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https://issues.apache.org/jira/browse/PHOENIX-6141?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17736568#comment-17736568
]
ASF GitHub Bot commented on PHOENIX-6141:
-----------------------------------------
tkhurana commented on code in PR #1575:
URL: https://github.com/apache/phoenix/pull/1575#discussion_r1240087262
##########
phoenix-core/src/main/java/org/apache/phoenix/coprocessor/tasks/ChildLinkScanTask.java:
##########
@@ -0,0 +1,58 @@
+package org.apache.phoenix.coprocessor.tasks;
+
+import org.apache.phoenix.coprocessor.TaskRegionObserver;
+import org.apache.phoenix.jdbc.PhoenixConnection;
+import org.apache.phoenix.schema.task.Task;
+import
org.apache.phoenix.thirdparty.com.google.common.annotations.VisibleForTesting;
+import org.apache.phoenix.util.QueryUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.sql.ResultSet;
+
+/*
+Task to run a simple select * query on SYSTEM.CHILD_LINK table
+to trigger read repair and verify any unverified rows.
+ */
+public class ChildLinkScanTask extends BaseTask {
+
+ private static final Logger LOGGER =
LoggerFactory.getLogger(ChildLinkScanTask.class);
+ private static final String CHILD_LINK_QUERY = "SELECT COUNT(*) FROM
SYSTEM.CHILD_LINK";
+ private static boolean isDisabled = false;
+
+ @VisibleForTesting
+ public static void disableChildLinkScanTask(boolean disable) {
+ isDisabled = disable;
+ }
+
+ @Override
+ public TaskRegionObserver.TaskResult run(Task.TaskRecord taskRecord) {
+
+ if (isDisabled) {
+ return new
TaskRegionObserver.TaskResult(TaskRegionObserver.TaskResultCode.FAIL,
+ "ChildLinkScan task is disabled.");
+ }
+
+ int count = 0;
+ try {
+ PhoenixConnection pconn = QueryUtil.getConnectionOnServer(
+ env.getConfiguration()).unwrap(PhoenixConnection.class);
+ ResultSet rs =
pconn.createStatement().executeQuery(CHILD_LINK_QUERY);
+ rs.next();
Review Comment:
You should check the return value of rs.next()
> Ensure consistency between SYSTEM.CATALOG and SYSTEM.CHILD_LINK
> ---------------------------------------------------------------
>
> Key: PHOENIX-6141
> URL: https://issues.apache.org/jira/browse/PHOENIX-6141
> Project: Phoenix
> Issue Type: Improvement
> Affects Versions: 5.0.0, 4.15.0
> Reporter: Chinmay Kulkarni
> Assignee: Palash Chauhan
> Priority: Blocker
> Fix For: 5.2.0, 5.1.4
>
>
> Before 4.15, "CREATE/DROP VIEW" was an atomic operation since we were issuing
> batch mutations on just the 1 SYSTEM.CATALOG region. In 4.15 we introduced
> SYSTEM.CHILD_LINK to store the parent->child links and so a CREATE VIEW is no
> longer atomic since it consists of 2 separate RPCs (1 to SYSTEM.CHILD_LINK
> to add the linking row and another to SYSTEM.CATALOG to write metadata for
> the new view).
> If the second RPC i.e. the RPC to write metadata to SYSTEM.CATALOG fails
> after the 1st RPC has already gone through, there will be an inconsistency
> between both metadata tables. We will see orphan parent->child linking rows
> in SYSTEM.CHILD_LINK in this case. This can cause the following issues:
> # ALTER TABLE calls on the base table will fail
> # DROP TABLE without CASCADE will fail
> # The upgrade path has calls like UpgradeUtil.upgradeTable() which will fail
> # Any metadata consistency checks can be thrown off
> # Unnecessary extra storage of orphan links
> The first 3 issues happen because we wrongly deduce that a base table has
> child views due to the orphan linking rows.
> This Jira aims at trying to come up with a way to make mutations among
> SYSTEM.CATALOG and SYSTEM.CHILD_LINK an atomic transaction. We can use a
> 2-phase commit approach like in global indexing or also potentially explore
> using a transaction manager.
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