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Overview
Comment:When pinning a temp register after it is reused by the column cache, make sure all instances of that register in the cache are pinned so that the register is never reused for a different purpose. Ticket #3879. (CVS 6676)
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SHA1: 5f358e63712e8de93bd6fecc5131badeef0292be
User & Date: drh 2009-05-25 11:46:29.000
Context
2009-05-25
14:17
Fix the rtree test module so that it works even if the ext/ subfolder is omitted from the tree. (CVS 6679) (check-in: 086206e1f5 user: drh tags: trunk)
11:46
When pinning a temp register after it is reused by the column cache, make sure all instances of that register in the cache are pinned so that the register is never reused for a different purpose. Ticket #3879. (CVS 6676) (check-in: 5f358e6371 user: drh tags: trunk)
11:46
Add a test case for ticket #3879. (CVS 6675) (check-in: 5b9b66f47b user: danielk1977 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 1.435 2009/05/21 20:41:32 drh Exp $
*/
#include "sqliteInt.h"

/*
** Return the 'affinity' of the expression pExpr if any.
**
** If pExpr is a column, a reference to a column via an 'AS' alias,








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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 1.436 2009/05/25 11:46:29 drh Exp $
*/
#include "sqliteInt.h"

/*
** Return the 'affinity' of the expression pExpr if any.
**
** If pExpr is a column, a reference to a column via an 'AS' alias,
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  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg && p->iLevel>pParse->iCacheLevel ){
      cacheEntryClear(pParse, p);
      p->iReg = 0;
    }
  }
}

















/*
** Generate code that will extract the iColumn-th column from
** table pTab and store the column value in a register.  An effort
** is made to store the column value in register iReg, but this is
** not guaranteed.  The location of the column value is returned.
**








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  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg && p->iLevel>pParse->iCacheLevel ){
      cacheEntryClear(pParse, p);
      p->iReg = 0;
    }
  }
}

/*
** When a cached column is reused, make sure that its register is
** no longer available as a temp register.  ticket #3879:  that same
** register might be in the cache in multiple places, so be sure to
** get them all.
*/
static void sqlite3ExprCachePinRegister(Parse *pParse, int iReg){
  int i;
  struct yColCache *p;
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg==iReg ){
      p->tempReg = 0;
    }
  }
}

/*
** Generate code that will extract the iColumn-th column from
** table pTab and store the column value in a register.  An effort
** is made to store the column value in register iReg, but this is
** not guaranteed.  The location of the column value is returned.
**
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    if( p->iReg>0 && p->iTable==iTable && p->iColumn==iColumn
           && (!p->affChange || allowAffChng) ){
#if 0
      sqlite3VdbeAddOp0(v, OP_Noop);
      VdbeComment((v, "OPT: tab%d.col%d -> r%d", iTable, iColumn, p->iReg));
#endif
      p->lru = pParse->iCacheCnt++;
      p->tempReg = 0;  /* This pins the register, but also leaks it */
      return p->iReg;
    }
  }  
  assert( v!=0 );
  if( iColumn<0 ){
    sqlite3VdbeAddOp2(v, OP_Rowid, iTable, iReg);
  }else if( pTab==0 ){








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    if( p->iReg>0 && p->iTable==iTable && p->iColumn==iColumn
           && (!p->affChange || allowAffChng) ){
#if 0
      sqlite3VdbeAddOp0(v, OP_Noop);
      VdbeComment((v, "OPT: tab%d.col%d -> r%d", iTable, iColumn, p->iReg));
#endif
      p->lru = pParse->iCacheCnt++;
      sqlite3ExprCachePinRegister(pParse, p->iReg);
      return p->iReg;
    }
  }  
  assert( v!=0 );
  if( iColumn<0 ){
    sqlite3VdbeAddOp2(v, OP_Rowid, iTable, iReg);
  }else if( pTab==0 ){
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