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https://issues.apache.org/jira/browse/FLINK-3849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15925441#comment-15925441
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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_r106073030
--- 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]()
+
+ def getFields: Array[Int] = fields.toArray
+
+ override def visitInputRef(inputRef: RexInputRef): Unit =
+ fields += inputRef.getIndex
+
+ override def visitCall(call: RexCall): Unit =
+ call.operands.foreach(operand => operand.accept(this))
+}
+
+/**
+ * An RexVisitor to convert RexNode to Expression.
+ *
+ * @param inputNames The input names of the relation node
+ * @param functionCatalog The function catalog
+ */
+class ConvertToExpression(
+ inputNames: Array[String],
+ functionCatalog: FunctionCatalog)
+ extends RexVisitor[Option[Expression]] {
+
+ override def visitInputRef(inputRef: RexInputRef): Option[Expression] = {
+ Preconditions.checkArgument(inputRef.getIndex < inputNames.length)
+ Option(ResolvedFieldReference(
+ inputNames(inputRef.getIndex),
+ FlinkTypeFactory.toTypeInfo(inputRef.getType)
+ ))
+ }
+
+ override def visitLocalRef(localRef: RexLocalRef): Option[Expression] = {
+ throw new TableException("Bug: RefLocalRef should have been expanded")
+ }
+
+ override def visitLiteral(literal: RexLiteral): Option[Expression] = {
+ Option(Literal(literal.getValue,
FlinkTypeFactory.toTypeInfo(literal.getType)))
+ }
+
+ override def visitCall(call: RexCall): Option[Expression] = {
+ val operands = call.getOperands.map(
+ operand => operand.accept(this).orNull
+ )
+
+ // return null if we cannot translate all the operands of the call
+ if (operands.contains(null)) {
+ Option.empty
--- End diff --
I think, `None` is more brief than `Option.empty`
> 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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