** be a pointer to an sqlite3_vtab structure. Otherwise
  ** sqlite3ViewGetColumnNames() would have picked up the error. 
  */
  assert( pTab->azModuleArg && pTab->azModuleArg[0] );
  assert( sqlite3GetVTable(pParse->db, pTab) );

  /* Try once or twice.  On the first attempt, allow IN optimizations.
  ** If an IN optimization is accepted, but does not set the
  ** pInfo->aConstrainUsage.omit flag, then it will not work (because it
  ** will allow duplicate rows in the result set) so try again with
  ** IN optimizations disabled.


  */
  for(bAllowIN=1; bAllowIN>=0; bAllowIN--){


    /* Set the aConstraint[].usable fields and initialize all 
    ** output variables to zero.
    **
    ** aConstraint[].usable is true for constraints where the right-hand
    ** side contains only references to tables to the left of the current
    ** table.  In other words, if the constraint is of the form:
    **

  ** be a pointer to an sqlite3_vtab structure. Otherwise
  ** sqlite3ViewGetColumnNames() would have picked up the error. 
  */
  assert( pTab->azModuleArg && pTab->azModuleArg[0] );
  assert( sqlite3GetVTable(pParse->db, pTab) );

  /* Try once or twice.  On the first attempt, allow IN optimizations.
  ** If an IN optimization is accepted by the virtual table xBestIndex
  ** method, but the  pInfo->aConstrainUsage.omit flag is not set, then
  ** the query will not work because it might allow duplicate rows in
  ** output.  In that case, run the xBestIndex method a second time
  ** without the IN constraints.  Usually this loop only runs once.
  ** The loop will exit using a "break" statement.
  */
  for(bAllowIN=1; 1; bAllowIN--){
    assert( bAllowIN==0 || bAllowIN==1 );

    /* Set the aConstraint[].usable fields and initialize all 
    ** output variables to zero.
    **
    ** aConstraint[].usable is true for constraints where the right-hand
    ** side contains only references to tables to the left of the current
    ** table.  In other words, if the constraint is of the form:
    **