2011/5/21 Michael Glaesemann <grzm@xxxxxxxxxxxxxxx>: > > On May 21, 2011, at 9:41, Dan S wrote: > >> Hi ! >> >> I'm running "PostgreSQL 9.0.2, compiled by Visual C++ build 1500, 32-bit" >> >> I have found an odd behaviour in pl/pgsql when using 'return query execute' >> The function produce the dynamic query 'select * from tbl1 where col1 < 4' >> and executes it. >> I would have expected to have 3 rows back with the values 1,2,3 or maybe >> 3,3,3 but it returns all rows in the table ?? >> Here is a self contained test case that shows the behaviour. >> And yes I do know that I can fix the problem by renaming the output column >> to something else than i , I'm just curious about the behaviour and if it >> should work like this and why. >> >> create table tbl1 ( col1 int, constraint pk_tb1 primary key (col1)); >> >> insert into tbl1 values (1),(2),(3),(4),(5),(6); >> >> CREATE OR REPLACE FUNCTION dynamic_query(i int) RETURNS TABLE (i int) as $$ >> DECLARE >> Â Âstmt text; >> Â Âcond text; >> BEGIN >> Â Âstmt := 'select * from tbl1 '; >> >> Â ÂIF (i IS NOT NULL) THEN cond := ' col1 < $1 '; END IF; >> Â ÂIF (cond IS NOT NULL) THEN stmt := stmt || 'where ' || cond; END IF; >> Â ÂRETURN QUERY EXECUTE stmt USING i; >> RETURN; >> END; >> $$ language plpgsql; >> >> select * from dynamic_query(4); > > I couldn't see immediately what the issue was from the description as the example, so I came up with a couple of additional examples that helped me see what was going on: > > CREATE OR REPLACE FUNCTION dynamic_query_4(i int) > RETURNS TABLE (i int) > LANGUAGE PLPGSQL > AS $body$ > DECLARE > Âv_sql TEXT := 'SELECT col1 FROM tbl1 WHERE col1 < $1'; > BEGIN > ÂRETURN QUERY EXECUTE v_sql USING i; > END; > $body$; > > SELECT * FROM dynamic_query_4(4); > Âi > --- > (0 rows) > > CREATE OR REPLACE FUNCTION dynamic_query_5(i int) > RETURNS TABLE (i int) > LANGUAGE PLPGSQL > AS $body$ > DECLARE > Âv_sql TEXT := 'SELECT col1 FROM tbl1'; > BEGIN > ÂRAISE NOTICE 'i IS NULL => %', i IS NULL; > ÂIF i IS NOT NULL THEN > Â Âv_sql := v_sql || ' WHERE col1 < $1'; > ÂEND IF; > ÂRAISE NOTICE 'v_sql: %', v_sql; > ÂRETURN QUERY EXECUTE v_sql USING i; > END; > $body$; > > SELECT * FROM dynamic_query_5(4); > > NOTICE: Âi IS NULL => t > NOTICE: Âv_sql: SELECT col1 FROM tbl1 > Âi > --- > Â1 > Â2 > Â3 > Â4 > Â5 > Â6 > (6 rows) > > It looks like it's just column names stomping on variable names, which is a known issue. This is why a lot of developers (including myself) have conventions of prefixing parameters and variable names (I use in_ for input parameters, v_ for internally defined variables). > It is not this case. There is two plpgsql variables with same name in one namespace - the last OUT variable has higher priority. Regards Pavel > Michael Glaesemann > grzm seespotcode net > > > > > -- > Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general > -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
