diff options
Diffstat (limited to 'doc/src/sgml/ref/create_table.sgml')
| -rw-r--r-- | doc/src/sgml/ref/create_table.sgml | 74 |
1 files changed, 71 insertions, 3 deletions
diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml index fb5e2b2a550..0e10991c43b 100644 --- a/doc/src/sgml/ref/create_table.sgml +++ b/doc/src/sgml/ref/create_table.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_table.sgml,v 1.42 2001/05/03 17:50:55 tgl Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_table.sgml,v 1.43 2001/08/10 18:57:32 tgl Exp $ Postgres documentation --> @@ -25,8 +25,9 @@ Postgres documentation <synopsis> CREATE [ TEMPORARY | TEMP ] TABLE <replaceable class="PARAMETER">table_name</replaceable> ( { <replaceable class="PARAMETER">column_name</replaceable> <replaceable class="PARAMETER">type</replaceable> [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ] - | <replaceable>table_constraint</replaceable> } [, ... ] - ) [ INHERITS ( <replaceable>parent_table</replaceable> [, ... ] ) ] + | <replaceable>table_constraint</replaceable> } [, ... ] ) + [ INHERITS ( <replaceable>parent_table</replaceable> [, ... ] ) ] + [ WITH OIDS | WITHOUT OIDS ] where <replaceable class="PARAMETER">column_constraint</replaceable> can be: [ CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> ] @@ -109,6 +110,18 @@ and <replaceable class="PARAMETER">table_constraint</replaceable> can be: </varlistentry> <varlistentry> + <term>WITH OIDS or WITHOUT OIDS</term> + <listitem> + <para> + This optional clause specifies whether rows of the new table should + have OIDs (object identifiers) assigned to them. The default is + WITH OIDS. (If the new table inherits from any tables that have OIDs, + then WITH OIDS is forced even if the command says WITHOUT OIDS.) + </para> + </listitem> + </varlistentry> + + <varlistentry> <term><replaceable class="PARAMETER">constraint_name</replaceable></term> <listitem> <para> @@ -303,6 +316,49 @@ INHERITS ( <replaceable class="PARAMETER">parent_table</replaceable> [, ... ] ) </para> </refsect1> + <refsect1 id="R1-SQL-OIDSCLAUSE-1"> + <title id="R1-SQL-OIDSCLAUSE-1-TITLE"> + OIDS Clause + </title> + <para> + <synopsis> + WITH OIDS | WITHOUT OIDS + </synopsis> + </para> + + <para> + This clause controls whether an OID (object ID) is generated and assigned + to each row inserted into the table. The default is WITH OIDS. + Specifying WITHOUT OIDS allows the user to suppress generation of + OIDs for rows of a table. This may be worthwhile for large + tables, since it will reduce OID consumption and thereby postpone + wraparound of the 32-bit OID counter. Once the counter wraps around, + uniqueness of OIDs can no longer be assumed, which considerably reduces + their usefulness. + </para> + + <para> + Whenever an application makes use of OIDs to identify specific rows of + a table, it is recommended that you create a unique index on OID for + that table, to ensure that OIDs in the table will indeed uniquely + identify rows even after counter wraparound. (An index on OID is needed + anyway for fast lookup of rows by OID.) Avoid assuming that OIDs are + unique across tables --- if you need a database-wide unique identifier, + use the combination of tableoid and row OID for the purpose. (It is + likely that future Postgres releases will use a separate OID counter + for each table, so that it will be <emphasis>necessary</> not optional + to include tableoid to have a unique identifier database-wide.) + </para> + + <tip> + <para> + WITHOUT OIDS is not recommended for tables with no primary key, since + without either an OID or a unique data key, it is difficult to identify + specific rows. + </para> + </tip> + </refsect1> + <refsect1 id="R1-SQL-DEFAULTCLAUSE-1"> <title id="R1-SQL-DEFAULTCLAUSE-1-TITLE"> DEFAULT Clause @@ -2098,6 +2154,18 @@ ALTER DOMAIN cities supported by <productname>Postgres</productname>. </para> </refsect3> + + <refsect3 id="R3-SQL-INHERITANCE-1"> + <title> + Object IDs + </title> + <para> + The <productname>Postgres</productname> concept of OIDs is not + standard. SQL99 (but not SQL92) has a notion of object ID, but + the syntax and semantics are different --- SQL99 associates OIDs + with individual values, not with rows. + </para> + </refsect3> </refsect2> </refsect1> </refentry> |