SQLite

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the virtual table interfaces.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test8.c,v 1.26 2006/06/19 12:02:59 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include "os.h"
#include <stdlib.h>
#include <string.h>

static int echoBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
  int ii;
  char *zQuery = 0;
  char *zNew;
  int nArg = 0;
  const char *zSep = "WHERE";
  echo_vtab *pVtab = (echo_vtab *)tab;
  sqlite3_stmt *pStmt = 0;

  int nRow;
  int useIdx = 0;
  int rc = SQLITE_OK;

  /* Determine the number of rows in the table and store this value in local
  ** variable nRow. The 'estimated-cost' of the scan will be the number of
  ** rows in the table for a linear scan, or the log (base 2) of the 
  ** number of rows if the proposed scan uses an index.  
  */
  zQuery = sqlite3_mprintf("SELECT count(*) FROM %Q", pVtab->zTableName);
  rc = sqlite3_prepare(pVtab->db, zQuery, -1, &pStmt, 0);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  sqlite3_step(pStmt);
  nRow = sqlite3_column_int(pStmt, 0);
  rc = sqlite3_finalize(pStmt);
  if( rc!=SQLITE_OK ){
    return rc;
  }

  zQuery = sqlite3_mprintf("SELECT rowid, * FROM %Q", pVtab->zTableName);
  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
    const struct sqlite3_index_constraint *pConstraint;
    struct sqlite3_index_constraint_usage *pUsage;

    pConstraint = &pIdxInfo->aConstraint[ii];
    pUsage = &pIdxInfo->aConstraintUsage[ii];

    int iCol = pConstraint->iColumn;
    if( pVtab->aIndex[iCol] ){
      char *zCol = pVtab->aCol[iCol];
      char *zOp = 0;
      useIdx = 1;
      if( iCol<0 ){
        zCol = "rowid";
      }
      switch( pConstraint->op ){
        case SQLITE_INDEX_CONSTRAINT_EQ:
          zOp = "="; break;
        case SQLITE_INDEX_CONSTRAINT_LT:

  appendToEchoModule(pVtab->interp, "xBestIndex");;
  appendToEchoModule(pVtab->interp, zQuery);

  pIdxInfo->idxNum = hashString(zQuery);
  pIdxInfo->idxStr = zQuery;
  pIdxInfo->needToFreeIdxStr = 1;
  if( useIdx ){
    /* Approximation of log2(nRow). */
    for( ii=0; ii<(sizeof(int)*8); ii++ ){
      if( nRow & (1<<ii) ){
        pIdxInfo->estimatedCost = (double)ii;
      }
    }
  } else {
    pIdxInfo->estimatedCost = (double)nRow;
  }
  return rc;
}

static void string_concat(char **pzStr, char *zAppend, int doFree){
  char *zIn = *pzStr;
  if( zIn ){
    char *zTemp = zIn;
    zIn = sqlite3_mprintf("%s%s", zIn, zAppend);

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is reponsible 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 1.220 2006/06/19 12:02:59 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)

  sqlite3_index_info *pIdxInfo;
  struct sqlite3_index_constraint *pIdxCons;
  struct sqlite3_index_orderby *pIdxOrderBy;
  struct sqlite3_index_constraint_usage *pUsage;
  WhereTerm *pTerm;
  int i, j;
  int nOrderBy;
  int rc;

  /* If the sqlite3_index_info structure has not been previously
  ** allocated and initialized for this virtual table, then allocate
  ** and initialize it now
  */
  pIdxInfo = *ppIdxInfo;
  if( pIdxInfo==0 ){

  pIdxInfo->needToFreeIdxStr = 0;
  pIdxInfo->orderByConsumed = 0;
  pIdxInfo->estimatedCost = SQLITE_BIG_DBL;
  nOrderBy = pIdxInfo->nOrderBy;
  if( pIdxInfo->nOrderBy && !orderByUsable ){
    *(int*)&pIdxInfo->nOrderBy = 0;
  }

  sqlite3SafetyOff(pParse->db);
  pTab->pVtab->pModule->xBestIndex(pTab->pVtab, pIdxInfo);
  rc = sqlite3SafetyOn(pParse->db);
  if( rc!=SQLITE_OK ){
    sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
  }

  *(int*)&pIdxInfo->nOrderBy = nOrderBy;
  return pIdxInfo->estimatedCost;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

/*
** Find the best index for accessing a particular table.  Return a pointer