Note: XCONLY: The following description applies only to Postgres-XC.
Please note that this section describes the task of individual Coordinator and Datanode.
Note: The following description applies both to Postgres-XC and PostgreSQL if not described explicitly. You can read PostgreSQL as Postgres-XC except for version number, which is specific to each product.
A database administrator frequently wonders, "What is the system doing right now?" This chapter discusses how to find that out.
Several tools are available for monitoring database activity and analyzing performance. Most of this chapter is devoted to describing PostgreSQL's statistics collector, but one should not neglect regular Unix monitoring programs such as ps, top, iostat, and vmstat. Also, once one has identified a poorly-performing query, further investigation might be needed using PostgreSQL's EXPLAIN command. Section 14.1 discusses EXPLAIN and other methods for understanding the behavior of an individual query.