Fix the min/max optimizer so that it works when the FROM clause is a

subquery.  Ticket #658. (CVS 1293)

FossilOrigin-Name: 31c94acc72d318b5dec0fef1485621943add45c8

manifest

@@ -1,5 +1,5 @@
-C Typecast\sto\swork\saround\sa\sbug\sin\s{quote:\sCodeWarrior}\sStudio\sv9.1.\nTicket\s#654.\s(CVS\s1292)
+C Fix\sthe\smin/max\soptimizer\sso\sthat\sit\sworks\swhen\sthe\sFROM\sclause\sis\sa\nsubquery.\s\sTicket\s#658.\s(CVS\s1293)
-D 2004-03-10T18:57:32
+D 2004-03-13T14:00:36
 F Makefile.in 46788b65500865e3fd965f7617d41697da8a11a1
 F Makefile.linux-gcc b86a99c493a5bfb402d1d9178dcdc4bd4b32f906
 F README f1de682fbbd94899d50aca13d387d1b3fd3be2dd
@@ -38,7 +38,7 @@ F src/hash.h 3247573ab95b9dd90bcca0307a75d9a16da1ccc7
 F src/insert.c c0485ee2d1b99322894e2d1e0b576fd05ed75616
 F src/main.c 8e1b406d661c6475cc27d4b2b9422d1d2ab94cf7
 F src/md5.c fe4f9c9c6f71dfc26af8da63e4d04489b1430565
-F src/os.c afcc304d13b0d28755984aa1636e66370210d3e3
+F src/os.c 5f11382733805d4529ec2a30800e117f30995ea8
 F src/os.h 250a3789be609adfee5c5aa20137ce8683276f24
 F src/pager.c b246986e5ba31b15aa3cf91d3b9ec2e608aceb8e
 F src/pager.h 82332878799280145639a48d88cdb4058925e3f6
@@ -46,7 +46,7 @@ F src/parse.y 023720cb8c3bef74e51738bca78335d0dc6d2cfd
 F src/pragma.c 621d319580e9e23712ec232e8be1786cdae06b36
 F src/printf.c 8c58b7b6d4069eec6ebe2d46bdbc3a89a367bf95
 F src/random.c 775913e0b7fbd6295d21f12a7bd35b46387c44b2
-F src/select.c fb4360976fdf7b73f5252f274f8129540d5cd141
+F src/select.c 3833e2b64cc6d249385ee44e13bf49c9ae5b903d
 F src/shell.c 01fdfff666631cfe7f8047cfe9a8a62e56b37b50
 F src/sqlite.h.in 01a7009223517d151da9780b0bb7b748777015dd
 F src/sqliteInt.h 235ce244b62bb26cc9ab394fb7a0724dd4e65c83
@@ -107,7 +107,7 @@ F test/main.test 6a851b5992c4881a725a3d9647e629199df8de9d
 F test/malloc.test 2cfcffb7c858640e01e6520ee1cd54ca57d98e80
 F test/memdb.test 6ece25c7c0e6500199d3662607a3edca081abb2a
 F test/memleak.test 4d5d374c8ea1fc5ac634aed58cac1047848ce65e
-F test/minmax.test d7da9183013ac814a5b032b3542f9caf4c88af42
+F test/minmax.test 9dcf52f713b1b9e61d0a88a51eb8bb2e3c52d0ab
 F test/misc1.test 0b98d493b0cf55cb5f53e1f3df8107c166eecb5a
 F test/misc2.test 10c2ce26407d37411b96273e552d5095393732be
 F test/misc3.test 3eac0f13a3d8ae71c1c5ec884b0192bd68ae7e5f
@@ -188,7 +188,7 @@ F www/sqlite.tcl 3c83b08cf9f18aa2d69453ff441a36c40e431604
 F www/tclsqlite.tcl b9271d44dcf147a93c98f8ecf28c927307abd6da
 F www/vdbe.tcl 9b9095d4495f37697fd1935d10e14c6015e80aa1
 F www/whentouse.tcl a8335bce47cc2fddb07f19052cb0cb4d9129a8e4
-P af19ab32c5b329b053f3daf3c812eb593b89cd7f
+P 5864fc6937b933b7da0c00e6c4c2ee1b9b939cff
-R dff85ec6dfa3604f2a2a05aec54cbadc
+R 38ce5fb591e7b91ddde53b0f21b20e52
 U drh
-Z 014525b4ccfa6c0ddef9fa2856342ff1
+Z b929c36981acffd0768f9e08052aab34

manifest.uuid

@@ -1 +1 @@
-5864fc6937b933b7da0c00e6c4c2ee1b9b939cff
+31c94acc72d318b5dec0fef1485621943add45c8

src/os.c

@@ -1781,7 +1781,7 @@ char *sqliteOsFullPathname(const char *zRelative){
 }
 
 /*
-** The following variable, if set to a now-zero value, become the result
+** The following variable, if set to a non-zero value, becomes the result
 ** returned from sqliteOsCurrentTime().  This is used for testing.
 */
 #ifdef SQLITE_TEST

src/select.c

@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** to handle SELECT statements in SQLite.
 **
-** $Id: select.c,v 1.160 2004/03/02 18:37:41 drh Exp $
+** $Id: select.c,v 1.161 2004/03/13 14:00:36 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -1836,18 +1836,23 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
   Vdbe *v;
   int seekOp;
   int cont;
-  ExprList eList;
+  ExprList *pEList, *pList, eList;
   struct ExprList_item eListItem;
+  SrcList *pSrc;
+  
 
   /* Check to see if this query is a simple min() or max() query.  Return
   ** zero if it is  not.
   */
   if( p->pGroupBy || p->pHaving || p->pWhere ) return 0;
-  if( p->pSrc->nSrc!=1 ) return 0;
+  pSrc = p->pSrc;
-  if( p->pEList->nExpr!=1 ) return 0;
+  if( pSrc->nSrc!=1 ) return 0;
-  pExpr = p->pEList->a[0].pExpr;
+  pEList = p->pEList;
+  if( pEList->nExpr!=1 ) return 0;
+  pExpr = pEList->a[0].pExpr;
   if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
-  if( pExpr->pList==0 || pExpr->pList->nExpr!=1 ) return 0;
+  pList = pExpr->pList;
+  if( pList==0 || pList->nExpr!=1 ) return 0;
   if( pExpr->token.n!=3 ) return 0;
   if( sqliteStrNICmp(pExpr->token.z,"min",3)==0 ){
     seekOp = OP_Rewind;
@@ -1856,10 +1861,10 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
   }else{
     return 0;
   }
-  pExpr = pExpr->pList->a[0].pExpr;
+  pExpr = pList->a[0].pExpr;
   if( pExpr->op!=TK_COLUMN ) return 0;
   iCol = pExpr->iColumn;
-  pTab = p->pSrc->a[0].pTab;
+  pTab = pSrc->a[0].pTab;
 
   /* If we get to here, it means the query is of the correct form.
   ** Check to make sure we have an index and make pIdx point to the
@@ -1899,10 +1904,12 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
   ** or last entry in the main table.
   */
   sqliteCodeVerifySchema(pParse, pTab->iDb);
-  base = p->pSrc->a[0].iCursor;
+  base = pSrc->a[0].iCursor;
   computeLimitRegisters(pParse, p);
-  sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
+  if( pSrc->a[0].pSelect==0 ){
-  sqliteVdbeOp3(v, OP_OpenRead, base, pTab->tnum, pTab->zName, 0);
+    sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
+    sqliteVdbeOp3(v, OP_OpenRead, base, pTab->tnum, pTab->zName, 0);
+  }
   cont = sqliteVdbeMakeLabel(v);
   if( pIdx==0 ){
     sqliteVdbeAddOp(v, seekOp, base, 0);
@@ -1921,6 +1928,7 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
   selectInnerLoop(pParse, p, &eList, 0, 0, 0, -1, eDest, iParm, cont, cont);
   sqliteVdbeResolveLabel(v, cont);
   sqliteVdbeAddOp(v, OP_Close, base, 0);
+  
   return 1;
 }
 
@@ -2161,14 +2169,6 @@ int sqliteSelect(
     generateColumnNames(pParse, pTabList, pEList);
   }
 
-  /* Check for the special case of a min() or max() function by itself
-  ** in the result set.
-  */
-  if( simpleMinMaxQuery(pParse, p, eDest, iParm) ){
-    rc = 0;
-    goto select_end;
-  }
-
   /* Generate code for all sub-queries in the FROM clause
   */
   for(i=0; i<pTabList->nSrc; i++){
@@ -2198,6 +2198,14 @@ int sqliteSelect(
     isDistinct = p->isDistinct;
   }
 
+  /* Check for the special case of a min() or max() function by itself
+  ** in the result set.
+  */
+  if( simpleMinMaxQuery(pParse, p, eDest, iParm) ){
+    rc = 0;
+    goto select_end;
+  }
+
   /* Check to see if this is a subquery that can be "flattened" into its parent.
   ** If flattening is a possiblity, do so and return immediately.  
   */

test/minmax.test

@@ -13,7 +13,7 @@
 # aggregate min() and max() functions and which are handled as
 # as a special case.
 #
-# $Id: minmax.test,v 1.8 2004/02/25 13:47:34 drh Exp $
+# $Id: minmax.test,v 1.9 2004/03/13 14:00:37 drh Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
@@ -258,5 +258,22 @@ do_test minmax-8.2 {
   }
 } {34 1234}
 
+# Ticket #658:  Test the min()/max() optimization when the FROM clause
+# is a subquery.
+#
+do_test minmax-9.1 {
+  execsql {
+    SELECT max(rowid) FROM (
+      SELECT max(rowid) FROM t4 UNION SELECT max(rowid) FROM t5
+    )
+  }
+} {1}
+do_test minmax-9.2 {
+  execsql {
+    SELECT max(rowid) FROM (
+      SELECT max(rowid) FROM t4 EXCEPT SELECT max(rowid) FROM t5
+    )
+  }
+} {{}}
 
 finish_test