net.hydromatic.optiq.impl.AbstractSchema.java Source code

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Here is the source code for net.hydromatic.optiq.impl.AbstractSchema.java

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/*
// Licensed to Julian Hyde under one or more contributor license
// agreements. See the NOTICE file distributed with this work for
// additional information regarding copyright ownership.
//
// Julian Hyde licenses this file to you under the Apache License,
// Version 2.0 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at:
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
*/
package net.hydromatic.optiq.impl;

import net.hydromatic.linq4j.expressions.Expression;

import net.hydromatic.optiq.*;
import net.hydromatic.optiq.Table;

import com.google.common.collect.*;

import java.util.*;

/**
 * Abstract implementation of {@link Schema}.
 *
 * <p>Behavior is as follows:</p>
 * <ul>
 *   <li>The schema has no tables unless you override
 *       {@link #getTableMap()}.</li>
 *   <li>The schema has no table-functions unless you override
 *       {@link #getTableFunctionMultimap()}.</li>
 *   <li>The schema has no sub-schemas unless you override
 *       {@link #getSubSchemaMap()}.</li>
 *   <li>The schema is mutable unless you override
 *       {@link #isMutable()}.</li>
 *   <li>The name and parent schema are as specified in the constructor
 *       arguments.</li>
 * </ul>
 *
 * <p>For constructing custom maps and multi-maps, we recommend
 * {@link com.google.common.base.Suppliers} and
 * {@link com.google.common.collect.Maps}.</p>
 */
public class AbstractSchema implements Schema {
    protected final SchemaPlus parentSchema;
    protected final String name;

    public AbstractSchema(SchemaPlus parentSchema, String name) {
        this.parentSchema = parentSchema;
        this.name = name;
    }

    public SchemaPlus getParentSchema() {
        return parentSchema;
    }

    public String getName() {
        return name;
    }

    public boolean isMutable() {
        return true;
    }

    public Expression getExpression() {
        return Schemas.subSchemaExpression(parentSchema, name, getClass());
    }

    /**
     * Returns a map of tables in this schema by name.
     *
     * <p>The implementations of {@link #getTableNames()}
     * and {@link #getTable(String)} depend on this map.
     * The default implementation of this method returns the empty map.
     * Override this method to change their behavior.</p>
     */
    protected Map<String, Table> getTableMap() {
        return ImmutableMap.of();
    }

    public final Set<String> getTableNames() {
        return getTableMap().keySet();
    }

    public final Table getTable(String name) {
        return getTableMap().get(name);
    }

    /**
     * Returns a multi-map of table-functions in this schema by name.
     * It is a multi-map because functions are overloaded; there may be more than
     * one function in a schema with a given name (as long as they have different
     * parameter lists).
     *
     * <p>The implementations of {@link #getTableFunctionNames()}
     * and {@link #getTableFunctions(String)} depend on this map.
     * The default implementation of this method returns the empty multi-map.
     * Override this method to change their behavior.</p>
     */
    protected Multimap<String, TableFunction> getTableFunctionMultimap() {
        return ImmutableMultimap.of();
    }

    public final Collection<TableFunction> getTableFunctions(String name) {
        return getTableFunctionMultimap().get(name);
    }

    public final Set<String> getTableFunctionNames() {
        return getTableFunctionMultimap().keySet();
    }

    /**
     * Returns a map of tables in this schema by name.
     *
     * <p>The implementations of {@link #getTableNames()}
     * and {@link #getTable(String)} depend on this map.
     * The default implementation of this method returns the empty map.
     * Override this method to change their behavior.</p>
     */
    protected Map<String, Schema> getSubSchemaMap() {
        return ImmutableMap.of();
    }

    public final Set<String> getSubSchemaNames() {
        return getSubSchemaMap().keySet();
    }

    public final Schema getSubSchema(String name) {
        return getSubSchemaMap().get(name);
    }
}

// End AbstractSchema.java