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Check-in [cf41d6a00f]
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Overview
Comment:Fix a code comment in select.c. No code changes. (CVS 4539)
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SHA1: cf41d6a00f658d2cd64ff9811a3b1270ad1a580b
User & Date: danielk1977 2007-11-12 15:40:42.000
Context
2007-11-12
17:56
Another attempt at fixing a memory leak in the TCL interface. See check-in (4338) for the first attempt. Ticket #2597. (CVS 4540) (check-in: 68a43c99f1 user: drh tags: trunk)
15:40
Fix a code comment in select.c. No code changes. (CVS 4539) (check-in: cf41d6a00f user: danielk1977 tags: trunk)
15:29
Where possible, transform the DISTINCT qualifier to a GROUP BY clause. GROUP BY clauses may be optimized by indices, DISTINCT qualifiers cannot. (CVS 4538) (check-in: e563312347 user: danielk1977 tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
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 1.360 2007/11/12 15:29:19 danielk1977 Exp $
*/
#include "sqliteInt.h"


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








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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 1.361 2007/11/12 15:40:42 danielk1977 Exp $
*/
#include "sqliteInt.h"


/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.
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  if( pParent && pParentAgg &&
      flattenSubquery(db, pParent, parentTab, *pParentAgg, isAgg) ){
    if( isAgg ) *pParentAgg = 1;
    goto select_end;
  }
#endif

  /* If possible, rewrite the query to use GROUP BY instead of 

  */
  if( p->isDistinct && !p->isAgg && !p->pGroupBy ){
    p->pGroupBy = sqlite3ExprListDup(db, p->pEList);
    pGroupBy = p->pGroupBy;
    p->isDistinct = 0;
    isDistinct = 0;
  }








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  if( pParent && pParentAgg &&
      flattenSubquery(db, pParent, parentTab, *pParentAgg, isAgg) ){
    if( isAgg ) *pParentAgg = 1;
    goto select_end;
  }
#endif

  /* If possible, rewrite the query to use GROUP BY instead of DISTINCT.
  ** GROUP BY may use an index, DISTINCT never does.
  */
  if( p->isDistinct && !p->isAgg && !p->pGroupBy ){
    p->pGroupBy = sqlite3ExprListDup(db, p->pEList);
    pGroupBy = p->pGroupBy;
    p->isDistinct = 0;
    isDistinct = 0;
  }
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