How to execute PostgreSQL slash methods on ActiveRecord?

Question

I am using Rails 4. I am trying to list all PostgreSQL databases with '\l' using 'execute' method from ActiveRecord. Connection is correctly established.

p = ActiveRecord::Tasks::PostgreSQLDatabaseTasks.new(configuration)
p.send 'establish_master_connection'
p.connection.execute('\l')

Here is the error:

ActiveRecord::StatementInvalid (PG::SyntaxError: ERROR: syntax error at or near "l"

When I use 'no slash' method it works fine

connection.execute("DROP DATABASE IF EXISTS NOTHING")
=> #<PG::Result:0xc5e6094 status=PGRES_COMMAND_OK ntuples=0 nfields=0 cmd_tuples=0>

Any idea?

Answer 1

You can't. Commands beginning with \ are meta commands implemented by the psql shell itself - the database server itself doesn't know what they mean.

In the particular case of the commands listing various things, this normally boils down to querying tables in pg_catalog e.g.

SELECT * FROM pg_catalog.pg_database 

for databases

SELECT * FROM pg_catalog.pg_table

for tables. These are documented here