}

/************************************************************************/
/*                           TestCapability()                           */
/************************************************************************/

int OGRGenSQLResultsLayer::TestCapability( const char *pszCap )

{
    swq_select *psSelectInfo = (swq_select *) pSelectInfo;

    if( EQUAL(pszCap,OLCFastSetNextByIndex) )
    {
        if( psSelectInfo->query_mode == SWQM_SUMMARY_RECORD 
            || psSelectInfo->query_mode == SWQM_DISTINCT_LIST 
            || panFIDIndex != NULL )
            return TRUE;
        else 
            return poSrcLayer->TestCapability( pszCap );
    }

    if( psSelectInfo->query_mode == SWQM_RECORDSET
        && (EQUAL(pszCap,OLCFastFeatureCount) 
            || EQUAL(pszCap,OLCRandomRead) 
            || EQUAL(pszCap,OLCFastGetExtent)) )
        return poSrcLayer->TestCapability( pszCap );

    else if( psSelectInfo->query_mode != SWQM_RECORDSET )
    {
        if( EQUAL(pszCap,OLCFastFeatureCount) )
            return TRUE;
    }

    return FALSE;
}

/************************************************************************/
/*                           PrepareSummary()                           */
/************************************************************************/

int OGRGenSQLResultsLayer::PrepareSummary()

{
    swq_select *psSelectInfo = (swq_select *) pSelectInfo;

    if( poSummaryFeature != NULL )
        return TRUE;

    poSummaryFeature = new OGRFeature( poDefn );
    poSummaryFeature->SetFID( 0 );

/* -------------------------------------------------------------------- */
/*      Ensure our query parameters are in place on the source          */
/*      layer.  And initialize reading.                                 */
/* -------------------------------------------------------------------- */
    poSrcLayer->SetAttributeFilter( psSelectInfo->whole_where_clause );
    
    poSrcLayer->SetSpatialFilter( m_poFilterGeom );
        
    poSrcLayer->ResetReading();

/* -------------------------------------------------------------------- */
/*      We treat COUNT(*) (or COUNT of anything without distinct) as    */
/*      a special case, and fill with GetFeatureCount().                */
/* -------------------------------------------------------------------- */

    if( psSelectInfo->result_columns == 1 
        && psSelectInfo->column_defs[0].col_func == SWQCF_COUNT
        && !psSelectInfo->column_defs[0].distinct_flag )
    {
        poSummaryFeature->SetField( 0, poSrcLayer->GetFeatureCount( TRUE ) );
        return TRUE;
    }

/* -------------------------------------------------------------------- */
/*      Otherwise, process all source feature through the summary       */
/*      building facilities of SWQ.                                     */
/* -------------------------------------------------------------------- */
    const char *pszError;
    OGRFeature *poSrcFeature;

    while( (poSrcFeature = poSrcLayer->GetNextFeature()) != NULL )
    {
        for( int iField = 0; iField < psSelectInfo->result_columns; iField++ )
        {
            swq_col_def *psColDef = psSelectInfo->column_defs + iField;

            pszError = swq_select_summarize( psSelectInfo, iField, 
                                          poSrcFeature->GetFieldAsString( 
                                              psColDef->field_index ) );
            
            if( pszError != NULL )
            {
                delete poSummaryFeature;
                poSummaryFeature = NULL;

                CPLError( CE_Failure, CPLE_AppDefined, "%s", pszError );
                return FALSE;
            }
        }

        delete poSrcFeature;
    }

    pszError = swq_select_finish_summarize( psSelectInfo );
    if( pszError != NULL )
    {
        delete poSummaryFeature;
        poSummaryFeature = NULL;
        
        CPLError( CE_Failure, CPLE_AppDefined, "%s", pszError );
        return FALSE;
    }

/* -------------------------------------------------------------------- */
/*      If we have run out of features on the source layer, clear       */
/*      away the filters we have installed till a next run through      */
/*      the features.                                                   */
/* -------------------------------------------------------------------- */
    if( poSrcFeature == NULL )
        ClearFilters();

/* -------------------------------------------------------------------- */
/*      Now apply the values to the summary feature.  If we are in      */
/*      DISTINCT_LIST mode we don't do this step.                       */
/* -------------------------------------------------------------------- */
    if( psSelectInfo->query_mode == SWQM_SUMMARY_RECORD 
        && psSelectInfo->column_summary != NULL )
    {
        for( int iField = 0; iField < psSelectInfo->result_columns; iField++ )
        {
            swq_col_def *psColDef = psSelectInfo->column_defs + iField;
            swq_summary *psSummary = psSelectInfo->column_summary + iField;

            if( psColDef->col_func == SWQCF_AVG )
                poSummaryFeature->SetField( iField, 
                                        psSummary->sum / psSummary->count );
            else if( psColDef->col_func == SWQCF_MIN )
                poSummaryFeature->SetField( iField, psSummary->min );
            else if( psColDef->col_func == SWQCF_MAX )
                poSummaryFeature->SetField( iField, psSummary->max );
            else if( psColDef->col_func == SWQCF_COUNT )
                poSummaryFeature->SetField( iField, psSummary->count );
            else if( psColDef->col_func == SWQCF_SUM )
                poSummaryFeature->SetField( iField, psSummary->sum );
        }
    }

    return TRUE;
}

/************************************************************************/
/*                          TranslateFeature()                          */
/************************************************************************/

OGRFeature *OGRGenSQLResultsLayer::TranslateFeature( OGRFeature *poSrcFeat )

{
    swq_select *psSelectInfo = (swq_select *) pSelectInfo;
    OGRFeature *poDstFeat;

    if( poSrcFeat == NULL )
        return NULL;

    m_nFeaturesRead++;

/* -------------------------------------------------------------------- */
/*      Create destination feature.                                     */
/* -------------------------------------------------------------------- */
    poDstFeat = new OGRFeature( poDefn );

    poDstFeat->SetFID( poSrcFeat->GetFID() );

    poDstFeat->SetGeometry( poSrcFeat->GetGeometryRef() );
    
/* -------------------------------------------------------------------- */
/*      Copy fields from primary record to the destination feature.     */
/* -------------------------------------------------------------------- */
    for( int iField = 0; iField < psSelectInfo->result_columns; iField++ )
    {
        swq_col_def *psColDef = psSelectInfo->column_defs + iField;

        if ( psColDef->field_index >= iFIDFieldIndex &&
            psColDef->field_index < iFIDFieldIndex + SPECIAL_FIELD_COUNT )
        {
            switch (SpecialFieldTypes[psColDef->field_index - iFIDFieldIndex])
            {
              case SWQ_INTEGER:
                poDstFeat->SetField( iField, poSrcFeat->GetFieldAsInteger(psColDef->field_index) );
                break;
              default:
                poDstFeat->SetField( iField, poSrcFeat->GetFieldAsString(psColDef->field_index) );
            }
        }
        else if( psColDef->table_index == 0 )
            poDstFeat->SetField( iField,
                         poSrcFeat->GetRawFieldRef( psColDef->field_index ) );
    }

/* -------------------------------------------------------------------- */
/*      Copy values from any joined tables.                             */
/* -------------------------------------------------------------------- */
    int iJoin;

    for( iJoin = 0; iJoin < psSelectInfo->join_count; iJoin++ )
    {
        char szFilter[512];

        swq_join_def *psJoinInfo = psSelectInfo->join_defs + iJoin;
        OGRLayer *poJoinLayer = papoTableLayers[psJoinInfo->secondary_table];
        
        // if source key is null, we can't do join.
        if( !poSrcFeat->IsFieldSet( psJoinInfo->primary_field ) )
            continue;

        // Prepare attribute query to express fetching on the joined variable
        sprintf( szFilter, "%s = ", 
                 poJoinLayer->GetLayerDefn()->GetFieldDefn( 
                     psJoinInfo->secondary_field )->GetNameRef() );

        OGRField *psSrcField = 
            poSrcFeat->GetRawFieldRef(psJoinInfo->primary_field);

        switch( poSrcLayer->GetLayerDefn()->GetFieldDefn( 
                    psJoinInfo->primary_field )->GetType() )
        {
          case OFTInteger:
            sprintf( szFilter+strlen(szFilter), "%d", psSrcField->Integer );
            break;

          case OFTReal:
            sprintf( szFilter+strlen(szFilter), "%.16g", psSrcField->Real );
            break;

          case OFTString:
            // the string really ought to be escaped. 
            sprintf( szFilter+strlen(szFilter), "\"%s\"", 
                     psSrcField->String );
            break;

          default:
            CPLAssert( FALSE );
            continue;
        }

        poJoinLayer->ResetReading();
        if( poJoinLayer->SetAttributeFilter( szFilter ) != OGRERR_NONE )
            continue;

        // Fetch first joined feature.
        OGRFeature *poJoinFeature;

        poJoinFeature = poJoinLayer->GetNextFeature();

        if( poJoinFeature == NULL )
            continue;

        // Copy over selected field values. 
        for( int iField = 0; iField < psSelectInfo->result_columns; iField++ )
        {
            swq_col_def *psColDef = psSelectInfo->column_defs + iField;
            
            if( psColDef->table_index == psJoinInfo->secondary_table )
                poDstFeat->SetField( iField,
                                     poJoinFeature->GetRawFieldRef( 
                                         psColDef->field_index ) );
        }

        delete poJoinFeature;
    }

    return poDstFeat;
}

/************************************************************************/
/*                           GetNextFeature()                           */
/************************************************************************/

OGRFeature *OGRGenSQLResultsLayer::GetNextFeature()

{
    swq_select *psSelectInfo = (swq_select *) pSelectInfo;

/* -------------------------------------------------------------------- */
/*      Handle summary sets.                                            */
/* -------------------------------------------------------------------- */
    if( psSelectInfo->query_mode == SWQM_SUMMARY_RECORD 
        || psSelectInfo->query_mode == SWQM_DISTINCT_LIST )
        return GetFeature( nNextIndexFID++ );

/* -------------------------------------------------------------------- */
/*      Handle ordered sets.                                            */
/* -------------------------------------------------------------------- */
    while( TRUE )
    {
        OGRFeature *poFeature;

        if( panFIDIndex != NULL )
            poFeature =  GetFeature( nNextIndexFID++ );
        else
        {
            OGRFeature *poSrcFeat = poSrcLayer->GetNextFeature();

            if( poSrcFeat == NULL )
                return NULL;
            
            poFeature = TranslateFeature( poSrcFeat );
            delete poSrcFeat;
        }

        if( poFeature == NULL )
            return NULL;

        if( m_poAttrQuery == NULL
            || m_poAttrQuery->Evaluate( poFeature ) )
            return poFeature;

        delete poFeature;
    }

    return NULL;
}

/************************************************************************/
/*                             GetFeature()                             */
/************************************************************************/

OGRFeature *OGRGenSQLResultsLayer::GetFeature( long nFID )

{
    swq_select *psSelectInfo = (swq_select *) pSelectInfo;

/* -------------------------------------------------------------------- */
/*      Handle request for summary record.                              */
/* -------------------------------------------------------------------- */
    if( psSelectInfo->query_mode == SWQM_SUMMARY_RECORD )
    {
        if( !PrepareSummary() || nFID != 0 || poSummaryFeature == NULL )
            return NULL;
        else
            return poSummaryFeature->Clone();
    }

/* -------------------------------------------------------------------- */
/*      Handle request for distinct list record.                        */
/* -------------------------------------------------------------------- */
    if( psSelectInfo->query_mode == SWQM_DISTINCT_LIST )
    {
        if( !PrepareSummary() )
            return NULL;

        swq_summary *psSummary = psSelectInfo->column_summary + 0;

        if( psSummary == NULL )