Re: [HACKERS] pg-dump bug (at 6.4)

I have investigated further the bug in pg_dump relating to inherited
check constraints. This arises in src/bin/pg_dump/pg_dump.c in getTables(), where the query recovers all the constraints for a table, whether or not
they are inherited:

1477 sprintf(query, "SELECT rcname, rcsrc from pg_relcheck "
1478 "where rcrelid = '%s'::oid ",
1479 tblinfo[i].oid);

In the following example, a constraint is inherited from the
table `individual':

bray=> select oid, relname from pg_class
where oid in
(select rcrelid from pg_relcheck
where rcname = 'is_named')
order by oid desc;
oid|relname
-----+----------
67552|staff
67436|outworker
67111|individual
(3 rows)

bray=> select rcrelid, rcname, rcsrc from pg_relcheck
where rcname = 'is_named'
order by rcrelid desc;
rcrelid|rcname |rcsrc
-------+--------+---------------------------------------------
67552|is_named|NOT ( surname IS NULL AND forenames IS NULL )
67436|is_named|NOT ( surname IS NULL AND forenames IS NULL )
67111|is_named|NOT ( surname IS NULL AND forenames IS NULL )
(3 rows)

pg_dump writes all three constraints into its output, which causes the
table creation to fail on the inherited tables when the database is
restored.

We actually need to select a check constraint only if, for each constraint,
tblinfo[i].oid = min(rcrelid). However, I cannot work out how
to write the query (not least because there is no min()
function for oids).

Can anyone take this further, please?

--
Oliver Elphick Oliver(dot)Elphick(at)lfix(dot)co(dot)uk
Isle of Wight http://www.lfix.co.uk/oliver
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