>Marc Mamin-2 wrote >> I would misuse GUC variables for this. >> (using the functions current_setting and set_config) >> >> define a set get and switch fuction (I use operators for better >> readability) >> something like: >> >> select 'a' ==> 'foo' >> 'a' >> select 'b' <==> 'foo' >> 'a' >> select <== 'foo' >> 'b' >> >> >> and in your query: >> >> SELECT >> case when test then col <==> 'foo' else <== 'foo' end > >Is it possible to alter GUC on a record-by-record basis? yes, the underlying functions are volatile. Which quite certainly imply that you cannot repeat the statement within a GROUP or ORDER BY... And you must of course ensure that it get called on an ordered set. >Is this something you have actually done? yes > >Even if it does technically work this seems like a last-resort kind of >solution. The syntax (though that could be hidden in a wrapper function) is >definitely unusual and the abuse of the GUC system in this manner is >surprising. Sure. There are a some caveat too: - it is quite slow - you should first initialize the GUC to avoid testing it in each call. This should be feasable with an extra function in a top WITH clause - GUC are stored as text. You need to define functions for each type you are interested in. This implies extra work for casting/decasting - NULLs are transformed to empty strings per default, so you may need to care for this in your functions. Marc Mamin > >David J. > > -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
