SQLite

  statInit,        /* xFunc */
  0,               /* xStep */
  0,               /* xFinalize */
  "stat_init",     /* zName */
  0,               /* pHash */
  0                /* pDestructor */
};

#ifdef SQLITE_ENABLE_STAT4
/*
** pNew and pOld are both candidate non-periodic samples selected for 
** the same column (pNew->iCol==pOld->iCol). Ignoring this column and 
** considering only any trailing columns and the sample hash value, this
** function returns true if sample pNew is to be preferred over pOld.
** In other words, if we assume that the cardinalities of the selected
** column for pNew and pOld are equal, is pNew to be preferred over pOld.
**
** This function assumes that for each argument sample, the contents of
** the anEq[] array from pSample->anEq[pSample->iCol+1] onwards are valid. 
*/
static int sampleIsBetterPost(
  Stat4Accum *pAccum, 
  Stat4Sample *pNew, 
  Stat4Sample *pOld
){
  int nCol = pAccum->nCol;
  int i;
  assert( pNew->iCol==pOld->iCol );
  for(i=pNew->iCol+1; i<nCol; i++){
    if( pNew->anEq[i]>pOld->anEq[i] ) return 1;
    if( pNew->anEq[i]<pOld->anEq[i] ) return 0;
  }
  if( pNew->iHash>pOld->iHash ) return 1;
  return 0;
}
#endif

#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
/*
** Return true if pNew is to be preferred over pOld.
**
** This function assumes that for each argument sample, the contents of
** the anEq[] array from pSample->anEq[pSample->iCol] onwards are valid. 
*/
static int sampleIsBetter(
  Stat4Accum *pAccum, 
  Stat4Sample *pNew, 
  Stat4Sample *pOld
){
  tRowcnt nEqNew = pNew->anEq[pNew->iCol];
  tRowcnt nEqOld = pOld->anEq[pOld->iCol];

  assert( pOld->isPSample==0 && pNew->isPSample==0 );
  assert( IsStat4 || (pNew->iCol==0 && pOld->iCol==0) );

  if( (nEqNew>nEqOld) ) return 1;
#ifdef SQLITE_ENABLE_STAT4
  if( nEqNew==nEqOld ){
    if( pNew->iCol<pOld->iCol ) return 1;

    return (pNew->iCol==pOld->iCol && sampleIsBetterPost(pAccum, pNew, pOld));
  }
  return 0;
#else
  return (nEqNew==nEqOld && pNew->iHash>pOld->iHash);
#endif
}

/*
** Copy the contents of object (*pFrom) into (*pTo).
*/
void sampleCopy(Stat4Accum *p, Stat4Sample *pTo, Stat4Sample *pFrom){
  pTo->iRowid = pFrom->iRowid;

/*
** Copy the contents of sample *pNew into the p->a[] array. If necessary,
** remove the least desirable sample from p->a[] to make room.
*/
static void sampleInsert(Stat4Accum *p, Stat4Sample *pNew, int nEqZero){
  Stat4Sample *pSample;
  int i;



  assert( IsStat4 || nEqZero==0 );

  if( pNew->isPSample==0 ){
    Stat4Sample *pUpgrade = 0;
    assert( pNew->anEq[pNew->iCol]>0 );

    /* This sample is being added because the prefix that ends in column 
    ** iCol occurs many times in the table. However, if we have already
    ** added a sample that shares this prefix, there is no need to add
    ** this one. Instead, upgrade the priority of the highest priority
    ** existing sample that shares this prefix.  */
    for(i=p->nSample-1; i>=0; i--){
      Stat4Sample *pOld = &p->a[i];
      if( pOld->anEq[pNew->iCol]==0 ){
        if( pOld->isPSample ) return;
        assert( pOld->iCol>pNew->iCol );
        assert( sampleIsBetter(p, pNew, pOld) );
        if( pUpgrade==0 || sampleIsBetter(p, pOld, pUpgrade) ){
          pUpgrade = pOld;
        }
      }
    }
    if( pUpgrade ){
      pUpgrade->iCol = pNew->iCol;
      pUpgrade->anEq[pUpgrade->iCol] = pNew->anEq[pUpgrade->iCol];

       || pNew->anLt[p->nCol-1] > p->a[p->nSample-1].anLt[p->nCol-1] );
#endif

  /* Insert the new sample */
  pSample = &p->a[p->nSample];
  sampleCopy(p, pSample, pNew);
  p->nSample++;




















  /* Zero the first nEqZero entries in the anEq[] array. */
  memset(pSample->anEq, 0, sizeof(tRowcnt)*nEqZero);

 find_new_min:
  if( p->nSample>=p->mxSample ){
    int iMin = -1;
    for(i=0; i<p->mxSample; i++){
      if( p->a[i].isPSample ) continue;
      if( iMin<0 || sampleIsBetter(p, &p->a[iMin], &p->a[i]) ){
        iMin = i;
      }
    }
    assert( iMin>=0 );
    p->iMin = iMin;
  }
}

#ifdef SQLITE_ENABLE_STAT4
  int i;

  /* Check if any samples from the aBest[] array should be pushed
  ** into IndexSample.a[] at this point.  */
  for(i=(p->nCol-2); i>=iChng; i--){
    Stat4Sample *pBest = &p->aBest[i];
    pBest->anEq[i] = p->current.anEq[i];
    if( p->nSample<p->mxSample || sampleIsBetter(p, pBest, &p->a[p->iMin]) ){


      sampleInsert(p, pBest, i);
    }
  }

  /* Update the anEq[] fields of any samples already collected. */
  for(i=p->nSample-1; i>=0; i--){
    int j;

    if( (nLt/p->nPSample)!=(nLt+nEq)/p->nPSample ){
      p->current.isPSample = 1;
      sampleInsert(p, &p->current, 0);
      p->current.isPSample = 0;
    }else 

    /* Or if it is a non-periodic sample. Add it in this case too. */
    if( p->nSample<p->mxSample 
     || sampleIsBetter(p, &p->current, &p->a[p->iMin]) 
    ){
      sampleInsert(p, &p->current, 0);
    }
  }
#endif
}

/*

      sampleInsert(p, &p->current, p->nCol-1);
      p->current.isPSample = 0;
    }

    /* Update the aBest[] array. */
    for(i=0; i<(p->nCol-1); i++){
      p->current.iCol = i;
      if( i>=iChng || sampleIsBetterPost(p, &p->current, &p->aBest[i]) ){
        sampleCopy(p, &p->aBest[i], &p->current);
      }
    }
  }
#endif
}
static const FuncDef statPushFuncdef = {

    neq,
    lrange(nlt, 0, 2),
    lrange(ndlt, 0, 2),
    lrange(test_decode(sample), 0, 1)
    FROM sqlite_stat4
  ORDER BY rowid DESC LIMIT 2;
} {
  {2 1 1 1} {295 295 295} {120 121 124} {201 3} 
  {5 3 1 1} {290 290 292} {119 119 121} {200 1}
}

do_execsql_test 4.4 { SELECT count(DISTINCT c) FROM t1 WHERE c<201 } 120
do_execsql_test 4.5 { SELECT count(DISTINCT c) FROM t1 WHERE c<200 } 119

# Check that the perioidic samples are present.

    execsql {
      CREATE TABLE t1(x, y);
      CREATE VIEW v1 AS SELECT * FROM t1;
    }
    catchsql ANALYZE
  } {1 {not authorized}}
}

#-------------------------------------------------------------------------
#
reset_db
proc r {args} { expr rand() }
db func r r
db func lrange lrange
do_test 20.1 {
  execsql {
    CREATE TABLE t1(a,b,c,d);
    CREATE INDEX i1 ON t1(a,b,c,d);
  }
  for {set i 0} {$i < 16} {incr i} {
    execsql {
      INSERT INTO t1 VALUES($i, r(), r(), r());
      INSERT INTO t1 VALUES($i, $i,  r(), r());
      INSERT INTO t1 VALUES($i, $i,  $i,  r());
      INSERT INTO t1 VALUES($i, $i,  $i,  $i);
      INSERT INTO t1 VALUES($i, $i,  $i,  $i);
      INSERT INTO t1 VALUES($i, $i,  $i,  r());
      INSERT INTO t1 VALUES($i, $i,  r(), r());
      INSERT INTO t1 VALUES($i, r(), r(), r());
    }
  }
} {}
do_execsql_test 20.2 { ANALYZE }
for {set i 0} {$i<16} {incr i} {
    set val "$i $i $i $i"
    do_execsql_test 20.3.$i {
      SELECT count(*) FROM sqlite_stat4 
      WHERE lrange(test_decode(sample), 0, 3)=$val
    } {1}
}

finish_test