dengzhhu653 commented on PR #6159:
URL: https://github.com/apache/hive/pull/6159#issuecomment-3524602503
Thank you @deniskuzZ for the comment.
```sql
String updateSQL = "UPDATE \"TABLE_PARAMS\" " + "SET \"PARAM_VALUE\" = '"
+ newVersion + "' " +
"WHERE \"TBL_ID\" = " + tblId + " AND \"PARAM_KEY\" = '" +
versionParamKey + "' " +
AND \"PARAM_VALUE\" = '" + expectedVersion + "'"; // ✅ CHECK
SNAPSHOT!
```
The result of this query seems important to the example, let's say there is
a row(`TBL_ID`, `PARAM_KEY`, `PARAM_VALUE`) (1, `hive.metastore.table.version`,
1) on the table `TABLE_PARAMS`, if transaction A and B happens to execute the
update(set hive.metastore.table.version = 2) at the same time, say if A takes
the row lock, then B needs to wait for A committing or rollbacking to release
the row before B is allowed to update this row, then B re-evaluates the `where`
condition and see there is no row matched, then return 0.
If there are more transactions to update this row, then they are piled up to
get a change to take over the row lock. In my opinion, this is similar to the
s4u way I proposed in the old PR.
--
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.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
