org.apache.calcite.schema.impl.AbstractSchema.java Source code

Introduction

Here is the source code for org.apache.calcite.schema.impl.AbstractSchema.java

Source

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 org.apache.calcite.schema.impl;

import org.apache.calcite.linq4j.tree.Expression;
import org.apache.calcite.schema.Function;
import org.apache.calcite.schema.Schema;
import org.apache.calcite.schema.SchemaFactory;
import org.apache.calcite.schema.SchemaPlus;
import org.apache.calcite.schema.Schemas;
import org.apache.calcite.schema.Table;

import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.Multimap;

import java.util.Collection;
import java.util.Map;
import java.util.Set;

/**
 * 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 functions unless you override
 *       {@link #getFunctionMultimap()}.</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 {
    public AbstractSchema() {
    }

    public boolean isMutable() {
        return true;
    }

    public boolean contentsHaveChangedSince(long lastCheck, long now) {
        return false;
    }

    public Expression getExpression(SchemaPlus parentSchema, String name) {
        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>
     *
     * @return Map of tables in this schema by name
     */
    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 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 #getFunctionNames()}
     * and {@link Schema#getFunctions(String)} depend on this map.
     * The default implementation of this method returns the empty multi-map.
     * Override this method to change their behavior.</p>
     *
     * @return Multi-map of functions in this schema by name
     */
    protected Multimap<String, Function> getFunctionMultimap() {
        return ImmutableMultimap.of();
    }

    public final Collection<Function> getFunctions(String name) {
        return getFunctionMultimap().get(name); // never null
    }

    public final Set<String> getFunctionNames() {
        return getFunctionMultimap().keySet();
    }

    /**
     * Returns a map of sub-schemas in this schema by name.
     *
     * <p>The implementations of {@link #getSubSchemaNames()}
     * and {@link #getSubSchema(String)} depend on this map.
     * The default implementation of this method returns the empty map.
     * Override this method to change their behavior.</p>
     *
     * @return Map of sub-schemas in this schema by name
     */
    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);
    }

    /** Schema factory that creates an
     * {@link org.apache.calcite.schema.impl.AbstractSchema}. */
    public static class Factory implements SchemaFactory {
        public static final Factory INSTANCE = new Factory();

        private Factory() {
        }

        public Schema create(SchemaPlus parentSchema, String name, Map<String, Object> operand) {
            return new AbstractSchema();
        }
    }
}

// End AbstractSchema.java