org.apache.flink.table.api.GroupedTable Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of flink-table-api-java Show documentation

This module contains the Table/SQL API for writing table programs within the table ecosystem using the Java programming language.

There is a newer version: 2.0-preview1

Show newest version

/*
 * 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.flink.table.api;

import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.table.expressions.Expression;

/** A table that has been grouped on a set of grouping keys. */
@PublicEvolving
public interface GroupedTable {

    /**
     * Performs a selection operation on a grouped table. Similar to an SQL SELECT statement. The
     * field expressions can contain complex expressions and aggregations.
     *
     * Example:
     *
     * 
{@code
     * tab.groupBy($("key")).select($("key"), $("value").avg().plus(" The average").as("average"));
     * }
     *
     * Scala Example:
     *
     * 
{@code
     * tab.groupBy($"key").select($"key", $"value".avg + " The average" as "average")
     * }
     */
    Table select(Expression... fields);

    /**
     * Performs an aggregate operation with an aggregate function. You have to close the {@link
     * #aggregate(Expression)} with a select statement. The output will be flattened if the output
     * type is a composite type.
     *
     * Example:
     *
     * 
{@code
     * tableEnv.createTemporarySystemFunction("aggFunc", MyAggregateFunction.class);
     * tab.groupBy($("key"))
     *   .aggregate(call("aggFunc", $("a"), $("b")).as("f0", "f1", "f2"))
     *   .select($("key"), $("f0"), $("f1"));
     * }
     *
     * Scala Example:
     *
     * 
{@code
     * val aggFunc = new MyAggregateFunction
     * table.groupBy($"key")
     *   .aggregate(aggFunc($"a", $"b") as ("f0", "f1", "f2"))
     *   .select($"key", $"f0", $"f1")
     * }
     */
    AggregatedTable aggregate(Expression aggregateFunction);

    /**
     * Performs a flatAggregate operation on a grouped table. FlatAggregate takes a
     * TableAggregateFunction which returns multiple rows. Use a selection after flatAggregate.
     *
     * Example:
     *
     * 
{@code
     * tableEnv.createTemporarySystemFunction("tableAggFunc", MyTableAggregateFunction.class);
     * tab.groupBy($("key"))
     *   .flatAggregate(call("tableAggFunc", $("a"), $("b")).as("x", "y", "z"))
     *   .select($("key"), $("x"), $("y"), $("z"));
     * }
     *
     * Scala Example:
     *
     * 
{@code
     * val tableAggFunc: TableAggregateFunction = new MyTableAggregateFunction
     * tab.groupBy($"key")
     *   .flatAggregate(tableAggFunc($"a", $"b") as ("x", "y", "z"))
     *   .select($"key", $"x", $"y", $"z")
     * }
     */
    FlatAggregateTable flatAggregate(Expression tableAggFunction);
}