Make sure that an index that covers a proper superset of the WHERE clause
terms of some other index has a lower cost than the other index. FossilOrigin-Name: ea8b0910040198751551b0b960e6b783913607df
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drh
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manifest
15
manifest
@ -1,5 +1,5 @@
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C Experiments\sin\spicking\sbetter\squery\splans,\sespecially\swhen\sthe\susage\sof\sone\nindex\sis\sa\ssubset\sof\sanother.
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D 2014-03-29T21:16:07.103
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C Make\ssure\sthat\san\sindex\sthat\scovers\sa\sproper\ssuperset\sof\sthe\sWHERE\sclause\nterms\sof\ssome\sother\sindex\shas\sa\slower\scost\sthan\sthe\sother\sindex.
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D 2014-03-31T18:24:18.867
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F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
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F Makefile.in 2ef13430cd359f7b361bb863504e227b25cc7f81
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F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
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@ -291,7 +291,7 @@ F src/vtab.c 21b932841e51ebd7d075e2d0ad1415dce8d2d5fd
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F src/wal.c 76e7fc6de229bea8b30bb2539110f03a494dc3a8
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F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
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F src/walker.c 11edb74d587bc87b33ca96a5173e3ec1b8389e45
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F src/where.c 26c6f6260b0cc2b0038dcc68ace0d7db20c7dcee
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F src/where.c 50ac3154473b5c8df15c7b8dbd19da385fa859e1
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F src/whereInt.h 2564055b440e44ebec8b47f237bbccae6719b7af
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F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
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F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
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@ -1159,10 +1159,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
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F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
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F tool/warnings.sh d1a6de74685f360ab718efda6265994b99bbea01
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F tool/win/sqlite.vsix 030f3eeaf2cb811a3692ab9c14d021a75ce41fff
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P 27deb6e49bcc76714dbdc61b34748603155ac770
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R 1df7985395668b26c614cc4e641f29c8
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T *branch * query-plan-experiments
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T *sym-query-plan-experiments *
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T -sym-trunk *
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P 8f869ca7a6eaa9ca7a08102290e6c606735f9090
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R 76b8d8088ba83ec014dc8bf476fa6749
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U drh
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Z 1c5ff3f986da6bbe350c60cf72c963dd
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Z ecebe13d1c9f7ea1da970c5f6118dc52
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@ -1 +1 @@
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8f869ca7a6eaa9ca7a08102290e6c606735f9090
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ea8b0910040198751551b0b960e6b783913607df
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99
src/where.c
99
src/where.c
@ -3711,6 +3711,51 @@ static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
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}
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}
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/*
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** Compare every WhereLoop X on the list p against pTemplate. If:
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**
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** (1) both X and pTemplate refer to the same table, and
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** (2) both X and pTemplate use a single index, and
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** (3) pTemplate uses all the same WHERE clause terms as X plus
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** at least one more term,
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**
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** then make sure the cost pTemplate is less than the cost of X, adjusting
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** the cost of pTemplate downward if necessary.
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**
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** Example: When computing the query plan for the SELECT below:
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**
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** CREATE TABLE t1(a,b,c,d);
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** CREATE INDEX t1abc ON t1(a,b,c);
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** CREATE INDEX t1bc ON t1(b,c);
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** SELECT d FROM t1 WHERE a=? AND b=? AND c>=? ORDER BY c;
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**
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** Make sure the cost of using three three columns of index t1abc is less
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** than the cost of using both columns of t1bc.
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*/
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static void whereLoopAdjustCost(const WhereLoop *p, WhereLoop *pTemplate){
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if( (pTemplate->wsFlags & WHERE_INDEXED)==0 ) return;
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if( pTemplate->nLTerm==0 ) return;
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for(; p; p=p->pNextLoop){
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if( p->iTab==pTemplate->iTab
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&& (p->wsFlags & WHERE_INDEXED)!=0
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&& p->nLTerm<pTemplate->nLTerm
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&& (p->rRun<pTemplate->rRun || (p->rRun==pTemplate->rRun &&
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p->nOut<=pTemplate->nOut))
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){
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int i, j;
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for(j=0, i=p->nLTerm-1; i>=0 && j>=0; i--){
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for(j=pTemplate->nLTerm-1; j>=0; j--){
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if( pTemplate->aLTerm[j]==p->aLTerm[i] ) break;
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}
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}
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if( j>=0 ){
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pTemplate->rRun = p->rRun;
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pTemplate->nOut = p->nOut - 1;
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}
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}
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}
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}
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/*
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** Search the list of WhereLoops in *ppPrev looking for one that can be
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** supplanted by pTemplate.
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@ -3747,39 +3792,30 @@ static WhereLoop **whereLoopFindLesser(
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** rSetup. Call this SETUP-INVARIANT */
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assert( p->rSetup>=pTemplate->rSetup );
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if( (p->prereq & pTemplate->prereq)==p->prereq
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&& p->rSetup<=pTemplate->rSetup
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&& p->rRun<=pTemplate->rRun
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&& p->nOut<=pTemplate->nOut
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/* If existing WhereLoop p is better than pTemplate, pTemplate can be
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** discarded. WhereLoop p is better if:
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** (1) p has no more dependencies than pTemplate, and
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** (2) p has an equal or lower cost than pTemplate
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*/
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if( (p->prereq & pTemplate->prereq)==p->prereq /* (1) */
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&& p->rSetup<=pTemplate->rSetup /* (2a) */
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&& p->rRun<=pTemplate->rRun /* (2b) */
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&& p->nOut<=pTemplate->nOut /* (2c) */
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){
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/* This branch taken when p is equal or better than pTemplate in
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** all of (1) dependencies (2) setup-cost, (3) run-cost, and
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** (4) number of output rows. */
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assert( p->rSetup==pTemplate->rSetup );
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if( p->prereq==pTemplate->prereq
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&& p->nLTerm<pTemplate->nLTerm
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&& (p->wsFlags & pTemplate->wsFlags & WHERE_INDEXED)!=0
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&& (p->u.btree.pIndex==pTemplate->u.btree.pIndex
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|| pTemplate->rRun+p->nLTerm<=p->rRun+pTemplate->nLTerm)
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){
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/* Overwrite an existing WhereLoop with an similar one that uses
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** more terms of the index */
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break;
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}else{
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/* There is an existing WhereLoop that is better than pTemplate */
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return 0;
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}
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return 0; /* Discard pTemplate */
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}
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if( (p->prereq & pTemplate->prereq)==pTemplate->prereq
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&& p->rRun>=pTemplate->rRun
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&& p->nOut>=pTemplate->nOut
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/* If pTemplate is always better than p, then cause p to be overwritten
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** with pTemplate. pTemplate is better than p if:
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** (1) pTemplate has no more dependences than p, and
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** (2) pTemplate has an equal or lower cost than p.
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*/
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if( (p->prereq & pTemplate->prereq)==pTemplate->prereq /* (1) */
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&& p->rRun>=pTemplate->rRun /* (2a) */
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&& p->nOut>=pTemplate->nOut /* (2b) */
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){
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/* Overwrite an existing WhereLoop with a better one: one that is
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** better at one of (1) dependencies, (2) setup-cost, (3) run-cost
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** or (4) number of output rows, and is no worse in any of those
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** categories. */
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assert( p->rSetup>=pTemplate->rSetup ); /* SETUP-INVARIANT above */
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break;
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break; /* Cause p to be overwritten by pTemplate */
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}
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}
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return ppPrev;
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@ -3801,15 +3837,13 @@ static WhereLoop **whereLoopFindLesser(
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**
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** When accumulating multiple loops (when pBuilder->pOrSet is NULL) we
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** still might overwrite similar loops with the new template if the
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** template is better. Loops may be overwritten if the following
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** new template is better. Loops may be overwritten if the following
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** conditions are met:
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**
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** (1) They have the same iTab.
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** (2) They have the same iSortIdx.
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** (3) The template has same or fewer dependencies than the current loop
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** (4) The template has the same or lower cost than the current loop
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** (5) The template uses more terms of the same index but has no additional
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** dependencies
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*/
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static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
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WhereLoop **ppPrev, *p;
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@ -3837,6 +3871,7 @@ static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
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/* Look for an existing WhereLoop to replace with pTemplate
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*/
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whereLoopAdjustCost(pWInfo->pLoops, pTemplate);
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ppPrev = whereLoopFindLesser(&pWInfo->pLoops, pTemplate);
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if( ppPrev==0 ){
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