Which System Catalogs in DWS Cannot Undergo the VACUUM FULL Operation?

Version 8.1.3 or Later

• For clusters of version 8.1.3 or later, AUTO VACUUM is enabled by default (controlled by the autovacuum parameter). After you set the parameter, the system automatically performs VACUUM FULL on all system catalogs and row-store tables.
  • If the value of autovacuum_max_workers is 0, neither on the system catalogs nor on ordinary tables will VACUUM FULL be automatically performed.
  • If autovacuum is set to off, VACUUM FULL will be automatically performed only on the system catalogs.
• This applies only to row-store tables. To automatically trigger AUTO VACUUM for column-store tables, you need to configure intelligent scheduling tasks on the management console. For details, see O&M plan.

Version 8.1.1 or Earlier

1. Reforming VACUUM FULL on the following system catalogs affects all services. Perform this operation in an idle time window or when services are stopped.
   • pg_statistic (Statistics information. You are advised not to clear it because it affects service query performance.)
   • pg_attribute
   • pgxc_class
   • pg_type
   • pg_depend
   • pg_class
   • pg_index
   • pg_proc
   • pg_partition
   • pg_object
   • pg_shdepend
2. The following system catalogs affect resource monitoring and table size query interfaces, but do not affect other services.
   • gs_wlm_user_resource_history
   • gs_wlm_session_info
   • gs_wlm_instance_history
   • gs_respool_resource_history
   • pg_relfilenode_size
3. Other system catalogs do not occupy space and do not need to be cleared.
4. During routine O&M, you are advised to monitor the sizes of the system catalogs in the following statement every week. If the space must be reclaimed, process key system catalogs first.
   The statement is as follows:

   1	SELECT c.oid,c.relname, c.relkind, pg_relation_size(c.oid) AS size FROM pg_class c WHERE c.relkind IN ('r') AND c.oid <16385 ORDER BY size DESC;