org.apache.beam.sdk.extensions.sql.impl.rule.AggregateWindowFactory.java Source code

Introduction

Here is the source code for org.apache.beam.sdk.extensions.sql.impl.rule.AggregateWindowFactory.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.beam.sdk.extensions.sql.impl.rule;

import java.util.List;
import java.util.Optional;
import org.apache.beam.sdk.transforms.windowing.FixedWindows;
import org.apache.beam.sdk.transforms.windowing.Sessions;
import org.apache.beam.sdk.transforms.windowing.SlidingWindows;
import org.apache.beam.sdk.transforms.windowing.WindowFn;
import org.apache.calcite.rex.RexCall;
import org.apache.calcite.rex.RexLiteral;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.sql.SqlKind;
import org.joda.time.Duration;

/** Creates {@link WindowFn} wrapper based on HOP/TUMBLE/SESSION call in a query. */
class AggregateWindowFactory {

    /**
     * Returns optional of {@link AggregateWindowField} which represents a windowing function
     * specified by HOP/TUMBLE/SESSION in the SQL query.
     *
     * <p>If no known windowing function is specified in the query, then {@link Optional#empty()} is
     * returned.
     *
     * <p>Throws {@link UnsupportedOperationException} if it cannot convert SQL windowing function
     * call to Beam model, see {@link #getWindowFieldAt(RexCall, int)} for details.
     */
    static Optional<AggregateWindowField> getWindowFieldAt(RexCall call, int groupField) {

        Optional<WindowFn> windowFnOptional = createWindowFn(call.operands, call.op.kind);

        return windowFnOptional.map(
                windowFn -> AggregateWindowField.builder().setFieldIndex(groupField).setWindowFn(windowFn).build());
    }

    /**
     * Returns a {@link WindowFn} based on the SQL windowing function defined by {#code operatorKind}.
     * Supported {@link SqlKind}s:
     *
     * <ul>
     *   <li>{@link SqlKind#TUMBLE}, mapped to {@link FixedWindows};
     *   <li>{@link SqlKind#HOP}, mapped to {@link SlidingWindows};
     *   <li>{@link SqlKind#SESSION}, mapped to {@link Sessions};
     * </ul>
     *
     * <p>For example:
     *
     * <pre>{@code
     * SELECT event_timestamp, COUNT(*)
     * FROM PCOLLECTION
     * GROUP BY TUMBLE(event_timestamp, INTERVAL '1' HOUR)
     * }</pre>
     *
     * <p>SQL window functions support optional window_offset parameter which indicates a how window
     * definition is offset from the event time. Offset is zero if not specified.
     *
     * <p>Beam model does not support offset for session windows, so this method will throw {@link
     * UnsupportedOperationException} if offset is specified in SQL query for {@link SqlKind#SESSION}.
     */
    private static Optional<WindowFn> createWindowFn(List<RexNode> parameters, SqlKind operatorKind) {
        switch (operatorKind) {
        case TUMBLE:

            // Fixed-size, non-intersecting time-based windows, for example:
            //   every hour aggregate elements from the previous hour;
            //
            // SQL Syntax:
            //   TUMBLE(monotonic_field, window_size [, window_offset])
            //
            // Example:
            //   TUMBLE(event_timestamp_field, INTERVAL '1' HOUR)

            FixedWindows fixedWindows = FixedWindows.of(durationParameter(parameters, 1));
            if (parameters.size() == 3) {
                fixedWindows = fixedWindows.withOffset(durationParameter(parameters, 2));
            }

            return Optional.of(fixedWindows);
        case HOP:

            // Sliding, fixed-size, intersecting time-based windows, for example:
            //   every minute aggregate elements from the previous hour;
            //
            // SQL Syntax:
            //   HOP(monotonic_field, emit_frequency, window_size [, window_offset])
            //
            // Example:
            //   HOP(event_timestamp_field, INTERVAL '1' MINUTE, INTERVAL '1' HOUR)

            SlidingWindows slidingWindows = SlidingWindows.of(durationParameter(parameters, 2))
                    .every(durationParameter(parameters, 1));

            if (parameters.size() == 4) {
                slidingWindows = slidingWindows.withOffset(durationParameter(parameters, 3));
            }

            return Optional.of(slidingWindows);
        case SESSION:

            // Session windows, for example:
            //   aggregate events after a gap of 1 minute of no events;
            //
            // SQL Syntax:
            //   SESSION(monotonic_field, session_gap)
            //
            // Example:
            //   SESSION(event_timestamp_field, INTERVAL '1' MINUTE)

            Sessions sessions = Sessions.withGapDuration(durationParameter(parameters, 1));
            if (parameters.size() == 3) {
                throw new UnsupportedOperationException(
                        "Specifying alignment (offset) is not supported for session windows");
            }

            return Optional.of(sessions);
        default:
            return Optional.empty();
        }
    }

    private static Duration durationParameter(List<RexNode> parameters, int parameterIndex) {
        return Duration.millis(intValue(parameters.get(parameterIndex)));
    }

    private static long intValue(RexNode operand) {
        if (operand instanceof RexLiteral) {
            return RexLiteral.intValue(operand);
        } else {
            throw new IllegalArgumentException(String.format("[%s] is not valid.", operand));
        }
    }
}