org.partiql.lang.eval.physical.EvaluatorState.kt Maven / Gradle / Ivy

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An implementation of PartiQL for the JVM written in Kotlin.

There is a newer version: 1.0.0-perf.1

/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates.  All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 *  You may not use this file except in compliance with the License.
 * A copy of the License is located at:
 *
 *      http://aws.amazon.com/apache2.0/
 *
 *  or in the "license" file accompanying this file. This file 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.partiql.lang.eval.physical

import org.partiql.lang.eval.EvaluationSession
import org.partiql.lang.eval.ExprValue
import org.partiql.lang.eval.ExprValueFactory

/**
 * Contains state needed during query evaluation such as an instance of [EvaluationSession] and an array of [registers]
 * for each local variable that is part of the query.
 *
 * Since the elements of [registers] are mutable, when/if we decide to make query execution multi-threaded, we'll have
 * to take care to not share [EvaluatorState] instances among different threads.
 *
 * @param session The evaluation session.
 */
class EvaluatorState(
    /** The current [EvaluationSession]. */
    val session: EvaluationSession,

    /** The current [ExprValueFactory], provided here as a convenience. */
    val valueFactory: ExprValueFactory,

    /**
     * An array of registers containing [ExprValue]s needed during query execution.  Generally, there is
     * one register per local variable.  This is an array (and not a [List]) because its semantics match exactly what
     * we need: fixed length with mutable elements.
     *
     * This state should not be modified by customer provided operator implementations except through instances
     * of [SetVariableFunc] that were provided by this library, thus it is marked as `internal`.
     */
    internal val registers: Array
) {
    internal fun load(registers: Array) = registers.forEachIndexed { index, exprValue ->
        this.registers[index] = exprValue
    }
}