foxx.spline.services.observed-writes-by-read.js Maven / Gradle / Ivy

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/*
 * Copyright 2020 ABSA Group Limited
 *
 * Licensed 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.
 */

'use strict';
const {db, aql} = require('@arangodb');

/**
 * Returns a list of execution events which writes are visible from any read of the given execution event
 *
 * @param readEvent za.co.absa.spline.persistence.model.Progress
 * @returns za.co.absa.spline.persistence.model.Progress[]
 */
function observedWritesByRead(readEvent) {
    return readEvent && db._query(aql`
        WITH progress, progressOf, executionPlan, executes, operation, depends, writesTo, dataSource
        LET readTime = ${readEvent}.timestamp
        FOR rds IN 2 OUTBOUND ${readEvent} progressOf, depends
            LET maybeObservedOverwrite = SLICE(
                (FOR wo IN 1 INBOUND rds writesTo
                    FILTER !wo.append
                    FOR e IN 2 INBOUND wo executes, progressOf
                        FILTER e.timestamp < readTime
                        SORT e.timestamp DESC
                        LIMIT 1
                        RETURN e
                ), 0, 1)
            LET observedAppends = (
                FOR wo IN 1 INBOUND rds writesTo
                    FILTER wo.append
                    FOR e IN 2 INBOUND wo executes, progressOf
                        FILTER e.timestamp > maybeObservedOverwrite[0].timestamp
                           AND e.timestamp < readTime
                        SORT e.timestamp ASC
                        RETURN e
                )
            LET allObservedEvents = APPEND(maybeObservedOverwrite, observedAppends)
            FOR e IN allObservedEvents RETURN e
    `).toArray();
}

module.exports = {
    observedWritesByRead
};