6.4 Aggregate Bug - Mailing list pgsql-hackers

While testing  my 6.4 patch to allow functions/expressions to be
specified in the ORDER/GROUP BY  clause (and not in the target list)  I
came across a nasty little bug.     A segmentation fault gets thrown
somewhere in replace_agg_clause() when using aggregates, in combination
with a function or expression.   (I  am still tracking down the
offending lines of code.  Sorry, the Linux/GCC environment is still new
to me.)

I backed out my patch, and discovered  the bug was still present.  The
bug does not exist in version 6.3.2.  Here is an example:

-- This crashes the backend
    select upper(a) as x, count(k) from t group by x;

--  This works fine
    select upper(a) as x, count(a) from t group by x;

Notice how in the first query, (the one that does not work) upper() has
a different argument than count().  And  in the second query (the one
that works) upper() has the same argument as count().     When using
count(*) it will always fail.

This is the the pattern that I have observed.   If the arguments in the
aggregate and non-aggregate functions are the same, it runs; if the
arguments in the aggregate and non-aggregate functions are different, it
crashes.

I have attached a test script for anyone able to help with (or verify)
this problem.



create table t  (
    j integer,
    k integer,
    a varchar
);
insert into t values (1, 1, 'a');
insert into t values (2, 2, 'b');
insert into t values (2, 3, 'c');
insert into t values (3, 4, 'A');
insert into t values (3, 5, 'B');
insert into t values (3, 6, 'C');
insert into t values (4, 7, 'a');
insert into t values (4, 8, 'b');
insert into t values (4, 9, 'c');
insert into t values (4, 0, 'a');

-- OK
select upper(a) as x, count(a) from t group by x;

-- OK
select k/2 as x, max(k) from t group by x;

-- OK
-- select k as x, max(j) from t group by x;

-- OK
select upper(a) as x, count(k), count(a) from t group by x;

-- CRASH
select k/2 as x, max(j) from t group by x;

-- CRASH
select upper(a) as x, count(k) from t group by x;

-- CRASH
select upper(a) as x, count(xmin) from t group by x;

-- CRASH
select upper(a) as x, count(oid) from t group by x;

-- CRASH
select upper(a) as x, count(*) from t group by x;