On Wed, Nov 29, 2006 at 04:55:49PM -0500, Tom Lane wrote: > "Matt Miller" <pgsql@xxxxxxxxxxxxxxxxxxxxxxxx> writes: > > I thought I saw a thread (here or on -hackers, or somewhere) where > > someone created a C program or something to automatically convert > > Oracle's DECODE expression into an ANSI CASE expression. > > You could just use a compatibility function: > > create function decode(anyelement,anyelement,anyelement,anyelement) > returns anyelement as $$ > select case $1 when $2 then $3 else $4 end > $$ language sql immutable; > > create function decode(anyelement,anyelement,anyelement,anyelement,anyelement,anyelement) > returns anyelement as $$ > select case $1 when $2 then $3 when $4 then $5 else $6 end > $$ language sql immutable; > > -- repeat up to the most number of decode items you need to support > > It's annoying that we only have one "anyelement" pseudotype; this > formulation constrains the input and result types to be the same, > when logically they could be different. Perhaps this example is > a sufficient argument for inventing "anyelement2". Then it'd look like > > create function decode(anyelement,anyelement,anyelement2,anyelement,anyelement2,anyelement2) > returns anyelement2 as ... > > I remember we talked about multiple placeholder types back when we > designed the polymorphic-function feature, but we didn't put it in > for lack of a compelling use-case. Is this one? Yes. I don't know whether it's pertinent, but it would be really nice to have functions that can take SETOF as input, too. Cheers, D -- David Fetter <david@xxxxxxxxxx> http://fetter.org/ phone: +1 415 235 3778 AIM: dfetter666 Skype: davidfetter Remember to vote!
