Reduce memory requirements for ORDER BY combined with LIMIT. Ticket #1586. (CVS...

FossilOrigin-Name: 55e703ecac6e03d7364c2d919ba18d7293d6b7f6

diff --git a/manifest b/manifest
index ee076b812536d3c564b6a988b71da09095b23dd9..27a9c4b50822b8a4f916aa00cbf3a7ba9d6fa29c 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Invalidate\sall\sVDBE\scursor\srow\scaches\sin\sbetween\scalls\sto\ssqlite3_step()\nsince\sthe\semphemeral\scontent\sthat\sthose\scaches\spoint\sto\smight\schange\sif\nthe\sstatement\sis\sREAD\sUNCOMMITTED.\s(CVS\s2886)
-D 2006-01-07T18:48:26
+C Reduce\smemory\srequirements\sfor\sORDER\sBY\scombined\swith\sLIMIT.\s\sTicket\s#1586.\s(CVS\s2887)
+D 2006-01-08T05:02:55
 F Makefile.in c79fbdaa264c6afcd435f2fb492551de5a8cf80d
 F Makefile.linux-gcc aee18d8a05546dcf1888bd4547e442008a49a092
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -66,7 +66,7 @@ F src/pragma.c ae8b135531e7a4d692c60bd909c819d0b3fc588a
 F src/prepare.c fef89dc92703d345251142af966b60e44a66cfc5
 F src/printf.c f47a2f4b5387cd2ebb12e9117a1a5d6bd9a2b812
 F src/random.c d40f8d356cecbd351ccfab6eaedd7ec1b54f5261
-F src/select.c 77bcb71f609ff95247a529acf7dfc1c1ec09154b
+F src/select.c ad632ffd92ac280d9f8565fe27256e0c4e94c2c9
 F src/shell.c 66b073375efbdee19045e7e0cd38b85f9aff71da
 F src/sqlite.h.in ba3a29daa6a16e054191ccb384a981964e882a1d
 F src/sqliteInt.h 40c3511c05df83c7c1c244d0432baa9497feee4d
@@ -335,7 +335,7 @@ F www/tclsqlite.tcl bb0d1357328a42b1993d78573e587c6dcbc964b9
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl a99cf5f6d8bd4d5537584a2b342f0fb9fa601d8b
 F www/whentouse.tcl 97e2b5cd296f7d8057e11f44427dea8a4c2db513
-P 15fda14ee0c0524d3064d767f48edd689c090d95
-R 8b6ba0a7cf083b8ec0fb5215eb91310f
+P 0ae461313c1642a49a9f6cda608c42c7c0053ce4
+R 79c569a066edb0857c89ee545cff9b3e
 U drh
-Z c1686b0c208bc7bdd63ff2b9442034c8
+Z e2eb2297d27afb66b9b69713714cfa42

diff --git a/manifest.uuid b/manifest.uuid
index 7f3a78821a19f3bf4eee6a054b80470db004d50f..dd1dcb56b2a83a8c08b210ddfaf91afd2e5d5cab 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-0ae461313c1642a49a9f6cda608c42c7c0053ce4
\ No newline at end of file
+55e703ecac6e03d7364c2d919ba18d7293d6b7f6
\ No newline at end of file

diff --git a/src/select.c b/src/select.c
index c1eaec9bf02fed07c9ee12f174e8c75b9f7808d1..b482de90d8cd0cfdf0df1ec2c343b8e6ac68b55d 100644 (file)
--- 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 1.286 2006/01/07 13:21:04 danielk1977 Exp $
+** $Id: select.c,v 1.287 2006/01/08 05:02:55 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -351,12 +351,28 @@ void sqlite3SelectDelete(Select *p){
 ** Insert code into "v" that will push the record on the top of the
 ** stack into the sorter.
 */
-static void pushOntoSorter(Parse *pParse, Vdbe *v, ExprList *pOrderBy){
+static void pushOntoSorter(
+  Parse *pParse,         /* Parser context */
+  ExprList *pOrderBy,    /* The ORDER BY clause */
+  Select *pSelect        /* The whole SELECT statement */
+){
+  Vdbe *v = pParse->pVdbe;
   sqlite3ExprCodeExprList(pParse, pOrderBy);
   sqlite3VdbeAddOp(v, OP_Sequence, pOrderBy->iECursor, 0);
   sqlite3VdbeAddOp(v, OP_Pull, pOrderBy->nExpr + 1, 0);
   sqlite3VdbeAddOp(v, OP_MakeRecord, pOrderBy->nExpr + 2, 0);
   sqlite3VdbeAddOp(v, OP_IdxInsert, pOrderBy->iECursor, 0);
+  if( pSelect->iLimit>=0 ){
+    int addr1;
+    sqlite3VdbeAddOp(v, OP_MemIncr, pSelect->iLimit+1, 0);
+    addr1 = sqlite3VdbeAddOp(v, OP_IfMemPos, pSelect->iLimit+1, 0);
+    sqlite3VdbeAddOp(v, OP_Goto, 0, 0);
+    sqlite3VdbeJumpHere(v, addr1);
+    sqlite3VdbeAddOp(v, OP_Last, pOrderBy->iECursor, 0);
+    sqlite3VdbeAddOp(v, OP_Delete, pOrderBy->iECursor, 0);
+    sqlite3VdbeJumpHere(v, addr1+1);
+    pSelect->iLimit = -1;
+  }
 }
 
 /*
@@ -504,7 +520,7 @@ static int selectInnerLoop(
     case SRT_VirtualTab: {
       sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
       if( pOrderBy ){
-        pushOntoSorter(pParse, v, pOrderBy);
+        pushOntoSorter(pParse, pOrderBy, p);
       }else{
         sqlite3VdbeAddOp(v, OP_NewRowid, iParm, 0);
         sqlite3VdbeAddOp(v, OP_Pull, 1, 0);
@@ -531,7 +547,7 @@ static int selectInnerLoop(
         ** ORDER BY in this case since the order of entries in the set
         ** does not matter.  But there might be a LIMIT clause, in which
         ** case the order does matter */
-        pushOntoSorter(pParse, v, pOrderBy);
+        pushOntoSorter(pParse, pOrderBy, p);
       }else{
         char aff = (iParm>>16)&0xFF;
         aff = sqlite3CompareAffinity(pEList->a[0].pExpr, aff);
@@ -558,7 +574,7 @@ static int selectInnerLoop(
     case SRT_Mem: {
       assert( nColumn==1 );
       if( pOrderBy ){
-        pushOntoSorter(pParse, v, pOrderBy);
+        pushOntoSorter(pParse, pOrderBy, p);
       }else{
         sqlite3VdbeAddOp(v, OP_MemStore, iParm, 1);
         /* The LIMIT clause will jump out of the loop for us */
@@ -575,7 +591,7 @@ static int selectInnerLoop(
     case SRT_Callback: {
       if( pOrderBy ){
         sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
-        pushOntoSorter(pParse, v, pOrderBy);
+        pushOntoSorter(pParse, pOrderBy, p);
       }else if( eDest==SRT_Subroutine ){
         sqlite3VdbeAddOp(v, OP_Gosub, 0, iParm);
       }else{
@@ -1358,7 +1374,7 @@ Vdbe *sqlite3GetVdbe(Parse *pParse){
 ** the limit and offset.  If there is no limit and/or offset, then 
 ** iLimit and iOffset are negative.
 **
-** This routine changes the values if iLimit and iOffset only if
+** This routine changes the values of iLimit and iOffset only if
 ** 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.
@@ -1375,13 +1391,14 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
   ** no rows.
   */
   if( p->pLimit ){
-    int iMem = pParse->nMem++;
+    int iMem = pParse->nMem;
+    pParse->nMem += 2;
     Vdbe *v = sqlite3GetVdbe(pParse);
     if( v==0 ) return;
     sqlite3ExprCode(pParse, p->pLimit);
     sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);
     sqlite3VdbeAddOp(v, OP_Negative, 0, 0);
-    sqlite3VdbeAddOp(v, OP_MemStore, iMem, 1);
+    sqlite3VdbeAddOp(v, OP_MemStore, iMem, 0);
     VdbeComment((v, "# LIMIT counter"));
     sqlite3VdbeAddOp(v, OP_IfMemZero, iMem, iBreak);
     p->iLimit = iMem;
@@ -1393,10 +1410,18 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
     sqlite3ExprCode(pParse, p->pOffset);
     sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);
     sqlite3VdbeAddOp(v, OP_Negative, 0, 0);
-    sqlite3VdbeAddOp(v, OP_MemStore, iMem, 1);
+    sqlite3VdbeAddOp(v, OP_MemStore, iMem, p->pLimit==0);
     VdbeComment((v, "# OFFSET counter"));
+    if( p->pLimit ){
+      sqlite3VdbeAddOp(v, OP_Add, 0, 0);
+    }
     p->iOffset = iMem;
   }
+  if( p->pLimit ){
+    Vdbe *v = pParse->pVdbe;
+    sqlite3VdbeAddOp(v, OP_MemStore, p->iLimit+1, 1);
+    VdbeComment((v, "# LIMIT+OFFSET"));
+  }
 }
 
 /*