Metadata from a postgresql-database - postgresql

Question

I want to get data about all relationships from a PostgreSql-database with query like
SELECT
[creatorUser].[primTableName].[primColumnName] AS primary_column,
[creatorUser].[foreignTableName].[foreignColumnName] AS foreign_column,
FROM
sys.sysidx si,
sysidxcol sic,
sys.SYSFKCOL sfc,
sysusers su,
sys.systable st,
sys.syscolumn sc
WHERE
si.table_id=sic.table_id AND
si.index_id=sic.index_id AND
sfc.primary_column_id=sic.primary_column_id AND
sfc.foreign_table_id=sic.table_id AND
st.table_id=sfc.foreign_table_id AND
su.uid=st.creator AND
sc.column_name=si.index_name
Can anybody help, how to get that data? How to be a correct query
owner1.table1.primCol1 owner1.table1.foreignCol1
owner1.table1.primCol2 owner1.table1.foreignCol2
..
?

Answer 1

PostgreSQL has no sys tables, so it's not clear how you could possibly expect that query to work. Given your comments, I'm guessing that's the query you use on Sybase, and you want to translate it for PostgreSQL.
Well, assuming that the Sybase syntax:
[creatorUser].[primTableName].[primColumnName] AS primary_column,
[creatorUser].[foreignTableName].[foreignColumnName] AS foreign_column,
means "Concatenate the user who created the relationship, the table name, and the column name" I'd probably do something in PostgreSQL like:
SELECT
format('%I.%I.%I', fk.table_schema, fk.table_name, fk.column_name) AS foreign_side,
format('%I.%I.%I', pk.table_schema, pk.table_name, pk.column_name) AS target_side
FROM
information_schema.referential_constraints rc
INNER JOIN information_schema.key_column_usage fk
ON (rc.constraint_catalog = fk.constraint_catalog
AND rc.constraint_schema = fk.constraint_schema
AND rc.constraint_name = fk.constraint_name)
INNER JOIN information_schema.constraint_column_usage pk
ON (rc.unique_constraint_catalog = pk.constraint_catalog
AND rc.unique_constraint_schema = rc.constraint_schema
AND rc.unique_constraint_name = pk.constraint_name);
Except for the format(...) that'll work on Sybase too, with some luck.
Output like:
foreign_side | target_side
---------------------+---------------------------------
public.users.id_cat | public.usercategories.id_numcat
(1 row)
That's schema.table.column . I'm guessing Sybase's "creatorUser" is really "schema" in this case.

Answer 2

You should query appropriate tables under pg_catalog or information_schema schemas. The easiest way to figure out the correct query is to run (... = other command-line options like user, database, ...)
psql -E ...
and then psql displays meta-data queries used in internal commands like \d, \dt, \dv, ... From manual:
-E
--echo-hidden
Echo the actual queries generated by \d and other backslash commands. You can use this to study psql's internal operations. This is equivalent to setting the variable ECHO_HIDDEN from within psql.
information_schema is same as pg_catalog but more portalbe (it is defined in SQL standard). If your app uses postgres only then I would use pg_catalog instead of information_schema