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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3848) Add ProjectableTableSource interface and translation rule
Date Mon, 28 Nov 2016 14:12:59 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3848?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15702033#comment-15702033
] 

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

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

    https://github.com/apache/flink/pull/2810#discussion_r89760306
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/rules/dataSet/BatchProjectableTableSourceScanRule.scala
---
    @@ -0,0 +1,85 @@
    +/*
    + * 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
    + *
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    + * 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.{RelOptRule, RelOptRuleCall, RelTraitSet}
    +import org.apache.calcite.rel.core.TableScan
    +import org.apache.calcite.rel.logical.{LogicalProject, LogicalTableScan}
    +import org.apache.calcite.rex.RexInputRef
    +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}
    +
    +import scala.collection.JavaConverters._
    +
    +/** Rule to convert a [[LogicalTableScan]] with [[LogicalProject]]
    +  * into a [[BatchProjectableTableSourceScan]].
    +  */
    +class BatchProjectableTableSourceScanRule
    +  extends RelOptRule(
    +    operand(classOf[LogicalProject], operand(classOf[TableScan], none())),
    --- End diff --
    
    Please check for `LogicalCalc` instead of `LogicalProject`.
    Calcite starts with `LogicalProjectยด but merges those with other `LogicalProject` and
`LogicalFilter` into `LogicalCalc`. So after predicate and projection push-down, we might
only have a `LogicalCalc` and not a `LogicalProject` anymore.


> 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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