[
https://issues.apache.org/jira/browse/HIVE-21075?focusedWorklogId=602804&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-602804
]
ASF GitHub Bot logged work on HIVE-21075:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 27/May/21 08:40
Start Date: 27/May/21 08:40
Worklog Time Spent: 10m
Work Description: oleksiy-sayankin commented on a change in pull request
#2323:
URL: https://github.com/apache/hive/pull/2323#discussion_r640409691
##########
File path:
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/ObjectStore.java
##########
@@ -5269,6 +5293,32 @@ private void preDropStorageDescriptor(MStorageDescriptor
msd) {
removeUnusedColumnDescriptor(mcd);
}
+ /**
+ * Get a list of storage descriptors that reference a particular Column
Descriptor
+ * @param oldCD the column descriptor to get storage descriptors for
+ * @return a list of storage descriptors
+ */
+ private List<MStorageDescriptor>
listStorageDescriptorsWithCD(MColumnDescriptor oldCD, Query query) {
+ boolean success = false;
+ List<MStorageDescriptor> sds = null;
+ try {
+ openTransaction();
Review comment:
And what do you think of method _listStorageDescriptorsWithCD_? It also
uses open/commit transaction and If I implement open/commit transaction in
_removeUnusedColumnDescriptor()_ it seems to be like this
removeUnusedColumnDescriptor(){
openTransaction()
if (isPostgres()) {
listStorageDescriptorsWithCD {
openTransaction() <--- do we need this?
1. SELECT * FROM "SDS" "A0" WHERE "A0"."CD_ID" = $1 limit 1)
commitTransaction() <--- do we need this?
}
} else {
2. select count(1) from
org.apache.hadoop.hive.metastore.model.MStorageDescriptor where (this.cd ==
inCD)
}
3. pm.deletePersistentAll(mConstraintsList);
4. pm.deletePersistent(oldCD);
commitTransaction()
}
so open/commit transaction inside _listStorageDescriptorsWithCD()_ is
redundant. Agree?
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Issue Time Tracking
-------------------
Worklog Id: (was: 602804)
Time Spent: 1.5h (was: 1h 20m)
> 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: 1.5h
> 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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