SQLite

**    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 1.394 2008/09/17 00:13:12 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Return the 'affinity' of the expression pExpr if any.
**

**
** Return the number of elements evaluated.
*/
int sqlite3ExprCodeExprList(
  Parse *pParse,     /* Parsing context */
  ExprList *pList,   /* The expression list to be coded */
  int target,        /* Where to write results */
  int doHardCopy     /* Make a hard copy of every element */
){
  struct ExprList_item *pItem;
  int i, n;
  assert( pList!=0 );
  assert( target>0 );
  n = pList->nExpr;
  for(pItem=pList->a, i=0; i<n; i++, pItem++){

    if( pItem->iAlias ){
      int iReg = codeAlias(pParse, pItem->iAlias, pItem->pExpr);
      Vdbe *v = sqlite3GetVdbe(pParse);
      sqlite3VdbeAddOp2(v, OP_SCopy, iReg, target+i);
    }else{


      sqlite3ExprCode(pParse, pItem->pExpr, target+i);
    }
    if( doHardCopy ){
      sqlite3ExprHardCopy(pParse, target, n);
    }
  }
  return n;
}

/*
** Generate code for a boolean expression such that a jump is made
** to the label "dest" if the expression is true but execution

**    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 1.475 2008/09/17 00:13:12 drh Exp $
*/
#include "sqliteInt.h"


/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.

  int regPrev;          /* A range of registers to hold previous output */
  int savedLimit;       /* Saved value of p->iLimit */
  int savedOffset;      /* Saved value of p->iOffset */
  int labelCmpr;        /* Label for the start of the merge algorithm */
  int labelEnd;         /* Label for the end of the overall SELECT stmt */
  int j1;               /* Jump instructions that get retargetted */
  int op;               /* One of TK_ALL, TK_UNION, TK_EXCEPT, TK_INTERSECT */
  KeyInfo *pKeyDup;     /* Comparison information for duplicate removal */
  KeyInfo *pKeyMerge;   /* Comparison information for merging rows */
  sqlite3 *db;          /* Database connection */
  ExprList *pOrderBy;   /* The ORDER BY clause */
  int nOrderBy;         /* Number of terms in the ORDER BY clause */
  int *aPermute;        /* Mapping from ORDER BY terms to result set columns */

  assert( p->pOrderBy!=0 );

    int iAMem;          /* First Mem address for storing current GROUP BY */
    int iBMem;          /* First Mem address for previous GROUP BY */
    int iUseFlag;       /* Mem address holding flag indicating that at least
                        ** one row of the input to the aggregator has been
                        ** processed */
    int iAbortFlag;     /* Mem address which causes query abort if positive */
    int groupBySort;    /* Rows come from source in GROUP BY order */
    int addrEnd;        /* End of processing for this SELECT */

    /* Remove any and all aliases between the result set and the
    ** GROUP BY clause.
    */
    if( pGroupBy ){
      int i;                        /* Loop counter */
      struct ExprList_item *pItem;  /* For looping over expression in a list */

      for(i=p->pEList->nExpr, pItem=p->pEList->a; i>0; i--, pItem++){
        pItem->iAlias = 0;
      }
      for(i=pGroupBy->nExpr, pItem=pGroupBy->a; i>0; i--, pItem++){
        pItem->iAlias = 0;
      }
    }


 
    /* Create a label to jump to when we want to abort the query */
    addrEnd = sqlite3VdbeMakeLabel(v);

    /* Convert TK_COLUMN nodes into TK_AGG_COLUMN and make entries in
    ** sAggInfo for all TK_AGG_FUNCTION nodes in expressions of the
    ** SELECT statement.
    */
    memset(&sNC, 0, sizeof(sNC));

    if( db->mallocFailed ) goto select_end;

    /* Processing for aggregates with GROUP BY is very different and
    ** much more complex than aggregates without a GROUP BY.
    */
    if( pGroupBy ){
      KeyInfo *pKeyInfo;  /* Keying information for the group by clause */
      int j1;             /* A-vs-B comparision jump */
      int addrOutputRow;  /* Start of subroutine that outputs a result row */
      int regOutputRow;   /* Return address register for output subroutine */
      int addrSetAbort;   /* Set the abort flag and return */
      int addrTopOfLoop;  /* Top of the input loop */
      int addrSortingIdx; /* The OP_OpenEphemeral for the sorting index */
      int addrReset;      /* Subroutine for resetting the accumulator */
      int regReset;       /* Return address register for reset subroutine */

      /* If there is a GROUP BY clause we might need a sorting index to
      ** implement it.  Allocate that sorting index now.  If it turns out
      ** that we do not need it after all, the OpenEphemeral instruction
      ** will be converted into a Noop.  
      */
      sAggInfo.sortingIdx = pParse->nTab++;
      pKeyInfo = keyInfoFromExprList(pParse, pGroupBy);
      addrSortingIdx = sqlite3VdbeAddOp4(v, OP_OpenEphemeral, 
          sAggInfo.sortingIdx, sAggInfo.nSortingColumn, 
          0, (char*)pKeyInfo, P4_KEYINFO_HANDOFF);

      /* Initialize memory locations used by GROUP BY aggregate processing
      */
      iUseFlag = ++pParse->nMem;
      iAbortFlag = ++pParse->nMem;
      regOutputRow = ++pParse->nMem;
      addrOutputRow = sqlite3VdbeMakeLabel(v);
      regReset = ++pParse->nMem;
      addrReset = sqlite3VdbeMakeLabel(v);
      iAMem = pParse->nMem + 1;
      pParse->nMem += pGroupBy->nExpr;
      iBMem = pParse->nMem + 1;
      pParse->nMem += pGroupBy->nExpr;
      sqlite3VdbeAddOp2(v, OP_Integer, 0, iAbortFlag);
      VdbeComment((v, "clear abort flag"));
      sqlite3VdbeAddOp2(v, OP_Integer, 0, iUseFlag);
      VdbeComment((v, "indicate accumulator empty"));



































      /* Begin a loop that will extract all source rows in GROUP BY order.
      ** This might involve two separate loops with an OP_Sort in between, or
      ** it might be a single loop that uses an index to extract information
      ** in the right order to begin with.
      */

      sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pGroupBy, 0);
      if( pWInfo==0 ) goto select_end;
      if( pGroupBy==0 ){
        /* The optimizer is able to deliver rows in group by order so
        ** we do not have to sort.  The OP_OpenEphemeral table will be
        ** cancelled later because we still need to use the pKeyInfo

        sqlite3VdbeChangeToNoop(v, addrSortingIdx, 1);
      }

      /* Output the final row of result
      */
      sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
      VdbeComment((v, "output final row"));

      /* Jump over the subroutines
      */
      sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEnd);

      /* Generate a subroutine that outputs a single row of the result
      ** set.  This subroutine first looks at the iUseFlag.  If iUseFlag
      ** is less than or equal to zero, the subroutine is a no-op.  If
      ** the processing calls for the query to abort, this subroutine
      ** increments the iAbortFlag memory location before returning in
      ** order to signal the caller to abort.
      */
      addrSetAbort = sqlite3VdbeCurrentAddr(v);
      sqlite3VdbeAddOp2(v, OP_Integer, 1, iAbortFlag);
      VdbeComment((v, "set abort flag"));
      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
      sqlite3VdbeResolveLabel(v, addrOutputRow);
      addrOutputRow = sqlite3VdbeCurrentAddr(v);
      sqlite3VdbeAddOp2(v, OP_IfPos, iUseFlag, addrOutputRow+2);
      VdbeComment((v, "Groupby result generator entry point"));
      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
      finalizeAggFunctions(pParse, &sAggInfo);
      if( pHaving ){
        sqlite3ExprIfFalse(pParse, pHaving, addrOutputRow+1, SQLITE_JUMPIFNULL);
      }
      selectInnerLoop(pParse, p, p->pEList, 0, 0, pOrderBy,
                      distinct, pDest,
                      addrOutputRow+1, addrSetAbort);
      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
      VdbeComment((v, "end groupby result generator"));

      /* Generate a subroutine that will reset the group-by accumulator
      */
      sqlite3VdbeResolveLabel(v, addrReset);
      resetAccumulator(pParse, &sAggInfo);
      sqlite3VdbeAddOp1(v, OP_Return, regReset);
     
    } /* endif pGroupBy */
    else {
      ExprList *pMinMax = 0;
      ExprList *pDel = 0;
      u8 flag;

      /* Check if the query is of one of the following forms:

# 2008 September 16
#
# 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. 
#
# $Id: selectC.test,v 1.3 2008/09/17 00:13:12 drh Exp $

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

# Ticket #
do_test selectC-1.1 {
  execsql {

  execsql {
    SELECT upper(b) AS x
      FROM t1
     GROUP BY x
     ORDER BY x
  }
} {AAA CCC}
do_test selectC-1.14 {
  execsql {
    SELECT upper(b) AS x
      FROM t1
     ORDER BY x DESC
  }
} {CCC AAA AAA}

finish_test