jiihye opened a new pull request, #5793:
URL: https://github.com/apache/hive/pull/5793
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### What changes were proposed in this pull request?
This PR proposes to optimize the SQL query generated by the `get_table_meta`
API in Hive Metastore by removing the use of the LOWER() function.
- before
``` diff
# JDOQL
SELECT FROM org.apache.hadoop.hive.metastore.model.MTable
+ WHERE (database.catalogName == hive ) &&
(database.name.matches((?i)db_name) )
```
- after
``` diff
# JDOQL
SELECT FROM org.apache.hadoop.hive.metastore.model.MTable
+ WHERE (database.catalogName == hive ) && (database.name.matches(db_name) )
```
### Why are the changes needed?
In production environments with a large number of tables, we observed that
the SQL query generated by `get_table_meta` caused full scans on the TBLS
table, resulting in high CPU usage on the Metastore's MySQL backend.
https://issues.apache.org/jira/projects/HIVE/issues/HIVE-28899?filter=allopenissues
### Does this PR introduce _any_ user-facing change?
No. Since both database names and table names are already stored in
lowercase in the Metastore DB, this change should not have any impact on users.
This change is only applied to get_table_meta to minimize risk. Other
commands were left unchanged as we are not yet certain about potential side
effects in those paths.
### How was this patch tested?
- Verified the generated SQL via logging.
- Manually tested the change in a local Hive Metastore instance with MySQL
5.7 and a large dataset.
- Observed a significant drop in CPU usage during repeated get_table_meta
requests.
-
https://issues.apache.org/jira/projects/HIVE/issues/HIVE-28899?filter=allopenissues
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