Avoid computing the values for unused result-set columns in subqueries.
Performance optimization request [baa5bb76c35a124c]. FossilOrigin-Name: 7c2d3406000dc8ac5a99cc205b036356b67e4b0b94738592ffc5680749696904
This commit is contained in:
drh
@@ -1,5 +1,5 @@
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C Update\sthe\sversion\snumber\sto\s3.42.0\sto\sbegin\sthe\snext\sdevelopment\scycle.
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D 2023-02-22T20:50:51.768
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C Avoid\scomputing\sthe\svalues\sfor\sunused\sresult-set\scolumns\sin\ssubqueries.\nPerformance\soptimization\srequest\s[baa5bb76c35a124c].
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D 2023-02-22T21:11:34.555
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F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
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F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
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F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
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@@ -621,12 +621,12 @@ F src/printf.c ff4b05e38bf928ff1b80d3dda4f977b10fe39ecbfe69c018224c7e5594fb2455
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F src/random.c 606b00941a1d7dd09c381d3279a058d771f406c5213c9932bbd93d5587be4b9c
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F src/resolve.c d62c5665279cc7485f9d45b5e20911cc7b19c203f268321a90d05d74f4725750
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F src/rowset.c ba9515a922af32abe1f7d39406b9d35730ed65efab9443dc5702693b60854c92
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F src/select.c f80d98f13fa64201ababf5e80d682c430559cd7ee00ab14ee99a1aeb27ac097d
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F src/select.c 751d2f021cb439abdf3e8e7b74c5d0532ca9793868e4fb4c5a73412aea274edc
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F src/shell.c.in 6f36f5ca05f1bebf74935a7fcf2dce983016e807a09cbd752a673583ad7da087
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F src/sqlite.h.in 662a2fa083d093896b92560c871dea6d86792b49dc4bf7b4e8dbeca8e7171488
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F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
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F src/sqlite3ext.h da473ce2b3d0ae407a6300c4a164589b9a6bfdbec9462688a8593ff16f3bb6e4
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F src/sqliteInt.h 4dcc36b21dd0c77efeb0bb38b0d31916bc63fb429c8a89d186c945eba0816447
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F src/sqliteInt.h 25f38ade2d93828231d6cd8614f635c0b084bee004360d970542861ad2e3e3d8
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F src/sqliteLimit.h d7323ffea5208c6af2734574bae933ca8ed2ab728083caa117c9738581a31657
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F src/status.c 160c445d7d28c984a0eae38c144f6419311ed3eace59b44ac6dafc20db4af749
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F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
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@@ -1457,11 +1457,12 @@ F test/select8.test 8c8f5ae43894c891efc5755ed905467d1d67ad5d
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F test/select9.test f7586b207ce2304ab80dc93d3146469a28fd4403621dd3a82d06644563d3c812
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F test/selectA.test 6aef8b2136a4ac7a3e2e4161d2b8ca7bc6ebe2779de084f9bb66ca9e2323a937
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F test/selectB.test 954e4e49cf1f896d61794e440669e03a27ceea25
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F test/selectC.test fec14c9015ed4ec941508bbc144f30b42e40ac34a4bb33001450369865dd0b75
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F test/selectC.test 38c530b0cc5728b793c3c11f52b52c70290d39822224acd39011c89c1853bd31
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F test/selectD.test 6d1909b49970bf92f45ce657505befcef5fc7cbc13544e18103a316d32189bfb
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F test/selectE.test a8730ca330fcf40ace158f134f4fe0eb00c7edbf
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F test/selectF.test 21c94e6438f76537b72532fa9fd4710cdd455fc3
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F test/selectG.test 089f7d3d7e6db91566f00b036cb353107a2cca6220eb1cb264085a836dae8840
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F test/selectH.test a1fed72a83a68ed858db6fcf6d8ddccc4a368645c0ef48dc3ac331d41efe34de
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F test/session.test 78fa2365e93d3663a6e933f86e7afc395adf18be
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F test/sessionfuzz-data1.db 1f8d5def831f19b1c74571037f0d53a588ea49a6c4ca2a028fc0c27ef896dbcb
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F test/sessionfuzz.c 5eef09af01eeff6f20250ae4c0112c2e576e4d2f2026cc9a49dc5be6886fa6ee
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@@ -1918,7 +1919,7 @@ F test/windowerr.tcl f5acd6fbc210d7b5546c0e879d157888455cd4a17a1d3f28f07c1c8a387
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F test/windowerr.test a8b752402109c15aa1c5efe1b93ccb0ce1ef84fa964ae1cd6684dd0b3cc1819b
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F test/windowfault.test 15094c1529424e62f798bc679e3fe9dfab6e8ba2f7dfe8c923b6248c31660a7c
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F test/windowpushd.test d8895d08870b7226f7693665bd292eb177e62ca06799184957b3ca7dc03067df
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F test/with1.test 9ad67fdeb2bbd808a5763c9060e214ea232f9b18d846ea3a59756dc38bdc3880
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F test/with1.test b93833890e5d2a368e78747f124503a0159aa029b98e9ed4795ebf630b2efd3d
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F test/with2.test a1df41b987198383b9b70bf5e5fda390582e46398653858dbc6ceb24253b28df
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F test/with3.test e7bf809bf75c1f44f98bca78bc331dbf542002c5227bf53c1261144db4e824c8
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F test/with4.test 257be66c0c67fee1defbbac0f685c3465e2cad037f21ce65f23f86084f198205
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@@ -2045,8 +2046,9 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
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F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
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F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
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F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
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P aa6bd6dff751223e302575c60f335707e4bb820bff716cab3706b564e18ed7ed
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R 311ae6e51c5af4c947ddc5fe5e93f886
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P 65910216393ed287dbc7e42a2598b6980183c62a64da6572cb691ff4ee23555d cf8f57c53425d89619ece10edc197d7d28946d3b23fcb4f526330196c76d9cc1
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R 34649150ad57f18afb1178077e5cdae5
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T +closed cf8f57c53425d89619ece10edc197d7d28946d3b23fcb4f526330196c76d9cc1
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U drh
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Z 558b030af06c9bbcf0267311941c1842
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Z c744fac449b59dcb5adcaf0108c5c30e
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# Remove this line to create a well-formed Fossil manifest.
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+1
-1
@@ -1 +1 @@
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65910216393ed287dbc7e42a2598b6980183c62a64da6572cb691ff4ee23555d
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7c2d3406000dc8ac5a99cc205b036356b67e4b0b94738592ffc5680749696904
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@@ -5227,6 +5227,76 @@ static int pushDownWhereTerms(
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}
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#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
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/*
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** Check to see if a subquery contains result-set columns that are
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** never used. If it does, change the value of those result-set columns
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** to NULL so that they do not cause unnecessary work to compute.
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**
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** Return the number of column that were changed to NULL.
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*/
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static int disableUnusedSubqueryResultColumns(SrcItem *pItem){
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int nCol;
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Select *pSub; /* The subquery to be simplified */
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Select *pX; /* For looping over compound elements of pSub */
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Table *pTab; /* The table that describes the subquery */
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int j; /* Column number */
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int nChng = 0; /* Number of columns converted to NULL */
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Bitmask colUsed; /* Columns that may not be NULLed out */
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assert( pItem!=0 );
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if( pItem->fg.isCorrelated || pItem->fg.isCte ){
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return 0;
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}
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assert( pItem->pTab!=0 );
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pTab = pItem->pTab;
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assert( pItem->pSelect!=0 );
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pSub = pItem->pSelect;
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assert( pSub->pEList->nExpr==pTab->nCol );
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if( (pSub->selFlags & (SF_Distinct|SF_Aggregate))!=0 ){
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testcase( pSub->selFlags & SF_Distinct );
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testcase( pSub->selFlags & SF_Aggregate );
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return 0;
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}
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for(pX=pSub; pX; pX=pX->pPrior){
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if( pX->pPrior && pX->op!=TK_ALL ){
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/* This optimization does not work for compound subqueries that
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** use UNION, INTERSECT, or EXCEPT. Only UNION ALL is allowed. */
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return 0;
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}
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if( pX->pWin ){
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/* This optimization does not work for subqueries that use window
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** functions. */
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return 0;
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}
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}
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colUsed = pItem->colUsed;
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if( pSub->pOrderBy ){
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ExprList *pList = pSub->pOrderBy;
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for(j=0; j<pList->nExpr; j++){
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u16 iCol = pList->a[j].u.x.iOrderByCol;
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if( iCol>0 ){
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iCol--;
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colUsed |= ((Bitmask)1)<<(iCol>=BMS ? BMS-1 : iCol);
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}
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}
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}
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nCol = pTab->nCol;
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for(j=0; j<nCol; j++){
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Select *pX;
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Bitmask m = j<BMS-1 ? MASKBIT(j) : TOPBIT;
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if( (m & colUsed)!=0 ) continue;
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for(pX=pSub; pX; pX=pX->pPrior) {
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Expr *pY = pX->pEList->a[j].pExpr;
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if( pY->op==TK_NULL ) continue;
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pY->op = TK_NULL;
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pX->selFlags |= SF_PushDown;
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nChng++;
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}
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}
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return nChng;
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}
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/*
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** The pFunc is the only aggregate function in the query. Check to see
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** if the query is a candidate for the min/max optimization.
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@@ -7326,6 +7396,22 @@ int sqlite3Select(
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TREETRACE(0x4000,pParse,p,("Push-down not possible\n"));
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}
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/* Convert unused result columns of the subquery into simple NULL
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** expressions, to avoid unneeded searching and computation.
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*/
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if( OptimizationEnabled(db, SQLITE_NullUnusedCols)
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&& disableUnusedSubqueryResultColumns(pItem)
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){
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#if TREETRACE_ENABLED
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if( sqlite3TreeTrace & 0x4000 ){
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TREETRACE(0x4000,pParse,p,
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("Change unused result columns to NULL for subquery %d:\n",
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pSub->selId));
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sqlite3TreeViewSelect(0, p, 0);
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}
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#endif
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}
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zSavedAuthContext = pParse->zAuthContext;
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pParse->zAuthContext = pItem->zName;
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@@ -1839,6 +1839,7 @@ struct sqlite3 {
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/* TH3 expects this value ^^^^^^^^^^ See flatten04.test */
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#define SQLITE_IndexedExpr 0x01000000 /* Pull exprs from index when able */
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#define SQLITE_Coroutines 0x02000000 /* Co-routines for subqueries */
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#define SQLITE_NullUnusedCols 0x04000000 /* NULL unused columns in subqueries */
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#define SQLITE_AllOpts 0xffffffff /* All optimizations */
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/*
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@@ -230,6 +230,11 @@ do_execsql_test selectC-4.2 {
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select a from (select distinct a, b from t_distinct_bug)
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} {1 1 1}
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do_execsql_test selectC-4.2b {
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CREATE VIEW v42b AS SELECT DISTINCT a, b FROM t_distinct_bug;
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SELECT a FROM v42b;
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} {1 1 1}
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do_execsql_test selectC-4.3 {
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select a, udf() from (select distinct a, b from t_distinct_bug)
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} {1 1 1 2 1 3}
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@@ -0,0 +1,110 @@
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# 2023-02-16
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#
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# The author disclaims copyright to this source code. In place of
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# a legal notice, here is a blessing:
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#
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# May you do good and not evil.
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# May you find forgiveness for yourself and forgive others.
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# May you share freely, never taking more than you give.
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#
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#***********************************************************************
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#
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# Test cases for the omit-unused-subquery-column optimization.
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#
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set testdir [file dirname $argv0]
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source $testdir/tester.tcl
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set testprefix selectH
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do_execsql_test 1.1 {
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CREATE TABLE t1(
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c0, c1, c2, c3, c4, c5, c6, c7, c8, c9,
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c10, c11, c12, c13, c14, c15, c16, c17, c18, c19,
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c20, c21, c22, c23, c24, c25, c26, c27, c28, c29,
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c30, c31, c32, c33, c34, c35, c36, c37, c38, c39,
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c40, c41, c42, c43, c44, c45, c46, c47, c48, c49,
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c50, c51, c52, c53, c54, c55, c56, c57, c58, c59,
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c60, c61, c62, c63, c64, c65
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);
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INSERT INTO t1 VALUES(
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
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10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
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20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
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30, 31, 32, 33, 34, 35, 36, 37, 38, 39,
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40, 41, 42, 43, 44, 45, 46, 47, 48, 49,
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50, 51, 52, 53, 54, 55, 56, 57, 58, 59,
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60, 61, 62, 63, 64, 65
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);
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CREATE INDEX t1c60 ON t1(c60);
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}
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# The SQL counter(N) function adjusts the value of the global
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# TCL variable ::selectH_cnt by the value N and returns the new
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# value. By putting calls to counter(N) as unused columns in a
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# view or subquery, we can check to see if the counter gets incremented,
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# and if not that means that the unused column was omitted.
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#
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unset -nocomplain selectH_cnt
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set selectH_cnt 0
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proc selectH_counter {amt} {
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global selectH_cnt
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incr selectH_cnt $amt
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return $selectH_cnt
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}
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db func counter selectH_counter
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do_execsql_test 1.2 {
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SELECT DISTINCT c44 FROM (
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SELECT c0 AS a, *, counter(1) FROM t1
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UNION ALL
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SELECT c1 AS a, *, counter(1) FROM t1
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) WHERE c60=60;
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} {44}
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do_test 1.3 {
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set ::selectH_cnt
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} {0}
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do_execsql_test 2.1 {
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SELECT a FROM (
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SELECT counter(1) AS cnt, c15 AS a, *, c62 AS b FROM t1
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UNION ALL
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SELECT counter(1) AS cnt, c16 AS a, *, c61 AS b FROM t1
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ORDER BY b
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);
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} {16 15}
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do_test 2.2 {
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set ::selectH_cnt
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} {0}
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do_execsql_test 3.1 {
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CREATE VIEW v1 AS
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SELECT c16 AS a, *, counter(1) AS x FROM t1
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UNION ALL
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SELECT c17 AS a, *, counter(1) AS x FROM t1
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UNION ALL
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SELECT c18 AS a, *, counter(1) AS x FROM t1
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UNION ALL
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SELECT c19 AS a, *, counter(1) AS x FROM t1;
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SELECT count(*) FROM v1 WHERE c60=60;
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} {4}
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do_test 3.2 {
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set ::selectH_cnt
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} {0}
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do_execsql_test 3.3 {
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SELECT count(a) FROM v1 WHERE c60=60;
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} {4}
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do_execsql_test 3.4 {
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SELECT a FROM v1 WHERE c60=60;
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} {16 17 18 19}
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do_test 3.5 {
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set ::selectH_cnt
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} {0}
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do_execsql_test 3.6 {
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SELECT x FROM v1 WHERE c60=60;
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} {1 2 3 4}
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do_test 3.7 {
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set ::selectH_cnt
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} {4}
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finish_test
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+1
-1
@@ -1124,7 +1124,7 @@ do_execsql_test 24.1 {
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CREATE VIEW v1 AS SELECT max(a), min(b) FROM t1 GROUP BY c;
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}
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do_test 24.1 {
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set program [db eval {EXPLAIN SELECT 1 FROM v1,v1,v1}]
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set program [db eval {EXPLAIN SELECT * FROM v1 AS aa, v1 AS bb, v1 AS cc}]
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expr [lsearch $program OpenDup]>0
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} {1}
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do_execsql_test 24.2 {
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