Application: gvSIG desktop

import static org.gvsig.expressionevaluator.impl.function.dataaccess.SelectFunction.removeOuterTablesReferences;

public class SelectCountFunction extends AbstractFeatureFunction {

  public SelectCountFunction() {

    super(DALFunctions.GROUP_DATA_ACCESS,

            FUNCTION_SELECT_COUNT,

            Range.between(1,2),

            "Returns the number of features of the table by applying the filter indicated.\n" +

                    "The syntax is:\n\n"+

                    "SELECT COUNT(*) FROM table WHERE boolean_expression;\n\n"+

                    "Indicate a filter expression with WHERE is optional.\n"+

                    "The SELECT statement must always end with a semicolon.",

            "SELECT COUNT(*) FROM {{table}} WHERE filter ;",

            new String[]{

              "table - Name of the table",

              "filter - boolean expression with the filter to apply",

            },

            "Long",

            false

    );

  }

  @Override

  public boolean isHidden() {

    return false;

  }

  @Override

  public boolean allowConstantFolding() {

    return false;

  }

  @Override

  public boolean useArgumentsInsteadObjects() {

    return true;

  }

  @Override

  public Object call(Interpreter interpreter, Object[] args) throws Exception {

    throw new UnsupportedOperationException();

  }

  @Override

  public Object call(Interpreter interpreter, Codes args) throws Exception {

    String storeName =  (String) getObject(interpreter, args, 0);

    Code where = args.get(1);

    if( where.code()==Code.CONSTANT ) {

        if( ((Code.Constant)where).value()==null ) {

            where = null;

    FeatureStore featureStore = null;

    FeatureSet set = null;

    try {

      DataStore store = this.getStore(storeName);

      if (store == null ) {

        throw new ExpressionRuntimeException("Cant locate the store '" + storeName + "' in function '" + FUNCTION_SELECT_COUNT + "'.");

      }

      if (!(store instanceof FeatureStore)) {

        throw new ExpressionRuntimeException("The store'" + storeName + "' is not valid for function '" + FUNCTION_SELECT_COUNT + "', a FeatureStore is required.");

      }

      featureStore = (FeatureStore) store;

      if (where == null ) {

        set = featureStore.getFeatureSet();

      } else {

          FeatureQuery query = featureStore.createFeatureQuery();

          Code where2 = removeOuterTablesReferences(interpreter, where);

          ExpressionEvaluator filter = new DefaultFeatureExpressionEvaluator(where2.toString());

          filter.toSymbolTable().addSymbolTable(interpreter.getSymbolTable());

          query.addFilter(filter);

          query.retrievesAllAttributes();

          set = featureStore.getFeatureSet(query);

      }

      return set.getSize();

    } catch (ExpressionRuntimeException ex) {

      throw ex;

    } catch (Exception ex) {

      throw new ExpressionRuntimeException("Problems calling '" + FUNCTION_SELECT_COUNT + "' function", ex);

    } finally {

      DisposeUtils.disposeQuietly(set);

      DisposeUtils.disposeQuietly(featureStore);

    }

  }

  protected DataStore getStore(String storeName) {

    DataManager dataManager = DALLocator.getDataManager();

    DataStore store = dataManager.getStoresRepository().getStore(storeName);

    return store;

  }