Application: gvSIG desktop

import org.gvsig.fmap.dal.DALLocator;

import org.gvsig.fmap.dal.DataManager;

import org.gvsig.expressionevaluator.spi.AbstractFunction;

public class SelectFunction 

        extends AbstractFunction 

        implements Optimizer.FunctionOptimizer

  {

  public SelectFunction() {

    super(DALFunctions.GROUP_DATA_ACCESS,

            FUNCTION_SELECT,

            Range.is(6),

            "Returns a list of features of the table by applying the filter, order and limit indicated.\n"+

                "The syntax is:\n\n"+

                "SELECT * FROM table WHERE boolean_expression ORDER BY order_column LIMIT limit;\n\n"+

                "Indicate a filter expression with WHERE, an order or LIMIT is optional.\n"+

                "You can use an asterisk or enter the column names you want to retrieve separated by commas.\n"+

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

            "SELECT * FROM table WHERE boolean_expression ORDER BY order_column LIMIT limit;",

            new String[]{

              "column_names/asterisk - Names of the columns table to retrieve.",

              "table_name - Name of the table",

              "filter - boolean expression to apply as filter",

              "order_column - the order used to retrieve the features. It is a list of column names separated by a comma. The column name can optionally be followed by ASC or DESC to indicate whether the order should be ascending or descending.",

              "limit - Maximum number of features to return"

            },

            "List",

            true

    );

  }

  @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();

  }

  private static final int COLUMNS = 0;

  private static final int TABLE = 1;

  private static final int WHERE = 2;

  private static final int ORDER = 3;

  private static final int ORDER_MODE = 4;

  private static final int LIMIT = 5;

  private Callable getTupleOrNull(Codes args, int argn) {

    Code code = args.get(argn);

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

      if( ((Code.Constant)code).value()!=null ) {

        throw new ExpressionRuntimeException("Tupple or null expected in argument "+argn+ " of function '" + FUNCTION_SELECT + "'.");

      }

      return null;

    if( code.code()!=Code.CALLABLE ) {

      throw new ExpressionRuntimeException("Tupple or null expected in argument "+argn+ " of function '" + FUNCTION_SELECT + "'.");

    }

    Callable caller = (Callable) code;

    if( !StringUtils.equalsIgnoreCase(FUNCTION_TUPLE, caller.name()) ) {

      throw new ExpressionRuntimeException("Tupple or null expected in argument "+argn+ " of function '" + FUNCTION_SELECT + "'.");

    }

    return caller;

  }

  @Override

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

    Code.Identifier storeName =  (Code.Identifier) args.get(TABLE);

    Code columns = getTupleOrNull(args, COLUMNS);

    Code where = args.get(WHERE);

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

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

            where = null;

        }

    Number limit = (Number) getObject(interpreter, args, LIMIT);

    Callable order = getTupleOrNull(args, ORDER);

    Callable order_mode = getTupleOrNull(args, ORDER_MODE);

    FeatureQueryOrder queryOrder = null;

    if( order!=null || order_mode!=null ) {

      for( int n=0 ; n<order.parameters().size(); n++) {

        String member = (String) interpreter.run(order.parameters().get(n));

        Boolean mode = (Boolean) interpreter.run(order_mode.parameters().get(n));

        if( queryOrder == null ) {

          queryOrder = new DefaultFeatureQueryOrder();

        }

        queryOrder.add(member, mode);

      }

    }

    // FIXME: add columns to query.addAttributeName() 

    try {

      DataStore store = this.getStore(storeName.name());

      if (store == null ) {

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

      }

      if (!(store instanceof FeatureStore)) {

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

      }

      FeatureStore featureStore = (FeatureStore) store;

      List<Feature> features;

      if (where == null && queryOrder == null && limit==null ) {

        features = featureStore.getFeatures();

      } else {

        FeatureQuery query = featureStore.createFeatureQuery();

        if (where != null) {

          Code where2 = removeOuterTablesReferences(interpreter, where);

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

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

          query.addFilter(filter);

        }

        if (queryOrder != null) {

          query.getOrder().copyFrom(queryOrder);

        }

        if( limit!=null ) {

          query.setLimit(limit.longValue());

        }

        query.retrievesAllAttributes();

        features = featureStore.getFeatures(query);

      }

      return features;

    } catch (ExpressionRuntimeException ex) {

      throw ex;

    } catch (Exception ex) {

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

    }

  }

  protected DataStore getStore(String storeName) {

    DataManager dataManager = DALLocator.getDataManager();

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

    return store;

  }

  public static Code removeOuterTablesReferences(Interpreter interpreter, Code where) {

    try {

      SymbolTable symbolTable = interpreter.getSymbolTable();

      TableAttributeHandler table = (TableAttributeHandler) symbolTable.value(SYMBOL_CURRENT_TABLE);

      List<Pair<Code,Code>>replaces = new ArrayList<>();

      CodeBuilder codeBuilder = ExpressionUtils.createCodeBuilder();

      final Set<Code> replacesToASkip = new HashSet<>();

      Code where2 = where.clone();

      where2.accept((Object o) -> {

        if( o == null ) {

            return;

        }

        Code code = (Code) o;

        switch(code.code()) {

            case Code.CALLABLE:

                Code.Callable caller = (Code.Callable) code;

                if( StringUtils.equalsIgnoreCase(caller.name(),FUNCTION_GETATTR) ) {

                  Codes args = caller.parameters();

                  Code arg0 = args.get(0);

                  Code arg1 = args.get(1);

                  replacesToASkip.add(arg1);

                  if( arg0 instanceof Code.Identifier && arg1 instanceof Code.Constant ) {

                    Object tt = symbolTable.value(((Code.Identifier)arg0).name());

                    if( tt instanceof TableAttributeHandler && 

                        StringUtils.equalsIgnoreCase(((TableAttributeHandler)tt).getName(), table.getName()) ) {

                      String columnName = Objects.toString(((Code.Constant)arg1).value(), null);

                      if( columnName!=null ) {

                        Object value = table.get(columnName);

                        replaces.add(

                                new ImmutablePair<>(

                                        caller,

                                        codeBuilder.constant(value)

                                )

                        );

                      }

                    }

                  }

                break;

      });

      where2.accept((Object o) -> {

        if( o == null ) {

            return;

        Code code = (Code) o;

        if( replacesToASkip.contains(code) ) {

            return;

        }

        switch(code.code()) {

            case Code.IDENTIFIER:

                Code.Identifier id = (Code.Identifier)code;

                if( symbolTable.exists(id.name()) ) {

                    Object value = symbolTable.value(id.name());

                    replaces.add(

                            new ImmutablePair<>(

                                    id,

                                    codeBuilder.constant(value)

                            )

                    );

                }

                break;

        }

      });

      if( replaces.isEmpty() ) {

          return where;

      }

      for (Pair<Code, Code> replace : replaces) {

        if( replace!=null ) {

          where2.replace(replace.getLeft(), replace.getRight());

        }

      }

      return where2;

    } catch (Exception ex) {

      throw new ExpressionRuntimeException("Can't remove references to outer tables.", ex);

  }

  @Override

  public Code optimize(Optimizer optimizer, Callable caller) {

    return caller; // Don't optimize SELECT

  }