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https://issues.apache.org/jira/browse/TAJO-838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14260814#comment-14260814
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ASF GitHub Bot commented on TAJO-838:
-------------------------------------
Github user jihoonson commented on a diff in the pull request:
https://github.com/apache/tajo/pull/231#discussion_r22339002
--- Diff:
tajo-plan/src/main/java/org/apache/tajo/plan/rewrite/rules/AccessPathRewriter.java
---
@@ -0,0 +1,126 @@
+/*
+ * 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.tajo.plan.rewrite.rules;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.tajo.OverridableConf;
+import org.apache.tajo.SessionVars;
+import org.apache.tajo.plan.LogicalPlan;
+import org.apache.tajo.plan.PlanningException;
+import org.apache.tajo.plan.logical.IndexScanNode;
+import org.apache.tajo.plan.logical.LogicalNode;
+import org.apache.tajo.plan.logical.RelationNode;
+import org.apache.tajo.plan.logical.ScanNode;
+import org.apache.tajo.plan.rewrite.RewriteRule;
+import org.apache.tajo.plan.util.PlannerUtil;
+import org.apache.tajo.plan.visitor.BasicLogicalPlanVisitor;
+
+import java.util.List;
+import java.util.Stack;
+
+public class AccessPathRewriter implements RewriteRule {
+ private static final Log LOG =
LogFactory.getLog(AccessPathRewriter.class);
+
+ private static final String NAME = "Access Path Rewriter";
+ private Rewriter rewriter = null;
+
+ @Override
+ public String getName() {
+ return NAME;
+ }
+
+ @Override
+ public boolean isEligible(OverridableConf conf, LogicalPlan plan) {
+ if (conf.getBool(SessionVars.INDEX_ENABLED)) {
+ for (LogicalPlan.QueryBlock block : plan.getQueryBlocks()) {
+ for (RelationNode relationNode : block.getRelations()) {
+ List<AccessPathInfo> accessPathInfos =
block.getAccessInfos(relationNode);
+ // If there are any alternative access paths
+ if (accessPathInfos.size() > 1) {
+ for (AccessPathInfo accessPathInfo : accessPathInfos) {
+ if (accessPathInfo.getScanType() ==
AccessPathInfo.ScanTypeControl.INDEX_SCAN) {
+ rewriter = new Rewriter(conf);
--- End diff --
Thank you for the good suggestion.
I'll follow your suggestion.
> Improve query planner to utilize index
> --------------------------------------
>
> Key: TAJO-838
> URL: https://issues.apache.org/jira/browse/TAJO-838
> Project: Tajo
> Issue Type: Sub-task
> Components: planner/optimizer
> Reporter: Jihoon Son
> Assignee: Jihoon Son
> Priority: Minor
>
> Index can improve the query performance when the selectivity of query is high.
> Thus, query planner should decide whether index is used or not for a given
> query.
> The selectivity can be guessed using statistics.
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