The primary key of a table.
The following query is executed by the current executor of the table to retrieve the primary key columns:
select a.attname as column from pg_class c join pg_index i on c.oid = i.indrelid join pg_attribute a on c.oid = a.attrelid where c.relname = \$1 and a.attnum = any(i.indkey) and i.indisprimary order by a.attnum
The result of this query is cached in the metadata cache under the following key, where $table is converted to a string by pq\Gateway\Table::__toString():
Lookup the primary key of a table.
void pq\Gateway\Table\Identity::__construct(pq\Gateway\Table $table)
Retrieve the columns of the table identity.