LIBOBJS0 = alter.lo analyze.lo attach.lo auth.lo \
backup.lo bitvec.lo btmutex.lo btree.lo build.lo \
callback.lo complete.lo ctime.lo date.lo dbstat.lo delete.lo \
- expr.lo fault.lo fkey.lo \
+ expr.lo fault.lo fkey.lo flatten.lo \
fts3.lo fts3_aux.lo fts3_expr.lo fts3_hash.lo fts3_icu.lo \
fts3_porter.lo fts3_snippet.lo fts3_tokenizer.lo fts3_tokenizer1.lo \
fts3_tokenize_vtab.lo \
$(TOP)/src/expr.c \
$(TOP)/src/fault.c \
$(TOP)/src/fkey.c \
+ $(TOP)/src/flatten.c \
$(TOP)/src/func.c \
$(TOP)/src/global.c \
$(TOP)/src/hash.c \
fkey.lo: $(TOP)/src/fkey.c $(HDR)
$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/fkey.c
+flatten.lo: $(TOP)/src/flatten.c $(HDR)
+ $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/flatten.c
+
func.lo: $(TOP)/src/func.c $(HDR)
$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/func.c
LIBOBJS0 = vdbe.lo parse.lo alter.lo analyze.lo attach.lo auth.lo \
backup.lo bitvec.lo btmutex.lo btree.lo build.lo \
callback.lo complete.lo ctime.lo date.lo dbstat.lo delete.lo \
- expr.lo fault.lo fkey.lo \
+ expr.lo fault.lo fkey.lo flatten.lo \
fts3.lo fts3_aux.lo fts3_expr.lo fts3_hash.lo fts3_icu.lo \
fts3_porter.lo fts3_snippet.lo fts3_tokenizer.lo fts3_tokenizer1.lo \
fts3_tokenize_vtab.lo fts3_unicode.lo fts3_unicode2.lo fts3_write.lo \
$(TOP)\src\expr.c \
$(TOP)\src\fault.c \
$(TOP)\src\fkey.c \
+ $(TOP)\src\flatten.c \
$(TOP)\src\func.c \
$(TOP)\src\global.c \
$(TOP)\src\hash.c \
fkey.lo: $(TOP)\src\fkey.c $(HDR)
$(LTCOMPILE) $(CORE_COMPILE_OPTS) -c $(TOP)\src\fkey.c
+flatten.lo: $(TOP)\src\flatten.c $(HDR)
+ $(LTCOMPILE) $(CORE_COMPILE_OPTS) -c $(TOP)\src\flatten.c
+
func.lo: $(TOP)\src\func.c $(HDR)
$(LTCOMPILE) $(CORE_COMPILE_OPTS) -c $(TOP)\src\func.c
LIBOBJ+= vdbe.o parse.o \
alter.o analyze.o attach.o auth.o \
backup.o bitvec.o btmutex.o btree.o build.o \
- callback.o complete.o ctime.o date.o dbstat.o delete.o expr.o fault.o fkey.o \
+ callback.o complete.o ctime.o date.o dbstat.o delete.o expr.o \
+ fault.o fkey.o flatten.o \
fts3.o fts3_aux.o fts3_expr.o fts3_hash.o fts3_icu.o fts3_porter.o \
fts3_snippet.o fts3_tokenizer.o fts3_tokenizer1.o \
fts3_tokenize_vtab.o \
$(TOP)/src/expr.c \
$(TOP)/src/fault.c \
$(TOP)/src/fkey.c \
+ $(TOP)/src/flatten.c \
$(TOP)/src/func.c \
$(TOP)/src/global.c \
$(TOP)/src/hash.c \
-C Typo\sfixes\sand\sadditional\sbackground\sinformation\sin\sREADME.md.
-D 2015-06-01T11:10:39.796
+C Break\sout\sthe\squery\sflattener\sinto\sa\sseparate\ssource-code\sfile.
+D 2015-06-01T17:32:44.582
F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
-F Makefile.in 994bab32a3a69e0c35bd148b65cde49879772964
+F Makefile.in 901711bd45174dd11f3be4b2a9ebb52dd2947880
F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
-F Makefile.msc d37d2c2323df3acae6e24c71a478889421c17264
+F Makefile.msc 435b9902d78664073b4a86189b4383a1ab089012
F Makefile.vxworks e1b65dea203f054e71653415bd8f96dcaed47858
F README.md 8ecc12493ff9f820cdea6520a9016001cb2e59b7
F VERSION ce0ae95abd7121c534f6917c1c8f2b70d9acd4db
F install-sh 9d4de14ab9fb0facae2f48780b874848cbf2f895 x
F ltmain.sh 3ff0879076df340d2e23ae905484d8c15d5fdea8
F magic.txt 8273bf49ba3b0c8559cb2774495390c31fd61c60
-F main.mk 8d418497da6a152a59b00d64ae3d66f3c665974c
+F main.mk df00654d66ae489f5162b197e8ff000159840080
F mkopcodec.awk c2ff431854d702cdd2d779c9c0d1f58fa16fa4ea
F mkopcodeh.awk d5e22023b5238985bb54a72d33e0ac71fe4f8a32
F mkso.sh fd21c06b063bb16a5d25deea1752c2da6ac3ed83
F src/expr.c 3fb2ab3ab69d15b4b75ae53fceb4e317f64cb306
F src/fault.c 160a0c015b6c2629d3899ed2daf63d75754a32bb
F src/fkey.c c9b63a217d86582c22121699a47f22f524608869
+F src/flatten.c 1b2b33220480ca391776aecc11af03db661f6530
F src/func.c 5b8b8e77a0fb644eaf8947d413804622e32692b6
-F src/global.c 4f77cadbc5427d00139ba43d0f3979804cbb700e
+F src/global.c 5aee11be8fe662bee7f4277f8324117931078fe7
F src/hash.c 4263fbc955f26c2e8cdc0cf214bc42435aa4e4f5
F src/hash.h c8f3c31722cf3277d03713909761e152a5b81094
F src/hwtime.h d32741c8f4df852c7d959236615444e2b1063b08
F src/random.c ba2679f80ec82c4190062d756f22d0c358180696
F src/resolve.c 84c571794e3ee5806274d95158a4c0177c6c4708
F src/rowset.c eccf6af6d620aaa4579bd3b72c1b6395d9e9fa1e
-F src/select.c 5978cc521cb8fc1aa6a0089e35edaf531accb52a
+F src/select.c 38853592c5cad664516b6e18e153a269f3a0ec35
F src/shell.c 07dda7cd692911d2f22269953418d049f2e2c0ee
F src/sqlite.h.in d165beeceb6b40af60f352a4d4e37e02d9af7df0
F src/sqlite3.rc 992c9f5fb8285ae285d6be28240a7e8d3a7f2bad
F src/sqlite3ext.h 2ebeb634e751a61a6f0eebfa0f4669f46a42f6cd
-F src/sqliteInt.h bc8496de6a514ac66a5a938ee0e4f0d17d150c77
+F src/sqliteInt.h 76b6ada92a26eef5e2022fe297c9dfdc27c92175
F src/sqliteLimit.h 216557999cb45f2e3578ed53ebefe228d779cb46
F src/status.c f266ad8a2892d659b74f0f50cb6a88b6e7c12179
F src/table.c 51b46b2a62d1b3a959633d593b89bab5e2c9155e
F tool/mkpragmatab.tcl 40c287d3f929ece67da6e9e7c49885789960accf
F tool/mkspeedsql.tcl a1a334d288f7adfe6e996f2e712becf076745c97
F tool/mksqlite3c-noext.tcl 69bae8ce4aa52d2ff82d4a8a856bf283ec035b2e
-F tool/mksqlite3c.tcl fdeab4c1eed90b7ab741ec12a7bc5c2fb60188bd
+F tool/mksqlite3c.tcl 8f80ee6470478a08c6b989e15ea9ed1a2deeba64
F tool/mksqlite3h.tcl 44730d586c9031638cdd2eb443b801c0d2dbd9f8
F tool/mksqlite3internalh.tcl eb994013e833359137eb53a55acdad0b5ae1049b
F tool/mkvsix.tcl 3b58b9398f91c7dbf18d49eb87cefeee9efdbce1
F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32
F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P c864ff912db8bc0a3c3ecc1ceac61a25332e76c5
-R 36a9006d323883fc8b82cd3617fe7735
+P 9b8e5823bccf69f5cdedd8655e75df6e9718b809
+R afb2f46044fdfbf19f28b9766d9a237e
U drh
-Z 5f89713174f72e7e8f725e1fe0117a4f
+Z 6dc0d4f8ac2adb688c2f00112c8586f2
-9b8e5823bccf69f5cdedd8655e75df6e9718b809
\ No newline at end of file
+e3fa8b936b31a487eda5b3dc49f2d97ef7e2d419
\ No newline at end of file
--- /dev/null
+/*
+** 2015-06-01
+**
+** The author disclaims copyright to this source code. In place of
+** a legal notice, here is a blessing:
+**
+** May you do good and not evil.
+** May you find forgiveness for yourself and forgive others.
+** May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains C code used to transform FROM-clause subqueries
+** in ways that result in faster query evaluation.
+*/
+#include "sqliteInt.h"
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/* Forward Declarations */
+static void substExprList(sqlite3*, ExprList*, int, ExprList*);
+static void substSelect(sqlite3*, Select *, int, ExprList *);
+
+/*
+** Scan through the expression pExpr. Replace every reference to
+** a column in table number iTable with a copy of the iColumn-th
+** entry in pEList. (But leave references to the ROWID column
+** unchanged.)
+**
+** This routine is part of the flattening procedure. A subquery
+** whose result set is defined by pEList appears as entry in the
+** FROM clause of a SELECT such that the VDBE cursor assigned to that
+** FORM clause entry is iTable. This routine make the necessary
+** changes to pExpr so that it refers directly to the source table
+** of the subquery rather the result set of the subquery.
+*/
+static Expr *substExpr(
+ sqlite3 *db, /* Report malloc errors to this connection */
+ Expr *pExpr, /* Expr in which substitution occurs */
+ int iTable, /* Table to be substituted */
+ ExprList *pEList /* Substitute expressions */
+){
+ if( pExpr==0 ) return 0;
+ if( pExpr->op==TK_COLUMN && pExpr->iTable==iTable ){
+ if( pExpr->iColumn<0 ){
+ pExpr->op = TK_NULL;
+ }else{
+ Expr *pNew;
+ assert( pEList!=0 && pExpr->iColumn<pEList->nExpr );
+ assert( pExpr->pLeft==0 && pExpr->pRight==0 );
+ pNew = sqlite3ExprDup(db, pEList->a[pExpr->iColumn].pExpr, 0);
+ sqlite3ExprDelete(db, pExpr);
+ pExpr = pNew;
+ }
+ }else{
+ pExpr->pLeft = substExpr(db, pExpr->pLeft, iTable, pEList);
+ pExpr->pRight = substExpr(db, pExpr->pRight, iTable, pEList);
+ if( ExprHasProperty(pExpr, EP_xIsSelect) ){
+ substSelect(db, pExpr->x.pSelect, iTable, pEList);
+ }else{
+ substExprList(db, pExpr->x.pList, iTable, pEList);
+ }
+ }
+ return pExpr;
+}
+static void substExprList(
+ sqlite3 *db, /* Report malloc errors here */
+ ExprList *pList, /* List to scan and in which to make substitutes */
+ int iTable, /* Table to be substituted */
+ ExprList *pEList /* Substitute values */
+){
+ int i;
+ if( pList==0 ) return;
+ for(i=0; i<pList->nExpr; i++){
+ pList->a[i].pExpr = substExpr(db, pList->a[i].pExpr, iTable, pEList);
+ }
+}
+static void substSelect(
+ sqlite3 *db, /* Report malloc errors here */
+ Select *p, /* SELECT statement in which to make substitutions */
+ int iTable, /* Table to be replaced */
+ ExprList *pEList /* Substitute values */
+){
+ SrcList *pSrc;
+ struct SrcList_item *pItem;
+ int i;
+ if( !p ) return;
+ substExprList(db, p->pEList, iTable, pEList);
+ substExprList(db, p->pGroupBy, iTable, pEList);
+ substExprList(db, p->pOrderBy, iTable, pEList);
+ p->pHaving = substExpr(db, p->pHaving, iTable, pEList);
+ p->pWhere = substExpr(db, p->pWhere, iTable, pEList);
+ substSelect(db, p->pPrior, iTable, pEList);
+ pSrc = p->pSrc;
+ assert( pSrc ); /* Even for (SELECT 1) we have: pSrc!=0 but pSrc->nSrc==0 */
+ if( ALWAYS(pSrc) ){
+ for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
+ substSelect(db, pItem->pSelect, iTable, pEList);
+ }
+ }
+}
+
+/*
+** This routine attempts to flatten subqueries as a performance optimization.
+** This routine returns 1 if it makes changes and 0 if no flattening occurs.
+**
+** To understand the concept of flattening, consider the following
+** query:
+**
+** SELECT a FROM (SELECT x+y AS a FROM t1 WHERE z<100) WHERE a>5
+**
+** The default way of implementing this query is to execute the
+** subquery first and store the results in a temporary table, then
+** run the outer query on that temporary table. This requires two
+** passes over the data. Furthermore, because the temporary table
+** has no indices, the WHERE clause on the outer query cannot be
+** optimized.
+**
+** This routine attempts to rewrite queries such as the above into
+** a single flat select, like this:
+**
+** SELECT x+y AS a FROM t1 WHERE z<100 AND a>5
+**
+** The code generated for this simplification gives the same result
+** but only has to scan the data once. And because indices might
+** exist on the table t1, a complete scan of the data might be
+** avoided.
+**
+** Flattening is only attempted if all of the following are true:
+**
+** (1) The subquery and the outer query do not both use aggregates.
+**
+** (2) The subquery is not an aggregate or (2a) the outer query is not a join
+** and (2b) the outer query does not use subqueries other than the one
+** FROM-clause subquery that is a candidate for flattening. (2b is
+** due to ticket [2f7170d73bf9abf80] from 2015-02-09.)
+**
+** (3) The subquery is not the right operand of a left outer join
+** (Originally ticket #306. Strengthened by ticket #3300)
+**
+** (4) The subquery is not DISTINCT.
+**
+** (**) At one point restrictions (4) and (5) defined a subset of DISTINCT
+** sub-queries that were excluded from this optimization. Restriction
+** (4) has since been expanded to exclude all DISTINCT subqueries.
+**
+** (6) The subquery does not use aggregates or the outer query is not
+** DISTINCT.
+**
+** (7) The subquery has a FROM clause. TODO: For subqueries without
+** A FROM clause, consider adding a FROM close with the special
+** table sqlite_once that consists of a single row containing a
+** single NULL.
+**
+** (8) The subquery does not use LIMIT or the outer query is not a join.
+**
+** (9) The subquery does not use LIMIT or the outer query does not use
+** aggregates.
+**
+** (**) Restriction (10) was removed from the code on 2005-02-05 but we
+** accidently carried the comment forward until 2014-09-15. Original
+** text: "The subquery does not use aggregates or the outer query does not
+** use LIMIT."
+**
+** (11) The subquery and the outer query do not both have ORDER BY clauses.
+**
+** (**) Not implemented. Subsumed into restriction (3). Was previously
+** a separate restriction deriving from ticket #350.
+**
+** (13) The subquery and outer query do not both use LIMIT.
+**
+** (14) The subquery does not use OFFSET.
+**
+** (15) The outer query is not part of a compound select or the
+** subquery does not have a LIMIT clause.
+** (See ticket #2339 and ticket [02a8e81d44]).
+**
+** (16) The outer query is not an aggregate or the subquery does
+** not contain ORDER BY. (Ticket #2942) This used to not matter
+** until we introduced the group_concat() function.
+**
+** (17) The sub-query is not a compound select, or it is a UNION ALL
+** compound clause made up entirely of non-aggregate queries, and
+** the parent query:
+**
+** * is not itself part of a compound select,
+** * is not an aggregate or DISTINCT query, and
+** * is not a join
+**
+** The parent and sub-query may contain WHERE clauses. Subject to
+** rules (11), (13) and (14), they may also contain ORDER BY,
+** LIMIT and OFFSET clauses. The subquery cannot use any compound
+** operator other than UNION ALL because all the other compound
+** operators have an implied DISTINCT which is disallowed by
+** restriction (4).
+**
+** Also, each component of the sub-query must return the same number
+** of result columns. This is actually a requirement for any compound
+** SELECT statement, but all the code here does is make sure that no
+** such (illegal) sub-query is flattened. The caller will detect the
+** syntax error and return a detailed message.
+**
+** (18) If the sub-query is a compound select, then all terms of the
+** ORDER by clause of the parent must be simple references to
+** columns of the sub-query.
+**
+** (19) The subquery does not use LIMIT or the outer query does not
+** have a WHERE clause.
+**
+** (20) If the sub-query is a compound select, then it must not use
+** an ORDER BY clause. Ticket #3773. We could relax this constraint
+** somewhat by saying that the terms of the ORDER BY clause must
+** appear as unmodified result columns in the outer query. But we
+** have other optimizations in mind to deal with that case.
+**
+** (21) The subquery does not use LIMIT or the outer query is not
+** DISTINCT. (See ticket [752e1646fc]).
+**
+** (22) The subquery is not a recursive CTE.
+**
+** (23) The parent is not a recursive CTE, or the sub-query is not a
+** compound query. This restriction is because transforming the
+** parent to a compound query confuses the code that handles
+** recursive queries in multiSelect().
+**
+** (24) The subquery is not an aggregate that uses the built-in min() or
+** or max() functions. (Without this restriction, a query like:
+** "SELECT x FROM (SELECT max(y), x FROM t1)" would not necessarily
+** return the value X for which Y was maximal.)
+**
+**
+** In this routine, the "p" parameter is a pointer to the outer query.
+** The subquery is p->pSrc->a[iFrom]. isAgg is true if the outer query
+** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
+**
+** If flattening is not attempted, this routine is a no-op and returns 0.
+** If flattening is attempted this routine returns 1.
+**
+** All of the expression analysis must occur on both the outer query and
+** the subquery before this routine runs.
+*/
+int sqlite3FlattenSubquery(
+ Parse *pParse, /* Parsing context */
+ Select *p, /* The parent or outer SELECT statement */
+ int iFrom, /* Index in p->pSrc->a[] of the inner subquery */
+ int isAgg, /* True if outer SELECT uses aggregate functions */
+ int subqueryIsAgg /* True if the subquery uses aggregate functions */
+){
+ const char *zSavedAuthContext = pParse->zAuthContext;
+ Select *pParent;
+ Select *pSub; /* The inner query or "subquery" */
+ Select *pSub1; /* Pointer to the rightmost select in sub-query */
+ SrcList *pSrc; /* The FROM clause of the outer query */
+ SrcList *pSubSrc; /* The FROM clause of the subquery */
+ ExprList *pList; /* The result set of the outer query */
+ int iParent; /* VDBE cursor number of the pSub result set temp table */
+ int i; /* Loop counter */
+ Expr *pWhere; /* The WHERE clause */
+ struct SrcList_item *pSubitem; /* The subquery */
+ sqlite3 *db = pParse->db;
+
+ /* Check to see if flattening is permitted. Return 0 if not.
+ */
+ assert( p!=0 );
+ assert( p->pPrior==0 ); /* Unable to flatten compound queries */
+ if( OptimizationDisabled(db, SQLITE_QueryFlattener) ) return 0;
+ pSrc = p->pSrc;
+ assert( pSrc && iFrom>=0 && iFrom<pSrc->nSrc );
+ pSubitem = &pSrc->a[iFrom];
+ iParent = pSubitem->iCursor;
+ pSub = pSubitem->pSelect;
+ assert( pSub!=0 );
+ if( subqueryIsAgg ){
+ if( isAgg ) return 0; /* Restriction (1) */
+ if( pSrc->nSrc>1 ) return 0; /* Restriction (2a) */
+ if( (p->pWhere && ExprHasProperty(p->pWhere,EP_Subquery))
+ || (sqlite3ExprListFlags(p->pEList) & EP_Subquery)!=0
+ || (sqlite3ExprListFlags(p->pOrderBy) & EP_Subquery)!=0
+ ){
+ return 0; /* Restriction (2b) */
+ }
+ }
+
+ pSubSrc = pSub->pSrc;
+ assert( pSubSrc );
+ /* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
+ ** not arbitrary expressions, we allowed some combining of LIMIT and OFFSET
+ ** because they could be computed at compile-time. But when LIMIT and OFFSET
+ ** became arbitrary expressions, we were forced to add restrictions (13)
+ ** and (14). */
+ if( pSub->pLimit && p->pLimit ) return 0; /* Restriction (13) */
+ if( pSub->pOffset ) return 0; /* Restriction (14) */
+ if( (p->selFlags & SF_Compound)!=0 && pSub->pLimit ){
+ return 0; /* Restriction (15) */
+ }
+ if( pSubSrc->nSrc==0 ) return 0; /* Restriction (7) */
+ if( pSub->selFlags & SF_Distinct ) return 0; /* Restriction (5) */
+ if( pSub->pLimit && (pSrc->nSrc>1 || isAgg) ){
+ return 0; /* Restrictions (8)(9) */
+ }
+ if( (p->selFlags & SF_Distinct)!=0 && subqueryIsAgg ){
+ return 0; /* Restriction (6) */
+ }
+ if( p->pOrderBy && pSub->pOrderBy ){
+ return 0; /* Restriction (11) */
+ }
+ if( isAgg && pSub->pOrderBy ) return 0; /* Restriction (16) */
+ if( pSub->pLimit && p->pWhere ) return 0; /* Restriction (19) */
+ if( pSub->pLimit && (p->selFlags & SF_Distinct)!=0 ){
+ return 0; /* Restriction (21) */
+ }
+ testcase( pSub->selFlags & SF_Recursive );
+ testcase( pSub->selFlags & SF_MinMaxAgg );
+ if( pSub->selFlags & (SF_Recursive|SF_MinMaxAgg) ){
+ return 0; /* Restrictions (22) and (24) */
+ }
+ if( (p->selFlags & SF_Recursive) && pSub->pPrior ){
+ return 0; /* Restriction (23) */
+ }
+
+ /* OBSOLETE COMMENT 1:
+ ** Restriction 3: If the subquery is a join, make sure the subquery is
+ ** not used as the right operand of an outer join. Examples of why this
+ ** is not allowed:
+ **
+ ** t1 LEFT OUTER JOIN (t2 JOIN t3)
+ **
+ ** If we flatten the above, we would get
+ **
+ ** (t1 LEFT OUTER JOIN t2) JOIN t3
+ **
+ ** which is not at all the same thing.
+ **
+ ** OBSOLETE COMMENT 2:
+ ** Restriction 12: If the subquery is the right operand of a left outer
+ ** join, make sure the subquery has no WHERE clause.
+ ** An examples of why this is not allowed:
+ **
+ ** t1 LEFT OUTER JOIN (SELECT * FROM t2 WHERE t2.x>0)
+ **
+ ** If we flatten the above, we would get
+ **
+ ** (t1 LEFT OUTER JOIN t2) WHERE t2.x>0
+ **
+ ** But the t2.x>0 test will always fail on a NULL row of t2, which
+ ** effectively converts the OUTER JOIN into an INNER JOIN.
+ **
+ ** THIS OVERRIDES OBSOLETE COMMENTS 1 AND 2 ABOVE:
+ ** Ticket #3300 shows that flattening the right term of a LEFT JOIN
+ ** is fraught with danger. Best to avoid the whole thing. If the
+ ** subquery is the right term of a LEFT JOIN, then do not flatten.
+ */
+ if( (pSubitem->jointype & JT_OUTER)!=0 ){
+ return 0;
+ }
+
+ /* Restriction 17: If the sub-query is a compound SELECT, then it must
+ ** use only the UNION ALL operator. And none of the simple select queries
+ ** that make up the compound SELECT are allowed to be aggregate or distinct
+ ** queries.
+ */
+ if( pSub->pPrior ){
+ if( pSub->pOrderBy ){
+ return 0; /* Restriction 20 */
+ }
+ if( isAgg || (p->selFlags & SF_Distinct)!=0 || pSrc->nSrc!=1 ){
+ return 0;
+ }
+ for(pSub1=pSub; pSub1; pSub1=pSub1->pPrior){
+ testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
+ testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
+ assert( pSub->pSrc!=0 );
+ if( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))!=0
+ || (pSub1->pPrior && pSub1->op!=TK_ALL)
+ || pSub1->pSrc->nSrc<1
+ || pSub->pEList->nExpr!=pSub1->pEList->nExpr
+ ){
+ return 0;
+ }
+ testcase( pSub1->pSrc->nSrc>1 );
+ }
+
+ /* Restriction 18. */
+ if( p->pOrderBy ){
+ int ii;
+ for(ii=0; ii<p->pOrderBy->nExpr; ii++){
+ if( p->pOrderBy->a[ii].u.x.iOrderByCol==0 ) return 0;
+ }
+ }
+ }
+
+ /***** If we reach this point, flattening is permitted. *****/
+ SELECTTRACE(1,pParse,p,("flatten %s.%p from term %d\n",
+ pSub->zSelName, pSub, iFrom));
+
+ /* Authorize the subquery */
+ pParse->zAuthContext = pSubitem->zName;
+ TESTONLY(i =) sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0);
+ testcase( i==SQLITE_DENY );
+ pParse->zAuthContext = zSavedAuthContext;
+
+ /* If the sub-query is a compound SELECT statement, then (by restrictions
+ ** 17 and 18 above) it must be a UNION ALL and the parent query must
+ ** be of the form:
+ **
+ ** SELECT <expr-list> FROM (<sub-query>) <where-clause>
+ **
+ ** followed by any ORDER BY, LIMIT and/or OFFSET clauses. This block
+ ** creates N-1 copies of the parent query without any ORDER BY, LIMIT or
+ ** OFFSET clauses and joins them to the left-hand-side of the original
+ ** using UNION ALL operators. In this case N is the number of simple
+ ** select statements in the compound sub-query.
+ **
+ ** Example:
+ **
+ ** SELECT a+1 FROM (
+ ** SELECT x FROM tab
+ ** UNION ALL
+ ** SELECT y FROM tab
+ ** UNION ALL
+ ** SELECT abs(z*2) FROM tab2
+ ** ) WHERE a!=5 ORDER BY 1
+ **
+ ** Transformed into:
+ **
+ ** SELECT x+1 FROM tab WHERE x+1!=5
+ ** UNION ALL
+ ** SELECT y+1 FROM tab WHERE y+1!=5
+ ** UNION ALL
+ ** SELECT abs(z*2)+1 FROM tab2 WHERE abs(z*2)+1!=5
+ ** ORDER BY 1
+ **
+ ** We call this the "compound-subquery flattening".
+ */
+ for(pSub=pSub->pPrior; pSub; pSub=pSub->pPrior){
+ Select *pNew;
+ ExprList *pOrderBy = p->pOrderBy;
+ Expr *pLimit = p->pLimit;
+ Expr *pOffset = p->pOffset;
+ Select *pPrior = p->pPrior;
+ p->pOrderBy = 0;
+ p->pSrc = 0;
+ p->pPrior = 0;
+ p->pLimit = 0;
+ p->pOffset = 0;
+ pNew = sqlite3SelectDup(db, p, 0);
+ sqlite3SelectSetName(pNew, pSub->zSelName);
+ p->pOffset = pOffset;
+ p->pLimit = pLimit;
+ p->pOrderBy = pOrderBy;
+ p->pSrc = pSrc;
+ p->op = TK_ALL;
+ if( pNew==0 ){
+ p->pPrior = pPrior;
+ }else{
+ pNew->pPrior = pPrior;
+ if( pPrior ) pPrior->pNext = pNew;
+ pNew->pNext = p;
+ p->pPrior = pNew;
+ SELECTTRACE(2,pParse,p,
+ ("compound-subquery flattener creates %s.%p as peer\n",
+ pNew->zSelName, pNew));
+ }
+ if( db->mallocFailed ) return 1;
+ }
+
+ /* Begin flattening the iFrom-th entry of the FROM clause
+ ** in the outer query.
+ */
+ pSub = pSub1 = pSubitem->pSelect;
+
+ /* Delete the transient table structure associated with the
+ ** subquery
+ */
+ sqlite3DbFree(db, pSubitem->zDatabase);
+ sqlite3DbFree(db, pSubitem->zName);
+ sqlite3DbFree(db, pSubitem->zAlias);
+ pSubitem->zDatabase = 0;
+ pSubitem->zName = 0;
+ pSubitem->zAlias = 0;
+ pSubitem->pSelect = 0;
+
+ /* Defer deleting the Table object associated with the
+ ** subquery until code generation is
+ ** complete, since there may still exist Expr.pTab entries that
+ ** refer to the subquery even after flattening. Ticket #3346.
+ **
+ ** pSubitem->pTab is always non-NULL by test restrictions and tests above.
+ */
+ if( ALWAYS(pSubitem->pTab!=0) ){
+ Table *pTabToDel = pSubitem->pTab;
+ if( pTabToDel->nRef==1 ){
+ Parse *pToplevel = sqlite3ParseToplevel(pParse);
+ pTabToDel->pNextZombie = pToplevel->pZombieTab;
+ pToplevel->pZombieTab = pTabToDel;
+ }else{
+ pTabToDel->nRef--;
+ }
+ pSubitem->pTab = 0;
+ }
+
+ /* The following loop runs once for each term in a compound-subquery
+ ** flattening (as described above). If we are doing a different kind
+ ** of flattening - a flattening other than a compound-subquery flattening -
+ ** then this loop only runs once.
+ **
+ ** This loop moves all of the FROM elements of the subquery into the
+ ** the FROM clause of the outer query. Before doing this, remember
+ ** the cursor number for the original outer query FROM element in
+ ** iParent. The iParent cursor will never be used. Subsequent code
+ ** will scan expressions looking for iParent references and replace
+ ** those references with expressions that resolve to the subquery FROM
+ ** elements we are now copying in.
+ */
+ for(pParent=p; pParent; pParent=pParent->pPrior, pSub=pSub->pPrior){
+ int nSubSrc;
+ u8 jointype = 0;
+ pSubSrc = pSub->pSrc; /* FROM clause of subquery */
+ nSubSrc = pSubSrc->nSrc; /* Number of terms in subquery FROM clause */
+ pSrc = pParent->pSrc; /* FROM clause of the outer query */
+
+ if( pSrc ){
+ assert( pParent==p ); /* First time through the loop */
+ jointype = pSubitem->jointype;
+ }else{
+ assert( pParent!=p ); /* 2nd and subsequent times through the loop */
+ pSrc = pParent->pSrc = sqlite3SrcListAppend(db, 0, 0, 0);
+ if( pSrc==0 ){
+ assert( db->mallocFailed );
+ break;
+ }
+ }
+
+ /* The subquery uses a single slot of the FROM clause of the outer
+ ** query. If the subquery has more than one element in its FROM clause,
+ ** then expand the outer query to make space for it to hold all elements
+ ** of the subquery.
+ **
+ ** Example:
+ **
+ ** SELECT * FROM tabA, (SELECT * FROM sub1, sub2), tabB;
+ **
+ ** The outer query has 3 slots in its FROM clause. One slot of the
+ ** outer query (the middle slot) is used by the subquery. The next
+ ** block of code will expand the out query to 4 slots. The middle
+ ** slot is expanded to two slots in order to make space for the
+ ** two elements in the FROM clause of the subquery.
+ */
+ if( nSubSrc>1 ){
+ pParent->pSrc = pSrc = sqlite3SrcListEnlarge(db, pSrc, nSubSrc-1,iFrom+1);
+ if( db->mallocFailed ){
+ break;
+ }
+ }
+
+ /* Transfer the FROM clause terms from the subquery into the
+ ** outer query.
+ */
+ for(i=0; i<nSubSrc; i++){
+ sqlite3IdListDelete(db, pSrc->a[i+iFrom].pUsing);
+ pSrc->a[i+iFrom] = pSubSrc->a[i];
+ memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
+ }
+ pSrc->a[iFrom].jointype = jointype;
+
+ /* Now begin substituting subquery result set expressions for
+ ** references to the iParent in the outer query.
+ **
+ ** Example:
+ **
+ ** SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
+ ** \ \_____________ subquery __________/ /
+ ** \_____________________ outer query ______________________________/
+ **
+ ** We look at every expression in the outer query and every place we see
+ ** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
+ */
+ pList = pParent->pEList;
+ for(i=0; i<pList->nExpr; i++){
+ if( pList->a[i].zName==0 ){
+ char *zName = sqlite3DbStrDup(db, pList->a[i].zSpan);
+ sqlite3Dequote(zName);
+ pList->a[i].zName = zName;
+ }
+ }
+ substExprList(db, pParent->pEList, iParent, pSub->pEList);
+ if( isAgg ){
+ substExprList(db, pParent->pGroupBy, iParent, pSub->pEList);
+ pParent->pHaving = substExpr(db, pParent->pHaving, iParent, pSub->pEList);
+ }
+ if( pSub->pOrderBy ){
+ /* At this point, any non-zero iOrderByCol values indicate that the
+ ** ORDER BY column expression is identical to the iOrderByCol'th
+ ** expression returned by SELECT statement pSub. Since these values
+ ** do not necessarily correspond to columns in SELECT statement pParent,
+ ** zero them before transfering the ORDER BY clause.
+ **
+ ** Not doing this may cause an error if a subsequent call to this
+ ** function attempts to flatten a compound sub-query into pParent
+ ** (the only way this can happen is if the compound sub-query is
+ ** currently part of pSub->pSrc). See ticket [d11a6e908f]. */
+ ExprList *pOrderBy = pSub->pOrderBy;
+ for(i=0; i<pOrderBy->nExpr; i++){
+ pOrderBy->a[i].u.x.iOrderByCol = 0;
+ }
+ assert( pParent->pOrderBy==0 );
+ assert( pSub->pPrior==0 );
+ pParent->pOrderBy = pOrderBy;
+ pSub->pOrderBy = 0;
+ }else if( pParent->pOrderBy ){
+ substExprList(db, pParent->pOrderBy, iParent, pSub->pEList);
+ }
+ if( pSub->pWhere ){
+ pWhere = sqlite3ExprDup(db, pSub->pWhere, 0);
+ }else{
+ pWhere = 0;
+ }
+ if( subqueryIsAgg ){
+ assert( pParent->pHaving==0 );
+ pParent->pHaving = pParent->pWhere;
+ pParent->pWhere = pWhere;
+ pParent->pHaving = substExpr(db, pParent->pHaving, iParent, pSub->pEList);
+ pParent->pHaving = sqlite3ExprAnd(db, pParent->pHaving,
+ sqlite3ExprDup(db, pSub->pHaving, 0));
+ assert( pParent->pGroupBy==0 );
+ pParent->pGroupBy = sqlite3ExprListDup(db, pSub->pGroupBy, 0);
+ }else{
+ pParent->pWhere = substExpr(db, pParent->pWhere, iParent, pSub->pEList);
+ pParent->pWhere = sqlite3ExprAnd(db, pParent->pWhere, pWhere);
+ }
+
+ /* The flattened query is distinct if either the inner or the
+ ** outer query is distinct.
+ */
+ pParent->selFlags |= pSub->selFlags & SF_Distinct;
+
+ /*
+ ** SELECT ... FROM (SELECT ... LIMIT a OFFSET b) LIMIT x OFFSET y;
+ **
+ ** One is tempted to try to add a and b to combine the limits. But this
+ ** does not work if either limit is negative.
+ */
+ if( pSub->pLimit ){
+ pParent->pLimit = pSub->pLimit;
+ pSub->pLimit = 0;
+ }
+ }
+
+ /* Finially, delete what is left of the subquery and return
+ ** success.
+ */
+ sqlite3SelectDelete(db, pSub1);
+
+#if SELECTTRACE_ENABLED
+ if( sqlite3SelectTrace & 0x100 ){
+ sqlite3DebugPrintf("After flattening:\n");
+ sqlite3TreeViewSelect(0, p, 0);
+ }
+#endif
+
+ return 1;
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
** the vdbe.c file.
*/
const unsigned char sqlite3OpcodeProperty[] = OPFLG_INITIALIZER;
+
+/*
+** Enable or disable tracing of SELECT statement compilation.
+*/
+#if SELECTTRACE_ENABLED
+int sqlite3SelectTrace = 0;
+#endif
*/
#include "sqliteInt.h"
-/*
-** Trace output macros
-*/
-#if SELECTTRACE_ENABLED
-/***/ int sqlite3SelectTrace = 0;
-# define SELECTTRACE(K,P,S,X) \
- if(sqlite3SelectTrace&(K)) \
- sqlite3DebugPrintf("%*s%s.%p: ",(P)->nSelectIndent*2-2,"",(S)->zSelName,(S)),\
- sqlite3DebugPrintf X
-#else
-# define SELECTTRACE(K,P,S,X)
-#endif
-
-
/*
** An instance of the following object is used to record information about
** how to process the DISTINCT keyword, to simplify passing that information
}
#endif
-#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
-/* Forward Declarations */
-static void substExprList(sqlite3*, ExprList*, int, ExprList*);
-static void substSelect(sqlite3*, Select *, int, ExprList *);
-
-/*
-** Scan through the expression pExpr. Replace every reference to
-** a column in table number iTable with a copy of the iColumn-th
-** entry in pEList. (But leave references to the ROWID column
-** unchanged.)
-**
-** This routine is part of the flattening procedure. A subquery
-** whose result set is defined by pEList appears as entry in the
-** FROM clause of a SELECT such that the VDBE cursor assigned to that
-** FORM clause entry is iTable. This routine make the necessary
-** changes to pExpr so that it refers directly to the source table
-** of the subquery rather the result set of the subquery.
-*/
-static Expr *substExpr(
- sqlite3 *db, /* Report malloc errors to this connection */
- Expr *pExpr, /* Expr in which substitution occurs */
- int iTable, /* Table to be substituted */
- ExprList *pEList /* Substitute expressions */
-){
- if( pExpr==0 ) return 0;
- if( pExpr->op==TK_COLUMN && pExpr->iTable==iTable ){
- if( pExpr->iColumn<0 ){
- pExpr->op = TK_NULL;
- }else{
- Expr *pNew;
- assert( pEList!=0 && pExpr->iColumn<pEList->nExpr );
- assert( pExpr->pLeft==0 && pExpr->pRight==0 );
- pNew = sqlite3ExprDup(db, pEList->a[pExpr->iColumn].pExpr, 0);
- sqlite3ExprDelete(db, pExpr);
- pExpr = pNew;
- }
- }else{
- pExpr->pLeft = substExpr(db, pExpr->pLeft, iTable, pEList);
- pExpr->pRight = substExpr(db, pExpr->pRight, iTable, pEList);
- if( ExprHasProperty(pExpr, EP_xIsSelect) ){
- substSelect(db, pExpr->x.pSelect, iTable, pEList);
- }else{
- substExprList(db, pExpr->x.pList, iTable, pEList);
- }
- }
- return pExpr;
-}
-static void substExprList(
- sqlite3 *db, /* Report malloc errors here */
- ExprList *pList, /* List to scan and in which to make substitutes */
- int iTable, /* Table to be substituted */
- ExprList *pEList /* Substitute values */
-){
- int i;
- if( pList==0 ) return;
- for(i=0; i<pList->nExpr; i++){
- pList->a[i].pExpr = substExpr(db, pList->a[i].pExpr, iTable, pEList);
- }
-}
-static void substSelect(
- sqlite3 *db, /* Report malloc errors here */
- Select *p, /* SELECT statement in which to make substitutions */
- int iTable, /* Table to be replaced */
- ExprList *pEList /* Substitute values */
-){
- SrcList *pSrc;
- struct SrcList_item *pItem;
- int i;
- if( !p ) return;
- substExprList(db, p->pEList, iTable, pEList);
- substExprList(db, p->pGroupBy, iTable, pEList);
- substExprList(db, p->pOrderBy, iTable, pEList);
- p->pHaving = substExpr(db, p->pHaving, iTable, pEList);
- p->pWhere = substExpr(db, p->pWhere, iTable, pEList);
- substSelect(db, p->pPrior, iTable, pEList);
- pSrc = p->pSrc;
- assert( pSrc ); /* Even for (SELECT 1) we have: pSrc!=0 but pSrc->nSrc==0 */
- if( ALWAYS(pSrc) ){
- for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
- substSelect(db, pItem->pSelect, iTable, pEList);
- }
- }
-}
-#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
-
-#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
-/*
-** This routine attempts to flatten subqueries as a performance optimization.
-** This routine returns 1 if it makes changes and 0 if no flattening occurs.
-**
-** To understand the concept of flattening, consider the following
-** query:
-**
-** SELECT a FROM (SELECT x+y AS a FROM t1 WHERE z<100) WHERE a>5
-**
-** The default way of implementing this query is to execute the
-** subquery first and store the results in a temporary table, then
-** run the outer query on that temporary table. This requires two
-** passes over the data. Furthermore, because the temporary table
-** has no indices, the WHERE clause on the outer query cannot be
-** optimized.
-**
-** This routine attempts to rewrite queries such as the above into
-** a single flat select, like this:
-**
-** SELECT x+y AS a FROM t1 WHERE z<100 AND a>5
-**
-** The code generated for this simplification gives the same result
-** but only has to scan the data once. And because indices might
-** exist on the table t1, a complete scan of the data might be
-** avoided.
-**
-** Flattening is only attempted if all of the following are true:
-**
-** (1) The subquery and the outer query do not both use aggregates.
-**
-** (2) The subquery is not an aggregate or (2a) the outer query is not a join
-** and (2b) the outer query does not use subqueries other than the one
-** FROM-clause subquery that is a candidate for flattening. (2b is
-** due to ticket [2f7170d73bf9abf80] from 2015-02-09.)
-**
-** (3) The subquery is not the right operand of a left outer join
-** (Originally ticket #306. Strengthened by ticket #3300)
-**
-** (4) The subquery is not DISTINCT.
-**
-** (**) At one point restrictions (4) and (5) defined a subset of DISTINCT
-** sub-queries that were excluded from this optimization. Restriction
-** (4) has since been expanded to exclude all DISTINCT subqueries.
-**
-** (6) The subquery does not use aggregates or the outer query is not
-** DISTINCT.
-**
-** (7) The subquery has a FROM clause. TODO: For subqueries without
-** A FROM clause, consider adding a FROM close with the special
-** table sqlite_once that consists of a single row containing a
-** single NULL.
-**
-** (8) The subquery does not use LIMIT or the outer query is not a join.
-**
-** (9) The subquery does not use LIMIT or the outer query does not use
-** aggregates.
-**
-** (**) Restriction (10) was removed from the code on 2005-02-05 but we
-** accidently carried the comment forward until 2014-09-15. Original
-** text: "The subquery does not use aggregates or the outer query does not
-** use LIMIT."
-**
-** (11) The subquery and the outer query do not both have ORDER BY clauses.
-**
-** (**) Not implemented. Subsumed into restriction (3). Was previously
-** a separate restriction deriving from ticket #350.
-**
-** (13) The subquery and outer query do not both use LIMIT.
-**
-** (14) The subquery does not use OFFSET.
-**
-** (15) The outer query is not part of a compound select or the
-** subquery does not have a LIMIT clause.
-** (See ticket #2339 and ticket [02a8e81d44]).
-**
-** (16) The outer query is not an aggregate or the subquery does
-** not contain ORDER BY. (Ticket #2942) This used to not matter
-** until we introduced the group_concat() function.
-**
-** (17) The sub-query is not a compound select, or it is a UNION ALL
-** compound clause made up entirely of non-aggregate queries, and
-** the parent query:
-**
-** * is not itself part of a compound select,
-** * is not an aggregate or DISTINCT query, and
-** * is not a join
-**
-** The parent and sub-query may contain WHERE clauses. Subject to
-** rules (11), (13) and (14), they may also contain ORDER BY,
-** LIMIT and OFFSET clauses. The subquery cannot use any compound
-** operator other than UNION ALL because all the other compound
-** operators have an implied DISTINCT which is disallowed by
-** restriction (4).
-**
-** Also, each component of the sub-query must return the same number
-** of result columns. This is actually a requirement for any compound
-** SELECT statement, but all the code here does is make sure that no
-** such (illegal) sub-query is flattened. The caller will detect the
-** syntax error and return a detailed message.
-**
-** (18) If the sub-query is a compound select, then all terms of the
-** ORDER by clause of the parent must be simple references to
-** columns of the sub-query.
-**
-** (19) The subquery does not use LIMIT or the outer query does not
-** have a WHERE clause.
-**
-** (20) If the sub-query is a compound select, then it must not use
-** an ORDER BY clause. Ticket #3773. We could relax this constraint
-** somewhat by saying that the terms of the ORDER BY clause must
-** appear as unmodified result columns in the outer query. But we
-** have other optimizations in mind to deal with that case.
-**
-** (21) The subquery does not use LIMIT or the outer query is not
-** DISTINCT. (See ticket [752e1646fc]).
-**
-** (22) The subquery is not a recursive CTE.
-**
-** (23) The parent is not a recursive CTE, or the sub-query is not a
-** compound query. This restriction is because transforming the
-** parent to a compound query confuses the code that handles
-** recursive queries in multiSelect().
-**
-** (24) The subquery is not an aggregate that uses the built-in min() or
-** or max() functions. (Without this restriction, a query like:
-** "SELECT x FROM (SELECT max(y), x FROM t1)" would not necessarily
-** return the value X for which Y was maximal.)
-**
-**
-** In this routine, the "p" parameter is a pointer to the outer query.
-** The subquery is p->pSrc->a[iFrom]. isAgg is true if the outer query
-** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
-**
-** If flattening is not attempted, this routine is a no-op and returns 0.
-** If flattening is attempted this routine returns 1.
-**
-** All of the expression analysis must occur on both the outer query and
-** the subquery before this routine runs.
-*/
-static int flattenSubquery(
- Parse *pParse, /* Parsing context */
- Select *p, /* The parent or outer SELECT statement */
- int iFrom, /* Index in p->pSrc->a[] of the inner subquery */
- int isAgg, /* True if outer SELECT uses aggregate functions */
- int subqueryIsAgg /* True if the subquery uses aggregate functions */
-){
- const char *zSavedAuthContext = pParse->zAuthContext;
- Select *pParent;
- Select *pSub; /* The inner query or "subquery" */
- Select *pSub1; /* Pointer to the rightmost select in sub-query */
- SrcList *pSrc; /* The FROM clause of the outer query */
- SrcList *pSubSrc; /* The FROM clause of the subquery */
- ExprList *pList; /* The result set of the outer query */
- int iParent; /* VDBE cursor number of the pSub result set temp table */
- int i; /* Loop counter */
- Expr *pWhere; /* The WHERE clause */
- struct SrcList_item *pSubitem; /* The subquery */
- sqlite3 *db = pParse->db;
-
- /* Check to see if flattening is permitted. Return 0 if not.
- */
- assert( p!=0 );
- assert( p->pPrior==0 ); /* Unable to flatten compound queries */
- if( OptimizationDisabled(db, SQLITE_QueryFlattener) ) return 0;
- pSrc = p->pSrc;
- assert( pSrc && iFrom>=0 && iFrom<pSrc->nSrc );
- pSubitem = &pSrc->a[iFrom];
- iParent = pSubitem->iCursor;
- pSub = pSubitem->pSelect;
- assert( pSub!=0 );
- if( subqueryIsAgg ){
- if( isAgg ) return 0; /* Restriction (1) */
- if( pSrc->nSrc>1 ) return 0; /* Restriction (2a) */
- if( (p->pWhere && ExprHasProperty(p->pWhere,EP_Subquery))
- || (sqlite3ExprListFlags(p->pEList) & EP_Subquery)!=0
- || (sqlite3ExprListFlags(p->pOrderBy) & EP_Subquery)!=0
- ){
- return 0; /* Restriction (2b) */
- }
- }
-
- pSubSrc = pSub->pSrc;
- assert( pSubSrc );
- /* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
- ** not arbitrary expressions, we allowed some combining of LIMIT and OFFSET
- ** because they could be computed at compile-time. But when LIMIT and OFFSET
- ** became arbitrary expressions, we were forced to add restrictions (13)
- ** and (14). */
- if( pSub->pLimit && p->pLimit ) return 0; /* Restriction (13) */
- if( pSub->pOffset ) return 0; /* Restriction (14) */
- if( (p->selFlags & SF_Compound)!=0 && pSub->pLimit ){
- return 0; /* Restriction (15) */
- }
- if( pSubSrc->nSrc==0 ) return 0; /* Restriction (7) */
- if( pSub->selFlags & SF_Distinct ) return 0; /* Restriction (5) */
- if( pSub->pLimit && (pSrc->nSrc>1 || isAgg) ){
- return 0; /* Restrictions (8)(9) */
- }
- if( (p->selFlags & SF_Distinct)!=0 && subqueryIsAgg ){
- return 0; /* Restriction (6) */
- }
- if( p->pOrderBy && pSub->pOrderBy ){
- return 0; /* Restriction (11) */
- }
- if( isAgg && pSub->pOrderBy ) return 0; /* Restriction (16) */
- if( pSub->pLimit && p->pWhere ) return 0; /* Restriction (19) */
- if( pSub->pLimit && (p->selFlags & SF_Distinct)!=0 ){
- return 0; /* Restriction (21) */
- }
- testcase( pSub->selFlags & SF_Recursive );
- testcase( pSub->selFlags & SF_MinMaxAgg );
- if( pSub->selFlags & (SF_Recursive|SF_MinMaxAgg) ){
- return 0; /* Restrictions (22) and (24) */
- }
- if( (p->selFlags & SF_Recursive) && pSub->pPrior ){
- return 0; /* Restriction (23) */
- }
-
- /* OBSOLETE COMMENT 1:
- ** Restriction 3: If the subquery is a join, make sure the subquery is
- ** not used as the right operand of an outer join. Examples of why this
- ** is not allowed:
- **
- ** t1 LEFT OUTER JOIN (t2 JOIN t3)
- **
- ** If we flatten the above, we would get
- **
- ** (t1 LEFT OUTER JOIN t2) JOIN t3
- **
- ** which is not at all the same thing.
- **
- ** OBSOLETE COMMENT 2:
- ** Restriction 12: If the subquery is the right operand of a left outer
- ** join, make sure the subquery has no WHERE clause.
- ** An examples of why this is not allowed:
- **
- ** t1 LEFT OUTER JOIN (SELECT * FROM t2 WHERE t2.x>0)
- **
- ** If we flatten the above, we would get
- **
- ** (t1 LEFT OUTER JOIN t2) WHERE t2.x>0
- **
- ** But the t2.x>0 test will always fail on a NULL row of t2, which
- ** effectively converts the OUTER JOIN into an INNER JOIN.
- **
- ** THIS OVERRIDES OBSOLETE COMMENTS 1 AND 2 ABOVE:
- ** Ticket #3300 shows that flattening the right term of a LEFT JOIN
- ** is fraught with danger. Best to avoid the whole thing. If the
- ** subquery is the right term of a LEFT JOIN, then do not flatten.
- */
- if( (pSubitem->jointype & JT_OUTER)!=0 ){
- return 0;
- }
-
- /* Restriction 17: If the sub-query is a compound SELECT, then it must
- ** use only the UNION ALL operator. And none of the simple select queries
- ** that make up the compound SELECT are allowed to be aggregate or distinct
- ** queries.
- */
- if( pSub->pPrior ){
- if( pSub->pOrderBy ){
- return 0; /* Restriction 20 */
- }
- if( isAgg || (p->selFlags & SF_Distinct)!=0 || pSrc->nSrc!=1 ){
- return 0;
- }
- for(pSub1=pSub; pSub1; pSub1=pSub1->pPrior){
- testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
- testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
- assert( pSub->pSrc!=0 );
- if( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))!=0
- || (pSub1->pPrior && pSub1->op!=TK_ALL)
- || pSub1->pSrc->nSrc<1
- || pSub->pEList->nExpr!=pSub1->pEList->nExpr
- ){
- return 0;
- }
- testcase( pSub1->pSrc->nSrc>1 );
- }
-
- /* Restriction 18. */
- if( p->pOrderBy ){
- int ii;
- for(ii=0; ii<p->pOrderBy->nExpr; ii++){
- if( p->pOrderBy->a[ii].u.x.iOrderByCol==0 ) return 0;
- }
- }
- }
-
- /***** If we reach this point, flattening is permitted. *****/
- SELECTTRACE(1,pParse,p,("flatten %s.%p from term %d\n",
- pSub->zSelName, pSub, iFrom));
-
- /* Authorize the subquery */
- pParse->zAuthContext = pSubitem->zName;
- TESTONLY(i =) sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0);
- testcase( i==SQLITE_DENY );
- pParse->zAuthContext = zSavedAuthContext;
-
- /* If the sub-query is a compound SELECT statement, then (by restrictions
- ** 17 and 18 above) it must be a UNION ALL and the parent query must
- ** be of the form:
- **
- ** SELECT <expr-list> FROM (<sub-query>) <where-clause>
- **
- ** followed by any ORDER BY, LIMIT and/or OFFSET clauses. This block
- ** creates N-1 copies of the parent query without any ORDER BY, LIMIT or
- ** OFFSET clauses and joins them to the left-hand-side of the original
- ** using UNION ALL operators. In this case N is the number of simple
- ** select statements in the compound sub-query.
- **
- ** Example:
- **
- ** SELECT a+1 FROM (
- ** SELECT x FROM tab
- ** UNION ALL
- ** SELECT y FROM tab
- ** UNION ALL
- ** SELECT abs(z*2) FROM tab2
- ** ) WHERE a!=5 ORDER BY 1
- **
- ** Transformed into:
- **
- ** SELECT x+1 FROM tab WHERE x+1!=5
- ** UNION ALL
- ** SELECT y+1 FROM tab WHERE y+1!=5
- ** UNION ALL
- ** SELECT abs(z*2)+1 FROM tab2 WHERE abs(z*2)+1!=5
- ** ORDER BY 1
- **
- ** We call this the "compound-subquery flattening".
- */
- for(pSub=pSub->pPrior; pSub; pSub=pSub->pPrior){
- Select *pNew;
- ExprList *pOrderBy = p->pOrderBy;
- Expr *pLimit = p->pLimit;
- Expr *pOffset = p->pOffset;
- Select *pPrior = p->pPrior;
- p->pOrderBy = 0;
- p->pSrc = 0;
- p->pPrior = 0;
- p->pLimit = 0;
- p->pOffset = 0;
- pNew = sqlite3SelectDup(db, p, 0);
- sqlite3SelectSetName(pNew, pSub->zSelName);
- p->pOffset = pOffset;
- p->pLimit = pLimit;
- p->pOrderBy = pOrderBy;
- p->pSrc = pSrc;
- p->op = TK_ALL;
- if( pNew==0 ){
- p->pPrior = pPrior;
- }else{
- pNew->pPrior = pPrior;
- if( pPrior ) pPrior->pNext = pNew;
- pNew->pNext = p;
- p->pPrior = pNew;
- SELECTTRACE(2,pParse,p,
- ("compound-subquery flattener creates %s.%p as peer\n",
- pNew->zSelName, pNew));
- }
- if( db->mallocFailed ) return 1;
- }
-
- /* Begin flattening the iFrom-th entry of the FROM clause
- ** in the outer query.
- */
- pSub = pSub1 = pSubitem->pSelect;
-
- /* Delete the transient table structure associated with the
- ** subquery
- */
- sqlite3DbFree(db, pSubitem->zDatabase);
- sqlite3DbFree(db, pSubitem->zName);
- sqlite3DbFree(db, pSubitem->zAlias);
- pSubitem->zDatabase = 0;
- pSubitem->zName = 0;
- pSubitem->zAlias = 0;
- pSubitem->pSelect = 0;
-
- /* Defer deleting the Table object associated with the
- ** subquery until code generation is
- ** complete, since there may still exist Expr.pTab entries that
- ** refer to the subquery even after flattening. Ticket #3346.
- **
- ** pSubitem->pTab is always non-NULL by test restrictions and tests above.
- */
- if( ALWAYS(pSubitem->pTab!=0) ){
- Table *pTabToDel = pSubitem->pTab;
- if( pTabToDel->nRef==1 ){
- Parse *pToplevel = sqlite3ParseToplevel(pParse);
- pTabToDel->pNextZombie = pToplevel->pZombieTab;
- pToplevel->pZombieTab = pTabToDel;
- }else{
- pTabToDel->nRef--;
- }
- pSubitem->pTab = 0;
- }
-
- /* The following loop runs once for each term in a compound-subquery
- ** flattening (as described above). If we are doing a different kind
- ** of flattening - a flattening other than a compound-subquery flattening -
- ** then this loop only runs once.
- **
- ** This loop moves all of the FROM elements of the subquery into the
- ** the FROM clause of the outer query. Before doing this, remember
- ** the cursor number for the original outer query FROM element in
- ** iParent. The iParent cursor will never be used. Subsequent code
- ** will scan expressions looking for iParent references and replace
- ** those references with expressions that resolve to the subquery FROM
- ** elements we are now copying in.
- */
- for(pParent=p; pParent; pParent=pParent->pPrior, pSub=pSub->pPrior){
- int nSubSrc;
- u8 jointype = 0;
- pSubSrc = pSub->pSrc; /* FROM clause of subquery */
- nSubSrc = pSubSrc->nSrc; /* Number of terms in subquery FROM clause */
- pSrc = pParent->pSrc; /* FROM clause of the outer query */
-
- if( pSrc ){
- assert( pParent==p ); /* First time through the loop */
- jointype = pSubitem->jointype;
- }else{
- assert( pParent!=p ); /* 2nd and subsequent times through the loop */
- pSrc = pParent->pSrc = sqlite3SrcListAppend(db, 0, 0, 0);
- if( pSrc==0 ){
- assert( db->mallocFailed );
- break;
- }
- }
-
- /* The subquery uses a single slot of the FROM clause of the outer
- ** query. If the subquery has more than one element in its FROM clause,
- ** then expand the outer query to make space for it to hold all elements
- ** of the subquery.
- **
- ** Example:
- **
- ** SELECT * FROM tabA, (SELECT * FROM sub1, sub2), tabB;
- **
- ** The outer query has 3 slots in its FROM clause. One slot of the
- ** outer query (the middle slot) is used by the subquery. The next
- ** block of code will expand the out query to 4 slots. The middle
- ** slot is expanded to two slots in order to make space for the
- ** two elements in the FROM clause of the subquery.
- */
- if( nSubSrc>1 ){
- pParent->pSrc = pSrc = sqlite3SrcListEnlarge(db, pSrc, nSubSrc-1,iFrom+1);
- if( db->mallocFailed ){
- break;
- }
- }
-
- /* Transfer the FROM clause terms from the subquery into the
- ** outer query.
- */
- for(i=0; i<nSubSrc; i++){
- sqlite3IdListDelete(db, pSrc->a[i+iFrom].pUsing);
- pSrc->a[i+iFrom] = pSubSrc->a[i];
- memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
- }
- pSrc->a[iFrom].jointype = jointype;
-
- /* Now begin substituting subquery result set expressions for
- ** references to the iParent in the outer query.
- **
- ** Example:
- **
- ** SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
- ** \ \_____________ subquery __________/ /
- ** \_____________________ outer query ______________________________/
- **
- ** We look at every expression in the outer query and every place we see
- ** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
- */
- pList = pParent->pEList;
- for(i=0; i<pList->nExpr; i++){
- if( pList->a[i].zName==0 ){
- char *zName = sqlite3DbStrDup(db, pList->a[i].zSpan);
- sqlite3Dequote(zName);
- pList->a[i].zName = zName;
- }
- }
- substExprList(db, pParent->pEList, iParent, pSub->pEList);
- if( isAgg ){
- substExprList(db, pParent->pGroupBy, iParent, pSub->pEList);
- pParent->pHaving = substExpr(db, pParent->pHaving, iParent, pSub->pEList);
- }
- if( pSub->pOrderBy ){
- /* At this point, any non-zero iOrderByCol values indicate that the
- ** ORDER BY column expression is identical to the iOrderByCol'th
- ** expression returned by SELECT statement pSub. Since these values
- ** do not necessarily correspond to columns in SELECT statement pParent,
- ** zero them before transfering the ORDER BY clause.
- **
- ** Not doing this may cause an error if a subsequent call to this
- ** function attempts to flatten a compound sub-query into pParent
- ** (the only way this can happen is if the compound sub-query is
- ** currently part of pSub->pSrc). See ticket [d11a6e908f]. */
- ExprList *pOrderBy = pSub->pOrderBy;
- for(i=0; i<pOrderBy->nExpr; i++){
- pOrderBy->a[i].u.x.iOrderByCol = 0;
- }
- assert( pParent->pOrderBy==0 );
- assert( pSub->pPrior==0 );
- pParent->pOrderBy = pOrderBy;
- pSub->pOrderBy = 0;
- }else if( pParent->pOrderBy ){
- substExprList(db, pParent->pOrderBy, iParent, pSub->pEList);
- }
- if( pSub->pWhere ){
- pWhere = sqlite3ExprDup(db, pSub->pWhere, 0);
- }else{
- pWhere = 0;
- }
- if( subqueryIsAgg ){
- assert( pParent->pHaving==0 );
- pParent->pHaving = pParent->pWhere;
- pParent->pWhere = pWhere;
- pParent->pHaving = substExpr(db, pParent->pHaving, iParent, pSub->pEList);
- pParent->pHaving = sqlite3ExprAnd(db, pParent->pHaving,
- sqlite3ExprDup(db, pSub->pHaving, 0));
- assert( pParent->pGroupBy==0 );
- pParent->pGroupBy = sqlite3ExprListDup(db, pSub->pGroupBy, 0);
- }else{
- pParent->pWhere = substExpr(db, pParent->pWhere, iParent, pSub->pEList);
- pParent->pWhere = sqlite3ExprAnd(db, pParent->pWhere, pWhere);
- }
-
- /* The flattened query is distinct if either the inner or the
- ** outer query is distinct.
- */
- pParent->selFlags |= pSub->selFlags & SF_Distinct;
-
- /*
- ** SELECT ... FROM (SELECT ... LIMIT a OFFSET b) LIMIT x OFFSET y;
- **
- ** One is tempted to try to add a and b to combine the limits. But this
- ** does not work if either limit is negative.
- */
- if( pSub->pLimit ){
- pParent->pLimit = pSub->pLimit;
- pSub->pLimit = 0;
- }
- }
-
- /* Finially, delete what is left of the subquery and return
- ** success.
- */
- sqlite3SelectDelete(db, pSub1);
-
-#if SELECTTRACE_ENABLED
- if( sqlite3SelectTrace & 0x100 ){
- sqlite3DebugPrintf("After flattening:\n");
- sqlite3TreeViewSelect(0, p, 0);
- }
-#endif
-
- return 1;
-}
-#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
/*
** Based on the contents of the AggInfo structure indicated by the first
pParse->nHeight += sqlite3SelectExprHeight(p);
isAggSub = (pSub->selFlags & SF_Aggregate)!=0;
- if( flattenSubquery(pParse, p, i, isAgg, isAggSub) ){
+ if( sqlite3FlattenSubquery(pParse, p, i, isAgg, isAggSub) ){
/* This subquery can be absorbed into its parent. */
if( isAggSub ){
isAgg = 1;
#else
# define SELECTTRACE_ENABLED 0
#endif
+#if SELECTTRACE_ENABLED
+extern int sqlite3SelectTrace; /* Defined in global.c */
+# define SELECTTRACE(K,P,S,X) \
+ if(sqlite3SelectTrace&(K)) \
+ sqlite3DebugPrintf("%*s%s.%p: ",\
+ (P)->nSelectIndent*2-2,"",(S)->zSelName,(S)),\
+ sqlite3DebugPrintf X
+#else
+# define SELECTTRACE(K,P,S,X)
+#endif
/*
** An instance of the following structure is used to store the busy-handler
Index *sqlite3CreateIndex(Parse*,Token*,Token*,SrcList*,ExprList*,int,Token*,
Expr*, int, int);
void sqlite3DropIndex(Parse*, SrcList*, int);
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+int sqlite3FlattenSubquery(
+ Parse *pParse, /* Parsing context */
+ Select *p, /* The parent or outer SELECT statement */
+ int iFrom, /* Index in p->pSrc->a[] of the inner subquery */
+ int isAgg, /* True if outer SELECT uses aggregate functions */
+ int subqueryIsAgg /* True if the subquery uses aggregate functions */
+);
+#endif
int sqlite3Select(Parse*, Select*, SelectDest*);
Select *sqlite3SelectNew(Parse*,ExprList*,SrcList*,Expr*,ExprList*,
Expr*,ExprList*,u16,Expr*,Expr*);
loadext.c
pragma.c
prepare.c
+ flatten.c
select.c
table.c
trigger.c
projects / thirdparty / sqlite.git / commitdiff
