On Tue, 2012-04-10 at 16:15 -0400, Andy Chambers wrote: > Does anyone know the time complexity of the algorithm used to handle > triggers with a when clause? It's done with a linear scan of all triggers, testing the WHEN clause for each. > To make this a little more concrete, what is likely to perform better > > > a) A single trigger with "n" if/else clauses > b) A set of "n" triggers each using a different when clause. Both are essentially linear. If you want to scale to a large number of conditions, I would recommend using one trigger in a fast procedural language, and searching for the matching conditions using something better than a linear search. To beat a linear search, you need something resembling an index, which is dependent on the types of conditions. For instance, if your conditions are: 00 <= x < 10 10 <= x < 20 20 <= x < 30 ... you can use a tree structure. But, obviously, postgres won't know enough about the conditions to know that a tree structure is appropriate from a given sequence of WHEN clauses. So, you should use one trigger and code the condition matching yourself. Regards, Jeff Davis -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
