On Fri, Apr 15, 2005 at 03:42:40PM -0700, Cima wrote:
> someone has drawn my attention to the fact that oids may not be such a good
> idea to set as a primary key in a table. i have designed a relativley large
> database and defined oids as primary keys. i would like your opinions or
> recomendations on this.
See "Object Identifier Types" in the "Data Types" chapter of the
"The oid type is currently implemented as an unsigned four-byte
integer. Therefore, it is not large enough to provide database-wide
uniqueness in large databases, or even in large individual tables.
So, using a user-created table's OID column as a primary key is
discouraged. OIDs are best used only for references to system
See also "What is an OID? What is a TID?" in the FAQ:
"OIDs are autotomatically assigned unique 4-byte integers that are
unique across the entire installation. However, they overflow at
4 billion, and then the OIDs start being duplicated."
"To uniquely number columns in user tables, it is best to use SERIAL
rather than OIDs because SERIAL sequences are unique only within a
single table and are therefore less likely to overflow. SERIAL8
is available for storing eight-byte sequence values."
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