JingsongLi commented on a change in pull request #9876: [FLINK-14134][table] Introduce LimitableTableSource for optimizing limit URL: https://github.com/apache/flink/pull/9876#discussion_r338396708
########## File path: flink-table/flink-table-planner-blink/src/main/scala/org/apache/flink/table/planner/plan/rules/logical/PushLimitIntoTableSourceScanRule.scala ########## @@ -0,0 +1,105 @@ +/* + * 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.plan.stats.TableStats +import org.apache.flink.table.planner.plan.nodes.logical.{FlinkLogicalSort, FlinkLogicalTableSourceScan} +import org.apache.flink.table.planner.plan.schema.{FlinkRelOptTable, TableSourceTable} +import org.apache.flink.table.planner.plan.stats.FlinkStatistic +import org.apache.flink.table.sources.LimitableTableSource + +import org.apache.calcite.plan.RelOptRule.{none, operand} +import org.apache.calcite.plan.{RelOptRule, RelOptRuleCall} +import org.apache.calcite.rel.core.{Sort, TableScan} +import org.apache.calcite.rex.RexLiteral +import org.apache.calcite.tools.RelBuilder + +/** + * Planner rule that tries to push limit into a [[LimitableTableSource]]. + * The original limit will still be retained. + */ +class PushLimitIntoTableSourceScanRule extends RelOptRule( + operand(classOf[FlinkLogicalSort], + operand(classOf[FlinkLogicalTableSourceScan], none)), "PushLimitIntoTableSourceScanRule") { + + override def matches(call: RelOptRuleCall): Boolean = { + val sort = call.rel(0).asInstanceOf[Sort] + val fetch = sort.fetch + val offset = sort.offset + // Only push-down the limit whose offset equal zero. Because it is difficult to source based + // push to handle the non-zero offset. And the non-zero offset usually appear together with + // sort. + val onlyLimit = sort.getCollation.getFieldCollations.isEmpty && + (offset == null || RexLiteral.intValue(offset) == 0) && + fetch != null + + var supportPushDown = false + if (onlyLimit) { + supportPushDown = call.rel(1).asInstanceOf[TableScan] + .getTable.unwrap(classOf[TableSourceTable[_]]) match { + case table: TableSourceTable[_] => + table.tableSource match { + case source: LimitableTableSource[_] => !source.isLimitPushedDown Review comment: Do you have a better idea? I think it's a simple judgment. It doesn't need to be cleaner. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
