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Make OIDs optional, per discussions in pghackers. WITH OIDS is still the

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default, but OIDS are removed from many system catalogs that don't need them.
Some interesting side effects: TOAST pointers are 20 bytes not 32 now;
pg_description has a three-column key instead of one.

Bugs fixed in passing: BINARY cursors work again; pg_class.relhaspkey
has some usefulness; pg_dump dumps comments on indexes, rules, and
triggers in a valid order.

initdb forced.
This commit is contained in:
Tom Lane
2001-08-10 18:57:42 +00:00
parent d062f0f4e9
commit bf56f0759b
83 changed files with 1962 additions and 1583 deletions
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33
doc/src/sgml/syntax.sgml
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@@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.43 2001/06/19 22:39:08 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.44 2001/08/10 18:57:32 tgl Exp $
-->
<chapter id="sql-syntax">
@@ -641,8 +641,9 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> )
<primary>OID</primary>
</indexterm>
The unique identifier (object ID) of a row. This is a serial number
that is added by Postgres to all rows automatically. OIDs are not
reused and are 32-bit quantities.
that is automatically added by Postgres to all table rows (unless
the table was created WITHOUT OIDS, in which case this column is
not present).
</para>
</listitem>
</varlistentry>
@@ -686,8 +687,10 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> )
<listitem>
<para>
The identity (transaction ID) of the deleting transaction,
or zero for an undeleted tuple. In practice, this is never nonzero
for a visible tuple.
or zero for an undeleted tuple. It is possible for this field
to be nonzero in a visible tuple: that indicates that the
deleting transaction hasn't committed yet, or that an attempted
deletion was rolled back.
</para>
</listitem>
</varlistentry>
@@ -697,7 +700,6 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> )
<listitem>
<para>
The command identifier within the deleting transaction, or zero.
Again, this is never nonzero for a visible tuple.
</para>
</listitem>
</varlistentry>
@@ -720,10 +722,27 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> )
</variablelist>
</para>
<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 they are unique.
Recommended practice when using OIDs for row identification is to create
a unique index on the OID column of each table for which the OID will be
used. Never assume that OIDs are unique across tables; use the
combination of tableoid and row OID if you need a database-wide
identifier. (Future releases of Postgres are likely to use a separate
OID counter for each table, so that tableoid <emphasis>must</> be
included to arrive at a globally unique identifier.)
</para>
<para>
Transaction and command identifiers are 32-bit quantities.
</para>
<para>
For further information on the system attributes consult
<xref linkend="STON87a" endterm="STON87a">.
Transaction and command identifiers are 32-bit quantities.
</para>
</sect1>