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https://issues.apache.org/jira/browse/FLINK-3848?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15676036#comment-15676036
]
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_r88592516
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/nodes/dataset/BatchTableProject.scala
---
@@ -0,0 +1,67 @@
+/*
+ * 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.nodes.dataset
+
+import java.util
+
+import org.apache.calcite.plan.{RelOptCluster, RelOptCost, RelOptPlanner,
RelTraitSet}
+import org.apache.calcite.rel.RelNode
+import org.apache.calcite.rel.`type`.RelDataType
+import org.apache.calcite.rel.core.Project
+import org.apache.calcite.rel.metadata.RelMetadataQuery
+import org.apache.calcite.rex.{RexInputRef, RexNode}
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.api.java.DataSet
+import org.apache.flink.api.table.BatchTableEnvironment
+import org.apache.flink.api.table.plan.schema.TableSourceTable
+import org.apache.flink.api.table.sources.ProjectableTableSource
+
+import scala.collection.JavaConverters._
+
+class BatchTableProject(
+ cluster: RelOptCluster,
+ traits: RelTraitSet,
+ input: RelNode,
+ projects: util.List[_ <: RexNode],
+ projectionRowType: RelDataType)
+ extends Project(cluster, traits, input, projects, projectionRowType)
+ with DataSetRel {
+
+ override def copy(traitSet: RelTraitSet, input: RelNode,
+ projects: util.List[RexNode], scanRawType: RelDataType): Project = {
+ new BatchTableProject(cluster, traitSet, input, projects,
projectionRowType)
+ }
+
+ override def computeSelfCost(planner: RelOptPlanner, mq:
RelMetadataQuery): RelOptCost = {
+ super.computeSelfCost(planner, mq).multiplyBy(0.8)
+ }
+
+ override def translateToPlan(
+ tableEnv: BatchTableEnvironment,
+ expectedType: Option[TypeInformation[Any]]): DataSet[Any] = {
+
+ val projectableSource =
getInput.getTable.unwrap(classOf[TableSourceTable])
+ .tableSource.asInstanceOf[ProjectableTableSource[_]]
+
+ val indexes =
projects.asScala.map(_.asInstanceOf[RexInputRef].getIndex).toArray
+ projectableSource.setProjection(indexes)
+
+ getInput.asInstanceOf[DataSetRel].translateToPlan(tableEnv)
--- End diff --
We should convert the output type to expected type if needed. You can learn
from how `BatchTableSourceScan` did.
> 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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