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Overview
Comment: | Split FROM-clause subquery flattening and code generation into separate loops. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | view-optimization |
Files: | files | file ages | folders |
SHA1: |
be8e3fc70e4c13b28b07985df3457960 |
User & Date: | drh 2015-06-05 22:33:39.408 |
Context
2015-06-06
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00:18 | Minor cleanup of the sqlite3Select() procedure. (check-in: f4c90d06bb user: drh tags: view-optimization) | |
2015-06-05
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22:33 | Split FROM-clause subquery flattening and code generation into separate loops. (check-in: be8e3fc70e user: drh tags: view-optimization) | |
20:27 | Provide one final Select tree dump prior to WHERE clause analysis when ".selecttrace 0x400" tracing bit is set with SELECTTRACE_ENABLED. Analysis and debug changes only - normal builds are unaffected. (check-in: 283bf0b64d user: drh tags: trunk) | |
Changes
Changes to src/expr.c.
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3555 3556 3557 3558 3559 3560 3561 | if( zLabel==0 || zLabel[0]==0 ) zLabel = "LIST"; if( pList==0 ){ sqlite3TreeViewLine(pView, "%s (empty)", zLabel); }else{ sqlite3TreeViewLine(pView, "%s", zLabel); for(i=0; i<pList->nExpr; i++){ sqlite3TreeViewExpr(pView, pList->a[i].pExpr, i<pList->nExpr-1); | < < < < < < < < | 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 | if( zLabel==0 || zLabel[0]==0 ) zLabel = "LIST"; if( pList==0 ){ sqlite3TreeViewLine(pView, "%s (empty)", zLabel); }else{ sqlite3TreeViewLine(pView, "%s", zLabel); for(i=0; i<pList->nExpr; i++){ sqlite3TreeViewExpr(pView, pList->a[i].pExpr, i<pList->nExpr-1); } } sqlite3TreeViewPop(pView); } #endif /* SQLITE_DEBUG */ /* |
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Changes to src/select.c.
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4838 4839 4840 4841 4842 4843 4844 | */ #ifndef SQLITE_OMIT_SUBQUERY if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){ goto select_end; } #endif | | < > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | 4838 4839 4840 4841 4842 4843 4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856 4857 4858 4859 4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 4898 4899 | */ #ifndef SQLITE_OMIT_SUBQUERY if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){ goto select_end; } #endif /* Try to flatten subqueries in the FROM clause into the main query */ #if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) for(i=0; !p->pPrior && i<pTabList->nSrc; i++){ struct SrcList_item *pItem = &pTabList->a[i]; Select *pSub = pItem->pSelect; int isAggSub; if( pSub==0 ) continue; isAggSub = (pSub->selFlags & SF_Aggregate)!=0; if( flattenSubquery(pParse, p, i, isAgg, isAggSub) ){ /* This subquery can be absorbed into its parent. */ if( isAggSub ){ isAgg = 1; p->selFlags |= SF_Aggregate; } i = -1; } pTabList = p->pSrc; if( db->mallocFailed ) goto select_end; if( !IgnorableOrderby(pDest) ){ sSort.pOrderBy = p->pOrderBy; } } #endif #ifndef SQLITE_OMIT_COMPOUND_SELECT /* Handle compound SELECT statements using the separate multiSelect() ** procedure. */ if( p->pPrior ){ rc = multiSelect(pParse, p, pDest); explainSetInteger(pParse->iSelectId, iRestoreSelectId); #if SELECTTRACE_ENABLED SELECTTRACE(1,pParse,p,("end compound-select processing\n")); pParse->nSelectIndent--; #endif return rc; } #endif /* Generate code for all sub-queries in the FROM clause */ #if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) for(i=0; i<pTabList->nSrc; i++){ struct SrcList_item *pItem = &pTabList->a[i]; SelectDest dest; Select *pSub = pItem->pSelect; if( pSub==0 ) continue; /* Sometimes the code for a subquery will be generated more than ** once, if the subquery is part of the WHERE clause in a LEFT JOIN, ** for example. In that case, do not regenerate the code to manifest ** a view or the co-routine to implement a view. The first instance |
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4871 4872 4873 4874 4875 4876 4877 | ** may contain expression trees of at most ** (SQLITE_MAX_EXPR_DEPTH-Parse.nHeight) height. This is a bit ** more conservative than necessary, but much easier than enforcing ** an exact limit. */ pParse->nHeight += sqlite3SelectExprHeight(p); | < < < < < < < < < | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | < < < < < < < < < < < < < < < < < < < | 4911 4912 4913 4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988 4989 4990 4991 4992 4993 4994 4995 4996 4997 4998 4999 5000 5001 5002 5003 5004 | ** may contain expression trees of at most ** (SQLITE_MAX_EXPR_DEPTH-Parse.nHeight) height. This is a bit ** more conservative than necessary, but much easier than enforcing ** an exact limit. */ pParse->nHeight += sqlite3SelectExprHeight(p); if( (pItem->jointype & JT_OUTER)==0 && pushDownWhereTerms(db, pSub, p->pWhere, pItem->iCursor) ){ #if SELECTTRACE_ENABLED if( sqlite3SelectTrace & 0x100 ){ SELECTTRACE(0x100,pParse,p,("After WHERE-clause push-down:\n")); sqlite3TreeViewSelect(0, p, 0); } #endif } if( pTabList->nSrc==1 && (p->selFlags & SF_All)==0 && OptimizationEnabled(db, SQLITE_SubqCoroutine) ){ /* Implement a co-routine that will return a single row of the result ** set on each invocation. */ int addrTop = sqlite3VdbeCurrentAddr(v)+1; pItem->regReturn = ++pParse->nMem; sqlite3VdbeAddOp3(v, OP_InitCoroutine, pItem->regReturn, 0, addrTop); VdbeComment((v, "%s", pItem->pTab->zName)); pItem->addrFillSub = addrTop; sqlite3SelectDestInit(&dest, SRT_Coroutine, pItem->regReturn); explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId); sqlite3Select(pParse, pSub, &dest); pItem->pTab->nRowLogEst = sqlite3LogEst(pSub->nSelectRow); pItem->viaCoroutine = 1; pItem->regResult = dest.iSdst; sqlite3VdbeAddOp1(v, OP_EndCoroutine, pItem->regReturn); sqlite3VdbeJumpHere(v, addrTop-1); sqlite3ClearTempRegCache(pParse); }else{ /* Generate a subroutine that will fill an ephemeral table with ** the content of this subquery. pItem->addrFillSub will point ** to the address of the generated subroutine. pItem->regReturn ** is a register allocated to hold the subroutine return address */ int topAddr; int onceAddr = 0; int retAddr; assert( pItem->addrFillSub==0 ); pItem->regReturn = ++pParse->nMem; topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn); pItem->addrFillSub = topAddr+1; if( pItem->isCorrelated==0 ){ /* If the subquery is not correlated and if we are not inside of ** a trigger, then we only need to compute the value of the subquery ** once. */ onceAddr = sqlite3CodeOnce(pParse); VdbeCoverage(v); VdbeComment((v, "materialize \"%s\"", pItem->pTab->zName)); }else{ VdbeNoopComment((v, "materialize \"%s\"", pItem->pTab->zName)); } sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor); explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId); sqlite3Select(pParse, pSub, &dest); pItem->pTab->nRowLogEst = sqlite3LogEst(pSub->nSelectRow); if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr); retAddr = sqlite3VdbeAddOp1(v, OP_Return, pItem->regReturn); VdbeComment((v, "end %s", pItem->pTab->zName)); sqlite3VdbeChangeP1(v, topAddr, retAddr); sqlite3ClearTempRegCache(pParse); } if( db->mallocFailed ){ goto select_end; } pParse->nHeight -= sqlite3SelectExprHeight(p); } pEList = p->pEList; #endif pWhere = p->pWhere; pGroupBy = p->pGroupBy; pHaving = p->pHaving; sDistinct.isTnct = (p->selFlags & SF_Distinct)!=0; #if SELECTTRACE_ENABLED if( sqlite3SelectTrace & 0x400 ){ SELECTTRACE(0x400,pParse,p,("After all FROM-clause analysis:\n")); sqlite3TreeViewSelect(0, p, 0); } #endif /* If the query is DISTINCT with an ORDER BY but is not an aggregate, and ** if the select-list is the same as the ORDER BY list, then this query ** can be rewritten as a GROUP BY. In other words, this: ** ** SELECT DISTINCT xyz FROM ... ORDER BY xyz |
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