[
https://issues.apache.org/jira/browse/HIVE-25779?focusedWorklogId=787484&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-787484
]
ASF GitHub Bot logged work on HIVE-25779:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 04/Jul/22 04:54
Start Date: 04/Jul/22 04:54
Worklog Time Spent: 10m
Work Description: dengzhhu653 commented on code in PR #3221:
URL: https://github.com/apache/hive/pull/3221#discussion_r912625118
##########
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/ObjectStore.java:
##########
@@ -4959,13 +4993,20 @@ public Table alterTable(String catName, String dbname,
String name, Table newTab
oldt.setOwnerType(newt.getOwnerType());
// Fully copy over the contents of the new SD into the old SD,
// so we don't create an extra SD in the metastore db that has no
references.
- MColumnDescriptor oldCD = null;
MStorageDescriptor oldSD = oldt.getSd();
+ MColumnDescriptor oldCD = null;
+ MSerDeInfo oldSerDeInfo = null;
if (oldSD != null) {
oldCD = oldSD.getCD();
+ oldSerDeInfo = oldSD.getSerDeInfo();
}
copyMSD(newt.getSd(), oldt.getSd());
- removeUnusedColumnDescriptor(oldCD);
+ if (oldSD != null && oldSD.getCD() != oldCD) {
+ removeUnusedColumnDescriptor(oldCD);
+ }
+ if (oldSD != null && oldSD.getSerDeInfo() != oldSerDeInfo) {
Review Comment:
it seems that oldSD.getSerDeInfo() always be oldSerDeInfo
Issue Time Tracking
-------------------
Worklog Id: (was: 787484)
Time Spent: 1h 10m (was: 1h)
> Deduplicate SerDe Info
> ----------------------
>
> Key: HIVE-25779
> URL: https://issues.apache.org/jira/browse/HIVE-25779
> Project: Hive
> Issue Type: New Feature
> Components: Standalone Metastore
> Reporter: Yu-Wen Lai
> Assignee: Yu-Wen Lai
> Priority: Major
> Labels: pull-request-available
> Time Spent: 1h 10m
> Remaining Estimate: 0h
>
> The proposal is that we can reuse serde info as how we reuse column
> descriptors. (HIVE-2246)
> Currently, we store the metadata for partitions as PARTITIONS (N partitions)
> -> SDS (N locations) -> SERDES (N entries). However, all the SERDES for the
> partitions in a table are the same if we don't explicitly specify it. That
> is, each storage descriptor has a associated and exclusive serde info, but
> the partitions' serde infos are mostly just the same as the table's. By
> reusing the serde info, we can save some database storage and enhance the
> query performance from HMS to the backend database.
> For backward compatibility, we also need to introduce a config for this
> feature because there will be issues if HMS old instance and HMS new instance
> with this feature are running together. With this feature, we will need to
> check if others reference the serdes before deleting it, but the old instance
> will just delete it.
> The other thing we need to take care of is custom serdes. If a partition's
> serde is modified, we need to create a new record in SERDES so that we don't
> interfere other partitions.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
