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Overview
Comment: | Minor cleanup of the sqlite3Select() procedure. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | view-optimization |
Files: | files | file ages | folders |
SHA1: |
f4c90d06bb941453d8110680c7b279e4 |
User & Date: | drh 2015-06-06 00:18:01.663 |
Context
2015-06-06
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18:30 | Code simplifications in select.c and where.c. (check-in: 4f20ac90bc user: drh tags: view-optimization) | |
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) | |
Changes
Changes to src/select.c.
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4810 4811 4812 4813 4814 4815 4816 | p->pOrderBy = 0; p->selFlags &= ~SF_Distinct; } sqlite3SelectPrep(pParse, p, 0); memset(&sSort, 0, sizeof(sSort)); sSort.pOrderBy = p->pOrderBy; pTabList = p->pSrc; | < > < < < < < < | | | 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828 4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840 4841 4842 4843 4844 4845 4846 | p->pOrderBy = 0; p->selFlags &= ~SF_Distinct; } sqlite3SelectPrep(pParse, p, 0); memset(&sSort, 0, sizeof(sSort)); sSort.pOrderBy = p->pOrderBy; pTabList = p->pSrc; if( pParse->nErr || db->mallocFailed ){ goto select_end; } assert( p->pEList!=0 ); isAgg = (p->selFlags & SF_Aggregate)!=0; #if SELECTTRACE_ENABLED if( sqlite3SelectTrace & 0x100 ){ SELECTTRACE(0x100,pParse,p, ("after name resolution:\n")); sqlite3TreeViewSelect(0, p, 0); } #endif /* If writing to memory or generating a set ** only a single column may be output. */ #ifndef SQLITE_OMIT_SUBQUERY if( checkForMultiColumnSelectError(pParse, pDest, p->pEList->nExpr) ){ goto select_end; } #endif /* Try to flatten subqueries in the FROM clause up 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; |
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4863 4864 4865 4866 4867 4868 4869 4870 4871 4872 4873 4874 4875 4876 | 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); | > > > > | 4857 4858 4859 4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870 4871 4872 4873 4874 | if( db->mallocFailed ) goto select_end; if( !IgnorableOrderby(pDest) ){ sSort.pOrderBy = p->pOrderBy; } } #endif /* Get a pointer the VDBE under construction, allocating a new VDBE if one ** does not already exist */ v = sqlite3GetVdbe(pParse); if( v==0 ) goto select_end; #ifndef SQLITE_OMIT_COMPOUND_SELECT /* Handle compound SELECT statements using the separate multiSelect() ** procedure. */ if( p->pPrior ){ rc = multiSelect(pParse, p, pDest); |
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4886 4887 4888 4889 4890 4891 4892 | /* 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; | < | 4884 4885 4886 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 | /* 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 ** is sufficient, though the subroutine to manifest the view does need |
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4911 4912 4913 4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 | ** 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. */ | > > > > > > | 4908 4909 4910 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 | ** 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); /* Make copies of constant WHERE-clause terms in the outer query down ** inside the subquery. This can help the subquery to run more efficiently. */ 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 } /* Generate code to implement the subquery */ 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. */ |
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4974 4975 4976 4977 4978 4979 4980 | 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); } | | | | | | > < | 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988 4989 4990 4991 4992 4993 4994 4995 4996 4997 | 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); } #endif /* Various elements of the SELECT copied into local variables for convenience */ pEList = p->pEList; pWhere = p->pWhere; pGroupBy = p->pGroupBy; pHaving = p->pHaving; sDistinct.isTnct = (p->selFlags & SF_Distinct)!=0; #if SELECTTRACE_ENABLED if( sqlite3SelectTrace & 0x400 ){ |
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5009 5010 5011 5012 5013 5014 5015 | ** ** The second form is preferred as a single index (or temp-table) may be ** used for both the ORDER BY and DISTINCT processing. As originally ** written the query must use a temp-table for at least one of the ORDER ** BY and DISTINCT, and an index or separate temp-table for the other. */ if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct | | < | | | | | | | > | 5012 5013 5014 5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025 5026 5027 5028 5029 5030 5031 5032 5033 5034 5035 5036 5037 5038 5039 5040 5041 5042 | ** ** The second form is preferred as a single index (or temp-table) may be ** used for both the ORDER BY and DISTINCT processing. As originally ** written the query must use a temp-table for at least one of the ORDER ** BY and DISTINCT, and an index or separate temp-table for the other. */ if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct && sqlite3ExprListCompare(sSort.pOrderBy, pEList, -1)==0 ){ p->selFlags &= ~SF_Distinct; pGroupBy = p->pGroupBy = sqlite3ExprListDup(db, pEList, 0); /* Notice that even thought SF_Distinct has been cleared from p->selFlags, ** the sDistinct.isTnct is still set. Hence, isTnct represents the ** original setting of the SF_Distinct flag, not the current setting */ assert( sDistinct.isTnct ); } /* If there is an ORDER BY clause, then create an ephemeral index to ** do the sorting. But this sorting ephemeral index might end up ** being unused if the data can be extracted in pre-sorted order. ** If that is the case, then the OP_OpenEphemeral instruction will be ** changed to an OP_Noop once we figure out that the sorting index is ** not needed. The sSort.addrSortIndex variable is used to facilitate ** that change. */ if( sSort.pOrderBy ){ KeyInfo *pKeyInfo; pKeyInfo = keyInfoFromExprList(pParse, sSort.pOrderBy, 0, pEList->nExpr); sSort.iECursor = pParse->nTab++; sSort.addrSortIndex = sqlite3VdbeAddOp4(v, OP_OpenEphemeral, |
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5056 5057 5058 5059 5060 5061 5062 | p->nSelectRow = LARGEST_INT64; computeLimitRegisters(pParse, p, iEnd); if( p->iLimit==0 && sSort.addrSortIndex>=0 ){ sqlite3VdbeGetOp(v, sSort.addrSortIndex)->opcode = OP_SorterOpen; sSort.sortFlags |= SORTFLAG_UseSorter; } | | | 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 | p->nSelectRow = LARGEST_INT64; computeLimitRegisters(pParse, p, iEnd); if( p->iLimit==0 && sSort.addrSortIndex>=0 ){ sqlite3VdbeGetOp(v, sSort.addrSortIndex)->opcode = OP_SorterOpen; sSort.sortFlags |= SORTFLAG_UseSorter; } /* Open an ephemeral index to use for the distinct set. */ if( p->selFlags & SF_Distinct ){ sDistinct.tabTnct = pParse->nTab++; sDistinct.addrTnct = sqlite3VdbeAddOp4(v, OP_OpenEphemeral, sDistinct.tabTnct, 0, 0, (char*)keyInfoFromExprList(pParse, p->pEList,0,0), P4_KEYINFO); |
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5141 5142 5143 5144 5145 5146 5147 | pItem->u.x.iAlias = 0; } if( p->nSelectRow>100 ) p->nSelectRow = 100; }else{ p->nSelectRow = 1; } | < | | 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 | pItem->u.x.iAlias = 0; } if( p->nSelectRow>100 ) p->nSelectRow = 100; }else{ p->nSelectRow = 1; } /* If there is both a GROUP BY and an ORDER BY clause and they are ** identical, then it may be possible to disable the ORDER BY clause ** on the grounds that the GROUP BY will cause elements to come out ** in the correct order. It also may not - the GROUP BY might use a ** database index that causes rows to be grouped together as required ** but not actually sorted. Either way, record the fact that the ** ORDER BY and GROUP BY clauses are the same by setting the orderByGrp ** variable. */ if( sqlite3ExprListCompare(pGroupBy, sSort.pOrderBy, -1)==0 ){ orderByGrp = 1; } |
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