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Diffstat (limited to 'doc/src/sgml/ddl.sgml')
| -rw-r--r-- | doc/src/sgml/ddl.sgml | 58 |
1 files changed, 0 insertions, 58 deletions
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml index c8268222af..61c4a25460 100644 --- a/doc/src/sgml/ddl.sgml +++ b/doc/src/sgml/ddl.sgml @@ -939,24 +939,6 @@ CREATE TABLE circles ( <variablelist> <varlistentry> - <term><structfield>oid</structfield></term> - <listitem> - <para> - <indexterm> - <primary>OID</primary> - <secondary>column</secondary> - </indexterm> - The object identifier (object ID) of a row. This column is only - present if the table was created using <literal>WITH - OIDS</literal>, or if the <xref linkend="guc-default-with-oids"/> - configuration variable was set at the time. This column is of type - <type>oid</type> (same name as the column); see <xref - linkend="datatype-oid"/> for more information about the type. - </para> - </listitem> - </varlistentry> - - <varlistentry> <term><structfield>tableoid</structfield></term> <listitem> <indexterm> @@ -1057,46 +1039,6 @@ CREATE TABLE circles ( </variablelist> <para> - OIDs are 32-bit quantities and are assigned from a single - cluster-wide counter. In a large or long-lived database, it is - possible for the counter to wrap around. Hence, it is bad - practice to assume that OIDs are unique, unless you take steps to - ensure that this is the case. If you need to identify the rows in - a table, using a sequence generator is strongly recommended. - However, OIDs can be used as well, provided that a few additional - precautions are taken: - - <itemizedlist> - <listitem> - <para> - A unique constraint should be created on the OID column of each - table for which the OID will be used to identify rows. When such - a unique constraint (or unique index) exists, the system takes - care not to generate an OID matching an already-existing row. - (Of course, this is only possible if the table contains fewer - than 2<superscript>32</superscript> (4 billion) rows, and in practice the - table size had better be much less than that, or performance - might suffer.) - </para> - </listitem> - <listitem> - <para> - OIDs should never be assumed to be unique across tables; use - the combination of <structfield>tableoid</structfield> and row OID if you - need a database-wide identifier. - </para> - </listitem> - <listitem> - <para> - Of course, the tables in question must be created <literal>WITH - OIDS</literal>. As of <productname>PostgreSQL</productname> 8.1, - <literal>WITHOUT OIDS</literal> is the default. - </para> - </listitem> - </itemizedlist> - </para> - - <para> Transaction identifiers are also 32-bit quantities. In a long-lived database it is possible for transaction IDs to wrap around. This is not a fatal problem given appropriate maintenance |