Thread

1. Duplicate OIDs in pg_attribute

   jmitchell@greatbridge.com — 2001-02-06T19:52:47Z

   I noticed that pg_attribute has rows with the same OID!  You can
   verify this by running.
   
   # select count(oid),oid from pg_attribute group by oid having
   count(oid) > 1;
   
   We see that these duplicate OIDs appear to happen when
   pg_attibute rows are inserted for indexes and primary keys.
   
   select relname, attname
   from pg_attribute , pg_class
   where attrelid = pg_class.oid and
   pg_attribute.oid in (select oid
                   from pg_attribute
                   group by oid
                   having count(oid) > 1);
   
   I see:
                        relname             |   attname
           ---------------------------------+--------------
            pg_aggregate_name_type_index    | aggname
            pg_aggregate_name_type_index    | aggbasetype
            pg_amop_opid_index              | amopclaid
            pg_amop_opid_index              | amopopr
            pg_amop_opid_index              | amopid
            pg_amop_strategy_index          | amopid
            pg_amop_strategy_index          | amopclaid
            pg_amop_strategy_index          | amopstrategy
            pg_attribute_relid_attnam_index | attrelid
            pg_attribute_relid_attnam_index | attname
            pg_attribute_relid_attnum_index | attrelid
            pg_attribute_relid_attnum_index | attnum
            pg_inherits_relid_seqno_index   | inhrelid
            pg_inherits_relid_seqno_index   | inhseqno
            pg_largeobject_loid_pn_index    | loid
            pg_largeobject_loid_pn_index    | pageno
            pg_listener_pid_relname_index   | listenerpid
            pg_listener_pid_relname_index   | relname
            pg_operator_oprname_l_r_k_index | oprname
            pg_operator_oprname_l_r_k_index | oprleft
            pg_operator_oprname_l_r_k_index | oprright
            pg_operator_oprname_l_r_k_index | oprkind
            pg_proc_proname_narg_type_index | proname
            pg_proc_proname_narg_type_index | pronargs
            pg_proc_proname_narg_type_index | proargtypes
            pg_statistic_relid_att_index    | starelid
            pg_statistic_relid_att_index    | staattnum
            primarytest2_pkey               | col1
            primarytest2_pkey               | col2
           (29 rows)
   
   What do people think about this issue?  It doesn't seem to have
   major consequences now, but it should probably be fixed?  When
   system tables have referential integrity enforced, then it will be an
   issue.  Can this be put on the TODO list?
   
   Regards,
   
   Joe Mitchell
   Great Bridge LLC
   

2. Re: Duplicate OIDs in pg_attribute

   Tom Lane <tgl@sss.pgh.pa.us> — 2001-02-07T00:46:44Z

   Joe Mitchell <jmitchell@greatbridge.com> writes:
   > I noticed that pg_attribute has rows with the same OID!
   
   Joe previously asked me about this off-list, and I replied thus:
   
   This appears to be due to the incredibly grotty coding used in
   AppendAttributeTuples in src/backend/catalog/index.c --- rather than
   building tuples in any of several sane fashions, it's using an unholy
   combination of memmove and heap_modifytuple to update a single tuple
   object into successive states that correspond to the rows it needs to
   add to the table.  Unfortunately the OID assigned by the first
   heap_insert gets carried along to the subsequent states, so the later
   calls to heap_insert don't think they should assign new OIDs.
   
   Good catch, Joe!  This bug has probably been there since the beginning
   of time.  It's evidently got no serious consequences (since in reality,
   OID uniqueness is not assumed for this table), but it ought to be fixed.
   A quick-hack solution would be to zero out the tuple's OID before each
   heap_insert, but really AppendAttributeTuples should be rewritten to
   construct each tuple independently in the first place.
   
   A quick 'glimpse' shows no other uses of heap_modifytuple except to
   update an existing tuple, so evidently no one was foolish enough to
   copy this technique.
   
   I recommend putting this on the TODO for 7.2.  We can't fix it now
   unless we want to force an initdb.
   
   			regards, tom lane
   
   

3. Re: Duplicate OIDs in pg_attribute

   Bruce Momjian <pgman@candle.pha.pa.us> — 2001-02-07T00:52:27Z

   > Good catch, Joe!  This bug has probably been there since the beginning
   > of time.  It's evidently got no serious consequences (since in reality,
   > OID uniqueness is not assumed for this table), but it ought to be fixed.
   > A quick-hack solution would be to zero out the tuple's OID before each
   > heap_insert, but really AppendAttributeTuples should be rewritten to
   > construct each tuple independently in the first place.
   > 
   > A quick 'glimpse' shows no other uses of heap_modifytuple except to
   > update an existing tuple, so evidently no one was foolish enough to
   > copy this technique.
   > 
   > I recommend putting this on the TODO for 7.2.  We can't fix it now
   > unless we want to force an initdb.
   
   Added to TODO:
   
   	* Prevent pg_attribute from having duplicate oids for indexes
   
   
   -- 
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