On 15 November 2013 03:30, Peter Eisentraut <pete...@gmx.net> wrote: > A constraint trigger performs the actual checking.
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Good, that is consistent with other constraints. > This is not a performance feature. It's for things like, this table > should have at most 10 rows, or all the values in this table must be > bigger than all the values in that other table. It's a bit esoteric, > but it comes up again and again. While I accept it may never perform well, it needs to perform reasonably well. The key use cases for this are * enforcing "one and only one" relationships * enforcing quantified relationships like we do in XML: minoccurs and maxoccurs * enforcing only one sub-type across multiple sub-type tables etc So we'd need to get access to the changed rows, rather than re-executing a huge SQL command that re-checks every row of the table. That last point will make it unusable for sensible amounts of data. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
