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https://issues.apache.org/jira/browse/HIVE-21075?focusedWorklogId=602273&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-602273
]
ASF GitHub Bot logged work on HIVE-21075:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 26/May/21 11:49
Start Date: 26/May/21 11:49
Worklog Time Spent: 10m
Work Description: pvary commented on a change in pull request #2323:
URL: https://github.com/apache/hive/pull/2323#discussion_r639647076
##########
File path:
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/ObjectStore.java
##########
@@ -5218,31 +5218,55 @@ private void
removeUnusedColumnDescriptor(MColumnDescriptor oldCD) {
return;
}
- boolean success = false;
Query query = null;
+ LOG.debug("execute removeUnusedColumnDescriptor");
+ DatabaseProduct dbProduct =
DatabaseProduct.determineDatabaseProduct(MetaStoreDirectSql.getProductName(pm),
conf);
- try {
- openTransaction();
- LOG.debug("execute removeUnusedColumnDescriptor");
+ /**
+ * In order to workaround oracle not supporting limit statement caused
performance issue, HIVE-9447 makes
+ * all the backend DB run select count(1) from SDS where SDS.CD_ID=? to
check if the specific CD_ID is
+ * referenced in SDS table before drop a partition. This select count(1)
statement does not scale well in
+ * Postgres, and there is no index for CD_ID column in SDS table.
+ * For a SDS table with with 1.5 million rows, select count(1) has average
700ms without index, while in
+ * 10-20ms with index. But the statement before
+ * HIVE-9447( SELECT * FROM "SDS" "A0" WHERE "A0"."CD_ID" = $1 limit 1)
uses less than 10ms .
+ */
- query = pm.newQuery("select count(1) from " +
- "org.apache.hadoop.hive.metastore.model.MStorageDescriptor where
(this.cd == inCD)");
+ if (dbProduct.isPOSTGRES()) {
+ query = pm.newQuery(MStorageDescriptor.class, "this.cd == inCD");
query.declareParameters("MColumnDescriptor inCD");
- long count = ((Long)query.execute(oldCD)).longValue();
-
+ List<MStorageDescriptor> referencedSDs =
listStorageDescriptorsWithCD(oldCD, query);
Review comment:
My guess is that mysql could also use limit, so we might want to test
the performance for different engines and use the appropriate query for them.
What do you think?
Thanks,
Peter
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Issue Time Tracking
-------------------
Worklog Id: (was: 602273)
Time Spent: 40m (was: 0.5h)
> Metastore: Drop partition performance downgrade with Postgres DB
> ----------------------------------------------------------------
>
> Key: HIVE-21075
> URL: https://issues.apache.org/jira/browse/HIVE-21075
> Project: Hive
> Issue Type: Bug
> Components: Metastore
> Affects Versions: 3.0.0
> Reporter: Yongzhi Chen
> Assignee: Oleksiy Sayankin
> Priority: Major
> Labels: pull-request-available
> Time Spent: 40m
> Remaining Estimate: 0h
>
> In order to workaround oracle not supporting limit statement caused
> performance issue, HIVE-9447 makes all the backend DB run select count(1)
> from SDS where SDS.CD_ID=? to check if the specific CD_ID is referenced in
> SDS table before drop a partition. This select count(1) statement does not
> scale well in Postgres, and there is no index for CD_ID column in SDS table.
> For a SDS table with with 1.5 million rows, select count(1) has average 700ms
> without index, while in 10-20ms with index. But the statement before
> HIVE-9447( SELECT * FROM "SDS" "A0" WHERE "A0"."CD_ID" = $1 limit 1) uses
> less than 10ms .
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