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Overview
Comment:Add the experimental SQLITE_DEFAULT_INDEX_SHAPE=1 compile-time option that makes a much more pessimistic guess at the effectiveness of unanalyzed indices.
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SHA1: d8daaba7dae53c76858ff7d7de695af4763d9b1f
User & Date: drh 2013-09-02 23:40:47
Context
2013-09-02
23:40
Add the experimental SQLITE_DEFAULT_INDEX_SHAPE=1 compile-time option that makes a much more pessimistic guess at the effectiveness of unanalyzed indices. Leaf check-in: d8daaba7 user: drh tags: index-shape-1
20:22
Simplify branch coverage testing by interchanging the order of two tests in the whereLoopInsert() function. check-in: f7079b53 user: drh tags: trunk
Changes
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Changes to src/build.c.

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** how aiRowEst[] should be initialized.  The numbers generated here
** are based on typical values found in actual indices.
*/
void sqlite3DefaultRowEst(Index *pIdx){
  tRowcnt *a = pIdx->aiRowEst;
  int i;
  tRowcnt n;


  assert( a!=0 );
  a[0] = pIdx->pTable->nRowEst;
  if( a[0]<10 ) a[0] = 10;
  n = 10;
  for(i=1; i<=pIdx->nColumn; i++){
    a[i] = n;
    if( n>5 ) n--;
  }
  if( pIdx->onError!=OE_None ){
    a[pIdx->nColumn] = 1;
  }

















}

/*
** This routine will drop an existing named index.  This routine
** implements the DROP INDEX statement.
*/
void sqlite3DropIndex(Parse *pParse, SrcList *pName, int ifExists){







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** how aiRowEst[] should be initialized.  The numbers generated here
** are based on typical values found in actual indices.
*/
void sqlite3DefaultRowEst(Index *pIdx){
  tRowcnt *a = pIdx->aiRowEst;
  int i;
  tRowcnt n;

#if !defined(SQLITE_DEFAULT_INDEX_SHAPE) || SQLITE_DEFAULT_INDEX_SHAPE==0
  assert( a!=0 );
  a[0] = pIdx->pTable->nRowEst;
  if( a[0]<10 ) a[0] = 10;
  n = 10;
  for(i=1; i<=pIdx->nColumn; i++){
    a[i] = n;
    if( n>5 ) n--;
  }
  if( pIdx->onError!=OE_None ){
    a[pIdx->nColumn] = 1;
  }
#else /* if SQLITE_DEFAULT_INDEX_SHAPE==1 */
  tRowcnt x = 1, nMax = pIdx->pTable->nRowEst;
  int iLog;
  int isUnique = pIdx->onError!=OE_None;
  assert( a!=0 );
  a[0] = nMax;
  n = isUnique ? 1 : 10;
  for(iLog=1; n<nMax; iLog++, n<<=1){}
  i = pIdx->nColumn;
  x <<= iLog/i;
  //if( x>10 ) x = 10;
  a[i] = n = isUnique ? 1 : 10;
  while( i>1 ){
    n *= x;
    a[--i] = n;
  }
#endif
}

/*
** This routine will drop an existing named index.  This routine
** implements the DROP INDEX statement.
*/
void sqlite3DropIndex(Parse *pParse, SrcList *pName, int ifExists){