How enable EXPLAIN query plans on CitusDB

[awo...@silversky.com]

I want to understand how to tune a CitusDB database.  We plan to loading large volumes of data into pg_shard/cstore tables.  When I try to use EXPLAIN on one of our queries, I get "explain statements for distributed queries are currently unsupported"  I've seen some plans on this site, how can I get these for my queries?

Also, is there any guide to how to read them?  I'm sort of expecting to see full table scans on columns, and maybe that's not a problem with CitusDB.  Where do I find out?

Thanks,

Andrew Wolfe

[Murat Tuncer]

Hi Andrew

Your questions is more into citus product than cstore_fdw. Citus does not support distributed explain statements as you saw in the error message. We are planning to add this support in version 5.1

You can however, get the plans for queries sent to worker nodes. Setting up postgresql configuration parameter "log_min_duration_statement" to "0" in postgresql.conf at a worker node lets you print all incoming statements. You can issue explain command for that query in that particular worker afterwards.

The web site http://explain.depesz.com/ does very good job of "explaining" postgresql explain output.

Please let me know if you need further assistance with cstore_fdw.

thanks

Murat