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Overview
Comment:Improved WHERETRACE messages for the estimated output row reductions from range scans.
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SHA1: fdd478bb11eb9e244a7a1fb628ac27c53830fb24
User & Date: drh 2014-08-28 19:38:22.884
Context
2014-08-29
14:20
Not a fault after all, rather a testing mistake. Move this change back to trunk. Was: Avoid an unnecessary OP_Move operation for expression subqueries. (check-in: 2a74129a21 user: drh tags: trunk)
12:29
Contains a fault. Was: Avoid an unnecessary OP_Move operation for expression subqueries. (Closed-Leaf check-in: 462f42af52 user: drh tags: mistake)
11:24
Add the sqlite3VdbeChangeDest() routine that can be used to eliminate OP_Move opcodes. (Closed-Leaf check-in: 8c57bcc327 user: drh tags: experimental)
2014-08-28
19:38
Improved WHERETRACE messages for the estimated output row reductions from range scans. (check-in: fdd478bb11 user: drh tags: trunk)
17:30
Fix a problem causing an inaccurate stat4-based estimate for the number of rows visited by a range scan. (check-in: a9daf3ac44 user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/where.c.
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          nNew = sqlite3LogEst(iUpper - iLower);
        }else{
          nNew = 10;        assert( 10==sqlite3LogEst(2) );
        }
        if( nNew<nOut ){
          nOut = nNew;
        }
        WHERETRACE(0x10, ("range scan regions: %u..%u  est=%d\n",
                           (u32)iLower, (u32)iUpper, nOut));
      }
    }else{
      int bDone = 0;
      rc = whereRangeSkipScanEst(pParse, pLower, pUpper, pLoop, &bDone);
      if( bDone ) return rc;
    }








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          nNew = sqlite3LogEst(iUpper - iLower);
        }else{
          nNew = 10;        assert( 10==sqlite3LogEst(2) );
        }
        if( nNew<nOut ){
          nOut = nNew;
        }
        WHERETRACE(0x10, ("STAT4 range scan: %u..%u  est=%d\n",
                           (u32)iLower, (u32)iUpper, nOut));
      }
    }else{
      int bDone = 0;
      rc = whereRangeSkipScanEst(pParse, pLower, pUpper, pLoop, &bDone);
      if( bDone ) return rc;
    }
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  ** index. While a closed range (e.g. col BETWEEN ? AND ?) is estimated to
  ** match 1/64 of the index. */ 
  if( pLower && pUpper ) nNew -= 20;

  nOut -= (pLower!=0) + (pUpper!=0);
  if( nNew<10 ) nNew = 10;
  if( nNew<nOut ) nOut = nNew;






  pLoop->nOut = (LogEst)nOut;
  return rc;
}

#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
/*
** Estimate the number of rows that will be returned based on








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  ** index. While a closed range (e.g. col BETWEEN ? AND ?) is estimated to
  ** match 1/64 of the index. */ 
  if( pLower && pUpper ) nNew -= 20;

  nOut -= (pLower!=0) + (pUpper!=0);
  if( nNew<10 ) nNew = 10;
  if( nNew<nOut ) nOut = nNew;
#if defined(WHERETRACE_ENABLED)
  if( pLoop->nOut>nOut ){
    WHERETRACE(0x10,("Range scan lowers nOut from %d to %d\n",
                    pLoop->nOut, nOut));
  }
#endif
  pLoop->nOut = (LogEst)nOut;
  return rc;
}

#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
/*
** Estimate the number of rows that will be returned based on
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