From: drh <drh@noemail.net>
Date: Thu, 6 Oct 2005 16:53:14 +0000 (+0000)
Subject: More efficient handling of the LIMIT clause.  Scalar subqueries and EXISTS
X-Git-Tag: version-3.6.10~3413
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ec7429ae275e752c8fe65e93aa5815e98edf7e17;p=thirdparty%2Fsqlite.git

More efficient handling of the LIMIT clause.  Scalar subqueries and EXISTS
on compound SELECT statements now working properly.  Ticket #1473. (CVS 2747)

FossilOrigin-Name: edca8913ca012fc0c17343a27f819de95147b1bd
---

diff --git a/manifest b/manifest
index cdf00ff68d..e53c53ae5a 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Check-in\s(2744)\sas\sincomplete\sand\sbroke\spragma\sintegrity_check.\s\sThis\ncompletes\sthe\schange\sand\sfixes\sthe\sproblem.\s(CVS\s2746)
-D 2005-10-06T13:59:27
+C More\sefficient\shandling\sof\sthe\sLIMIT\sclause.\s\sScalar\ssubqueries\sand\sEXISTS\non\scompound\sSELECT\sstatements\snow\sworking\sproperly.\s\sTicket\s#1473.\s(CVS\s2747)
+D 2005-10-06T16:53:15
 F Makefile.in 12784cdce5ffc8dfb707300c34e4f1eb3b8a14f1
 F Makefile.linux-gcc aee18d8a05546dcf1888bd4547e442008a49a092
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -41,7 +41,7 @@ F src/complete.c 4de937dfdd4c79a501772ab2035b26082f337a79
 F src/date.c 7444b0900a28da77e57e3337a636873cff0ae940
 F src/delete.c 29dac493f4d83b05f91233b116827c133bcdab72
 F src/experimental.c 50c1e3b34f752f4ac10c36f287db095c2b61766d
-F src/expr.c bb2cf5d5b065eaa23d5ae2620f6de0568768147d
+F src/expr.c 6881c8dfe363c1ee5a5dcb463b880704acb77709
 F src/func.c f63d417248808ff2632a3b576536abffcc21d858
 F src/hash.c 8747cf51d12de46512880dfcf1b68b4e24072863
 F src/hash.h 1b0c445e1c89ff2aaad9b4605ba61375af001e84
@@ -64,11 +64,11 @@ F src/pragma.c 9ec219dc4ee2d4e78f4ec5c9d1422089758af13f
 F src/prepare.c fc098db25d2a121affb08686cf04833fd50452d4
 F src/printf.c bd421c1ad5e01013c89af63c60eab02852ccd15e
 F src/random.c 90adff4e73a3b249eb4f1fc2a6ff9cf78c7233a4
-F src/select.c 034c7f7447b8711f85bef578a437ea12ca7cac53
+F src/select.c 80c95f3cebd6f7096cdcad1968316e4bb96b18b2
 F src/shell.c 3596c1e559b82663057940d19ba533ad421c7dd3
 F src/sqlite.h.in 461b2535550cf77aedfd44385da11ef7d63e57a2
-F src/sqliteInt.h 53daa72541b4336c5e89773cf39717ed695bd523
-F src/table.c abc7b6946a2c2ee0603f067f8210ed004ea9a9ac
+F src/sqliteInt.h c9afda257c9649aef17f9ddb67ae443b800e2bae
+F src/table.c e03b60eaabaeb54a00d7e931566d77302dfc19b0
 F src/tclsqlite.c 4f274fae3d4a1863451a553dd8e5015747a5d91d
 F src/test1.c 0f1a66f65a54fba029f7e93b7500d49443dc959b
 F src/test2.c 4196848c845626e7df894470f27329e80bfe92aa
@@ -81,7 +81,7 @@ F src/update.c ac506fb7400158f826ec6c3a0dbe65e7ed3928d5
 F src/utf.c bda5eb85039ef16f2d17004c1e18c96e1ab0a80c
 F src/util.c 55caaffbb2716f9928ab452d20f3e9cbbeab872d
 F src/vacuum.c 829d9e1a6d7c094b80e0899686670932eafd768c
-F src/vdbe.c 3f1adcf4535dd35e4244d19d332fb6b515491c0d
+F src/vdbe.c c9aca7cc6dc381c4ce5a59c97ac148ed0659fb3c
 F src/vdbe.h 8729a4ee16ff9aeab2af9667df3cf300ff978e13
 F src/vdbeInt.h 7bedbb9553a10e86b53f75d99e197f3f00a732bf
 F src/vdbeapi.c 85bbe1d0243a89655433d60711b4bd71979b59cd
@@ -224,6 +224,7 @@ F test/tkt1435.test f768e5415d102fa1d8de3f548469d8fd1b79abd8
 F test/tkt1443.test 1e83b6a1e7f6e261682e67106ab3bc05f6c70e90
 F test/tkt1444.test 0f0fc1f277691f904dea2abece6db919dcae2351
 F test/tkt1449.test f8de8a84ec12ee805ed80055e1209560f8bee4d8
+F test/tkt1473.test e4637c27d606fd002de78113a8e1a142e48ffb18
 F test/trace.test 9fd28695c463b90c2d32c387a432e01eb26e8ccf
 F test/trans.test 10506dc30305cfb8c4098359f7f6f64786f69c5e
 F test/trigger1.test 152aed5a1fa90709fe171f2ca501a6b7f7901479
@@ -243,7 +244,7 @@ F test/vacuum.test 5d4857ae2afc9c20d0edb8acc58bdc8d630126a9
 F test/vacuum2.test 5d77e98c458bcdbeecc6327de5107179ba1aa095
 F test/varint.test ab7b110089a08b9926ed7390e7e97bdefeb74102
 F test/view.test ce0f0ad39fa4a3572acffcf1e634850ee151aae0
-F test/where.test ce21f4910ef6a0c08f8172857baecefca20a3b0c
+F test/where.test 752728413eab42e5854690d84c7319cdf7edc515
 F test/where2.test 503e2e2b6abe14c5c10222e72d08ef84c1bf1ffb
 F tool/diffdb.c 7524b1b5df217c20cd0431f6789851a4e0cb191b
 F tool/lemon.c c88936c67f6411608db8fa4254d254f509fa40f6
@@ -314,7 +315,7 @@ F www/tclsqlite.tcl ddcf912ea48695603c8ed7efb29f0812ef8d1b49
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl a99cf5f6d8bd4d5537584a2b342f0fb9fa601d8b
 F www/whentouse.tcl 97e2b5cd296f7d8057e11f44427dea8a4c2db513
-P 9709f0f6bcb2a1ed07e678b73cb518488b8ff333
-R 4e003316fcdb49418371e800e7deae56
+P 4862eaafd875eb1069076864c7cad600a76620c7
+R 24aa61823d2322d621f097e15a448b5d
 U drh
-Z 348c11fe0babe3db160a693e1bb13ff7
+Z e25e42a04ed4277adccd254634ad3dc4
diff --git a/manifest.uuid b/manifest.uuid
index 4de4a4c7bb..0598cb0fe5 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-4862eaafd875eb1069076864c7cad600a76620c7
\ No newline at end of file
+edca8913ca012fc0c17343a27f819de95147b1bd
\ No newline at end of file
diff --git a/src/expr.c b/src/expr.c
index c415e7ab55..f1eae86d64 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -12,7 +12,7 @@
 ** This file contains routines used for analyzing expressions and
 ** for generating VDBE code that evaluates expressions in SQLite.
 **
-** $Id: expr.c,v 1.230 2005/09/23 21:11:54 drh Exp $
+** $Id: expr.c,v 1.231 2005/10/06 16:53:15 drh Exp $
 */
 #include "sqliteInt.h"
 #include <ctype.h>
@@ -1390,21 +1390,25 @@ void sqlite3CodeSubselect(Parse *pParse, Expr *pExpr){
       ** value of this select in a memory cell and record the number
       ** of the memory cell in iColumn.
       */
-      int sop;
+      static const Token one = { "1", 0, 1 };
       Select *pSel;
+      int iMem;
+      int sop;
 
-      pExpr->iColumn = pParse->nMem++;
+      pExpr->iColumn = iMem = pParse->nMem++;
       pSel = pExpr->pSelect;
       if( pExpr->op==TK_SELECT ){
         sop = SRT_Mem;
+        sqlite3VdbeAddOp(v, OP_MemNull, iMem, 0);
+        VdbeComment((v, "# Init subquery result"));
       }else{
-        static const Token one = { "1", 0, 1 };
         sop = SRT_Exists;
-        sqlite3ExprListDelete(pSel->pEList);
-        pSel->pEList = sqlite3ExprListAppend(0, 
-                          sqlite3Expr(TK_INTEGER, 0, 0, &one), 0);
+        sqlite3VdbeAddOp(v, OP_MemInt, 0, iMem);
+        VdbeComment((v, "# Init EXISTS result"));
       }
-      sqlite3Select(pParse, pSel, sop, pExpr->iColumn, 0, 0, 0, 0);
+      sqlite3ExprDelete(pSel->pLimit);
+      pSel->pLimit = sqlite3Expr(TK_INTEGER, 0, 0, &one);
+      sqlite3Select(pParse, pSel, sop, iMem, 0, 0, 0, 0);
       break;
     }
   }
diff --git a/src/select.c b/src/select.c
index 3b99cf408c..fde787d872 100644
--- a/src/select.c
+++ b/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 1.276 2005/09/20 18:13:24 drh Exp $
+** $Id: select.c,v 1.277 2005/10/06 16:53:15 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -360,13 +360,12 @@ static void pushOntoSorter(Parse *pParse, Vdbe *v, ExprList *pOrderBy){
 }
 
 /*
-** Add code to implement the OFFSET and LIMIT
+** Add code to implement the OFFSET
 */
-static void codeLimiter(
+static void codeOffset(
   Vdbe *v,          /* Generate code into this VM */
   Select *p,        /* The SELECT statement being coded */
   int iContinue,    /* Jump here to skip the current record */
-  int iBreak,       /* Jump here to end the loop */
   int nPop          /* Number of times to pop stack when jumping */
 ){
   if( p->iOffset>=0 && iContinue!=0 ){
@@ -380,10 +379,6 @@ static void codeLimiter(
     sqlite3VdbeAddOp(v, OP_Goto, 0, iContinue);
     VdbeComment((v, "# skip OFFSET records"));
   }
-  if( p->iLimit>=0 && iBreak!=0 ){
-    sqlite3VdbeAddOp(v, OP_MemIncr, p->iLimit, iBreak);
-    VdbeComment((v, "# exit when LIMIT reached"));
-  }
 }
 
 /*
@@ -449,7 +444,7 @@ static int selectInnerLoop(
   */
   hasDistinct = distinct>=0 && pEList && pEList->nExpr>0;
   if( pOrderBy==0 && !hasDistinct ){
-    codeLimiter(v, p, iContinue, iBreak, 0);
+    codeOffset(v, p, iContinue, 0);
   }
 
   /* Pull the requested columns.
@@ -471,7 +466,7 @@ static int selectInnerLoop(
     int n = pEList->nExpr;
     codeDistinct(v, distinct, iContinue, n, n+1);
     if( pOrderBy==0 ){
-      codeLimiter(v, p, iContinue, iBreak, nColumn);
+      codeOffset(v, p, iContinue, nColumn);
     }
   }
 
@@ -547,18 +542,26 @@ static int selectInnerLoop(
       break;
     }
 
+    /* If any row exists in the result set, record that fact and abort.
+    */
+    case SRT_Exists: {
+      sqlite3VdbeAddOp(v, OP_MemInt, 1, iParm);
+      sqlite3VdbeAddOp(v, OP_Pop, nColumn, 0);
+      /* The LIMIT clause will terminate the loop for us */
+      break;
+    }
+
     /* If this is a scalar select that is part of an expression, then
     ** store the results in the appropriate memory cell and break out
     ** of the scan loop.
     */
-    case SRT_Exists:
     case SRT_Mem: {
       assert( nColumn==1 );
       if( pOrderBy ){
         pushOntoSorter(pParse, v, pOrderBy);
       }else{
         sqlite3VdbeAddOp(v, OP_MemStore, iParm, 1);
-        sqlite3VdbeAddOp(v, OP_Goto, 0, iBreak);
+        /* The LIMIT clause will jump out of the loop for us */
       }
       break;
     }
@@ -594,6 +597,13 @@ static int selectInnerLoop(
     }
 #endif
   }
+
+  /* Jump to the end of the loop if the LIMIT is reached.
+  */
+  if( p->iLimit>=0 && pOrderBy==0 ){
+    sqlite3VdbeAddOp(v, OP_MemIncr, p->iLimit, 0);
+    sqlite3VdbeAddOp(v, OP_IfMemZero, p->iLimit, iBreak);
+  }
   return 0;
 }
 
@@ -661,7 +671,7 @@ static void generateSortTail(
 
   iTab = pOrderBy->iECursor;
   addr = 1 + sqlite3VdbeAddOp(v, OP_Sort, iTab, brk);
-  codeLimiter(v, p, cont, brk, 0);
+  codeOffset(v, p, cont, 0);
   sqlite3VdbeAddOp(v, OP_Column, iTab, pOrderBy->nExpr + 1);
   switch( eDest ){
     case SRT_Table:
@@ -681,11 +691,10 @@ static void generateSortTail(
       sqlite3VdbeAddOp(v, OP_IdxInsert, (iParm&0x0000FFFF), 0);
       break;
     }
-    case SRT_Exists:
     case SRT_Mem: {
       assert( nColumn==1 );
       sqlite3VdbeAddOp(v, OP_MemStore, iParm, 1);
-      sqlite3VdbeAddOp(v, OP_Goto, 0, brk);
+      /* The LIMIT clause will terminate the loop for us */
       break;
     }
 #endif
@@ -710,6 +719,16 @@ static void generateSortTail(
       break;
     }
   }
+
+  /* Jump to the end of the loop when the LIMIT is reached
+  */
+  if( p->iLimit>=0 ){
+    sqlite3VdbeAddOp(v, OP_MemIncr, p->iLimit, 0);
+    sqlite3VdbeAddOp(v, OP_IfMemZero, p->iLimit, brk);
+  }
+
+  /* The bottom of the loop
+  */
   sqlite3VdbeResolveLabel(v, cont);
   sqlite3VdbeAddOp(v, OP_Next, iTab, addr);
   sqlite3VdbeResolveLabel(v, brk);
@@ -1328,7 +1347,7 @@ Vdbe *sqlite3GetVdbe(Parse *pParse){
 
 /*
 ** Compute the iLimit and iOffset fields of the SELECT based on the
-** pLimit and pOffset expressions.  nLimit and nOffset hold the expressions
+** pLimit and pOffset expressions.  pLimit and pOffset hold the expressions
 ** that appear in the original SQL statement after the LIMIT and OFFSET
 ** keywords.  Or NULL if those keywords are omitted. iLimit and iOffset 
 ** are the integer memory register numbers for counters used to compute 
@@ -1336,15 +1355,15 @@ Vdbe *sqlite3GetVdbe(Parse *pParse){
 ** iLimit and iOffset are negative.
 **
 ** This routine changes the values if iLimit and iOffset only if
-** a limit or offset is defined by nLimit and nOffset.  iLimit and
+** a limit or offset is defined by pLimit and pOffset.  iLimit and
 ** iOffset should have been preset to appropriate default values
 ** (usually but not always -1) prior to calling this routine.
-** Only if nLimit>=0 or nOffset>0 do the limit registers get
+** Only if pLimit!=0 or pOffset!=0 do the limit registers get
 ** redefined.  The UNION ALL operator uses this property to force
 ** the reuse of the same limit and offset registers across multiple
 ** SELECT statements.
 */
-static void computeLimitRegisters(Parse *pParse, Select *p){
+static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
   /* 
   ** "LIMIT -1" always shows all rows.  There is some
   ** contraversy about what the correct behavior should be.
@@ -1360,6 +1379,7 @@ static void computeLimitRegisters(Parse *pParse, Select *p){
     sqlite3VdbeAddOp(v, OP_Negative, 0, 0);
     sqlite3VdbeAddOp(v, OP_MemStore, iMem, 1);
     VdbeComment((v, "# LIMIT counter"));
+    sqlite3VdbeAddOp(v, OP_IfMemZero, iMem, iBreak);
     p->iLimit = iMem;
   }
   if( p->pOffset ){
@@ -1519,6 +1539,7 @@ static int multiSelect(
   switch( p->op ){
     case TK_ALL: {
       if( pOrderBy==0 ){
+        int addr = 0;
         assert( !pPrior->pLimit );
         pPrior->pLimit = p->pLimit;
         pPrior->pOffset = p->pOffset;
@@ -1531,11 +1552,18 @@ static int multiSelect(
         p->iOffset = pPrior->iOffset;
         p->pLimit = 0;
         p->pOffset = 0;
+        if( p->iLimit>=0 ){
+          addr = sqlite3VdbeAddOp(v, OP_IfMemZero, p->iLimit, 0);
+          VdbeComment((v, "# Jump ahead if LIMIT reached"));
+        }
         rc = sqlite3Select(pParse, p, eDest, iParm, 0, 0, 0, aff);
         p->pPrior = pPrior;
         if( rc ){
           goto multi_select_end;
         }
+        if( addr ){
+          sqlite3VdbeJumpHere(v, addr);
+        }
         break;
       }
       /* For UNION ALL ... ORDER BY fall through to the next case */
@@ -1622,8 +1650,8 @@ static int multiSelect(
         }
         iBreak = sqlite3VdbeMakeLabel(v);
         iCont = sqlite3VdbeMakeLabel(v);
+        computeLimitRegisters(pParse, p, iBreak);
         sqlite3VdbeAddOp(v, OP_Rewind, unionTab, iBreak);
-        computeLimitRegisters(pParse, p);
         iStart = sqlite3VdbeCurrentAddr(v);
         rc = selectInnerLoop(pParse, p, p->pEList, unionTab, p->pEList->nExpr,
                              pOrderBy, -1, eDest, iParm, 
@@ -1698,8 +1726,8 @@ static int multiSelect(
       }
       iBreak = sqlite3VdbeMakeLabel(v);
       iCont = sqlite3VdbeMakeLabel(v);
+      computeLimitRegisters(pParse, p, iBreak);
       sqlite3VdbeAddOp(v, OP_Rewind, tab1, iBreak);
-      computeLimitRegisters(pParse, p);
       iStart = sqlite3VdbeAddOp(v, OP_RowKey, tab1, 0);
       sqlite3VdbeAddOp(v, OP_NotFound, tab2, iCont);
       rc = selectInnerLoop(pParse, p, p->pEList, tab1, p->pEList->nExpr,
@@ -2166,10 +2194,10 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
   int base;
   Vdbe *v;
   int seekOp;
-  int cont;
   ExprList *pEList, *pList, eList;
   struct ExprList_item eListItem;
   SrcList *pSrc;
+  int brk;
 
   /* Check to see if this query is a simple min() or max() query.  Return
   ** zero if it is  not.
@@ -2233,11 +2261,11 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
   */
   sqlite3CodeVerifySchema(pParse, pTab->iDb);
   base = pSrc->a[0].iCursor;
-  computeLimitRegisters(pParse, p);
+  brk = sqlite3VdbeMakeLabel(v);
+  computeLimitRegisters(pParse, p, brk);
   if( pSrc->a[0].pSelect==0 ){
     sqlite3OpenTableForReading(v, base, pTab);
   }
-  cont = sqlite3VdbeMakeLabel(v);
   if( pIdx==0 ){
     sqlite3VdbeAddOp(v, seekOp, base, 0);
   }else{
@@ -2266,8 +2294,8 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
   memset(&eListItem, 0, sizeof(eListItem));
   eList.a = &eListItem;
   eList.a[0].pExpr = pExpr;
-  selectInnerLoop(pParse, p, &eList, 0, 0, 0, -1, eDest, iParm, cont, cont, 0);
-  sqlite3VdbeResolveLabel(v, cont);
+  selectInnerLoop(pParse, p, &eList, 0, 0, 0, -1, eDest, iParm, brk, brk, 0);
+  sqlite3VdbeResolveLabel(v, brk);
   sqlite3VdbeAddOp(v, OP_Close, base, 0);
   
   return 1;
@@ -2615,6 +2643,7 @@ int sqlite3Select(
   int rc = 1;            /* Value to return from this function */
   int addrSortIndex;     /* Address of an OP_OpenVirtual instruction */
   AggInfo sAggInfo;      /* Information used by aggregate queries */
+  int iEnd;              /* Address of the end of the query */
 
   if( sqlite3_malloc_failed || pParse->nErr || p==0 ) return 1;
   if( sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0) ) return 1;
@@ -2663,7 +2692,6 @@ int sqlite3Select(
   /* If writing to memory or generating a set
   ** only a single column may be output.
   */
-  assert( eDest!=SRT_Exists || pEList->nExpr==1 );
 #ifndef SQLITE_OMIT_SUBQUERY
   if( (eDest==SRT_Mem || eDest==SRT_Set) && pEList->nExpr>1 ){
     sqlite3ErrorMsg(pParse, "only a single result allowed for "
@@ -2772,7 +2800,8 @@ int sqlite3Select(
 
   /* Set the limiter.
   */
-  computeLimitRegisters(pParse, p);
+  iEnd = sqlite3VdbeMakeLabel(v);
+  computeLimitRegisters(pParse, p, iEnd);
 
   /* If the output is destined for a temporary table, open that table.
   */
@@ -2780,15 +2809,6 @@ int sqlite3Select(
     sqlite3VdbeAddOp(v, OP_OpenVirtual, iParm, pEList->nExpr);
   }
 
-
-  /* Initialize the memory cell to NULL for SRT_Mem or 0 for SRT_Exists
-  */
-  if( eDest==SRT_Mem ){
-    sqlite3VdbeAddOp(v, OP_MemNull, iParm, 0);
-  }else if( eDest==SRT_Exists ){
-    sqlite3VdbeAddOp(v, OP_MemInt, 0, iParm);
-  }
-
   /* Open a virtual index to use for the distinct set.
   */
   if( isDistinct ){
@@ -3112,6 +3132,10 @@ int sqlite3Select(
   }
 #endif
 
+  /* Jump here to skip this query
+  */
+  sqlite3VdbeResolveLabel(v, iEnd);
+
   /* The SELECT was successfully coded.   Set the return code to 0
   ** to indicate no errors.
   */
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index beb198f087..9d172a227a 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -11,7 +11,7 @@
 *************************************************************************
 ** Internal interface definitions for SQLite.
 **
-** @(#) $Id: sqliteInt.h,v 1.421 2005/09/19 21:05:49 drh Exp $
+** @(#) $Id: sqliteInt.h,v 1.422 2005/10/06 16:53:15 drh Exp $
 */
 #ifndef _SQLITEINT_H_
 #define _SQLITEINT_H_
@@ -1149,7 +1149,7 @@ struct Select {
 #define SRT_Table        7  /* Store result as data with an automatic rowid */
 #define SRT_VirtualTab   8  /* Create virtual table and store like SRT_Table */
 #define SRT_Subroutine   9  /* Call a subroutine to handle results */
-#define SRT_Exists      10  /* Put 0 or 1 in a memory cell */
+#define SRT_Exists      10  /* Store 1 if the result is not empty */
 
 /*
 ** An SQL parser context.  A copy of this structure is passed through
diff --git a/src/table.c b/src/table.c
index a04b822764..2e1b7b42d4 100644
--- a/src/table.c
+++ b/src/table.c
@@ -196,4 +196,4 @@ void sqlite3_free_table(
   }
 }
 
-#endif SQLITE_OMIT_GET_TABLE
+#endif /* SQLITE_OMIT_GET_TABLE */
diff --git a/src/vdbe.c b/src/vdbe.c
index d7af8f0210..a10f1a2485 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -43,7 +43,7 @@
 ** in this file for details.  If in doubt, do not deviate from existing
 ** commenting and indentation practices when changing or adding code.
 **
-** $Id: vdbe.c,v 1.491 2005/09/20 17:42:23 drh Exp $
+** $Id: vdbe.c,v 1.492 2005/10/06 16:53:16 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -4141,7 +4141,7 @@ case OP_MemMax: {        /* no-push */
 /* Opcode: MemIncr P1 P2 *
 **
 ** Increment the integer valued memory cell P1 by 1.  If P2 is not zero
-** and the result after the increment is exactly 1, then jump
+** and the result after the increment is exactly 0, then jump
 ** to P2.
 **
 ** This instruction throws an error if the memory cell is not initially
@@ -4154,7 +4154,7 @@ case OP_MemIncr: {        /* no-push */
   pMem = &p->aMem[i];
   assert( pMem->flags==MEM_Int );
   pMem->i++;
-  if( pOp->p2>0 && pMem->i==1 ){
+  if( pOp->p2>0 && pMem->i==0 ){
      pc = pOp->p2 - 1;
   }
   break;
@@ -4162,16 +4162,31 @@ case OP_MemIncr: {        /* no-push */
 
 /* Opcode: IfMemPos P1 P2 *
 **
-** If the value of memory cell P1 is 1 or greater, jump to P2. This
-** opcode assumes that memory cell P1 holds an integer value.
+** If the value of memory cell P1 is 1 or greater, jump to P2.  If
+** the memory cell holds an integer of 0 or less or if it holds something
+** that is not an integer, then fall thru.
 */
 case OP_IfMemPos: {        /* no-push */
   int i = pOp->p1;
   Mem *pMem;
   assert( i>=0 && i<p->nMem );
   pMem = &p->aMem[i];
-  assert( pMem->flags==MEM_Int );
-  if( pMem->i>0 ){
+  if( pMem->flags==MEM_Int && pMem->i>0 ){
+     pc = pOp->p2 - 1;
+  }
+  break;
+}
+
+/* Opcode: IfMemZero P1 P2 *
+**
+** If the value of memory cell P1 is exactly 0, jump to P2.
+*/
+case OP_IfMemZero: {        /* no-push */
+  int i = pOp->p1;
+  Mem *pMem;
+  assert( i>=0 && i<p->nMem );
+  pMem = &p->aMem[i];
+  if( pMem->flags==MEM_Int && pMem->i==0 ){
      pc = pOp->p2 - 1;
   }
   break;
diff --git a/test/tkt1473.test b/test/tkt1473.test
new file mode 100644
index 0000000000..bc53de3a8e
--- /dev/null
+++ b/test/tkt1473.test
@@ -0,0 +1,716 @@
+# 2005 September 19
+#
+# 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 implements regression tests for SQLite library.
+#
+# This file implements tests to verify that ticket #1473 has been
+# fixed.  
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+
+do_test tkt1473-1.1 {
+  execsql {
+    CREATE TABLE t1(a,b);
+    INSERT INTO t1 VALUES(1,2);
+    INSERT INTO t1 VALUES(3,4);
+    SELECT * FROM t1
+  }
+} {1 2 3 4}
+
+do_test tkt1473-1.2 {
+  execsql {
+    SELECT 1 FROM t1 WHERE a=1 UNION ALL SELECT 2 FROM t1 WHERE b=0
+  }
+} {1}
+do_test tkt1473-1.3 {
+  execsql {
+    SELECT 1 FROM t1 WHERE a=1 UNION SELECT 2 FROM t1 WHERE b=0
+  }
+} {1}
+do_test tkt1473-1.4 {
+  execsql {
+    SELECT 1 FROM t1 WHERE a=1 UNION ALL SELECT 2 FROM t1 WHERE b=4
+  }
+} {1 2}
+do_test tkt1473-1.5 {
+  execsql {
+    SELECT 1 FROM t1 WHERE a=1 UNION SELECT 2 FROM t1 WHERE b=4
+  }
+} {1 2}
+do_test tkt1473-1.6 {
+  execsql {
+    SELECT 1 FROM t1 WHERE a=0 UNION ALL SELECT 2 FROM t1 WHERE b=4
+  }
+} {2}
+do_test tkt1473-1.7 {
+  execsql {
+    SELECT 1 FROM t1 WHERE a=0 UNION SELECT 2 FROM t1 WHERE b=4
+  }
+} {2}
+do_test tkt1473-1.8 {
+  execsql {
+    SELECT 1 FROM t1 WHERE a=0 UNION ALL SELECT 2 FROM t1 WHERE b=0
+  }
+} {}
+do_test tkt1473-1.9 {
+  execsql {
+    SELECT 1 FROM t1 WHERE a=0 UNION SELECT 2 FROM t1 WHERE b=0
+  }
+} {}
+
+do_test tkt1473-2.2 {
+  execsql {
+    SELECT (SELECT 1 FROM t1 WHERE a=1 UNION ALL SELECT 2 FROM t1 WHERE b=0)
+  }
+} {1}
+do_test tkt1473-2.3 {
+  execsql {
+    SELECT (SELECT 1 FROM t1 WHERE a=1 UNION SELECT 2 FROM t1 WHERE b=0)
+  }
+} {1}
+do_test tkt1473-2.4 {
+  execsql {
+    SELECT (SELECT 1 FROM t1 WHERE a=1 UNION ALL SELECT 2 FROM t1 WHERE b=4)
+  }
+} {1}
+do_test tkt1473-2.5 {
+  execsql {
+    SELECT (SELECT 1 FROM t1 WHERE a=1 UNION SELECT 2 FROM t1 WHERE b=4)
+  }
+} {1}
+do_test tkt1473-2.6 {
+  execsql {
+    SELECT (SELECT 1 FROM t1 WHERE a=0 UNION ALL SELECT 2 FROM t1 WHERE b=4)
+  }
+} {2}
+do_test tkt1473-2.7 {
+  execsql {
+    SELECT (SELECT 1 FROM t1 WHERE a=0 UNION SELECT 2 FROM t1 WHERE b=4)
+  }
+} {2}
+do_test tkt1473-2.8 {
+  execsql {
+    SELECT (SELECT 1 FROM t1 WHERE a=0 UNION ALL SELECT 2 FROM t1 WHERE b=0)
+  }
+} {{}}
+do_test tkt1473-2.9 {
+  execsql {
+    SELECT (SELECT 1 FROM t1 WHERE a=0 UNION SELECT 2 FROM t1 WHERE b=0)
+  }
+} {{}}
+
+do_test tkt1473-3.2 {
+  execsql {
+    SELECT EXISTS
+      (SELECT 1 FROM t1 WHERE a=1 UNION ALL SELECT 2 FROM t1 WHERE b=0)
+  }
+} {1}
+do_test tkt1473-3.3 {
+  execsql {
+    SELECT EXISTS
+      (SELECT 1 FROM t1 WHERE a=1 UNION SELECT 2 FROM t1 WHERE b=0)
+  }
+} {1}
+do_test tkt1473-3.4 {
+  execsql {
+    SELECT EXISTS
+      (SELECT 1 FROM t1 WHERE a=1 UNION ALL SELECT 2 FROM t1 WHERE b=4)
+  }
+} {1}
+do_test tkt1473-3.5 {
+  execsql {
+    SELECT EXISTS
+      (SELECT 1 FROM t1 WHERE a=1 UNION SELECT 2 FROM t1 WHERE b=4)
+  }
+} {1}
+do_test tkt1473-3.6 {
+  execsql {
+    SELECT EXISTS
+      (SELECT 1 FROM t1 WHERE a=0 UNION ALL SELECT 2 FROM t1 WHERE b=4)
+  }
+} {1}
+do_test tkt1473-3.7 {
+  execsql {
+    SELECT EXISTS
+      (SELECT 1 FROM t1 WHERE a=0 UNION SELECT 2 FROM t1 WHERE b=4)
+  }
+} {1}
+do_test tkt1473-3.8 {
+  execsql {
+    SELECT EXISTS
+      (SELECT 1 FROM t1 WHERE a=0 UNION ALL SELECT 2 FROM t1 WHERE b=0)
+  }
+} {0}
+do_test tkt1473-3.9 {
+  execsql {
+    SELECT EXISTS
+      (SELECT 1 FROM t1 WHERE a=0 UNION SELECT 2 FROM t1 WHERE b=0)
+  }
+} {0}
+
+do_test tkt1473-4.1 {
+  execsql {
+    CREATE TABLE t2(x,y);
+    INSERT INTO t2 VALUES(1,2);
+    INSERT INTO t2 SELECT x+2, y+2 FROM t2;
+    INSERT INTO t2 SELECT x+4, y+4 FROM t2;
+    INSERT INTO t2 SELECT x+8, y+8 FROM t2;
+    INSERT INTO t2 SELECT x+16, y+16 FROM t2;
+    INSERT INTO t2 SELECT x+32, y+32 FROM t2;
+    INSERT INTO t2 SELECT x+64, y+64 FROM t2;
+    SELECT count(*), sum(x), sum(y) FROM t2;
+  }
+} {64 4096 4160}
+do_test tkt1473-4.2 {
+  execsql {
+    SELECT 1 FROM t2 WHERE x=0
+    UNION ALL
+    SELECT 2 FROM t2 WHERE x=1
+    UNION ALL
+    SELECT 3 FROM t2 WHERE x=2
+    UNION ALL
+    SELECT 4 FROM t2 WHERE x=3
+    UNION ALL
+    SELECT 5 FROM t2 WHERE x=4
+    UNION ALL
+    SELECT 6 FROM t2 WHERE y=0
+    UNION ALL
+    SELECT 7 FROM t2 WHERE y=1
+    UNION ALL
+    SELECT 8 FROM t2 WHERE y=2
+    UNION ALL
+    SELECT 9 FROM t2 WHERE y=3
+    UNION ALL
+    SELECT 10 FROM t2 WHERE y=4
+  }
+} {2 4 8 10}
+do_test tkt1473-4.3 {
+  execsql {
+    SELECT (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION ALL
+      SELECT 2 FROM t2 WHERE x=1
+      UNION ALL
+      SELECT 3 FROM t2 WHERE x=2
+      UNION ALL
+      SELECT 4 FROM t2 WHERE x=3
+      UNION ALL
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION ALL
+      SELECT 7 FROM t2 WHERE y=1
+      UNION ALL
+      SELECT 8 FROM t2 WHERE y=2
+      UNION ALL
+      SELECT 9 FROM t2 WHERE y=3
+      UNION ALL
+      SELECT 10 FROM t2 WHERE y=4
+    )
+  }
+} {2}
+do_test tkt1473-4.4 {
+  execsql {
+    SELECT (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION ALL
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION ALL
+      SELECT 3 FROM t2 WHERE x=2
+      UNION ALL
+      SELECT 4 FROM t2 WHERE x=3
+      UNION ALL
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION ALL
+      SELECT 7 FROM t2 WHERE y=1
+      UNION ALL
+      SELECT 8 FROM t2 WHERE y=2
+      UNION ALL
+      SELECT 9 FROM t2 WHERE y=3
+      UNION ALL
+      SELECT 10 FROM t2 WHERE y=4
+    )
+  }
+} {4}
+do_test tkt1473-4.5 {
+  execsql {
+    SELECT (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION ALL
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION ALL
+      SELECT 3 FROM t2 WHERE x=2
+      UNION ALL
+      SELECT 4 FROM t2 WHERE x=-1
+      UNION ALL
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION ALL
+      SELECT 7 FROM t2 WHERE y=1
+      UNION ALL
+      SELECT 8 FROM t2 WHERE y=2
+      UNION ALL
+      SELECT 9 FROM t2 WHERE y=3
+      UNION ALL
+      SELECT 10 FROM t2 WHERE y=-4
+    )
+  }
+} {8}
+do_test tkt1473-4.6 {
+  execsql {
+    SELECT (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION ALL
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION ALL
+      SELECT 3 FROM t2 WHERE x=2
+      UNION ALL
+      SELECT 4 FROM t2 WHERE x=-2
+      UNION ALL
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION ALL
+      SELECT 7 FROM t2 WHERE y=1
+      UNION ALL
+      SELECT 8 FROM t2 WHERE y=-3
+      UNION ALL
+      SELECT 9 FROM t2 WHERE y=3
+      UNION ALL
+      SELECT 10 FROM t2 WHERE y=4
+    )
+  }
+} {10}
+do_test tkt1473-4.7 {
+  execsql {
+    SELECT (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION ALL
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION ALL
+      SELECT 3 FROM t2 WHERE x=2
+      UNION ALL
+      SELECT 4 FROM t2 WHERE x=-2
+      UNION ALL
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION ALL
+      SELECT 7 FROM t2 WHERE y=1
+      UNION ALL
+      SELECT 8 FROM t2 WHERE y=-3
+      UNION ALL
+      SELECT 9 FROM t2 WHERE y=3
+      UNION ALL
+      SELECT 10 FROM t2 WHERE y=-4
+    )
+  }
+} {{}}
+
+do_test tkt1473-5.3 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION ALL
+      SELECT 2 FROM t2 WHERE x=1
+      UNION ALL
+      SELECT 3 FROM t2 WHERE x=2
+      UNION ALL
+      SELECT 4 FROM t2 WHERE x=3
+      UNION ALL
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION ALL
+      SELECT 7 FROM t2 WHERE y=1
+      UNION ALL
+      SELECT 8 FROM t2 WHERE y=2
+      UNION ALL
+      SELECT 9 FROM t2 WHERE y=3
+      UNION ALL
+      SELECT 10 FROM t2 WHERE y=4
+    )
+  }
+} {1}
+do_test tkt1473-5.4 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION ALL
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION ALL
+      SELECT 3 FROM t2 WHERE x=2
+      UNION ALL
+      SELECT 4 FROM t2 WHERE x=3
+      UNION ALL
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION ALL
+      SELECT 7 FROM t2 WHERE y=1
+      UNION ALL
+      SELECT 8 FROM t2 WHERE y=2
+      UNION ALL
+      SELECT 9 FROM t2 WHERE y=3
+      UNION ALL
+      SELECT 10 FROM t2 WHERE y=4
+    )
+  }
+} {1}
+
+do_test tkt1473-5.5 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION ALL
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION ALL
+      SELECT 3 FROM t2 WHERE x=2
+      UNION ALL
+      SELECT 4 FROM t2 WHERE x=-1
+      UNION ALL
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION ALL
+      SELECT 7 FROM t2 WHERE y=1
+      UNION ALL
+      SELECT 8 FROM t2 WHERE y=2
+      UNION ALL
+      SELECT 9 FROM t2 WHERE y=3
+      UNION ALL
+      SELECT 10 FROM t2 WHERE y=-4
+    )
+  }
+} {1}
+do_test tkt1473-5.6 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION ALL
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION ALL
+      SELECT 3 FROM t2 WHERE x=2
+      UNION ALL
+      SELECT 4 FROM t2 WHERE x=-2
+      UNION ALL
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION ALL
+      SELECT 7 FROM t2 WHERE y=1
+      UNION ALL
+      SELECT 8 FROM t2 WHERE y=-3
+      UNION ALL
+      SELECT 9 FROM t2 WHERE y=3
+      UNION ALL
+      SELECT 10 FROM t2 WHERE y=4
+    )
+  }
+} {1}
+do_test tkt1473-5.7 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION ALL
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION ALL
+      SELECT 3 FROM t2 WHERE x=2
+      UNION ALL
+      SELECT 4 FROM t2 WHERE x=-2
+      UNION ALL
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION ALL
+      SELECT 7 FROM t2 WHERE y=1
+      UNION ALL
+      SELECT 8 FROM t2 WHERE y=-3
+      UNION ALL
+      SELECT 9 FROM t2 WHERE y=3
+      UNION ALL
+      SELECT 10 FROM t2 WHERE y=-4
+    )
+  }
+} {0}
+
+do_test tkt1473-6.3 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION
+      SELECT 2 FROM t2 WHERE x=1
+      UNION
+      SELECT 3 FROM t2 WHERE x=2
+      UNION
+      SELECT 4 FROM t2 WHERE x=3
+      UNION
+      SELECT 5 FROM t2 WHERE x=4
+      UNION
+      SELECT 6 FROM t2 WHERE y=0
+      UNION
+      SELECT 7 FROM t2 WHERE y=1
+      UNION
+      SELECT 8 FROM t2 WHERE y=2
+      UNION
+      SELECT 9 FROM t2 WHERE y=3
+      UNION
+      SELECT 10 FROM t2 WHERE y=4
+    )
+  }
+} {1}
+do_test tkt1473-6.4 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION
+      SELECT 3 FROM t2 WHERE x=2
+      UNION
+      SELECT 4 FROM t2 WHERE x=3
+      UNION
+      SELECT 5 FROM t2 WHERE x=4
+      UNION
+      SELECT 6 FROM t2 WHERE y=0
+      UNION
+      SELECT 7 FROM t2 WHERE y=1
+      UNION
+      SELECT 8 FROM t2 WHERE y=2
+      UNION
+      SELECT 9 FROM t2 WHERE y=3
+      UNION
+      SELECT 10 FROM t2 WHERE y=4
+    )
+  }
+} {1}
+
+do_test tkt1473-6.5 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION
+      SELECT 3 FROM t2 WHERE x=2
+      UNION
+      SELECT 4 FROM t2 WHERE x=-1
+      UNION
+      SELECT 5 FROM t2 WHERE x=4
+      UNION
+      SELECT 6 FROM t2 WHERE y=0
+      UNION
+      SELECT 7 FROM t2 WHERE y=1
+      UNION
+      SELECT 8 FROM t2 WHERE y=2
+      UNION
+      SELECT 9 FROM t2 WHERE y=3
+      UNION
+      SELECT 10 FROM t2 WHERE y=-4
+    )
+  }
+} {1}
+do_test tkt1473-6.6 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION
+      SELECT 3 FROM t2 WHERE x=2
+      UNION
+      SELECT 4 FROM t2 WHERE x=-2
+      UNION
+      SELECT 5 FROM t2 WHERE x=4
+      UNION
+      SELECT 6 FROM t2 WHERE y=0
+      UNION
+      SELECT 7 FROM t2 WHERE y=1
+      UNION
+      SELECT 8 FROM t2 WHERE y=-3
+      UNION
+      SELECT 9 FROM t2 WHERE y=3
+      UNION
+      SELECT 10 FROM t2 WHERE y=4
+    )
+  }
+} {1}
+do_test tkt1473-6.7 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION
+      SELECT 3 FROM t2 WHERE x=2
+      UNION
+      SELECT 4 FROM t2 WHERE x=-2
+      UNION
+      SELECT 5 FROM t2 WHERE x=4
+      UNION
+      SELECT 6 FROM t2 WHERE y=0
+      UNION
+      SELECT 7 FROM t2 WHERE y=1
+      UNION
+      SELECT 8 FROM t2 WHERE y=-3
+      UNION
+      SELECT 9 FROM t2 WHERE y=3
+      UNION
+      SELECT 10 FROM t2 WHERE y=-4
+    )
+  }
+} {0}
+do_test tkt1473-6.8 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION
+      SELECT 3 FROM t2 WHERE x=2
+      UNION
+      SELECT 4 FROM t2 WHERE x=-2
+      UNION
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION
+      SELECT 7 FROM t2 WHERE y=1
+      UNION
+      SELECT 8 FROM t2 WHERE y=-3
+      UNION
+      SELECT 9 FROM t2 WHERE y=3
+      UNION
+      SELECT 10 FROM t2 WHERE y=4
+    )
+  }
+} {1}
+do_test tkt1473-6.9 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0
+      UNION
+      SELECT 2 FROM t2 WHERE x=-1
+      UNION
+      SELECT 3 FROM t2 WHERE x=2
+      UNION
+      SELECT 4 FROM t2 WHERE x=-2
+      UNION
+      SELECT 5 FROM t2 WHERE x=4
+      UNION ALL
+      SELECT 6 FROM t2 WHERE y=0
+      UNION
+      SELECT 7 FROM t2 WHERE y=1
+      UNION
+      SELECT 8 FROM t2 WHERE y=-3
+      UNION
+      SELECT 9 FROM t2 WHERE y=3
+      UNION
+      SELECT 10 FROM t2 WHERE y=-4
+    )
+  }
+} {0}
+
+do_test tkt1473-7.1 {
+  execsql {
+    SELECT 1 FROM t2 WHERE x=1 EXCEPT SELECT 2 FROM t2 WHERE y=2
+  }
+} {1}
+do_test tkt1473-7.2 {
+  execsql {
+    SELECT (
+      SELECT 1 FROM t2 WHERE x=1 EXCEPT SELECT 2 FROM t2 WHERE y=2
+    )
+  }
+} {1}
+do_test tkt1473-7.3 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=1 EXCEPT SELECT 2 FROM t2 WHERE y=2
+    )
+  }
+} {1}
+do_test tkt1473-7.4 {
+  execsql {
+    SELECT (
+      SELECT 1 FROM t2 WHERE x=0 EXCEPT SELECT 2 FROM t2 WHERE y=2
+    )
+  }
+} {{}}
+do_test tkt1473-7.5 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=0 EXCEPT SELECT 2 FROM t2 WHERE y=2
+    )
+  }
+} {0}
+
+do_test tkt1473-8.1 {
+  execsql {
+    SELECT 1 FROM t2 WHERE x=1 INTERSECT SELECT 2 FROM t2 WHERE y=2
+  }
+} {}
+do_test tkt1473-8.1 {
+  execsql {
+    SELECT 1 FROM t2 WHERE x=1 INTERSECT SELECT 1 FROM t2 WHERE y=2
+  }
+} {1}
+do_test tkt1473-8.3 {
+  execsql {
+    SELECT (
+      SELECT 1 FROM t2 WHERE x=1 INTERSECT SELECT 2 FROM t2 WHERE y=2
+    )
+  }
+} {{}}
+do_test tkt1473-8.4 {
+  execsql {
+    SELECT (
+      SELECT 1 FROM t2 WHERE x=1 INTERSECT SELECT 1 FROM t2 WHERE y=2
+    )
+  }
+} {1}
+do_test tkt1473-8.5 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=1 INTERSECT SELECT 2 FROM t2 WHERE y=2
+    )
+  }
+} {0}
+do_test tkt1473-8.6 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=1 INTERSECT SELECT 1 FROM t2 WHERE y=2
+    )
+  }
+} {1}
+do_test tkt1473-8.7 {
+  execsql {
+    SELECT (
+      SELECT 1 FROM t2 WHERE x=0 INTERSECT SELECT 1 FROM t2 WHERE y=2
+    )
+  }
+} {{}}
+do_test tkt1473-8.8 {
+  execsql {
+    SELECT EXISTS (
+      SELECT 1 FROM t2 WHERE x=1 INTERSECT SELECT 1 FROM t2 WHERE y=0
+    )
+  }
+} {0}
+
+
+
+
+finish_test
diff --git a/test/where.test b/test/where.test
index b946684fae..dcceb8e0d3 100644
--- a/test/where.test
+++ b/test/where.test
@@ -11,7 +11,7 @@
 # This file implements regression tests for SQLite library.  The
 # focus of this file is testing the use of indices in WHERE clases.
 #
-# $Id: where.test,v 1.36 2005/09/08 10:37:02 drh Exp $
+# $Id: where.test,v 1.37 2005/10/06 16:53:17 drh Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
@@ -306,7 +306,7 @@ do_test where-4.2 {
   count {
     SELECT * FROM t1 WHERE 1 LIMIT 1
   }
-} {1 0 4 1}
+} {1 0 4 0}
 do_test where-4.3 {
   execsql {
     SELECT 99 WHERE 0