com.dimajix.flowman.spec.target.BlackholeTarget.scala Maven / Gradle / Ivy

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A Spark based ETL tool
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/*
 * Copyright (C) 2018 The Flowman Authors
 *
 * 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.
 */

package com.dimajix.flowman.spec.target

import com.fasterxml.jackson.annotation.JsonProperty

import com.dimajix.common.No
import com.dimajix.common.Trilean
import com.dimajix.common.Yes
import com.dimajix.flowman.execution.Context
import com.dimajix.flowman.execution.Execution
import com.dimajix.flowman.execution.MappingUtils
import com.dimajix.flowman.execution.Phase
import com.dimajix.flowman.model.BaseTarget
import com.dimajix.flowman.model.MappingOutputIdentifier
import com.dimajix.flowman.model.ResourceIdentifier
import com.dimajix.flowman.model.Target


final case class BlackholeTarget(
    instanceProperties:Target.Properties,
    mapping:MappingOutputIdentifier
) extends BaseTarget {
    /**
     * Returns all phases which are implemented by this target in the execute method
     * @return
     */
    override def phases : Set[Phase] = Set(Phase.BUILD)

    /**
      * Returns a list of physical resources required by this target
      * @return
      */
    override def requires(phase: Phase) : Set[ResourceIdentifier] = {
        phase match {
            case Phase.BUILD => MappingUtils.requires(context, mapping.mapping)
            case _ => Set()
        }
    }

    /**
     * Returns the state of the target, specifically of any artifacts produces. If this method return [[Yes]],
     * then an [[execute]] should update the output, such that the target is not 'dirty' any more.
     * @param execution
     * @param phase
     * @return
     */
    override def dirty(execution: Execution, phase: Phase) : Trilean = {
        phase match {
            case Phase.BUILD => Yes
            case _ => No
        }
    }

    /**
      * Abstract method which will perform the output operation. All required tables need to be
      * registered as temporary tables in the Spark session before calling the execute method.
      *
      * @param executor
      */
    override def build(executor:Execution) : Unit = {
        val mapping = context.getMapping(this.mapping.mapping)
        val df = executor.instantiate(mapping, this.mapping.output)
        df.write.format("null").save()
    }
}



class BlackholeTargetSpec extends TargetSpec {
    @JsonProperty(value = "mapping", required=true) private var mapping:String = _

    override def instantiate(context: Context, properties:Option[Target.Properties] = None): BlackholeTarget = {
        BlackholeTarget(
            instanceProperties(context, properties),
            MappingOutputIdentifier.parse(context.evaluate(mapping))
        )
    }
}