pg_dump fails for views with UNION and SELECT DISTINCT

Started by Sam O'Connoralmost 24 years ago2 messagesbugs
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#1Sam O'Connor
sam@panviva.com

If I create a view like this:
CREATE VIEW v AS
SELECT i FROM a
UNION
SELECT DISTINCT i FROM b

It functions as expected but it causes pg_dump to produce
bad output. "ORDER BY b.i" is added to the view definition.
On restore this causes:
ERROR: ORDER BY on a UNION/INTERSECT/EXCEPT result must be on one of
the result columns

Full setup and steps taken are below.

Regards,

Sam

My setup:

Debian woody.
Linux 2.4.18.
PostgreSQL 7.2.1
./configure --with-maxbackends=64 --with-gnu-ld --enable-odbc
--enable-syslog

What I did:

# cat > test.sql << EOF
SELECT version();
CREATE TABLE foo (i int);
CREATE TABLE bar (i int);

CREATE VIEW this_is_ok
AS SELECT i
FROM foo
UNION
SELECT i FROM bar;

CREATE VIEW this_causes_a_broken_dump
AS SELECT i
FROM foo
UNION
SELECT DISTINCT i FROM bar;

CREATE VIEW this_causes_a_broken_dump_too
AS SELECT i
FROM foo
UNION
SELECT DISTINCT i FROM bar x;
EOF

# createdb test
CREATE DATABASE

# psql test < test.sql
version
---------------------------------------------------------------
PostgreSQL 7.2.1 on i686-pc-linux-gnu, compiled by GCC 2.95.4
(1 row)

CREATE
CREATE
CREATE
CREATE
CREATE

# pg_dump test
-- snip --

CREATE VIEW "this_is_ok" as SELECT foo.i FROM foo UNION SELECT bar.i
FROM bar;

-- snip --

CREATE VIEW "this_causes_a_broken_dump" as SELECT foo.i FROM foo UNION
SELECT DISTINCT bar.i FROM bar ORDER BY bar.i;

-- snip --

CREATE VIEW "this_causes_a_broken_dump_too" as SELECT foo.i FROM foo
UNION SELECT DISTINCT x.i FROM bar x ORDER BY x.i;

-- snip --

# createdb test2
CREATE DATABASE

# pg_dump test | psql test2
CREATE
CREATE
CREATE
ERROR: ORDER BY on a UNION/INTERSECT/EXCEPT result must be on one of
the result columns
ERROR: Relation "x" does not exist

#2Tom Lane
tgl@sss.pgh.pa.us
In reply to: Sam O'Connor (#1)
Re: pg_dump fails for views with UNION and SELECT DISTINCT

"Sam O'Connor" <sam@panviva.com> writes:

If I create a view like this:
CREATE VIEW v AS
SELECT i FROM a
UNION
SELECT DISTINCT i FROM b

It functions as expected but it causes pg_dump to produce
bad output. "ORDER BY b.i" is added to the view definition.

This appears to be fixed already in current sources --- the problem
is the lack of parentheses around the arms of the UNION. There's
a difference between
SELECT foo UNION SELECT bar ORDER BY baz;
and
SELECT foo UNION (SELECT bar ORDER BY baz);
and the rule dumper was not being careful about it :-(

I'll see about backpatching this change for 7.2.2.

regards, tom lane