godfreyhe commented on a change in pull request #13291:
URL: https://github.com/apache/flink/pull/13291#discussion_r525680552



##########
File path: 
flink-table/flink-table-planner-blink/src/main/scala/org/apache/flink/table/planner/plan/rules/logical/CorrelateSortToRankRule.scala
##########
@@ -0,0 +1,186 @@
+/*
+ * 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.planner.plan.rules.logical
+
+import org.apache.flink.table.planner.calcite.FlinkRelBuilder
+import org.apache.flink.table.runtime.operators.rank.{ConstantRankRange, 
RankType}
+
+import org.apache.calcite.plan.RelOptRule.{any, operand}
+import org.apache.calcite.plan.{RelOptRule, RelOptRuleCall}
+import org.apache.calcite.rel.RelCollations
+import org.apache.calcite.rel.`type`.RelDataType
+import org.apache.calcite.rel.core.{Aggregate, Correlate, Filter, JoinRelType, 
Project, Sort}
+import org.apache.calcite.rex.{RexCall, RexCorrelVariable, RexFieldAccess, 
RexInputRef, RexLiteral, RexNode}
+import org.apache.calcite.sql.SqlKind
+import org.apache.calcite.util.ImmutableBitSet
+
+import java.util
+
+import scala.collection.JavaConversions._
+
+/**
+ * Planner rule that rewrites sort correlation to a Rank.
+ * Typically, the following plan
+ *
+ * {{{
+ *   LogicalProject(state=[$0], name=[$1])
+ *   +- LogicalCorrelate(correlation=[$cor0], joinType=[inner], 
requiredColumns=[{0}])
+ *      :- LogicalAggregate(group=[{0}])
+ *      :  +- LogicalProject(state=[$1])
+ *      :     +- LogicalTableScan(table=[[default_catalog, default_database, 
cities]])
+ *      +- LogicalSort(sort0=[$1], dir0=[DESC-nulls-last], fetch=[3])
+ *         +- LogicalProject(name=[$0], pop=[$2])
+ *            +- LogicalFilter(condition=[=($1, $cor0.state)])
+ *               +- LogicalTableScan(table=[[default_catalog, 
default_database, cities]])
+ * }}}
+ *
+ * <p>would be transformed to
+ *
+ * {{{
+ *   LogicalProject(state=[$0], name=[$1])
+ *    +- LogicalProject(state=[$1], name=[$0], pop=[$2])
+ *       +- LogicalRank(rankType=[ROW_NUMBER], rankRange=[rankStart=1, 
rankEnd=3],
+ *            partitionBy=[$1], orderBy=[$2 DESC], select=[name=$0, state=$1, 
pop=$2])
+ *          +- LogicalTableScan(table=[[default_catalog, default_database, 
cities]])
+ * }}}
+ *
+ * <p>To match the Correlate, the LHS needs to be a global Aggregate on a 
scan, the RHS should
+ * be a Sort with an equal Filter predicate whose keys are same with the LHS 
grouping keys.
+ *
+ * <p>This rule can only be used in HepPlanner.
+ */
+class CorrelateSortToRankRule extends RelOptRule(
+  operand(classOf[Correlate],
+    operand(classOf[Aggregate],
+      operand(classOf[Project], any())),
+    operand(classOf[Sort],
+      operand(classOf[Project],
+        operand(classOf[Filter], any())))),
+  "CorrelateSortToRankRule") {
+
+  override def matches(call: RelOptRuleCall): Boolean = {
+    val correlate: Correlate = call.rel(0)
+    if (correlate.getJoinType != JoinRelType.INNER) {
+      return false
+    }
+    val agg: Aggregate = call.rel(1)
+    if (agg.getAggCallList.size() > 0
+      || agg.getGroupSets.size() > 1
+      || agg.getGroupSet.cardinality() != 1) {
+      // only one group field is supported now
+      return false
+    }
+    val aggInput: Project = call.rel(2)
+    if (!aggInput.isMapping) {
+      return false
+    }
+    val sort: Sort = call.rel(3)
+    if (sort.offset != null || sort.fetch == null) {
+      // 1. we can not describe the offset using rank
+      // 2. there is no need to transform to rank if no fetch limit
+      return false
+    }
+    val sortInput: Project = call.rel(4)
+    if (!sortInput.isMapping) {
+      return false
+    }
+    val filter: Filter = call.rel(5)
+    val condition = filter.getCondition
+    if (condition.getKind != SqlKind.EQUALS) {
+      return false
+    }
+    // only support one partition key
+    val (inputRef, fieldAccess) = resolveFilterCondition(condition)
+    if (inputRef == null) {
+      return false
+    }
+    val variable = fieldAccess.getReferenceExpr.asInstanceOf[RexCorrelVariable]
+    if (!variable.id.equals(correlate.getCorrelationId)) {
+      return false
+    }
+    aggInput.getInput.getDigest.equals(filter.getInput.getDigest)
+  }
+
+  /**
+   * Resolves the filter condition with specific pattern: input ref and field 
access.
+   *
+   * @param condition The join condition
+   * @return tuple of operands (RexInputRef, RexFieldAccess),
+   *         or null if the pattern does not match
+   */
+  def resolveFilterCondition(condition: RexNode): (RexInputRef, 
RexFieldAccess) = {
+    val condCall = condition.asInstanceOf[RexCall]
+    val operand0 = condCall.getOperands.get(0)
+    val operand1 = condCall.getOperands.get(1)
+    if (operand0.isA(SqlKind.INPUT_REF) && operand1.isA(SqlKind.FIELD_ACCESS)) 
{
+      (operand0.asInstanceOf[RexInputRef], 
operand1.asInstanceOf[RexFieldAccess])
+    } else if (operand0.isA(SqlKind.FIELD_ACCESS) && 
operand1.isA(SqlKind.INPUT_REF)) {
+      (operand1.asInstanceOf[RexInputRef], 
operand0.asInstanceOf[RexFieldAccess])
+    } else {
+      (null, null)
+    }
+  }
+
+  override def onMatch(call: RelOptRuleCall): Unit = {
+    val oriBuilder = call.builder()
+    val builder = FlinkRelBuilder.of(oriBuilder.getCluster, 
oriBuilder.getRelOptSchema)
+
+    val sort: Sort = call.rel(3)
+    val sortInput: Project = call.rel(4)
+    val filter: Filter = call.rel(5)
+
+    val partitionKey: ImmutableBitSet =
+      
ImmutableBitSet.of(resolveFilterCondition(filter.getCondition)._1.getIndex)
+
+    val baseType: RelDataType = sortInput.getInput().getRowType
+    val projects = new util.ArrayList[RexNode]()
+    partitionKey.asList().foreach(k => projects.add(RexInputRef.of(k, 
baseType)))
+    projects.addAll(sortInput.getProjects)
+
+    val oriCollation = sort.getCollation
+    val newFieldCollations = oriCollation.getFieldCollations.map { fc =>
+      val newFieldIdx = sortInput.getProjects.get(fc.getFieldIndex)
+        .asInstanceOf[RexInputRef].getIndex
+      fc.withFieldIndex(newFieldIdx)
+    }
+    val newCollation = RelCollations.of(newFieldCollations)
+
+    val newRel = builder
+      .push(filter.getInput()).asInstanceOf[FlinkRelBuilder]
+      .rank(
+        partitionKey,
+        newCollation,
+        RankType.ROW_NUMBER,
+        new ConstantRankRange(
+          1,
+          
sort.fetch.asInstanceOf[RexLiteral].getValueAs(classOf[java.lang.Long])),

Review comment:
       we can use `SortUtil.getLimitEnd`

##########
File path: 
flink-table/flink-table-planner-blink/src/main/scala/org/apache/flink/table/planner/plan/rules/logical/CorrelateSortToRankRule.scala
##########
@@ -0,0 +1,186 @@
+/*
+ * 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.planner.plan.rules.logical
+
+import org.apache.flink.table.planner.calcite.FlinkRelBuilder
+import org.apache.flink.table.runtime.operators.rank.{ConstantRankRange, 
RankType}
+
+import org.apache.calcite.plan.RelOptRule.{any, operand}
+import org.apache.calcite.plan.{RelOptRule, RelOptRuleCall}
+import org.apache.calcite.rel.RelCollations
+import org.apache.calcite.rel.`type`.RelDataType
+import org.apache.calcite.rel.core.{Aggregate, Correlate, Filter, JoinRelType, 
Project, Sort}
+import org.apache.calcite.rex.{RexCall, RexCorrelVariable, RexFieldAccess, 
RexInputRef, RexLiteral, RexNode}
+import org.apache.calcite.sql.SqlKind
+import org.apache.calcite.util.ImmutableBitSet
+
+import java.util
+
+import scala.collection.JavaConversions._
+
+/**
+ * Planner rule that rewrites sort correlation to a Rank.
+ * Typically, the following plan
+ *
+ * {{{
+ *   LogicalProject(state=[$0], name=[$1])
+ *   +- LogicalCorrelate(correlation=[$cor0], joinType=[inner], 
requiredColumns=[{0}])
+ *      :- LogicalAggregate(group=[{0}])
+ *      :  +- LogicalProject(state=[$1])
+ *      :     +- LogicalTableScan(table=[[default_catalog, default_database, 
cities]])
+ *      +- LogicalSort(sort0=[$1], dir0=[DESC-nulls-last], fetch=[3])
+ *         +- LogicalProject(name=[$0], pop=[$2])
+ *            +- LogicalFilter(condition=[=($1, $cor0.state)])
+ *               +- LogicalTableScan(table=[[default_catalog, 
default_database, cities]])
+ * }}}
+ *
+ * <p>would be transformed to
+ *
+ * {{{
+ *   LogicalProject(state=[$0], name=[$1])
+ *    +- LogicalProject(state=[$1], name=[$0], pop=[$2])
+ *       +- LogicalRank(rankType=[ROW_NUMBER], rankRange=[rankStart=1, 
rankEnd=3],
+ *            partitionBy=[$1], orderBy=[$2 DESC], select=[name=$0, state=$1, 
pop=$2])
+ *          +- LogicalTableScan(table=[[default_catalog, default_database, 
cities]])
+ * }}}
+ *
+ * <p>To match the Correlate, the LHS needs to be a global Aggregate on a 
scan, the RHS should
+ * be a Sort with an equal Filter predicate whose keys are same with the LHS 
grouping keys.
+ *
+ * <p>This rule can only be used in HepPlanner.
+ */
+class CorrelateSortToRankRule extends RelOptRule(
+  operand(classOf[Correlate],
+    operand(classOf[Aggregate],
+      operand(classOf[Project], any())),
+    operand(classOf[Sort],
+      operand(classOf[Project],
+        operand(classOf[Filter], any())))),
+  "CorrelateSortToRankRule") {
+
+  override def matches(call: RelOptRuleCall): Boolean = {
+    val correlate: Correlate = call.rel(0)
+    if (correlate.getJoinType != JoinRelType.INNER) {
+      return false
+    }
+    val agg: Aggregate = call.rel(1)
+    if (agg.getAggCallList.size() > 0
+      || agg.getGroupSets.size() > 1
+      || agg.getGroupSet.cardinality() != 1) {
+      // only one group field is supported now
+      return false
+    }
+    val aggInput: Project = call.rel(2)
+    if (!aggInput.isMapping) {
+      return false
+    }
+    val sort: Sort = call.rel(3)
+    if (sort.offset != null || sort.fetch == null) {
+      // 1. we can not describe the offset using rank
+      // 2. there is no need to transform to rank if no fetch limit
+      return false
+    }
+    val sortInput: Project = call.rel(4)
+    if (!sortInput.isMapping) {
+      return false
+    }
+    val filter: Filter = call.rel(5)
+    val condition = filter.getCondition
+    if (condition.getKind != SqlKind.EQUALS) {
+      return false
+    }
+    // only support one partition key
+    val (inputRef, fieldAccess) = resolveFilterCondition(condition)
+    if (inputRef == null) {
+      return false
+    }
+    val variable = fieldAccess.getReferenceExpr.asInstanceOf[RexCorrelVariable]
+    if (!variable.id.equals(correlate.getCorrelationId)) {
+      return false
+    }
+    aggInput.getInput.getDigest.equals(filter.getInput.getDigest)
+  }
+
+  /**
+   * Resolves the filter condition with specific pattern: input ref and field 
access.
+   *
+   * @param condition The join condition
+   * @return tuple of operands (RexInputRef, RexFieldAccess),
+   *         or null if the pattern does not match
+   */
+  def resolveFilterCondition(condition: RexNode): (RexInputRef, 
RexFieldAccess) = {
+    val condCall = condition.asInstanceOf[RexCall]
+    val operand0 = condCall.getOperands.get(0)
+    val operand1 = condCall.getOperands.get(1)
+    if (operand0.isA(SqlKind.INPUT_REF) && operand1.isA(SqlKind.FIELD_ACCESS)) 
{
+      (operand0.asInstanceOf[RexInputRef], 
operand1.asInstanceOf[RexFieldAccess])
+    } else if (operand0.isA(SqlKind.FIELD_ACCESS) && 
operand1.isA(SqlKind.INPUT_REF)) {
+      (operand1.asInstanceOf[RexInputRef], 
operand0.asInstanceOf[RexFieldAccess])
+    } else {
+      (null, null)
+    }
+  }
+
+  override def onMatch(call: RelOptRuleCall): Unit = {
+    val oriBuilder = call.builder()
+    val builder = FlinkRelBuilder.of(oriBuilder.getCluster, 
oriBuilder.getRelOptSchema)

Review comment:
       nit: one simply way is: using `FlinkRelFactories.FLINK_REL_BUILDER`  to 
construct `RelOptRule`, and then we can cast `call.builder()` as 
`FlinkRelBuilder`. one example is `FlinkSubQueryRemoveRule`

##########
File path: 
flink-table/flink-table-planner-blink/src/main/scala/org/apache/flink/table/planner/plan/rules/logical/CorrelateSortToRankRule.scala
##########
@@ -0,0 +1,186 @@
+/*
+ * 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.planner.plan.rules.logical
+
+import org.apache.flink.table.planner.calcite.FlinkRelBuilder
+import org.apache.flink.table.runtime.operators.rank.{ConstantRankRange, 
RankType}
+
+import org.apache.calcite.plan.RelOptRule.{any, operand}
+import org.apache.calcite.plan.{RelOptRule, RelOptRuleCall}
+import org.apache.calcite.rel.RelCollations
+import org.apache.calcite.rel.`type`.RelDataType
+import org.apache.calcite.rel.core.{Aggregate, Correlate, Filter, JoinRelType, 
Project, Sort}
+import org.apache.calcite.rex.{RexCall, RexCorrelVariable, RexFieldAccess, 
RexInputRef, RexLiteral, RexNode}
+import org.apache.calcite.sql.SqlKind
+import org.apache.calcite.util.ImmutableBitSet
+
+import java.util
+
+import scala.collection.JavaConversions._
+
+/**
+ * Planner rule that rewrites sort correlation to a Rank.
+ * Typically, the following plan
+ *
+ * {{{
+ *   LogicalProject(state=[$0], name=[$1])
+ *   +- LogicalCorrelate(correlation=[$cor0], joinType=[inner], 
requiredColumns=[{0}])
+ *      :- LogicalAggregate(group=[{0}])
+ *      :  +- LogicalProject(state=[$1])
+ *      :     +- LogicalTableScan(table=[[default_catalog, default_database, 
cities]])
+ *      +- LogicalSort(sort0=[$1], dir0=[DESC-nulls-last], fetch=[3])
+ *         +- LogicalProject(name=[$0], pop=[$2])
+ *            +- LogicalFilter(condition=[=($1, $cor0.state)])
+ *               +- LogicalTableScan(table=[[default_catalog, 
default_database, cities]])
+ * }}}
+ *
+ * <p>would be transformed to
+ *
+ * {{{
+ *   LogicalProject(state=[$0], name=[$1])
+ *    +- LogicalProject(state=[$1], name=[$0], pop=[$2])
+ *       +- LogicalRank(rankType=[ROW_NUMBER], rankRange=[rankStart=1, 
rankEnd=3],
+ *            partitionBy=[$1], orderBy=[$2 DESC], select=[name=$0, state=$1, 
pop=$2])
+ *          +- LogicalTableScan(table=[[default_catalog, default_database, 
cities]])
+ * }}}

Review comment:
       Thanks for the explanation

##########
File path: 
flink-table/flink-table-planner-blink/src/main/scala/org/apache/flink/table/planner/plan/rules/logical/CorrelateSortToRankRule.scala
##########
@@ -0,0 +1,186 @@
+/*
+ * 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.planner.plan.rules.logical
+
+import org.apache.flink.table.planner.calcite.FlinkRelBuilder
+import org.apache.flink.table.runtime.operators.rank.{ConstantRankRange, 
RankType}
+
+import org.apache.calcite.plan.RelOptRule.{any, operand}
+import org.apache.calcite.plan.{RelOptRule, RelOptRuleCall}
+import org.apache.calcite.rel.RelCollations
+import org.apache.calcite.rel.`type`.RelDataType
+import org.apache.calcite.rel.core.{Aggregate, Correlate, Filter, JoinRelType, 
Project, Sort}
+import org.apache.calcite.rex.{RexCall, RexCorrelVariable, RexFieldAccess, 
RexInputRef, RexLiteral, RexNode}
+import org.apache.calcite.sql.SqlKind
+import org.apache.calcite.util.ImmutableBitSet
+
+import java.util
+
+import scala.collection.JavaConversions._
+
+/**
+ * Planner rule that rewrites sort correlation to a Rank.
+ * Typically, the following plan
+ *
+ * {{{
+ *   LogicalProject(state=[$0], name=[$1])
+ *   +- LogicalCorrelate(correlation=[$cor0], joinType=[inner], 
requiredColumns=[{0}])
+ *      :- LogicalAggregate(group=[{0}])
+ *      :  +- LogicalProject(state=[$1])
+ *      :     +- LogicalTableScan(table=[[default_catalog, default_database, 
cities]])
+ *      +- LogicalSort(sort0=[$1], dir0=[DESC-nulls-last], fetch=[3])
+ *         +- LogicalProject(name=[$0], pop=[$2])
+ *            +- LogicalFilter(condition=[=($1, $cor0.state)])
+ *               +- LogicalTableScan(table=[[default_catalog, 
default_database, cities]])
+ * }}}
+ *
+ * <p>would be transformed to
+ *
+ * {{{
+ *   LogicalProject(state=[$0], name=[$1])
+ *    +- LogicalProject(state=[$1], name=[$0], pop=[$2])
+ *       +- LogicalRank(rankType=[ROW_NUMBER], rankRange=[rankStart=1, 
rankEnd=3],
+ *            partitionBy=[$1], orderBy=[$2 DESC], select=[name=$0, state=$1, 
pop=$2])
+ *          +- LogicalTableScan(table=[[default_catalog, default_database, 
cities]])
+ * }}}
+ *
+ * <p>To match the Correlate, the LHS needs to be a global Aggregate on a 
scan, the RHS should
+ * be a Sort with an equal Filter predicate whose keys are same with the LHS 
grouping keys.
+ *
+ * <p>This rule can only be used in HepPlanner.
+ */
+class CorrelateSortToRankRule extends RelOptRule(
+  operand(classOf[Correlate],
+    operand(classOf[Aggregate],
+      operand(classOf[Project], any())),
+    operand(classOf[Sort],
+      operand(classOf[Project],
+        operand(classOf[Filter], any())))),
+  "CorrelateSortToRankRule") {
+
+  override def matches(call: RelOptRuleCall): Boolean = {
+    val correlate: Correlate = call.rel(0)
+    if (correlate.getJoinType != JoinRelType.INNER) {
+      return false
+    }
+    val agg: Aggregate = call.rel(1)
+    if (agg.getAggCallList.size() > 0
+      || agg.getGroupSets.size() > 1
+      || agg.getGroupSet.cardinality() != 1) {

Review comment:
       > agg.getGroupSet.cardinality() != 1
   
   we should support multiple equal conditions, such as: `state = states.state 
and name = states.name`

##########
File path: 
flink-table/flink-table-planner-blink/src/main/scala/org/apache/flink/table/planner/plan/rules/logical/CorrelateSortToRankRule.scala
##########
@@ -0,0 +1,186 @@
+/*
+ * 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.planner.plan.rules.logical
+
+import org.apache.flink.table.planner.calcite.FlinkRelBuilder
+import org.apache.flink.table.runtime.operators.rank.{ConstantRankRange, 
RankType}
+
+import org.apache.calcite.plan.RelOptRule.{any, operand}
+import org.apache.calcite.plan.{RelOptRule, RelOptRuleCall}
+import org.apache.calcite.rel.RelCollations
+import org.apache.calcite.rel.`type`.RelDataType
+import org.apache.calcite.rel.core.{Aggregate, Correlate, Filter, JoinRelType, 
Project, Sort}
+import org.apache.calcite.rex.{RexCall, RexCorrelVariable, RexFieldAccess, 
RexInputRef, RexLiteral, RexNode}
+import org.apache.calcite.sql.SqlKind
+import org.apache.calcite.util.ImmutableBitSet
+
+import java.util
+
+import scala.collection.JavaConversions._
+
+/**
+ * Planner rule that rewrites sort correlation to a Rank.
+ * Typically, the following plan
+ *
+ * {{{
+ *   LogicalProject(state=[$0], name=[$1])
+ *   +- LogicalCorrelate(correlation=[$cor0], joinType=[inner], 
requiredColumns=[{0}])
+ *      :- LogicalAggregate(group=[{0}])
+ *      :  +- LogicalProject(state=[$1])
+ *      :     +- LogicalTableScan(table=[[default_catalog, default_database, 
cities]])
+ *      +- LogicalSort(sort0=[$1], dir0=[DESC-nulls-last], fetch=[3])
+ *         +- LogicalProject(name=[$0], pop=[$2])
+ *            +- LogicalFilter(condition=[=($1, $cor0.state)])
+ *               +- LogicalTableScan(table=[[default_catalog, 
default_database, cities]])
+ * }}}
+ *
+ * <p>would be transformed to
+ *
+ * {{{
+ *   LogicalProject(state=[$0], name=[$1])
+ *    +- LogicalProject(state=[$1], name=[$0], pop=[$2])
+ *       +- LogicalRank(rankType=[ROW_NUMBER], rankRange=[rankStart=1, 
rankEnd=3],
+ *            partitionBy=[$1], orderBy=[$2 DESC], select=[name=$0, state=$1, 
pop=$2])
+ *          +- LogicalTableScan(table=[[default_catalog, default_database, 
cities]])
+ * }}}
+ *
+ * <p>To match the Correlate, the LHS needs to be a global Aggregate on a 
scan, the RHS should
+ * be a Sort with an equal Filter predicate whose keys are same with the LHS 
grouping keys.
+ *
+ * <p>This rule can only be used in HepPlanner.
+ */
+class CorrelateSortToRankRule extends RelOptRule(
+  operand(classOf[Correlate],
+    operand(classOf[Aggregate],
+      operand(classOf[Project], any())),
+    operand(classOf[Sort],
+      operand(classOf[Project],
+        operand(classOf[Filter], any())))),
+  "CorrelateSortToRankRule") {
+
+  override def matches(call: RelOptRuleCall): Boolean = {
+    val correlate: Correlate = call.rel(0)
+    if (correlate.getJoinType != JoinRelType.INNER) {
+      return false
+    }
+    val agg: Aggregate = call.rel(1)
+    if (agg.getAggCallList.size() > 0
+      || agg.getGroupSets.size() > 1
+      || agg.getGroupSet.cardinality() != 1) {
+      // only one group field is supported now
+      return false
+    }
+    val aggInput: Project = call.rel(2)
+    if (!aggInput.isMapping) {
+      return false
+    }
+    val sort: Sort = call.rel(3)
+    if (sort.offset != null || sort.fetch == null) {
+      // 1. we can not describe the offset using rank
+      // 2. there is no need to transform to rank if no fetch limit
+      return false
+    }
+    val sortInput: Project = call.rel(4)
+    if (!sortInput.isMapping) {
+      return false
+    }
+    val filter: Filter = call.rel(5)
+    val condition = filter.getCondition
+    if (condition.getKind != SqlKind.EQUALS) {
+      return false
+    }
+    // only support one partition key
+    val (inputRef, fieldAccess) = resolveFilterCondition(condition)
+    if (inputRef == null) {
+      return false
+    }
+    val variable = fieldAccess.getReferenceExpr.asInstanceOf[RexCorrelVariable]
+    if (!variable.id.equals(correlate.getCorrelationId)) {
+      return false
+    }
+    aggInput.getInput.getDigest.equals(filter.getInput.getDigest)
+  }
+
+  /**
+   * Resolves the filter condition with specific pattern: input ref and field 
access.
+   *
+   * @param condition The join condition
+   * @return tuple of operands (RexInputRef, RexFieldAccess),
+   *         or null if the pattern does not match
+   */
+  def resolveFilterCondition(condition: RexNode): (RexInputRef, 
RexFieldAccess) = {
+    val condCall = condition.asInstanceOf[RexCall]
+    val operand0 = condCall.getOperands.get(0)
+    val operand1 = condCall.getOperands.get(1)
+    if (operand0.isA(SqlKind.INPUT_REF) && operand1.isA(SqlKind.FIELD_ACCESS)) 
{
+      (operand0.asInstanceOf[RexInputRef], 
operand1.asInstanceOf[RexFieldAccess])
+    } else if (operand0.isA(SqlKind.FIELD_ACCESS) && 
operand1.isA(SqlKind.INPUT_REF)) {
+      (operand1.asInstanceOf[RexInputRef], 
operand0.asInstanceOf[RexFieldAccess])
+    } else {
+      (null, null)
+    }
+  }
+
+  override def onMatch(call: RelOptRuleCall): Unit = {
+    val oriBuilder = call.builder()
+    val builder = FlinkRelBuilder.of(oriBuilder.getCluster, 
oriBuilder.getRelOptSchema)
+
+    val sort: Sort = call.rel(3)
+    val sortInput: Project = call.rel(4)
+    val filter: Filter = call.rel(5)
+
+    val partitionKey: ImmutableBitSet =
+      
ImmutableBitSet.of(resolveFilterCondition(filter.getCondition)._1.getIndex)
+
+    val baseType: RelDataType = sortInput.getInput().getRowType
+    val projects = new util.ArrayList[RexNode]()
+    partitionKey.asList().foreach(k => projects.add(RexInputRef.of(k, 
baseType)))
+    projects.addAll(sortInput.getProjects)
+
+    val oriCollation = sort.getCollation
+    val newFieldCollations = oriCollation.getFieldCollations.map { fc =>
+      val newFieldIdx = sortInput.getProjects.get(fc.getFieldIndex)
+        .asInstanceOf[RexInputRef].getIndex
+      fc.withFieldIndex(newFieldIdx)
+    }
+    val newCollation = RelCollations.of(newFieldCollations)
+
+    val newRel = builder
+      .push(filter.getInput()).asInstanceOf[FlinkRelBuilder]
+      .rank(
+        partitionKey,
+        newCollation,
+        RankType.ROW_NUMBER,
+        new ConstantRankRange(
+          1,
+          
sort.fetch.asInstanceOf[RexLiteral].getValueAs(classOf[java.lang.Long])),
+        null,
+        outputRankNumber = false)
+      .project(projects)
+      .build()
+
+    call.transformTo(newRel)
+  }
+}
+
+object CorrelateSortToRankRule {
+  val INSTANCE = new CorrelateSortToRankRule
+}
+
+

Review comment:
       nit: redundant line




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