On Sunday, June 28, 2015, Pavel Stehule <pavel.steh...@gmail.com> wrote:
> > > 2015-06-28 14:26 GMT+02:00 Tomas Vondra <tomas.von...@2ndquadrant.com > <javascript:_e(%7B%7D,'cvml','tomas.von...@2ndquadrant.com');>>: > >> Hi, >> >> On 06/28/2015 08:01 AM, Pavel Stehule wrote: >> >>> >>> you can use PL/pgSQL - but there are some limits >>> >>> * maintenance large plpgsql functions >>> >>> * the plpgsql functions or anonymous functions create a transaction >>> borders - what should not be wanted >>> >> >> But why is that a problem? Generally (sub)transactions are a good thing, >> but if you want, you may create one huge function. If you want to >> modularize this a bit, you may split that into multiple functions, but >> that's an option, not a requirement. >> >> >>> * I cannot to use psql variables simply in plpgsql code (plpgsql has >>> not any macro language) - so some patterns are implemented in plpgsql >>> less readable >>> >>> for example, if you can create a script that create some plpgsql >>> function for specified PostgreSQL version, then using PLpgSQL for this >>> purpose is suboptimal due less readability and maintainability >>> >> >> I don't really see how a block of PL/pgSQL code is less maintainable than >> a similar block of code written in a pseudo-scripting language specific to >> psql. Actually I'd expect exactly the opposite, as PL/pgSQL has neat >> features like exception handling and such, which is completely absent in >> psql, or proper variables, which is somehow mimicked by session variables >> in psql. >> >> If you really need to do the scripting outsite PL/pgSQL, there's plenty >> of suitable tools for that purpose IMHO. Starting with bash, or languages >> like Perl or Python. >> > > <b>I don't propose psql scripting.</b> > > I propose simple statement for conditional statement execution. The core > of my proposal are commands > > \if_ver_gt, \if_ver_lt > > Example: > > \if_ver_le 8.3.0 > > CREATE OR REPLACE FUNCTION unnest(anyarray) > RETURNS SETOF anyelement AS $$ > BEGIN ... END > $$ LANGUAGE plpgsql; > > \endif > > instead > > DO $xx$ > BEGIN > IF version_le(version(), '8.3.0') THEN > > CREATE OR REPLACE FUNCTION unnest(anyarray) > RETURNS SETOF anyelement AS $$ > BEGIN ... END > $$ LANGUAGE plpgsql; > > END IF; > END; > >> >> why require a script language in the first place, at least for this specific use case? CREATE FUNCTION IF (VERSION <= 8.3.0) unnest(...) Similar to the existing CINE syntax. I am partial to making psql more powerful and self-contained but conditionals on versions as a primitive (albeit extension) of SQL seems reasonable at first blush. David J.
