fc0438b4e8
Add WITHOUT OVERLAPS clause to PRIMARY KEY and UNIQUE constraints. These are backed by GiST indexes instead of B-tree indexes, since they are essentially exclusion constraints with = for the scalar parts of the key and && for the temporal part. (previously committed as 46a0cd4cefb, reverted by 46a0cd4cefb; the new part is this:) Because 'empty' && 'empty' is false, the temporal PK/UQ constraint allowed duplicates, which is confusing to users and breaks internal expectations. For instance, when GROUP BY checks functional dependencies on the PK, it allows selecting other columns from the table, but in the presence of duplicate keys you could get the value from any of their rows. So we need to forbid empties. This all means that at the moment we can only support ranges and multiranges for temporal PK/UQs, unlike the original patch (above). Documentation and tests for this are added. But this could conceivably be extended by introducing some more general support for the notion of "empty" for other types. Author: Paul A. Jungwirth <pj@illuminatedcomputing.com> Reviewed-by: Peter Eisentraut <peter@eisentraut.org> Reviewed-by: jian he <jian.universality@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.