Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3166#discussion_r102491504
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/util/RexProgramExpressionExtractor.scala
---
@@ -0,0 +1,163 @@
+/*
+ * 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.rel.core.TableScan
+import org.apache.calcite.rex._
+import org.apache.calcite.plan.RelOptUtil
+import org.apache.calcite.rel.`type`.RelDataType
+import org.apache.calcite.tools.RelBuilder
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.table.calcite.{FlinkTypeFactory, RexNodeWrapper}
+import org.apache.flink.table.expressions._
+import org.apache.flink.table.validate.FunctionCatalog
+
+import scala.collection.JavaConversions._
+import scala.collection.JavaConverters._
+import scala.collection.immutable.IndexedSeq
+
+object RexProgramExpressionExtractor {
+
+ /**
+ * converts a rexProgram condition into independent CNF expressions
+ *
+ * @param rexProgram The RexProgram to analyze
+ * @return converted expression
+ */
+ private[flink] def extractPredicateExpressions(
+ rexProgram: RexProgram,
+ rexBuilder: RexBuilder,
+ catalog: FunctionCatalog): Array[Expression] = {
+
+ val fieldNames = getInputsWithNames(rexProgram)
+
+ val condition = rexProgram.getCondition
+ if (condition == null) {
+ return Array.empty
+ }
+ val call = rexProgram.expandLocalRef(condition)
+ val cnf = RexUtil.toCnf(rexBuilder, call)
+ val conjunctions = RelOptUtil.conjunctions(cnf)
+ val expressions = conjunctions.asScala.map(
+ RexNodeWrapper.wrap(_, catalog).toExpression(fieldNames)
+ )
+ expressions.toArray
+ }
+
+ /**
+ * verify should we apply remained expressions on
+ *
+ * @param original initial expression
+ * @param remained remained part of original expression
+ * @return whether or not to decouple parts of the origin expression
+ */
+ private[flink] def verifyExpressions(
+ original: Array[Expression],
+ remained: Array[Expression]): Boolean =
+ remained forall (original contains)
+
+ /**
+ * Generates a new RexProgram based on new expression.
+ *
+ * @param rexProgram original RexProgram
+ * @param scan input source
+ * @param predicate filter condition (fields must be resolved)
+ * @param relBuilder builder for converting expression to Rex
+ */
+ private[flink] def rewriteRexProgram(
+ rexProgram: RexProgram,
+ scan: TableScan,
+ predicate: Array[Expression])(implicit relBuilder: RelBuilder):
RexProgram = {
+
+ relBuilder.push(scan)
+
+ val inType = rexProgram.getInputRowType
+ val resolvedExps = resolveFields(predicate, inType)
+ val projs = rexProgram.getProjectList.map(rexProgram.expandLocalRef)
+
+ RexProgram.create(
+ inType,
+ projs,
+ conjunct(resolvedExps).get.toRexNode,
+ rexProgram.getOutputRowType,
+ relBuilder.getRexBuilder)
+ }
+
+ private[flink] def getFilterExpressionAsRexNode(
+ inputTpe: RelDataType,
+ scan: TableScan,
+ exps: Array[Expression])(implicit relBuilder: RelBuilder): RexNode =
{
+ relBuilder.push(scan)
+ val resolvedExps = resolveFields(exps, inputTpe)
+ val fullExp = conjunct(resolvedExps)
+ if (fullExp.isDefined) {
+ fullExp.get.toRexNode
+ } else {
+ null
+ }
+ }
+
+ private def resolveFields(
+ predicate: Array[Expression],
+ inType: RelDataType): Array[Expression] = {
+ val fieldTypes: Map[String, TypeInformation[_]] = inType.getFieldList
+ .map(f => f.getName -> FlinkTypeFactory.toTypeInfo(f.getType))
+ .toMap
+ val rule: PartialFunction[Expression, Expression] = {
+ case u@UnresolvedFieldReference(name) =>
+ ResolvedFieldReference(name, fieldTypes(name))
+ }
+ predicate.map(_.postOrderTransform(rule))
+ }
+
+ private def conjunct(exps: Array[Expression]): Option[Expression] = {
--- End diff --
This method could be more more concise if we use `reduce` instead of
recursive pair-wise conjunctions, i.e.,
`AND(a, AND(b, AND (c, d)))` instead of `AND(AND(a, b), AND(c, d))`
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