SQLite

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.91 2009/01/02 18:10:42 drh Exp $
*/

#ifndef _PAGER_H_
#define _PAGER_H_

/*
** If defined as non-zero, auto-vacuum is enabled by default. Otherwise

int sqlite3PagerPagecount(Pager*, int*);
int sqlite3PagerTruncate(Pager*,Pgno);
int sqlite3PagerBegin(DbPage*, int exFlag);
int sqlite3PagerCommitPhaseOne(Pager*,const char *zMaster, int);
int sqlite3PagerCommitPhaseTwo(Pager*);
int sqlite3PagerRollback(Pager*);
u8 sqlite3PagerIsreadonly(Pager*);
int sqlite3PagerStmtBegin(Pager*);
int sqlite3PagerStmtCommit(Pager*);
int sqlite3PagerStmtRollback(Pager*);
void sqlite3PagerDontRollback(DbPage*);
int sqlite3PagerDontWrite(DbPage*);
int sqlite3PagerRefcount(Pager*);
void sqlite3PagerSetSafetyLevel(Pager*,int,int);
const char *sqlite3PagerFilename(Pager*);
const sqlite3_vfs *sqlite3PagerVfs(Pager*);
sqlite3_file *sqlite3PagerFile(Pager*);

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is responsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.356 2009/01/06 00:08:02 drh Exp $
*/
#include "sqliteInt.h"

/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)

    if( pTerm->eOperator==WO_OR 
        && ((pTerm->prereqAll & ~maskSrc) & notReady)==0
        && (pTerm->u.pOrInfo->indexable & maskSrc)!=0 ){
      WhereClause *pOrWC = &pTerm->u.pOrInfo->wc;
      WhereTerm *pOrTerm;
      int j;
      double rTotal = 0;
      double nRow = 0;
      for(j=0, pOrTerm=pOrWC->a; j<pOrWC->nTerm; j++, pOrTerm++){
        WhereCost sTermCost;
        WHERETRACE(("... Multi-index OR testing for term %d of %d....\n", j,i));
        if( pOrTerm->eOperator==WO_AND ){
          WhereClause *pAndWC = &pOrTerm->u.pAndInfo->wc;
          bestIndex(pParse, pAndWC, pSrc, notReady, 0, &sTermCost);
        }else if( pOrTerm->leftCursor==iCur ){

  /* Look at each index.
  */
  if( pSrc->pIndex ){
    pProbe = pSrc->pIndex;
  }
  for(; pProbe; pProbe=(pSrc->pIndex ? 0 : pProbe->pNext)){
    int i;                       /* Loop counter */
    double inMultiplier = 1;

    WHERETRACE(("... index %s:\n", pProbe->zName));

    /* Count the number of columns in the index that are satisfied
    ** by x=EXPR constraints or x IN (...) constraints.
    */

    ** The bottom of the loop looks like this:
    **
    **        Goto       0, A
    **     B:
    */
    int regOrRowset;       /* Register holding the RowSet object */
    int regNextRowid;      /* Register holding next rowid */
    WhereTerm *pTerm;      /* The complete OR-clause */
    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
    WhereTerm *pOrTerm;    /* A single subterm within the OR-clause */
    SrcList oneTab;        /* Shortened table list */
   
    pTerm = pLevel->plan.u.pTerm;
    assert( pTerm!=0 );
    assert( pTerm->eOperator==WO_OR );