[
https://issues.apache.org/jira/browse/HIVE-21075?focusedWorklogId=602828&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-602828
]
ASF GitHub Bot logged work on HIVE-21075:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 27/May/21 09:27
Start Date: 27/May/21 09:27
Worklog Time Spent: 10m
Work Description: pvary commented on a change in pull request #2323:
URL: https://github.com/apache/hive/pull/2323#discussion_r640453187
##########
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:
We the goal is with `openTransaction()` and the `commitTransaction()`
to allow embedding method calls and keeping / enforcing transactions around
them.
So if `listStorageDescriptorsWithCD()` is never called from
non-transactional methods then adding `openTransaction()` and
`commitTransaction()` is redundant. We wrap the calls into transactions if want
to make sure to run the code in a transaction whenever it is called.
Wrapping a read only query in a transaction does not really make sense. It
is either good without a transaction, or it requires a transaction because of
the wider context, and then it is the callers responsibility to handle the
transaction open/close. **So you are right, we do not need the transaction for
the select itself.**
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
Issue Time Tracking
-------------------
Worklog Id: (was: 602828)
Time Spent: 1h 40m (was: 1.5h)
> 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: 1h 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 .
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
