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Date: Sat, 26 Nov 2016 13:37:58 +0000 (UTC)
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Subject: [jira] [Commented] (FLINK-3848) Add ProjectableTableSource
 interface and translation rule
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archived-at: Sat, 26 Nov 2016 13:38:01 -0000


    [ https://issues.apache.org/jira/browse/FLINK-3848?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15697950#comment-15697950 ] 

ASF GitHub Bot commented on FLINK-3848:
---------------------------------------

Github user wuchong commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2810#discussion_r89670435
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/rules/dataSet/BatchProjectableTableSourceScanRule.scala ---
    @@ -0,0 +1,82 @@
    +/*
    + * 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.api.table.plan.rules.dataSet
    +
    +import org.apache.calcite.plan.RelOptRule._
    +import org.apache.calcite.plan.volcano.RelSubset
    +import org.apache.calcite.plan.{RelOptRule, RelOptRuleCall, RelOptRuleOperand, RelTraitSet}
    +import org.apache.calcite.rel.RelNode
    +import org.apache.calcite.rel.core.TableScan
    +import org.apache.calcite.rel.logical.LogicalProject
    +import org.apache.flink.api.table.plan.nodes.dataset.{BatchProjectableTableSourceScan, DataSetConvention}
    +import org.apache.flink.api.table.plan.schema.TableSourceTable
    +import org.apache.flink.api.table.sources.{BatchTableSource, ProjectableTableSource}
    +
    +class BatchProjectableTableSourceScanRule(
    +  operand: RelOptRuleOperand,
    +  description: String) extends RelOptRule(operand, description) {
    +
    +  override def matches(call: RelOptRuleCall): Boolean = {
    +    // check that table scan supports projections
    +    val project: LogicalProject = call.rel(0).asInstanceOf[LogicalProject]
    +    val original: RelNode = project.getInput.asInstanceOf[RelSubset].getOriginal
    +
    +    original match {
    +      case scan: TableScan =>
    +        val dataSetTable = scan.getTable.unwrap(classOf[TableSourceTable])
    +        dataSetTable match {
    +          case tst: TableSourceTable =>
    +            tst.tableSource match {
    +              case s: BatchTableSource[_] =>
    +                s.isInstanceOf[ProjectableTableSource[_]]
    +              case _ =>
    +                false
    +            }
    +          case _ =>
    +            false
    +        }
    +      case _ =>
    +        false
    +    }
    +  }
    +
    +  override def onMatch(call: RelOptRuleCall): Unit = {
    +    val project = call.rel(0).asInstanceOf[LogicalProject]
    +    val scan: TableScan = call.rel(1).asInstanceOf[TableScan]
    +
    +    val convInput = RelOptRule.convert(scan, DataSetConvention.INSTANCE)
    +    val traitSet: RelTraitSet = project.getTraitSet.replace(DataSetConvention.INSTANCE)
    +
    +    val newRel = new BatchProjectableTableSourceScan(
    +      scan.getCluster,
    +      traitSet,
    +      convInput,
    +      project.getProjects,
    +      project.getRowType,
    +      scan.getTable
    +    )
    +    call.transformTo(newRel)
    +  }
    +}
    +
    +object BatchProjectableTableSourceScanRule {
    +  val INSTANCE = new BatchProjectableTableSourceScanRule(
    +    operand(classOf[LogicalProject], operand(classOf[TableScan], none())),
    +    "BatchTableSourceProjectRule")
    --- End diff --
    
    Please rename the description the same as the class name.


> Add ProjectableTableSource interface and translation rule
> ---------------------------------------------------------
>
>                 Key: FLINK-3848
>                 URL: https://issues.apache.org/jira/browse/FLINK-3848
>             Project: Flink
>          Issue Type: New Feature
>          Components: Table API & SQL
>            Reporter: Fabian Hueske
>            Assignee: Anton Solovev
>
> Add a {{ProjectableTableSource}} interface for {{TableSource}} implementation that support projection push-down.
> The interface could look as follows
> {code}
> def trait ProjectableTableSource {
>   def setProjection(fields: Array[String]): Unit
> }
> {code}
> In addition we need Calcite rules to push a projection into a TableScan that refers to a {{ProjectableTableSource}}. We might need to tweak the cost model as well to push the optimizer in the right direction.
> Moreover, the {{CsvTableSource}} could be extended to implement {{ProjectableTableSource}}.


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