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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3849) Add FilterableTableSource interface and translation rule
Date Wed, 15 Mar 2017 02:32:41 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15925442#comment-15925442
] 

ASF GitHub Bot commented on FLINK-3849:
---------------------------------------

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

    https://github.com/apache/flink/pull/3520#discussion_r106072764
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/util/RexProgramExtractor.scala
---
    @@ -0,0 +1,184 @@
    +/*
    + * 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.table.plan.util
    +
    +import org.apache.calcite.plan.RelOptUtil
    +import org.apache.calcite.rex._
    +import org.apache.calcite.sql.{SqlFunction, SqlPostfixOperator}
    +import org.apache.flink.table.api.TableException
    +import org.apache.flink.table.calcite.FlinkTypeFactory
    +import org.apache.flink.table.expressions.{Expression, Literal, ResolvedFieldReference}
    +import org.apache.flink.table.validate.FunctionCatalog
    +import org.apache.flink.util.Preconditions
    +
    +import scala.collection.JavaConversions._
    +import scala.collection.JavaConverters._
    +import scala.collection.mutable
    +import scala.util.{Failure, Success, Try}
    +
    +object RexProgramExtractor {
    +
    +  /**
    +    * Extracts the indices of input fields which accessed by the RexProgram.
    +    *
    +    * @param rexProgram The RexProgram to analyze
    +    * @return The indices of accessed input fields
    +    */
    +  def extractRefInputFields(rexProgram: RexProgram): Array[Int] = {
    +    val visitor = new InputRefVisitor
    +
    +    // extract referenced input fields from projections
    +    rexProgram.getProjectList.foreach(
    +      exp => rexProgram.expandLocalRef(exp).accept(visitor))
    +
    +    // extract referenced input fields from condition
    +    val condition = rexProgram.getCondition
    +    if (condition != null) {
    +      rexProgram.expandLocalRef(condition).accept(visitor)
    +    }
    +
    +    visitor.getFields
    +  }
    +
    +  /**
    +    * Extract condition from RexProgram and convert it into independent CNF expressions.
    +    *
    +    * @param rexProgram The RexProgram to analyze
    +    * @return converted expressions as well as RexNodes which cannot be translated
    +    */
    +  def extractConjunctiveConditions(
    +      rexProgram: RexProgram,
    +      rexBuilder: RexBuilder,
    +      catalog: FunctionCatalog): (Array[Expression], Array[RexNode]) = {
    +
    +    rexProgram.getCondition match {
    +      case condition: RexLocalRef =>
    +        val expanded = rexProgram.expandLocalRef(condition)
    +        // converts the expanded expression to conjunctive normal form,
    +        // like "(a AND b) OR c" will be converted to "(a OR c) AND (b OR c)"
    +        val cnf = RexUtil.toCnf(rexBuilder, expanded)
    +        // converts the cnf condition to a list of AND conditions
    +        val conjunctions = RelOptUtil.conjunctions(cnf)
    +
    +        val convertedExpressions = new mutable.ArrayBuffer[Expression]
    +        val unconvertedRexNodes = new mutable.ArrayBuffer[RexNode]
    +        val inputNames = rexProgram.getInputRowType.getFieldNames.asScala.toArray
    +        val converter = new ConvertToExpression(inputNames, catalog)
    +
    +        conjunctions.asScala.foreach(rex => {
    +          rex.accept(converter) match {
    +            case Some(expression) => convertedExpressions += expression
    +            case None => unconvertedRexNodes += rex
    +          }
    +        })
    +        (convertedExpressions.toArray, unconvertedRexNodes.toArray)
    +
    +      case _ => (Array.empty, Array.empty)
    +    }
    +  }
    +}
    +
    +/**
    +  * An RexVisitor to extract all referenced input fields
    +  */
    +class InputRefVisitor extends RexVisitorImpl[Unit](true) {
    +
    +  private var fields = mutable.LinkedHashSet[Int]()
    --- End diff --
    
    `var` → `val`


> Add FilterableTableSource interface and translation rule
> --------------------------------------------------------
>
>                 Key: FLINK-3849
>                 URL: https://issues.apache.org/jira/browse/FLINK-3849
>             Project: Flink
>          Issue Type: New Feature
>          Components: Table API & SQL
>            Reporter: Fabian Hueske
>            Assignee: Kurt Young
>
> Add a {{FilterableTableSource}} interface for {{TableSource}} implementations which support
filter push-down.
> The interface could look as follows
> {code}
> def trait FilterableTableSource {
>   // returns unsupported predicate expression
>   def setPredicate(predicate: Expression): Expression
> }
> {code}
> In addition we need Calcite rules to push a predicate (or parts of it) into a TableScan
that refers to a {{FilterableTableSource}}. We might need to tweak the cost model as well
to push the optimizer in the right direction.



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