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Comment:Fix the LIMIT clause so that it applies to the entire query in a compound query. Prior to this change LIMITs on compound queries did not work at all. Ticket #393. (CVS 1058)
Downloads: Tarball | ZIP archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 543479e3aed77976a0c689cf40811bf88353f706
User & Date: drh 2003-07-20 01:16:47.000
Context
2003-07-22
00:39
Make sure temporary file names in windows have a full 15 characters of random text at the end. (CVS 1059) (check-in: 6ccb92b14f user: drh tags: trunk)
2003-07-20
01:16
Fix the LIMIT clause so that it applies to the entire query in a compound query. Prior to this change LIMITs on compound queries did not work at all. Ticket #393. (CVS 1058) (check-in: 543479e3ae user: drh tags: trunk)
2003-07-19
00:44
Make sure the min() and max() optimizer works correctly when there is a LIMIT clause. Ticket #396. (CVS 1057) (check-in: c35e507176 user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/expr.c.
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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.96 2003/05/31 16:21:12 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Construct a new expression node and return a pointer to it.  Memory
** for this node is obtained from sqliteMalloc().  The calling function







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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.97 2003/07/20 01:16:47 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Construct a new expression node and return a pointer to it.  Memory
** for this node is obtained from sqliteMalloc().  The calling function
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  pNew->pHaving = sqliteExprDup(p->pHaving);
  pNew->pOrderBy = sqliteExprListDup(p->pOrderBy);
  pNew->op = p->op;
  pNew->pPrior = sqliteSelectDup(p->pPrior);
  pNew->nLimit = p->nLimit;
  pNew->nOffset = p->nOffset;
  pNew->zSelect = 0;


  return pNew;
}


/*
** Add a new element to the end of an expression list.  If pList is
** initially NULL, then create a new expression list.







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  pNew->pHaving = sqliteExprDup(p->pHaving);
  pNew->pOrderBy = sqliteExprListDup(p->pOrderBy);
  pNew->op = p->op;
  pNew->pPrior = sqliteSelectDup(p->pPrior);
  pNew->nLimit = p->nLimit;
  pNew->nOffset = p->nOffset;
  pNew->zSelect = 0;
  pNew->iLimit = -1;
  pNew->iOffset = -1;
  return pNew;
}


/*
** Add a new element to the end of an expression list.  If pList is
** initially NULL, then create a new expression list.
Changes to src/select.c.
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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.144 2003/07/19 00:44:14 drh Exp $
*/
#include "sqliteInt.h"


/*
** Allocate a new Select structure and return a pointer to that
** structure.







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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.145 2003/07/20 01:16:47 drh Exp $
*/
#include "sqliteInt.h"


/*
** Allocate a new Select structure and return a pointer to that
** structure.
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    pNew->pGroupBy = pGroupBy;
    pNew->pHaving = pHaving;
    pNew->pOrderBy = pOrderBy;
    pNew->isDistinct = isDistinct;
    pNew->op = TK_SELECT;
    pNew->nLimit = nLimit;
    pNew->nOffset = nOffset;


  }
  return pNew;
}

/*
** Given 1 to 3 identifiers preceeding the JOIN keyword, determine the
** type of join.  Return an integer constant that expresses that type







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    pNew->pGroupBy = pGroupBy;
    pNew->pHaving = pHaving;
    pNew->pOrderBy = pOrderBy;
    pNew->isDistinct = isDistinct;
    pNew->op = TK_SELECT;
    pNew->nLimit = nLimit;
    pNew->nOffset = nOffset;
    pNew->iLimit = -1;
    pNew->iOffset = -1;
  }
  return pNew;
}

/*
** Given 1 to 3 identifiers preceeding the JOIN keyword, determine the
** type of join.  Return an integer constant that expresses that type
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  if( v==0 ) return 0;
  assert( pEList!=0 );

  /* If there was a LIMIT clause on the SELECT statement, then do the check
  ** to see if this row should be output.
  */
  if( pOrderBy==0 ){
    if( p->nOffset>0 ){
      int addr = sqliteVdbeCurrentAddr(v);
      sqliteVdbeAddOp(v, OP_MemIncr, p->nOffset, addr+2);
      sqliteVdbeAddOp(v, OP_Goto, 0, iContinue);
    }
    if( p->nLimit>=0 ){
      sqliteVdbeAddOp(v, OP_MemIncr, p->nLimit, iBreak);
    }
  }

  /* Pull the requested columns.
  */
  if( nColumn>0 ){
    for(i=0; i<nColumn; i++){







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  if( v==0 ) return 0;
  assert( pEList!=0 );

  /* If there was a LIMIT clause on the SELECT statement, then do the check
  ** to see if this row should be output.
  */
  if( pOrderBy==0 ){
    if( p->iOffset>=0 ){
      int addr = sqliteVdbeCurrentAddr(v);
      sqliteVdbeAddOp(v, OP_MemIncr, p->iOffset, addr+2);
      sqliteVdbeAddOp(v, OP_Goto, 0, iContinue);
    }
    if( p->iLimit>=0 ){
      sqliteVdbeAddOp(v, OP_MemIncr, p->iLimit, iBreak);
    }
  }

  /* Pull the requested columns.
  */
  if( nColumn>0 ){
    for(i=0; i<nColumn; i++){
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  int iParm        /* Optional parameter associated with eDest */
){
  int end = sqliteVdbeMakeLabel(v);
  int addr;
  if( eDest==SRT_Sorter ) return;
  sqliteVdbeAddOp(v, OP_Sort, 0, 0);
  addr = sqliteVdbeAddOp(v, OP_SortNext, 0, end);
  if( p->nOffset>0 ){
    sqliteVdbeAddOp(v, OP_MemIncr, p->nOffset, addr+4);
    sqliteVdbeAddOp(v, OP_Pop, 1, 0);
    sqliteVdbeAddOp(v, OP_Goto, 0, addr);
  }
  if( p->nLimit>=0 ){
    sqliteVdbeAddOp(v, OP_MemIncr, p->nLimit, end);
  }
  switch( eDest ){
    case SRT_Callback: {
      sqliteVdbeAddOp(v, OP_SortCallback, nColumn, 0);
      break;
    }
    case SRT_Table:







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  int iParm        /* Optional parameter associated with eDest */
){
  int end = sqliteVdbeMakeLabel(v);
  int addr;
  if( eDest==SRT_Sorter ) return;
  sqliteVdbeAddOp(v, OP_Sort, 0, 0);
  addr = sqliteVdbeAddOp(v, OP_SortNext, 0, end);
  if( p->iOffset>=0 ){
    sqliteVdbeAddOp(v, OP_MemIncr, p->iOffset, addr+4);
    sqliteVdbeAddOp(v, OP_Pop, 1, 0);
    sqliteVdbeAddOp(v, OP_Goto, 0, addr);
  }
  if( p->iLimit>=0 ){
    sqliteVdbeAddOp(v, OP_MemIncr, p->iLimit, end);
  }
  switch( eDest ){
    case SRT_Callback: {
      sqliteVdbeAddOp(v, OP_SortCallback, nColumn, 0);
      break;
    }
    case SRT_Table:
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    if( pE->dataType==SQLITE_SO_NUM ) continue;
    assert( pE->iColumn>=0 );
    if( pEList->nExpr>pE->iColumn ){
      pE->dataType = sqliteExprType(pEList->a[pE->iColumn].pExpr);
    }
  }
}















































/*
** This routine is called to process a query that is really the union
** or intersection of two or more separate queries.
**
** "p" points to the right-most of the two queries.  the query on the
** left is p->pPrior.  The left query could also be a compound query







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    if( pE->dataType==SQLITE_SO_NUM ) continue;
    assert( pE->iColumn>=0 );
    if( pEList->nExpr>pE->iColumn ){
      pE->dataType = sqliteExprType(pEList->a[pE->iColumn].pExpr);
    }
  }
}

/*
** Compute the iLimit and iOffset fields of the SELECT based on the
** nLimit and nOffset fields.  nLimit and nOffset hold the integers
** that appear in the original SQL statement after the LIMIT and OFFSET
** keywords.  Or that hold -1 and 0 if those keywords are omitted.
** iLimit and iOffset are the integer memory register numbers for
** counters used to compute 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
** a limit or offset is defined by nLimit and nOffset.  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
** 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){
  /* 
  ** If the comparison is p->nLimit>0 then "LIMIT 0" shows
  ** all rows.  It is the same as no limit. If the comparision is
  ** p->nLimit>=0 then "LIMIT 0" show no rows at all.
  ** "LIMIT -1" always shows all rows.  There is some
  ** contraversy about what the correct behavior should be.
  ** The current implementation interprets "LIMIT 0" to mean
  ** no rows.
  */
  if( p->nLimit>=0 ){
    int iMem = pParse->nMem++;
    Vdbe *v = sqliteGetVdbe(pParse);
    if( v==0 ) return;
    sqliteVdbeAddOp(v, OP_Integer, -p->nLimit, 0);
    sqliteVdbeAddOp(v, OP_MemStore, iMem, 1);
    p->iLimit = iMem;
  }
  if( p->nOffset>0 ){
    int iMem = pParse->nMem++;
    Vdbe *v = sqliteGetVdbe(pParse);
    if( v==0 ) return;
    sqliteVdbeAddOp(v, OP_Integer, -p->nOffset, 0);
    sqliteVdbeAddOp(v, OP_MemStore, iMem, 1);
    p->iOffset = iMem;
  }
}

/*
** This routine is called to process a query that is really the union
** or intersection of two or more separate queries.
**
** "p" points to the right-most of the two queries.  the query on the
** left is p->pPrior.  The left query could also be a compound query
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** individual selects always group from left to right.
*/
static int multiSelect(Parse *pParse, Select *p, int eDest, int iParm){
  int rc;             /* Success code from a subroutine */
  Select *pPrior;     /* Another SELECT immediately to our left */
  Vdbe *v;            /* Generate code to this VDBE */

  /* Make sure there is no ORDER BY clause on prior SELECTs.  Only the 
  ** last SELECT in the series may have an ORDER BY.
  */
  if( p==0 || p->pPrior==0 ) return 1;
  pPrior = p->pPrior;
  if( pPrior->pOrderBy ){
    sqliteErrorMsg(pParse,"ORDER BY clause should come after %s not before",
      selectOpName(p->op));
    return 1;





  }

  /* Make sure we have a valid query engine.  If not, create a new one.
  */
  v = sqliteGetVdbe(pParse);
  if( v==0 ) return 1;

  /* Create the destination temporary table if necessary
  */
  if( eDest==SRT_TempTable ){
    sqliteVdbeAddOp(v, OP_OpenTemp, iParm, 0);
    eDest = SRT_Table;
  }

  /* Generate code for the left and right SELECT statements.
  */
  switch( p->op ){
    case TK_ALL: {
      if( p->pOrderBy==0 ){


        rc = sqliteSelect(pParse, pPrior, eDest, iParm, 0, 0, 0);
        if( rc ) return rc;
        p->pPrior = 0;




        rc = sqliteSelect(pParse, p, eDest, iParm, 0, 0, 0);
        p->pPrior = pPrior;
        if( rc ) return rc;
        break;
      }
      /* For UNION ALL ... ORDER BY fall through to the next case */
    }
    case TK_EXCEPT:
    case TK_UNION: {
      int unionTab;    /* Cursor number of the temporary table holding result */
      int op;          /* One of the SRT_ operations to apply to self */
      int priorOp;     /* The SRT_ operation to apply to prior selects */

      ExprList *pOrderBy;  /* The ORDER BY clause for the right SELECT */

      priorOp = p->op==TK_ALL ? SRT_Table : SRT_Union;
      if( eDest==priorOp && p->pOrderBy==0 ){
        /* We can reuse a temporary table generated by a SELECT to our
        ** right.
        */
        unionTab = iParm;
      }else{
        /* We will need to create our own temporary table to hold the
        ** intermediate results.







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** individual selects always group from left to right.
*/
static int multiSelect(Parse *pParse, Select *p, int eDest, int iParm){
  int rc;             /* Success code from a subroutine */
  Select *pPrior;     /* Another SELECT immediately to our left */
  Vdbe *v;            /* Generate code to this VDBE */

  /* Make sure there is no ORDER BY or LIMIT clause on prior SELECTs.  Only
  ** the last SELECT in the series may have an ORDER BY or LIMIT.
  */
  if( p==0 || p->pPrior==0 ) return 1;
  pPrior = p->pPrior;
  if( pPrior->pOrderBy ){
    sqliteErrorMsg(pParse,"ORDER BY clause should come after %s not before",
      selectOpName(p->op));
    return 1;
  }
  if( pPrior->nLimit>=0 || pPrior->nOffset>0 ){
    sqliteErrorMsg(pParse,"LIMIT clause should come after %s not before",
      selectOpName(p->op));
    return 1;
  }

  /* Make sure we have a valid query engine.  If not, create a new one.
  */
  v = sqliteGetVdbe(pParse);
  if( v==0 ) return 1;

  /* Create the destination temporary table if necessary
  */
  if( eDest==SRT_TempTable ){
    sqliteVdbeAddOp(v, OP_OpenTemp, iParm, 0);
    eDest = SRT_Table;
  }

  /* Generate code for the left and right SELECT statements.
  */
  switch( p->op ){
    case TK_ALL: {
      if( p->pOrderBy==0 ){
        pPrior->nLimit = p->nLimit;
        pPrior->nOffset = p->nOffset;
        rc = sqliteSelect(pParse, pPrior, eDest, iParm, 0, 0, 0);
        if( rc ) return rc;
        p->pPrior = 0;
        p->iLimit = pPrior->iLimit;
        p->iOffset = pPrior->iOffset;
        p->nLimit = -1;
        p->nOffset = 0;
        rc = sqliteSelect(pParse, p, eDest, iParm, 0, 0, 0);
        p->pPrior = pPrior;
        if( rc ) return rc;
        break;
      }
      /* For UNION ALL ... ORDER BY fall through to the next case */
    }
    case TK_EXCEPT:
    case TK_UNION: {
      int unionTab;    /* Cursor number of the temporary table holding result */
      int op;          /* One of the SRT_ operations to apply to self */
      int priorOp;     /* The SRT_ operation to apply to prior selects */
      int nLimit, nOffset; /* Saved values of p->nLimit and p->nOffset */
      ExprList *pOrderBy;  /* The ORDER BY clause for the right SELECT */

      priorOp = p->op==TK_ALL ? SRT_Table : SRT_Union;
      if( eDest==priorOp && p->pOrderBy==0 && p->nLimit<0 && p->nOffset==0 ){
        /* We can reuse a temporary table generated by a SELECT to our
        ** right.
        */
        unionTab = iParm;
      }else{
        /* We will need to create our own temporary table to hold the
        ** intermediate results.
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         case TK_EXCEPT:  op = SRT_Except;   break;
         case TK_UNION:   op = SRT_Union;    break;
         case TK_ALL:     op = SRT_Table;    break;
      }
      p->pPrior = 0;
      pOrderBy = p->pOrderBy;
      p->pOrderBy = 0;




      rc = sqliteSelect(pParse, p, op, unionTab, 0, 0, 0);
      p->pPrior = pPrior;
      p->pOrderBy = pOrderBy;


      if( rc ) return rc;

      /* Convert the data in the temporary table into whatever form
      ** it is that we currently need.
      */      
      if( eDest!=priorOp || unionTab!=iParm ){
        int iCont, iBreak, iStart;
        assert( p->pEList );
        if( eDest==SRT_Callback ){
          generateColumnNames(pParse, 0, p->pEList);
          generateColumnTypes(pParse, p->pSrc, p->pEList);
        }
        iBreak = sqliteVdbeMakeLabel(v);
        iCont = sqliteVdbeMakeLabel(v);
        sqliteVdbeAddOp(v, OP_Rewind, unionTab, iBreak);

        iStart = sqliteVdbeCurrentAddr(v);
        multiSelectSortOrder(p, p->pOrderBy);
        rc = selectInnerLoop(pParse, p, p->pEList, unionTab, p->pEList->nExpr,
                             p->pOrderBy, -1, eDest, iParm, 
                             iCont, iBreak);
        if( rc ) return 1;
        sqliteVdbeResolveLabel(v, iCont);
        sqliteVdbeAddOp(v, OP_Next, unionTab, iStart);
        sqliteVdbeResolveLabel(v, iBreak);
        sqliteVdbeAddOp(v, OP_Close, unionTab, 0);
        if( p->pOrderBy ){
          generateSortTail(p, v, p->pEList->nExpr, eDest, iParm);
        }
      }
      break;
    }
    case TK_INTERSECT: {
      int tab1, tab2;
      int iCont, iBreak, iStart;


      /* INTERSECT is different from the others since it requires
      ** two temporary tables.  Hence it has its own case.  Begin
      ** by allocating the tables we will need.
      */
      tab1 = pParse->nTab++;
      tab2 = pParse->nTab++;







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         case TK_EXCEPT:  op = SRT_Except;   break;
         case TK_UNION:   op = SRT_Union;    break;
         case TK_ALL:     op = SRT_Table;    break;
      }
      p->pPrior = 0;
      pOrderBy = p->pOrderBy;
      p->pOrderBy = 0;
      nLimit = p->nLimit;
      p->nLimit = -1;
      nOffset = p->nOffset;
      p->nOffset = 0;
      rc = sqliteSelect(pParse, p, op, unionTab, 0, 0, 0);
      p->pPrior = pPrior;
      p->pOrderBy = pOrderBy;
      p->nLimit = nLimit;
      p->nOffset = nOffset;
      if( rc ) return rc;

      /* Convert the data in the temporary table into whatever form
      ** it is that we currently need.
      */      
      if( eDest!=priorOp || unionTab!=iParm ){
        int iCont, iBreak, iStart;
        assert( p->pEList );
        if( eDest==SRT_Callback ){
          generateColumnNames(pParse, 0, p->pEList);
          generateColumnTypes(pParse, p->pSrc, p->pEList);
        }
        iBreak = sqliteVdbeMakeLabel(v);
        iCont = sqliteVdbeMakeLabel(v);
        sqliteVdbeAddOp(v, OP_Rewind, unionTab, iBreak);
        computeLimitRegisters(pParse, p);
        iStart = sqliteVdbeCurrentAddr(v);
        multiSelectSortOrder(p, p->pOrderBy);
        rc = selectInnerLoop(pParse, p, p->pEList, unionTab, p->pEList->nExpr,
                             p->pOrderBy, -1, eDest, iParm, 
                             iCont, iBreak);
        if( rc ) return 1;
        sqliteVdbeResolveLabel(v, iCont);
        sqliteVdbeAddOp(v, OP_Next, unionTab, iStart);
        sqliteVdbeResolveLabel(v, iBreak);
        sqliteVdbeAddOp(v, OP_Close, unionTab, 0);
        if( p->pOrderBy ){
          generateSortTail(p, v, p->pEList->nExpr, eDest, iParm);
        }
      }
      break;
    }
    case TK_INTERSECT: {
      int tab1, tab2;
      int iCont, iBreak, iStart;
      int nLimit, nOffset;

      /* INTERSECT is different from the others since it requires
      ** two temporary tables.  Hence it has its own case.  Begin
      ** by allocating the tables we will need.
      */
      tab1 = pParse->nTab++;
      tab2 = pParse->nTab++;
1418
1419
1420
1421
1422
1423
1424




1425
1426


1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439

1440
1441
1442
1443
1444
1445
1446
      if( rc ) return rc;

      /* Code the current SELECT into temporary table "tab2"
      */
      sqliteVdbeAddOp(v, OP_OpenTemp, tab2, 1);
      sqliteVdbeAddOp(v, OP_KeyAsData, tab2, 1);
      p->pPrior = 0;




      rc = sqliteSelect(pParse, p, SRT_Union, tab2, 0, 0, 0);
      p->pPrior = pPrior;


      if( rc ) return rc;

      /* Generate code to take the intersection of the two temporary
      ** tables.
      */
      assert( p->pEList );
      if( eDest==SRT_Callback ){
        generateColumnNames(pParse, 0, p->pEList);
        generateColumnTypes(pParse, p->pSrc, p->pEList);
      }
      iBreak = sqliteVdbeMakeLabel(v);
      iCont = sqliteVdbeMakeLabel(v);
      sqliteVdbeAddOp(v, OP_Rewind, tab1, iBreak);

      iStart = sqliteVdbeAddOp(v, OP_FullKey, tab1, 0);
      sqliteVdbeAddOp(v, OP_NotFound, tab2, iCont);
      multiSelectSortOrder(p, p->pOrderBy);
      rc = selectInnerLoop(pParse, p, p->pEList, tab1, p->pEList->nExpr,
                             p->pOrderBy, -1, eDest, iParm, 
                             iCont, iBreak);
      if( rc ) return 1;







>
>
>
>


>
>













>







1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
      if( rc ) return rc;

      /* Code the current SELECT into temporary table "tab2"
      */
      sqliteVdbeAddOp(v, OP_OpenTemp, tab2, 1);
      sqliteVdbeAddOp(v, OP_KeyAsData, tab2, 1);
      p->pPrior = 0;
      nLimit = p->nLimit;
      p->nLimit = -1;
      nOffset = p->nOffset;
      p->nOffset = 0;
      rc = sqliteSelect(pParse, p, SRT_Union, tab2, 0, 0, 0);
      p->pPrior = pPrior;
      p->nLimit = nLimit;
      p->nOffset = nOffset;
      if( rc ) return rc;

      /* Generate code to take the intersection of the two temporary
      ** tables.
      */
      assert( p->pEList );
      if( eDest==SRT_Callback ){
        generateColumnNames(pParse, 0, p->pEList);
        generateColumnTypes(pParse, p->pSrc, p->pEList);
      }
      iBreak = sqliteVdbeMakeLabel(v);
      iCont = sqliteVdbeMakeLabel(v);
      sqliteVdbeAddOp(v, OP_Rewind, tab1, iBreak);
      computeLimitRegisters(pParse, p);
      iStart = sqliteVdbeAddOp(v, OP_FullKey, tab1, 0);
      sqliteVdbeAddOp(v, OP_NotFound, tab2, iCont);
      multiSelectSortOrder(p, p->pOrderBy);
      rc = selectInnerLoop(pParse, p, p->pEList, tab1, p->pEList->nExpr,
                             p->pOrderBy, -1, eDest, iParm, 
                             iCont, iBreak);
      if( rc ) return 1;
1865
1866
1867
1868
1869
1870
1871

1872
1873
1874
1875
1876
1877
1878
  /* Generating code to find the min or the max.  Basically all we have
  ** to do is find the first or the last entry in the chosen index.  If
  ** the min() or max() is on the INTEGER PRIMARY KEY, then find the first
  ** or last entry in the main table.
  */
  sqliteCodeVerifySchema(pParse, pTab->iDb);
  base = p->pSrc->a[0].iCursor;

  sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
  sqliteVdbeAddOp(v, OP_OpenRead, base, pTab->tnum);
  sqliteVdbeChangeP3(v, -1, pTab->zName, P3_STATIC);
  cont = sqliteVdbeMakeLabel(v);
  if( pIdx==0 ){
    sqliteVdbeAddOp(v, seekOp, base, 0);
  }else{







>







1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
  /* Generating code to find the min or the max.  Basically all we have
  ** to do is find the first or the last entry in the chosen index.  If
  ** the min() or max() is on the INTEGER PRIMARY KEY, then find the first
  ** or last entry in the main table.
  */
  sqliteCodeVerifySchema(pParse, pTab->iDb);
  base = p->pSrc->a[0].iCursor;
  computeLimitRegisters(pParse, p);
  sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
  sqliteVdbeAddOp(v, OP_OpenRead, base, pTab->tnum);
  sqliteVdbeChangeP3(v, -1, pTab->zName, P3_STATIC);
  cont = sqliteVdbeMakeLabel(v);
  if( pIdx==0 ){
    sqliteVdbeAddOp(v, seekOp, base, 0);
  }else{
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
  /* Identify column names if we will be using them in a callback.  This
  ** step is skipped if the output is going to some other destination.
  */
  if( eDest==SRT_Callback ){
    generateColumnNames(pParse, pTabList, pEList);
  }

  /* Set the limiter.
  **
  ** The phrase "LIMIT 0" means all rows are shown, not zero rows.
  ** If the comparison is p->nLimit<=0 then "LIMIT 0" shows
  ** all rows.  It is the same as no limit. If the comparision is
  ** p->nLimit<0 then "LIMIT 0" show no rows at all.
  ** "LIMIT -1" always shows all rows.  There is some
  ** contraversy about what the correct behavior should be.
  **
  ** Note that up until this point, the nLimit and nOffset hold
  ** the numeric values of the limit and offset that appeared in
  ** the original SQL.  After this code, the nLimit and nOffset hold
  ** the register number of counters used to track the limit and
  ** offset.
  */
  if( p->nLimit<0 ){
    p->nLimit = -1;
  }else{
    int iMem = pParse->nMem++;
    sqliteVdbeAddOp(v, OP_Integer, -p->nLimit, 0);
    sqliteVdbeAddOp(v, OP_MemStore, iMem, 1);
    p->nLimit = iMem;
  }
  if( p->nOffset<=0 ){
    p->nOffset = 0;
  }else{
    int iMem = pParse->nMem++;
    if( iMem==0 ) iMem = pParse->nMem++;
    sqliteVdbeAddOp(v, OP_Integer, -p->nOffset, 0);
    sqliteVdbeAddOp(v, OP_MemStore, iMem, 1);
    p->nOffset = iMem;
  }

  /* 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;
  }







<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<







2204
2205
2206
2207
2208
2209
2210

































2211
2212
2213
2214
2215
2216
2217
  /* Identify column names if we will be using them in a callback.  This
  ** step is skipped if the output is going to some other destination.
  */
  if( eDest==SRT_Callback ){
    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;
  }
2207
2208
2209
2210
2211
2212
2213




2214
2215
2216
2217
2218
2219
2220
  */
  if( pParent && pParentAgg &&
      flattenSubquery(pParse, pParent, parentTab, *pParentAgg, isAgg) ){
    if( isAgg ) *pParentAgg = 1;
    return rc;
  }





  /* Identify column types if we will be using a callback.  This
  ** step is skipped if the output is going to a destination other
  ** than a callback.
  **
  ** We have to do this separately from the creation of column names
  ** above because if the pTabList contains views then they will not
  ** have been resolved and we will not know the column types until







>
>
>
>







2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
  */
  if( pParent && pParentAgg &&
      flattenSubquery(pParse, pParent, parentTab, *pParentAgg, isAgg) ){
    if( isAgg ) *pParentAgg = 1;
    return rc;
  }

  /* Set the limiter.
  */
  computeLimitRegisters(pParse, p);

  /* Identify column types if we will be using a callback.  This
  ** step is skipped if the output is going to a destination other
  ** than a callback.
  **
  ** We have to do this separately from the creation of column names
  ** above because if the pTabList contains views then they will not
  ** have been resolved and we will not know the column types until
Changes to src/sqliteInt.h.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
/*
** 2001 September 15
**
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.193 2003/06/23 11:06:02 drh Exp $
*/
#include "config.h"
#include "sqlite.h"
#include "hash.h"
#include "vdbe.h"
#include "parse.h"
#include "btree.h"













|







1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
/*
** 2001 September 15
**
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.194 2003/07/20 01:16:47 drh Exp $
*/
#include "config.h"
#include "sqlite.h"
#include "hash.h"
#include "vdbe.h"
#include "parse.h"
#include "btree.h"
774
775
776
777
778
779
780
781
782


783
784
785
786
787
788
789
790

791
792
793
794
795
796
797
** nLimit is set to -1 if there is no LIMIT clause.  nOffset is set to 0.
** If there is a LIMIT clause, the parser sets nLimit to the value of the
** limit and nOffset to the value of the offset (or 0 if there is not
** offset).  But later on, nLimit and nOffset become the memory locations
** in the VDBE that record the limit and offset counters.
*/
struct Select {
  int isDistinct;        /* True if the DISTINCT keyword is present */
  ExprList *pEList;      /* The fields of the result */


  SrcList *pSrc;         /* The FROM clause */
  Expr *pWhere;          /* The WHERE clause */
  ExprList *pGroupBy;    /* The GROUP BY clause */
  Expr *pHaving;         /* The HAVING clause */
  ExprList *pOrderBy;    /* The ORDER BY clause */
  int op;                /* One of: TK_UNION TK_ALL TK_INTERSECT TK_EXCEPT */
  Select *pPrior;        /* Prior select in a compound select statement */
  int nLimit, nOffset;   /* LIMIT and OFFSET values.  -1 means not used */

  char *zSelect;         /* Complete text of the SELECT command */
};

/*
** The results of a select can be distributed in several ways.
*/
#define SRT_Callback     1  /* Invoke a callback with each row of result */







<

>
>





<


>







774
775
776
777
778
779
780

781
782
783
784
785
786
787
788

789
790
791
792
793
794
795
796
797
798
** nLimit is set to -1 if there is no LIMIT clause.  nOffset is set to 0.
** If there is a LIMIT clause, the parser sets nLimit to the value of the
** limit and nOffset to the value of the offset (or 0 if there is not
** offset).  But later on, nLimit and nOffset become the memory locations
** in the VDBE that record the limit and offset counters.
*/
struct Select {

  ExprList *pEList;      /* The fields of the result */
  u8 op;                 /* One of: TK_UNION TK_ALL TK_INTERSECT TK_EXCEPT */
  u8 isDistinct;         /* True if the DISTINCT keyword is present */
  SrcList *pSrc;         /* The FROM clause */
  Expr *pWhere;          /* The WHERE clause */
  ExprList *pGroupBy;    /* The GROUP BY clause */
  Expr *pHaving;         /* The HAVING clause */
  ExprList *pOrderBy;    /* The ORDER BY clause */

  Select *pPrior;        /* Prior select in a compound select statement */
  int nLimit, nOffset;   /* LIMIT and OFFSET values.  -1 means not used */
  int iLimit, iOffset;   /* Memory registers holding LIMIT & OFFSET counters */
  char *zSelect;         /* Complete text of the SELECT command */
};

/*
** The results of a select can be distributed in several ways.
*/
#define SRT_Callback     1  /* Invoke a callback with each row of result */
Changes to test/limit.test.
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing the LIMIT ... OFFSET ... clause
#  of SELECT statements.
#
# $Id: limit.test,v 1.9 2003/07/16 11:51:36 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Build some test data
#
set fd [open data1.txt w]







|







8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing the LIMIT ... OFFSET ... clause
#  of SELECT statements.
#
# $Id: limit.test,v 1.10 2003/07/20 01:16:48 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Build some test data
#
set fd [open data1.txt w]
208
209
210
211
212
213
214
215
















































































216
  }
} {}
do_test limit-6.8 {
  execsql {
    SELECT * FROM t6 LIMIT 0 OFFSET 1
  }
} {}

















































































finish_test








>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>

208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
  }
} {}
do_test limit-6.8 {
  execsql {
    SELECT * FROM t6 LIMIT 0 OFFSET 1
  }
} {}

# Make sure LIMIT works well with compound SELECT statements.
# Ticket #393
#
do_test limit-7.1.1 {
  catchsql {
    SELECT x FROM t2 LIMIT 5 UNION ALL SELECT a FROM t6;
  }
} {1 {LIMIT clause should come after UNION ALL not before}}
do_test limit-7.1.2 {
  catchsql {
    SELECT x FROM t2 LIMIT 5 UNION SELECT a FROM t6;
  }
} {1 {LIMIT clause should come after UNION not before}}
do_test limit-7.1.3 {
  catchsql {
    SELECT x FROM t2 LIMIT 5 EXCEPT SELECT a FROM t6 LIMIT 3;
  }
} {1 {LIMIT clause should come after EXCEPT not before}}
do_test limit-7.1.4 {
  catchsql {
    SELECT x FROM t2 LIMIT 0,5 INTERSECT SELECT a FROM t6;
  }
} {1 {LIMIT clause should come after INTERSECT not before}}
do_test limit-7.2 {
  execsql {
    SELECT x FROM t2 UNION ALL SELECT a FROM t6 LIMIT 5;
  }
} {31 30 1 2 3}
do_test limit-7.3 {
  execsql {
    SELECT x FROM t2 UNION ALL SELECT a FROM t6 LIMIT 3 OFFSET 1;
  }
} {30 1 2}
do_test limit-7.4 {
  execsql {
    SELECT x FROM t2 UNION ALL SELECT a FROM t6 ORDER BY 1 LIMIT 3 OFFSET 1;
  }
} {2 3 4}
do_test limit-7.5 {
  execsql {
    SELECT x FROM t2 UNION SELECT x+2 FROM t2 LIMIT 2 OFFSET 1;
  }
} {31 32}
do_test limit-7.6 {
  execsql {
    SELECT x FROM t2 UNION SELECT x+2 FROM t2 ORDER BY 1 DESC LIMIT 2 OFFSET 1;
  }
} {32 31}
do_test limit-7.7 {
  execsql {
    SELECT a+9 FROM t6 EXCEPT SELECT y FROM t2 LIMIT 2;
  }
} {11 12}
do_test limit-7.8 {
  execsql {
    SELECT a+9 FROM t6 EXCEPT SELECT y FROM t2 ORDER BY 1 DESC LIMIT 2;
  }
} {13 12}
do_test limit-7.9 {
  execsql {
    SELECT a+26 FROM t6 INTERSECT SELECT x FROM t2 LIMIT 1;
  }
} {30}
do_test limit-7.10 {
  execsql {
    SELECT a+27 FROM t6 INTERSECT SELECT x FROM t2 LIMIT 1;
  }
} {30}
do_test limit-7.11 {
  execsql {
    SELECT a+27 FROM t6 INTERSECT SELECT x FROM t2 LIMIT 1 OFFSET 1;
  }
} {31}
do_test limit-7.12 {
  execsql {
    SELECT a+27 FROM t6 INTERSECT SELECT x FROM t2 
       ORDER BY 1 DESC LIMIT 1 OFFSET 1;
  }
} {30}

finish_test
Changes to www/lang.tcl.
1
2
3
4
5
6
7
8
9
10
11
#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: lang.tcl,v 1.64 2003/07/16 11:51:36 drh Exp $}

puts {<html>
<head>
  <title>Query Language Understood By SQLite</title>
</head>
<body bgcolor=white>
<h1 align=center>



|







1
2
3
4
5
6
7
8
9
10
11
#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: lang.tcl,v 1.65 2003/07/20 01:16:48 drh Exp $}

puts {<html>
<head>
  <title>Query Language Understood By SQLite</title>
</head>
<body bgcolor=white>
<h1 align=center>
1548
1549
1550
1551
1552
1553
1554
1555





1556
1557
1558
1559
1560
1561
1562
expression must exactly match one of the result columns.  Each
sort expression may be optionally followed by ASC or DESC to specify
the sort order.</p>

<p>The LIMIT clause places an upper bound on the number of rows
returned in the result.  A negative LIMIT indicates no upper bound.
The optional OFFSET following LIMIT specifies how many
rows to skip at the beginning of the result set.</p>






<p>A compound SELECT is formed from two or more simple SELECTs connected
by one of the operators UNION, UNION ALL, INTERSECT, or EXCEPT.  In
a compound SELECT, all the constituent SELECTs must specify the
same number of result columns.  There may be only a single ORDER BY
clause at the end of the compound SELECT.  The UNION and UNION ALL
operators combine the results of the SELECTs to the right and left into







|
>
>
>
>
>







1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
expression must exactly match one of the result columns.  Each
sort expression may be optionally followed by ASC or DESC to specify
the sort order.</p>

<p>The LIMIT clause places an upper bound on the number of rows
returned in the result.  A negative LIMIT indicates no upper bound.
The optional OFFSET following LIMIT specifies how many
rows to skip at the beginning of the result set.
In a compound query, the LIMIT clause may only appear on the
final SELECT statement.
The limit is applied to the entire query not
to the individual SELECT statement to which it is attached.
</p>

<p>A compound SELECT is formed from two or more simple SELECTs connected
by one of the operators UNION, UNION ALL, INTERSECT, or EXCEPT.  In
a compound SELECT, all the constituent SELECTs must specify the
same number of result columns.  There may be only a single ORDER BY
clause at the end of the compound SELECT.  The UNION and UNION ALL
operators combine the results of the SELECTs to the right and left into