dengzhhu653 commented on code in PR #4569:
URL: https://github.com/apache/hive/pull/4569#discussion_r1331745899
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standalone-metastore/metastore-server/src/main/sql/mssql/hive-schema-4.0.0-beta-2.mssql.sql:
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@@ -661,6 +661,8 @@ ALTER TABLE NOTIFICATION_LOG ADD CONSTRAINT
NOTIFICATION_LOG_PK PRIMARY KEY (NL_
CREATE UNIQUE INDEX NOTIFICATION_LOG_EVENT_ID ON NOTIFICATION_LOG (EVENT_ID);
+CREATE UNIQUE INDEX NOTIFICATION_LOG_UNIQUE_DB ON NOTIFICATION_LOG (DB_NAME,
EVENT_ID);
Review Comment:
I'm wondering for some back dbs, for the case: event_id > 10 and db_name =
'default'
1. use index with event_id to filter the matched rows (event_id > 10)
2. on the result of the first step, apply the index with db_name (db_name =
'default')
if the event_id > 10 is only return one row from 1000 rows, then this is
better than using the index with db_name and event_id.
As the API is aim to fetch the latest event in most cases, so I think this
is common in real production.
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