BUG #5273: Unexpected function behavior/failure
The following bug has been logged online:
Bug reference: 5273
Logged by: Vee
Email address: sefer@hotmail.com
PostgreSQL version: 8.4.2
Operating system: Linux
Description: Unexpected function behavior/failure
Details:
Hi,
I have an odd problem using certain regular expressions (as opposed to any
other function) with PostgreSql 8.4.2, I was hoping you could enlighten me
as to what am I doing wrong.
-- Create the table and populate it.
create table test ( data text );
insert into test
values ('hello'), ('world'), ('bridge');
-- Test query.
select data, upper(data)
from test;
hello HELLO
world WORLD
bridge BRIDGE
-- The problem query
select data, regexp_matches(data, '(h..l)')
from test;
hello {hell}
Since I have no "where" clause, I would expect to see all the rows in the
result of the second case, with possibly a NULL value for the non-matched
rows.
But I would not expect a "select" clause to effectively filter out results
for me.
I'd appreciate your input on the matter.
Thanks,
Vee.
"Vee" <sefer@hotmail.com> writes:
-- The problem query
select data, regexp_matches(data, '(h..l)')
from test;
hello {hell}
Since I have no "where" clause, I would expect to see all the rows in the
result of the second case, with possibly a NULL value for the non-matched
rows.
No. regexp_matches() returns setof something, meaning a row per match.
When you have no match, you get no rows. And that in turn means that
the calling select produces no rows --- just as it could also produce
more than one row from a given table row.
I think the behavior you are after is probably more like that of
substring().
regards, tom lane
On Tue, Jan 12, 2010 at 7:45 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
"Vee" <sefer@hotmail.com> writes:
-- The problem query
select data, regexp_matches(data, '(h..l)')
from test;hello {hell}
Since I have no "where" clause, I would expect to see all the rows in the
result of the second case, with possibly a NULL value for the non-matched
rows.No. regexp_matches() returns setof something, meaning a row per match.
When you have no match, you get no rows. And that in turn means that
the calling select produces no rows --- just as it could also produce
more than one row from a given table row.I think the behavior you are after is probably more like that of
substring().
Or maybe the ~ operator.
...Robert