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https://issues.apache.org/jira/browse/PHOENIX-3744?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16023269#comment-16023269
]
ASF GitHub Bot commented on PHOENIX-3744:
-----------------------------------------
Github user JamesRTaylor commented on a diff in the pull request:
https://github.com/apache/phoenix/pull/239#discussion_r118313368
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/iterate/TableMRParallelScanGrouper.java
---
@@ -0,0 +1,99 @@
+package org.apache.phoenix.iterate;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Lists;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.HRegionInfo;
+import org.apache.hadoop.hbase.HRegionLocation;
+import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos;
+import org.apache.hadoop.hbase.protobuf.generated.SnapshotProtos;
+import org.apache.hadoop.hbase.snapshot.SnapshotDescriptionUtils;
+import org.apache.hadoop.hbase.snapshot.SnapshotManifest;
+import org.apache.phoenix.compile.StatementContext;
+import org.apache.phoenix.mapreduce.util.PhoenixConfigurationUtil;
+
+import java.sql.SQLException;
+import java.util.List;
+
+public class TableMRParallelScanGrouper extends
MapReduceParallelScanGrouper {
+
+ private static TableMRParallelScanGrouper INSTANCE = null;
--- End diff --
Same comment here - how can this be a singleton?
> Support snapshot scanners for MR-based queries
> ----------------------------------------------
>
> Key: PHOENIX-3744
> URL: https://issues.apache.org/jira/browse/PHOENIX-3744
> Project: Phoenix
> Issue Type: Bug
> Reporter: James Taylor
> Assignee: Akshita Malhotra
> Attachments: PHOENIX-3744.patch
>
>
> HBase support scanning over snapshots, with a SnapshotScanner that accesses
> the region directly in HDFS. We should make sure that Phoenix can support
> that.
> Not sure how we'd want to decide when to run a query over a snapshot. Some
> ideas:
> - if there's an SCN set (i.e. the query is running at a point in time in the
> past)
> - if the memstore is empty
> - if the query is being run at a timestamp earlier than any memstore data
> - as a config option on the table
> - as a query hint
> - based on some kind of optimizer rule (i.e. based on estimated # of bytes
> that will be scanned)
> Phoenix typically runs a query at the timestamp at which it was compiled. Any
> data committed after this time should not be seen while a query is running.
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