rc = sqlite3_prepare(db, zCommand, -1, ppStmt, NULL);
  free(zCommand);
  return rc;
}

/* end utility functions */


#define QUERY_GENERIC 0

#define QUERY_FULLTEXT 1


/* TODO(shess) CHUNK_MAX controls how much data we allow in segment 0
** before we start aggregating into larger segments.  Lower CHUNK_MAX
** means that for a given input we have more individual segments per
** term, which means more rows in the table and a bigger index (due to
** both more rows and bigger rowids).  But it also reduces the average
** cost of adding new elements to the segment 0 doclist, and it seems
................................................................................
  ** open.
  */
  sqlite3_stmt *pFulltextStatements[MAX_STMT];
} fulltext_vtab;

typedef struct fulltext_cursor {
  sqlite3_vtab_cursor base;
  int iCursorType;  /* QUERY_GENERIC or QUERY_FULLTEXT */

  sqlite3_stmt *pStmt;

  int eof;

  /* The following is used only when iCursorType == QUERY_FULLTEXT. */
  DocListReader result;
} fulltext_cursor;

static struct fulltext_vtab *cursor_vtab(fulltext_cursor *c){
  return (fulltext_vtab *) c->base.pVtab;
}

static const sqlite3_module fulltextModule;   /* forward declaration */
................................................................................
 * haven't implemented phrase searches or OR yet. */
static int fulltextBestIndex(sqlite3_vtab *pVTab, sqlite3_index_info *pInfo){
  int i;

  for(i=0; i<pInfo->nConstraint; ++i){
    const struct sqlite3_index_constraint *pConstraint;
    pConstraint = &pInfo->aConstraint[i];




    if( pConstraint->iColumn==0 &&
        pConstraint->op==SQLITE_INDEX_CONSTRAINT_MATCH &&
        pConstraint->usable ){   /* a full-text search */



      pInfo->aConstraintUsage[i].argvIndex = 1;
      pInfo->aConstraintUsage[i].omit = 1;
      pInfo->idxNum = QUERY_FULLTEXT;




      pInfo->estimatedCost = 1.0;   /* an arbitrary value for now */

      return SQLITE_OK;
    }
  }
  pInfo->idxNum = QUERY_GENERIC;
  TRACE(("FTS1 BestIndex\n"));
  return SQLITE_OK;
}
................................................................................

static int fulltextNext(sqlite3_vtab_cursor *pCursor){
  fulltext_cursor *c = (fulltext_cursor *) pCursor;
  sqlite_int64 iDocid;
  int rc;

  TRACE(("FTS1 Next %p\n", pCursor));
  switch( c->iCursorType ){
    case QUERY_GENERIC:
      /* TODO(shess) Handle SQLITE_SCHEMA AND SQLITE_BUSY. */
      rc = sqlite3_step(c->pStmt);
      switch( rc ){
        case SQLITE_ROW:
          c->eof = 0;
          return SQLITE_OK;
        case SQLITE_DONE:
          c->eof = 1;
          return SQLITE_OK;
        default:
          c->eof = 1;
          return rc;
      }
    case QUERY_FULLTEXT:

      rc = sqlite3_reset(c->pStmt);
      if( rc!=SQLITE_OK ) return rc;

      iDocid = nextValidDocid(&c->result);
      if( iDocid==0 ){
        c->eof = 1;
        return SQLITE_OK;
      }
      rc = sqlite3_bind_int64(c->pStmt, 1, iDocid);
      if( rc!=SQLITE_OK ) return rc;
      /* TODO(shess) Handle SQLITE_SCHEMA AND SQLITE_BUSY. */
      rc = sqlite3_step(c->pStmt);
      if( rc==SQLITE_ROW ){   /* the case we expect */
        c->eof = 0;
        return SQLITE_OK;
      }
      /* an error occurred; abort */
      return rc==SQLITE_DONE ? SQLITE_ERROR : rc;
    default:
      assert( 0 );
      return SQLITE_ERROR;  /* not reached */
  }
}

/* A single term in a query is represented by an instances of
** the following structure.
*/
typedef struct QueryTerm {
................................................................................

static int fulltextFilter(sqlite3_vtab_cursor *pCursor,
                          int idxNum, const char *idxStr,
                          int argc, sqlite3_value **argv){
  fulltext_cursor *c = (fulltext_cursor *) pCursor;
  fulltext_vtab *v = cursor_vtab(c);
  int rc;
  const char *zStatement;

  TRACE(("FTS1 Filter %p\n",pCursor));
  c->iCursorType = idxNum;
  switch( idxNum ){
    case QUERY_GENERIC:

      zStatement = "select rowid, content from %_content";








      break;

    case QUERY_FULLTEXT:   /* full-text search */
    {
      const char *zQuery = (const char *)sqlite3_value_text(argv[0]);
      DocList *pResult;
      assert( argc==1 );
      rc = fulltextQuery(v, zQuery, -1, &pResult);
      if( rc!=SQLITE_OK ) return rc;
      readerInit(&c->result, pResult);

      zStatement = "select rowid, content from %_content where rowid = ?";
      break;
    }

    default:
      assert( 0 );
  }

  rc = sql_prepare(v->db, v->zName, &c->pStmt, zStatement);
  if( rc!=SQLITE_OK ) return rc;

  return fulltextNext(pCursor);
}

static int fulltextEof(sqlite3_vtab_cursor *pCursor){
  fulltext_cursor *c = (fulltext_cursor *) pCursor;

  rc = sqlite3_prepare(db, zCommand, -1, ppStmt, NULL);
  free(zCommand);
  return rc;
}

/* end utility functions */

typedef enum QueryType {
  QUERY_GENERIC,     /* table scan */
  QUERY_ROWID,       /* lookup by rowid */
  QUERY_FULLTEXT    /* full-text search */
} QueryType;

/* TODO(shess) CHUNK_MAX controls how much data we allow in segment 0
** before we start aggregating into larger segments.  Lower CHUNK_MAX
** means that for a given input we have more individual segments per
** term, which means more rows in the table and a bigger index (due to
** both more rows and bigger rowids).  But it also reduces the average
** cost of adding new elements to the segment 0 doclist, and it seems
................................................................................
  ** open.
  */
  sqlite3_stmt *pFulltextStatements[MAX_STMT];
} fulltext_vtab;

typedef struct fulltext_cursor {
  sqlite3_vtab_cursor base;
  QueryType iCursorType;

  sqlite3_stmt *pStmt;

  int eof;

  DocListReader result;  /* used when iCursorType == QUERY_FULLTEXT */ 

} fulltext_cursor;

static struct fulltext_vtab *cursor_vtab(fulltext_cursor *c){
  return (fulltext_vtab *) c->base.pVtab;
}

static const sqlite3_module fulltextModule;   /* forward declaration */
................................................................................
 * haven't implemented phrase searches or OR yet. */
static int fulltextBestIndex(sqlite3_vtab *pVTab, sqlite3_index_info *pInfo){
  int i;

  for(i=0; i<pInfo->nConstraint; ++i){
    const struct sqlite3_index_constraint *pConstraint;
    pConstraint = &pInfo->aConstraint[i];
    if( pConstraint->usable ) {
      if( pConstraint->iColumn==-1 &&
          pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ ){
        pInfo->idxNum = QUERY_ROWID;      /* lookup by rowid */
      } else if( pConstraint->iColumn==0 &&
                 pConstraint->op==SQLITE_INDEX_CONSTRAINT_MATCH ){

        pInfo->idxNum = QUERY_FULLTEXT;   /* full-text search */
      } else continue;

      pInfo->aConstraintUsage[i].argvIndex = 1;
      pInfo->aConstraintUsage[i].omit = 1;


      /* An arbitrary value for now.
       * TODO: Perhaps rowid matches should be considered cheaper than
       * full-text searches. */
      pInfo->estimatedCost = 1.0;   

      return SQLITE_OK;
    }
  }
  pInfo->idxNum = QUERY_GENERIC;
  TRACE(("FTS1 BestIndex\n"));
  return SQLITE_OK;
}
................................................................................

static int fulltextNext(sqlite3_vtab_cursor *pCursor){
  fulltext_cursor *c = (fulltext_cursor *) pCursor;
  sqlite_int64 iDocid;
  int rc;

  TRACE(("FTS1 Next %p\n", pCursor));
  if( c->iCursorType != QUERY_FULLTEXT ){

    /* TODO(shess) Handle SQLITE_SCHEMA AND SQLITE_BUSY. */
    rc = sqlite3_step(c->pStmt);
    switch( rc ){
      case SQLITE_ROW:
        c->eof = 0;
        return SQLITE_OK;
      case SQLITE_DONE:
        c->eof = 1;
        return SQLITE_OK;
      default:
        c->eof = 1;
        return rc;
    }

  } else {  /* full-text query */
    rc = sqlite3_reset(c->pStmt);
    if( rc!=SQLITE_OK ) return rc;

    iDocid = nextValidDocid(&c->result);
    if( iDocid==0 ){
      c->eof = 1;
      return SQLITE_OK;
    }
    rc = sqlite3_bind_int64(c->pStmt, 1, iDocid);
    if( rc!=SQLITE_OK ) return rc;
    /* TODO(shess) Handle SQLITE_SCHEMA AND SQLITE_BUSY. */
    rc = sqlite3_step(c->pStmt);
    if( rc==SQLITE_ROW ){   /* the case we expect */
      c->eof = 0;
      return SQLITE_OK;
    }
    /* an error occurred; abort */
    return rc==SQLITE_DONE ? SQLITE_ERROR : rc;



  }
}

/* A single term in a query is represented by an instances of
** the following structure.
*/
typedef struct QueryTerm {
................................................................................

static int fulltextFilter(sqlite3_vtab_cursor *pCursor,
                          int idxNum, const char *idxStr,
                          int argc, sqlite3_value **argv){
  fulltext_cursor *c = (fulltext_cursor *) pCursor;
  fulltext_vtab *v = cursor_vtab(c);
  int rc;


  TRACE(("FTS1 Filter %p\n",pCursor));
  c->iCursorType = idxNum;
  switch( idxNum ){
    case QUERY_GENERIC:
      rc = sql_prepare(v->db, v->zName, &c->pStmt,
                       "select rowid, content from %_content");
      break;

    case QUERY_ROWID:
      rc = sql_prepare(v->db, v->zName, &c->pStmt,
                       "select rowid, content from %_content where rowid = ?");
      if( rc!=SQLITE_OK ) return rc;

      rc = sqlite3_bind_int64(c->pStmt, 1, sqlite3_value_int64(argv[0]));
      break;

    case QUERY_FULLTEXT:   /* full-text search */
    {
      const char *zQuery = (const char *)sqlite3_value_text(argv[0]);
      DocList *pResult;
      assert( argc==1 );
      rc = fulltextQuery(v, zQuery, -1, &pResult);
      if( rc!=SQLITE_OK ) return rc;
      readerInit(&c->result, pResult);
      rc = sql_prepare(v->db, v->zName, &c->pStmt,
                       "select rowid, content from %_content where rowid = ?");
      break;
    }

    default:
      assert( 0 );
  }


  if( rc!=SQLITE_OK ) return rc;

  return fulltextNext(pCursor);
}

static int fulltextEof(sqlite3_vtab_cursor *pCursor){
  fulltext_cursor *c = (fulltext_cursor *) pCursor;