In this post, I am sharing a script to find a list of distribution keys of a database. In the Greenplum MPP architecture, distribution keys are playing a primary role in selecting data.

If we define proper distribution key, we don’t require even table indexes.
‘ Using below script, Greenplum DBA can get the list of all distribution keys which further they can use for ad-hoc database reporting as well.

SELECT
	pgn.nspname as table_owner
	,pgc.relname as table_name
	,COALESCE(pga.attname,'DISTRIBUTED RANDOMLY') as distribution_keys
FROM
(
	SELECT
		gdp.localoid,
		CASE
			WHEN ( Array_upper(gdp.attrnums, 1) > 0 ) THEN
			Unnest(gdp.attrnums)
			ELSE NULL
		END AS attnum
	FROM gp_distribution_policy gdp
	ORDER BY gdp.localoid
) AS distrokey
INNER JOIN pg_class AS pgc
	ON distrokey.localoid = pgc.oid
INNER JOIN pg_namespace pgn
	ON pgc.relnamespace = pgn.oid
LEFT OUTER JOIN pg_attribute pga
	ON distrokey.attnum = pga.attnum
		and distrokey.localoid = pga.attrelid
ORDER BY pgn.nspname, pgc.relname;