be1d
F src/sqlite.h.in d2c03414a8ee5d4a6855c04dd7cd5998e45139b0fe66b65bae86d4223edd091f
F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
F src/sqlite3ext.h 2d1af80082edffd71c6f96f70ad1ce6a4fb46615ad10291fc77fe0dea9ff0197
F src/sqliteInt.h a1aa5457ca881cbf5adb55933bf81d7d4889375afb9a0a5df382a451c058087d
F src/sqliteInt.h 86ad0f9164cbadb2ba9598cc6cf5b32bdb47b343c0da5ca62f3d73b60be55b65
F src/sqliteLimit.h 95cb8479ca459496d9c1c6a9f76b38aee12203a56ce1092fe13e50ae2454c032
F src/status.c 4b8bc2a6905163a38b739854a35b826c737333fab5b1f8e03fa7eb9a4799c4c1
F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
@ -602,7 +602,7 @@ F src/threads.c 4ae07fa022a3dc7c5beb373cf744a85d3c5c6c3c
F src/tokenize.c 4dc01b267593537e2a0d0efe9f80dabe24c5b6f7627bc6971c487fa6a1dacbbf
F src/treeview.c 4b92992176fb2caefbe06ba5bd06e0e0ebcde3d5564758da672631f17aa51cda
F src/trigger.c ef67bde309a831515dc3c2173d792574309f2f42d45f8c078743fae9f7f98c75
F src/update.c fb15bec5b54fd098f4b84f6abc83c7103b45ba8484011fff8edf5ae31656eab6
F src/update.c 55a6203008d033fc1a9c125d7a0a61efdb79bbb2e6db427b917d1d427b4639be
F src/upsert.c 2920de71b20f04fe25eb00b655d086f0ba60ea133c59d7fa3325c49838818e78
F src/utf.c ee39565f0843775cc2c81135751ddd93eceb91a673ea2c57f61c76f288b041a0
F src/util.c c8bf30c4356b091bcc3b624d0e24b2b4d11b8be4d6c90d8e0705971e15cc819b
@ -622,9 +622,9 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
F src/wal.c 69e770e96fd56cc21608992bf2c6f1f3dc5cf2572d0495c6a643b06c3a679f14
F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
F src/walker.c 3df26a33dc4f54e8771600fb7fdebe1ece0896c2ad68c30ab40b017aa4395049
F src/where.c 2ea911238674e9baaeddf105dddabed92692a01996073c4d4983f9a7efe481f9
F src/whereInt.h 6b874aa15f94e43a2cec1080be64d955b04deeafeac90ffb5d6975c0d511be3c
F src/wherecode.c 8064fe5c042824853a9b1fda670054a51a49033a6c79059988c97751ccf8088e
F src/where.c 396ba2c62defd56283ef54a4b221f698f4733fe8fbfca4aa8b1cc4f8c58d12ee
F src/whereInt.h eb8c2847fb464728533777efec1682b3c074224293b2da73513c61a609efbeab
F src/wherecode.c cb9bc7cef99578c99baceafeea9c9bcc738d5be37f56dbfe3a1c61ea52483fd0
F src/whereexpr.c 264d58971eaf8256eb5b0917bcd7fc7a1f1109fdda183a8382308a1b18a2dce7
F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
@ -1879,7 +1879,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
P 613fb5c2525be77e48bad0a74e8b7bf53489365060fb9c7713a0caddb1820c71
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R fd23b928eb9c7a62b3f6e9653824ff24
T +closed 611b640442025e57b8e161f8ddac1f19bd3be9a3d5266f4cef287595c3ed9257
U drh
Z e2c81a93805f9b05654ffbbe167428db
Z 5d0dae315c2c275d1ce9160adcb43cdc

2
manifest.uuid
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@ -1 +1 @@
70f34f3df5358d36c8578afbc05756450c46da36b8dce339ed87fc0b9d4057cb
7fee0b1075d622835dc6828c061be516102da9e2809f52d9ab7c4bbef7dfb871

13
src/delete.c
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@ -425,7 +425,7 @@ void sqlite3DeleteFrom(
}else
#endif /* SQLITE_OMIT_TRUNCATE_OPTIMIZATION */
{
u16 wcf = WHERE_ONEPASS_DESIRED|WHERE_DUPLICATES_OK|WHERE_SEEK_TABLE;
u16 wcf = WHERE_ONEPASS_DESIRED|WHERE_DUPLICATES_OK;
if( sNC.ncFlags & NC_VarSelect ) bComplex = 1;
wcf |= (bComplex ? 0 : WHERE_ONEPASS_MULTIROW);
if( HasRowid(pTab) ){
@ -461,6 +461,9 @@ void sqlite3DeleteFrom(
assert( IsVirtual(pTab)==0 || eOnePass!=ONEPASS_MULTI );
assert( IsVirtual(pTab) || bComplex || eOnePass!=ONEPASS_OFF );
if( eOnePass!=ONEPASS_SINGLE ) sqlite3MultiWrite(pParse);
if( sqlite3WhereUsesDeferredSeek(pWInfo) ){
sqlite3VdbeAddOp1(v, OP_FinishSeek, iTabCur);
}
/* Keep track of the number of rows to be deleted */
if( memCnt ){
@ -495,6 +498,7 @@ void sqlite3DeleteFrom(
if( aiCurOnePass[0]>=0 ) aToOpen[aiCurOnePass[0]-iTabCur] = 0;
if( aiCurOnePass[1]>=0 ) aToOpen[aiCurOnePass[1]-iTabCur] = 0;
if( addrEphOpen ) sqlite3VdbeChangeToNoop(v, addrEphOpen);
addrBypass = sqlite3VdbeMakeLabel(pParse);
}else{
if( pPk ){
/* Add the PK key for this row to the temporary table */
@ -508,13 +512,6 @@ void sqlite3DeleteFrom(
nKey = 1; /* OP_DeferredSeek always uses a single rowid */
sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, iKey);
}
}
/* If this DELETE cannot use the ONEPASS strategy, this is the
** end of the WHERE loop */
if( eOnePass!=ONEPASS_OFF ){
addrBypass = sqlite3VdbeMakeLabel(pParse);
}else{
sqlite3WhereEnd(pWInfo);
}

4
src/sqliteInt.h
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@ -2953,9 +2953,9 @@ struct SrcList {
#define WHERE_DISTINCTBY 0x0080 /* pOrderby is really a DISTINCT clause */
#define WHERE_WANT_DISTINCT 0x0100 /* All output needs to be distinct */
#define WHERE_SORTBYGROUP 0x0200 /* Support sqlite3WhereIsSorted() */
#define WHERE_SEEK_TABLE 0x0400 /* Do not defer seeks on main table */
/* 0x0400 not currently used */
#define WHERE_ORDERBY_LIMIT 0x0800 /* ORDERBY+LIMIT on the inner loop */
#define WHERE_SEEK_UNIQ_TABLE 0x1000 /* Do not defer seeks if unique */
/* 0x1000 not currently used */
/* 0x2000 not currently used */
#define WHERE_USE_LIMIT 0x4000 /* Use the LIMIT in cost estimates */
/* 0x8000 not currently used */

2
src/update.c
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@ -705,7 +705,7 @@ void sqlite3Update(
** be deleted as a result of REPLACE conflict handling. Any of these
** things might disturb a cursor being used to scan through the table
** or index, causing a single-pass approach to malfunction. */
flags = WHERE_ONEPASS_DESIRED|WHERE_SEEK_UNIQ_TABLE;
flags = WHERE_ONEPASS_DESIRED;
if( !pParse->nested && !pTrigger && !hasFK && !chngKey && !bReplace ){
flags |= WHERE_ONEPASS_MULTIROW;
}

32
src/where.c
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@ -5246,6 +5246,7 @@ WhereInfo *sqlite3WhereBegin(
/* Done. */
VdbeModuleComment((v, "Begin WHERE-core"));
pWInfo->iEndWhere = sqlite3VdbeCurrentAddr(v);
return pWInfo;
/* Jump here if malloc fails */
@ -5289,6 +5290,7 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
WhereLoop *pLoop;
SrcList *pTabList = pWInfo->pTabList;
sqlite3 *db = pParse->db;
int iEnd = sqlite3VdbeCurrentAddr(v);
/* Generate loop termination code.
*/
@ -5426,7 +5428,7 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
assert( pWInfo->nLevel<=pTabList->nSrc );
for(i=0, pLevel=pWInfo->a; i<pWInfo->nLevel; i++, pLevel++){
int k, last;
VdbeOp *pOp;
VdbeOp *pOp, *pLastOp;
Index *pIdx = 0;
struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
Table *pTab = pTabItem->pTab;
@ -5484,20 +5486,31 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
pIdx = pLevel->u.pCovidx;
}
if( pIdx
&& (pWInfo->eOnePass==ONEPASS_OFF || !HasRowid(pIdx->pTable))
&& !db->mallocFailed
){
last = sqlite3VdbeCurrentAddr(v);
k = pLevel->addrBody;
if( pWInfo->eOnePass==ONEPASS_OFF || !HasRowid(pIdx->pTable) ){
last = iEnd;
}else{
last = pWInfo->iEndWhere;
}
k = pLevel->addrBody + 1;
#ifdef SQLITE_DEBUG
if( db->flags & SQLITE_VdbeAddopTrace ){
printf("TRANSLATE opcodes in range %d..%d\n", k, last-1);
}
/* Proof that the "+1" on the k value above is safe */
pOp = sqlite3VdbeGetOp(v, k - 1);
assert( pOp->opcode!=OP_Column || pOp->p1!=pLevel->iTabCur );
assert( pOp->opcode!=OP_Rowid || pOp->p1!=pLevel->iTabCur );
assert( pOp->opcode!=OP_IfNullRow || pOp->p1!=pLevel->iTabCur );
#endif
pOp = sqlite3VdbeGetOp(v, k);
for(; k<last; k++, pOp++){
if( pOp->p1!=pLevel->iTabCur ) continue;
if( pOp->opcode==OP_Column
pLastOp = pOp + (last - k);
assert( pOp<pLastOp );
do{
if( pOp->p1!=pLevel->iTabCur ){
/* no-op */
}else if( pOp->opcode==OP_Column
#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
|| pOp->opcode==OP_Offset
#endif
@ -5528,7 +5541,10 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
pOp->p1 = pLevel->iIdxCur;
OpcodeRewriteTrace(db, k, pOp);
}
}
#ifdef SQLITE_DEBUG
k++;
#endif
}while( (++pOp)<pLastOp );
#ifdef SQLITE_DEBUG
if( db->flags & SQLITE_VdbeAddopTrace ) printf("TRANSLATE complete\n");
#endif

1
src/whereInt.h
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@ -488,6 +488,7 @@ struct WhereInfo {
unsigned sorted :1; /* True if really sorted (not just grouped) */
LogEst nRowOut; /* Estimated number of output rows */
int iTop; /* The very beginning of the WHERE loop */
int iEndWhere; /* End of the WHERE clause itself */
WhereLoop *pLoops; /* List of all WhereLoop objects */
WhereExprMod *pExprMods; /* Expression modifications */
Bitmask revMask; /* Mask of ORDER BY terms that need reversing */

19
src/wherecode.c
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@ -1909,17 +1909,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
if( omitTable ){
/* pIdx is a covering index. No need to access the main table. */
}else if( HasRowid(pIdx->pTable) ){
if( (pWInfo->wctrlFlags & WHERE_SEEK_TABLE)
|| ( (pWInfo->wctrlFlags & WHERE_SEEK_UNIQ_TABLE)!=0
&& (pWInfo->eOnePass==ONEPASS_SINGLE || pLoop->nLTerm==0) )
){
iRowidReg = ++pParse->nMem;
sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, iRowidReg);
VdbeCoverage(v);
}else{
codeDeferredSeek(pWInfo, pIdx, iCur, iIdxCur);
}
codeDeferredSeek(pWInfo, pIdx, iCur, iIdxCur);
}else if( iCur!=iIdxCur ){
Index *pPk = sqlite3PrimaryKeyIndex(pIdx->pTable);
iRowidReg = sqlite3GetTempRange(pParse, pPk->nKeyCol);
@ -2046,7 +2036,6 @@ Bitmask sqlite3WhereCodeOneLoopStart(
int iRetInit; /* Address of regReturn init */
int untestedTerms = 0; /* Some terms not completely tested */
int ii; /* Loop counter */
u16 wctrlFlags; /* Flags for sub-WHERE clause */
Expr *pAndExpr = 0; /* An ".. AND (...)" expression */
Table *pTab = pTabItem->pTab;
@ -2147,7 +2136,6 @@ Bitmask sqlite3WhereCodeOneLoopStart(
** eliminating duplicates from other WHERE clauses, the action for each
** sub-WHERE clause is to to invoke the main loop body as a subroutine.
*/
wctrlFlags = WHERE_OR_SUBCLAUSE | (pWInfo->wctrlFlags & WHERE_SEEK_TABLE);
ExplainQueryPlan((pParse, 1, "MULTI-INDEX OR"));
for(ii=0; ii<pOrWc->nTerm; ii++){
WhereTerm *pOrTerm = &pOrWc->a[ii];
@ -2166,7 +2154,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
ExplainQueryPlan((pParse, 1, "INDEX %d", ii+1));
WHERETRACE(0xffff, ("Subplan for OR-clause:\n"));
pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
wctrlFlags, iCovCur);
WHERE_OR_SUBCLAUSE, iCovCur);
assert( pSubWInfo || pParse->nErr || db->mallocFailed );
if( pSubWInfo ){
WhereLoop *pSubLoop;
@ -2264,6 +2252,9 @@ Bitmask sqlite3WhereCodeOneLoopStart(
}else{
pCov = 0;
}
if( sqlite3WhereUsesDeferredSeek(pSubWInfo) ){
pWInfo->bDeferredSeek = 1;
}
/* Finish the loop through table entries that match term pOrTerm. */
sqlite3WhereEnd(pSubWInfo);