Frequently Asked Questions (FAQ) for PostgreSQL
- Last updated: Tue Nov 21 10:37:54 EST 2006
+ Last updated: Tue Nov 21 23:16:54 EST 2006
Current maintainer: Bruce Momjian (bruce@momjian.us)
4.12) What is an OID? What is a CTID?
- Every row that is created in PostgreSQL gets a unique OID unless
- created WITHOUT OIDS. OIDs are automatically 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.
- PostgreSQL uses OIDs to link its internal system tables together.
+ If a table is created WITH OIDS, each row gets a unique a OID. OIDs
+ are automatically 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. PostgreSQL uses OIDs to link
+ its internal system tables together.
To uniquely number rows in user tables, it is best to use SERIAL
rather than OIDs because SERIAL sequences are unique only within a
alink="#0000ff">
<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
- <P>Last updated: Tue Nov 21 10:37:54 EST 2006</P>
+ <P>Last updated: Tue Nov 21 23:16:54 EST 2006</P>
<P>Current maintainer: Bruce Momjian (<A href=
"mailto:bruce@momjian.us">bruce@momjian.us</A>)
<H3 id="item4.12">4.12) What is an <SMALL>OID</SMALL>? What is
a <SMALL>CTID</SMALL>?</H3>
- <P>Every row that is created in PostgreSQL gets a unique
- <SMALL>OID</SMALL> unless created <SMALL>WITHOUT OIDS</SMALL>.
- O<SMALL>ID</SMALL>s are automatically assigned unique 4-byte
- integers that are unique across the entire installation. However,
- they overflow at 4 billion, and then the O<SMALL>ID</SMALL>s start
- being duplicated. PostgreSQL uses <SMALL>OID</SMALL>s to link its
- internal system tables together.</P>
+ <P>If a table is created <SMALL>WITH OIDS</SMALL>, each row
+ gets a unique a <SMALL>OID</SMALL>. O<SMALL>ID</SMALL>s are
+ automatically assigned unique 4-byte integers that are unique
+ across the entire installation. However, they overflow at 4
+ billion, and then the O<SMALL>ID</SMALL>s start being duplicated.
+ PostgreSQL uses <SMALL>OID</SMALL>s to link its internal system
+ tables together.</P>
<P>To uniquely number rows in user tables, it is best to use
<SMALL>SERIAL</SMALL> rather than O<SMALL>ID</SMALL>s because