SQLite

**    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 1.273 2005/09/20 13:12:00 drh Exp $
*/
#include "sqliteInt.h"


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

    int addrSetAbort;       /* Set the abort flag and return */
    int addrInitializeLoop; /* Start of code that initializes the input loop */
    int addrTopOfLoop;      /* Top of the input loop */
    int addrGroupByChange;  /* Code that runs when any GROUP BY term changes */
    int addrProcessRow;     /* Code to process a single input row */
    int addrEnd;            /* End of all processing */
    int addrSortingIdx;     /* The OP_OpenVirtual for the sorting index */
    int addrReset;          /* Subroutine for resetting the accumulator */

    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.
    */

      rc = selectInnerLoop(pParse, p, p->pEList, 0, 0, pOrderBy,
                           distinct, eDest, iParm, 
                           addrOutputRow+1, addrSetAbort, aff);
      if( rc ){
        goto select_end;
      }
      sqlite3VdbeAddOp(v, OP_Return, 0, 0);

      /* Generate a subroutine that will reset the group-by accumulator
      */
      addrReset = sqlite3VdbeCurrentAddr(v);
      resetAccumulator(pParse, &sAggInfo);
      sqlite3VdbeAddOp(v, OP_Return, 0, 0);

      /* 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.
      */
      sqlite3VdbeResolveLabel(v, addrInitializeLoop);
      sqlite3VdbeAddOp(v, OP_Gosub, 0, addrReset);
      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pGroupBy);
      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_OpenVirtual table will be
        ** cancelled later because we still need to use the pKeyInfo
        */

      }
      for(j=pGroupBy->nExpr-1; j>=0; j--){
        if( j<pGroupBy->nExpr-1 ){
          sqlite3VdbeAddOp(v, OP_MemLoad, iBMem+j, 0);
        }
        sqlite3VdbeAddOp(v, OP_MemLoad, iAMem+j, 0);
        if( j==0 ){
          sqlite3VdbeAddOp(v, OP_Eq, 0x200, addrProcessRow);
        }else{
          sqlite3VdbeAddOp(v, OP_Ne, 0x300, addrGroupByChange);
        }
        sqlite3VdbeChangeP3(v, -1, (void*)pKeyInfo->aColl[j], P3_COLLSEQ);
      }

      /* Generate code that runs whenever the GROUP BY changes.
      ** Change in the GROUP BY are detected by the previous code
      ** block.  If there were no changes, this block is skipped.
      **
      ** This code copies current group by terms in b0,b1,b2,...
      ** over to a0,a1,a2.  It then calls the output subroutine
      ** and resets the aggregate accumulator registers in preparation
      ** for the next GROUP BY batch.
      */
      sqlite3VdbeResolveLabel(v, addrGroupByChange);
      for(j=0; j<pGroupBy->nExpr; j++){
        sqlite3VdbeAddOp(v, OP_MemLoad, iBMem+j, 0);
        sqlite3VdbeAddOp(v, OP_MemStore, iAMem+j, 1);
      }
      sqlite3VdbeAddOp(v, OP_Gosub, 0, addrOutputRow);
      sqlite3VdbeAddOp(v, OP_IfMemPos, iAbortFlag, addrEnd);
      sqlite3VdbeAddOp(v, OP_Gosub, 0, addrReset);

      /* Update the aggregate accumulators based on the content of
      ** the current row
      */
      sqlite3VdbeResolveLabel(v, addrProcessRow);
      updateAccumulator(pParse, &sAggInfo);
      sqlite3VdbeAddOp(v, OP_MemIncr, iUseFlag, 0);

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** 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 1.489 2005/09/20 13:12:00 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

/* Opcode: Eq P1 P2 P3
**
** Pop the top two elements from the stack.  If they are equal, then
** jump to instruction P2.  Otherwise, continue to the next instruction.
**
** If the 0x100 bit of P1 is true and either operand is NULL then take the
** jump.  If the 0x100 bit of P1 is clear then fall thru if either operand
** is NULL.  If the 0x200 bit of P1 is set and both operands are NULL, then
** return true or take the jump - treat NULL values as just another number.
**
** The least significant byte of P1 (mask 0xff) must be an affinity character -
** 'n', 't', 'i' or 'o' - or 0x00. An attempt is made to coerce both values
** according to the affinity before the comparison is made. If the byte is
** 0x00, then numeric affinity is used.
**
** Once any conversions have taken place, and neither value is NULL, 

  flags = pTos->flags|pNos->flags;

  /* If either value is a NULL P2 is not zero, take the jump if the least
  ** significant byte of P1 is true. If P2 is zero, then push a NULL onto
  ** the stack.
  */
  if( flags&MEM_Null ){
    if( (pOp->p1 & 0x200)!=0 && (pTos->flags & pNos->flags & MEM_Null)!=0 ){
      /* If the 0x200 bit of P1 is set and *both* operands are NULL, then
      ** pretend that both operands are integer 0.  This will cause the the
      ** various comparison operators to threat NULL just like any other value.
      */
      pTos->flags = pNos->flags = MEM_Int;
      pTos->i = pNos->i = 0;
    }else{
      /* If the 0x200 bit of P1 is clear or only one of the operands is NULL,
      ** then the result is always NULL.  The jump is taken if the 0x100 bit
      ** of P1 is set.
      */
      popStack(&pTos, 2);
      if( pOp->p2 ){
        if( pOp->p1 & 0x100 ){
          pc = pOp->p2-1;
        }
      }else{
        pTos++;
        pTos->flags = MEM_Null;
      }
      break;
    }
  }

  affinity = pOp->p1 & 0xFF;
  if( affinity ){
    applyAffinity(pNos, affinity, db->enc);
    applyAffinity(pTos, affinity, db->enc);
  }

#    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 aggregate functions and the
# GROUP BY and HAVING clauses of SELECT statements.
#
# $Id: select5.test,v 1.14 2005/09/20 13:12:00 drh Exp $

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

# Build some test data
#
execsql {

} {1 2 1 4 6 4}
do_test select5-5.5 {
  execsql {
    SELECT a, b FROM t2 GROUP BY a;
  } 
} {1 4 6 4}

# NULL compare equal to each other for the purposes of processing
# the GROUP BY clause.
#
do_test select5-6.1 {
  execsql {
    CREATE TABLE t3(x,y);
    INSERT INTO t3 VALUES(1,NULL);
    INSERT INTO t3 VALUES(2,NULL);
    INSERT INTO t3 VALUES(3,4);
    SELECT count(x), y FROM t3 GROUP BY y ORDER BY 1
  }
} {1 4 2 {}}
  
finish_test