mirror of
https://github.com/postgres/postgres.git
synced 2025-11-24 00:23:06 +03:00
5eed8ce50c
The existing range_minus function raises an exception when the range is "split", because then the result can't be represented by a single range. For example '[0,10)'::int4range - '[4,5)' would be '[0,4)' and '[5,10)'. This commit adds new set-returning functions so that callers can get results even in the case of splits. There is no risk of an exception for multiranges, but a set-returning function lets us handle them the same way we handle ranges. Both functions return zero results if the subtraction would give an empty range/multirange. The main use-case for these functions is to implement UPDATE/DELETE FOR PORTION OF, which must compute the application-time of "temporal leftovers": the part of history in an updated/deleted row that was not changed. To preserve the untouched history, we will implicitly insert one record for each result returned by range/multirange_minus_multi. Using a set-returning function will also let us support user-defined types for application-time update/delete in the future. Author: Paul A. Jungwirth <pj@illuminatedcomputing.com> Reviewed-by: Peter Eisentraut <peter@eisentraut.org> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/ec498c3d-5f2b-48ec-b989-5561c8aa2024%40illuminatedcomputing.com