Enables in-core computation of a query identifier. Query identifiers can be displayed in the EXPLAIN, or emitted in the log if configured via the log_line_prefix parameter. The pgstatstatements extension also requires a query identifier to be computed. Note that an external module can alternatively be used if the in-core query identifier computation method is not acceptable. In this case, in-core computation must be always disabled. Valid values are
off (always disabled),
on (always enabled) and
auto, which lets modules such as pgstatstatements automatically enable it. The default is
To ensure that only one query identifier is calculated and displayed, extensions that calculate query identifiers should throw an error if a query identifier has already been computed.