# File lib/active_record/connection_adapters/postgresql_adapter.rb, line 997 def primary_key(table) row = exec_query("SELECT attr.attname\nFROM pg_attribute attr\nINNER JOIN pg_constraint cons ON attr.attrelid = cons.conrelid AND attr.attnum = cons.conkey[1]\nWHERE cons.contype = 'p'\nAND cons.conrelid = '\#{quote_table_name(table)}'::regclass\n", 'SCHEMA').rows.first row && row.first end