foreign_keys

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 604
        def foreign_keys(table_name)
          scope = quoted_scope(table_name)
          fk_info = internal_exec_query(<<~SQL, "SCHEMA", allow_retry: true, materialize_transactions: false)
            SELECT t2.oid::regclass::text AS to_table, c.conname AS name, c.confupdtype AS on_update, c.confdeltype AS on_delete, c.convalidated AS valid, c.condeferrable AS deferrable, c.condeferred AS deferred, c.conrelid, c.confrelid,
              (
                SELECT array_agg(a.attname ORDER BY idx)
                FROM (
                  SELECT idx, c.conkey[idx] AS conkey_elem
                  FROM generate_subscripts(c.conkey, 1) AS idx
                ) indexed_conkeys
                JOIN pg_attribute a ON a.attrelid = t1.oid
                AND a.attnum = indexed_conkeys.conkey_elem
              ) AS conkey_names,
              (
                SELECT array_agg(a.attname ORDER BY idx)
                FROM (
                  SELECT idx, c.confkey[idx] AS confkey_elem
                  FROM generate_subscripts(c.confkey, 1) AS idx
                ) indexed_confkeys
                JOIN pg_attribute a ON a.attrelid = t2.oid
                AND a.attnum = indexed_confkeys.confkey_elem
              ) AS confkey_names
            FROM pg_constraint c
            JOIN pg_class t1 ON c.conrelid = t1.oid
            JOIN pg_class t2 ON c.confrelid = t2.oid
            JOIN pg_namespace n ON c.connamespace = n.oid
            WHERE c.contype = 'f'
              AND t1.relname = #{scope[:name]}
              AND n.nspname = #{scope[:schema]}
            ORDER BY c.conname
          SQL

          fk_info.map do |row|
            to_table = Utils.unquote_identifier(row["to_table"])

            column = decode_string_array(row["conkey_names"])
            primary_key = decode_string_array(row["confkey_names"])

            options = {
              column: column.size == 1 ? column.first : column,
              name: row["name"],
              primary_key: primary_key.size == 1 ? primary_key.first : primary_key
            }

            options[:on_delete] = extract_foreign_key_action(row["on_delete"])
            options[:on_update] = extract_foreign_key_action(row["on_update"])
            options[:deferrable] = extract_constraint_deferrable(row["deferrable"], row["deferred"])

            options[:validate] = row["valid"]

            ForeignKeyDefinition.new(table_name, to_table, options)
          end
        end