Обсуждение: Functions as first-class values
Hi, Is there support in PL/pgSQL for treating functions as first-class values? Consider the pseudo-code simple example below, which illustrates how this feature can be useful. I reckon that this behaviour can be emulated using EXECUTE, but I suspect there are serious performance penalties. Your thoughts? Thanks in advance! Jon CREATE FUNCTION f1 (int) RETURNS boolean ... CREATE FUNCTION f2 (int) RETURNS boolean ... CREATE FUNCTION f3 (int) RETURNS boolean ... CREATE FUNCTION do_stuff ... BEGIN CASE cond WHEN 'a' THEN func := f1; WHEN 'b' THEN func := f2; WHEN 'c' THEN func := f3; END CASE SELECT * FROM foobar WHERE func (foobar.age); END;
Hello 2011/4/6 Jon Smark <jon.smark@yahoo.com>: > Hi, > > Is there support in PL/pgSQL for treating functions as first-class values? > Consider the pseudo-code simple example below, which illustrates how this > feature can be useful. I reckon that this behaviour can be emulated using > EXECUTE, but I suspect there are serious performance penalties. > Your thoughts? > > Thanks in advance! > Jon > > > CREATE FUNCTION f1 (int) RETURNS boolean ... > CREATE FUNCTION f2 (int) RETURNS boolean ... > CREATE FUNCTION f3 (int) RETURNS boolean ... > > CREATE FUNCTION do_stuff ... > BEGIN > CASE cond > WHEN 'a' THEN func := f1; > WHEN 'b' THEN func := f2; > WHEN 'c' THEN func := f3; > END CASE > > SELECT * FROM foobar WHERE func (foobar.age); > END; > no it isn't possible. Regards Pavel Stehule > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general >
On Wed, Apr 6, 2011 at 9:10 AM, Pavel Stehule <pavel.stehule@gmail.com> wrote: > Hello > > 2011/4/6 Jon Smark <jon.smark@yahoo.com>: >> Hi, >> >> Is there support in PL/pgSQL for treating functions as first-class values? >> Consider the pseudo-code simple example below, which illustrates how this >> feature can be useful. I reckon that this behaviour can be emulated using >> EXECUTE, but I suspect there are serious performance penalties. >> Your thoughts? >> >> Thanks in advance! >> Jon >> >> >> CREATE FUNCTION f1 (int) RETURNS boolean ... >> CREATE FUNCTION f2 (int) RETURNS boolean ... >> CREATE FUNCTION f3 (int) RETURNS boolean ... >> >> CREATE FUNCTION do_stuff ... >> BEGIN >> CASE cond >> WHEN 'a' THEN func := f1; >> WHEN 'b' THEN func := f2; >> WHEN 'c' THEN func := f3; >> END CASE >> >> SELECT * FROM foobar WHERE func (foobar.age); >> END; >> > > no it isn't possible. it can be done with a small C wrapper though. see archives. merlin