5.5 Query Server Restarts and Metadata Persistence
You can refresh the Query Server metadata using Cloudera Manager, Apache Ambari, or a PL/SQL API.
The following key metadata can be saved so that they can be restored after a Query Server restart:
- Table statistics
Gathering statistics can be an expensive operation. Table Statistics are gathered automatically after each metadata synchronization. Subsequent statistics gathering may be captured using the following PL/SQL package procedure and parameters:
DBMS_BDSQS.GATHER_EXTERNAL_TABLE_STATS( tabname => <table-name>, estimate_percent => dbms_stats.auto_sample_size);
Note:
Stats gathered usingdbms_bdsqs.gather_external_table_stats
will persist a restart. See the DBMS_BDSQS PL/SQL Package. - Hive external tables that use the
ORACLE_HIVE
access driver. - HDFS external tables that use the
ORACLE_HDFS
access driver. - User-defined views.