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Subject [GitHub] [flink] godfreyhe commented on a change in pull request #8520: [FLINK-12600] [table-planner-blink] Introduce planner rules to do deterministic rewriting on RelNode
Date Tue, 28 May 2019 06:44:42 GMT
godfreyhe commented on a change in pull request #8520: [FLINK-12600] [table-planner-blink]
Introduce planner rules to do deterministic rewriting on RelNode
URL: https://github.com/apache/flink/pull/8520#discussion_r287949754
 
 

 ##########
 File path: flink-table/flink-table-planner-blink/src/main/scala/org/apache/flink/table/plan/rules/logical/FlinkRewriteSubQueryRule.scala
 ##########
 @@ -0,0 +1,154 @@
+/*
+ * 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.rules.logical
+
+import org.apache.calcite.plan.RelOptRule.{any, operandJ}
+import org.apache.calcite.plan.{RelOptRule, RelOptRuleCall, RelOptRuleOperand}
+import org.apache.calcite.rel.RelNode
+import org.apache.calcite.rel.core.{Aggregate, Filter, RelFactories}
+import org.apache.calcite.rex.{RexShuttle, _}
+import org.apache.calcite.sql.SqlKind
+import org.apache.calcite.sql.`type`.SqlTypeFamily
+import org.apache.calcite.sql.fun.SqlCountAggFunction
+import org.apache.calcite.tools.RelBuilderFactory
+
+import scala.collection.JavaConversions._
+
+/**
+  * Planner rule that rewrites filter condition like:
+  * `(select count(*) from T) > 0` to `exists(select * from T)`,
 
 Review comment:
   the original query is a scalar query, which will be converted to aggregate + join by Calcite
rules.
   for example, full sql like `SELECT * FROM x WHERE (SELECT COUNT(*) FROM y WHERE d >
10) > 0` ,the logical plan converted by Calcite rules is:
   
   
   LogicalProject(a=[$0], b=[$1], c=[$2])
   +- LogicalProject(a=[$0], b=[$1], c=[$2])
      +- LogicalFilter(condition=[>($3, 0)])
         +- LogicalJoin(condition=[true], joinType=[left])
            :- LogicalTableScan(table=[[x]])
            +- LogicalAggregate(group=[{}], EXPR$0=[COUNT()])
               +- LogicalProject($f0=[0])
                  +- LogicalFilter(condition=[>($0, 10)])
                     +- LogicalTableScan(table=[[y]])
   
   

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