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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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63
doc/src/sgml/catalogs.sgml
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@ -1,6 +1,6 @@
<!--
Documentation of the system catalogs, directed toward PostgreSQL developers
$Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.19 2001/07/15 22:48:15 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.20 2001/08/10 18:57:32 tgl Exp $
-->
<chapter id="catalogs">
@ -532,9 +532,9 @@
<para>
<structname>pg_class</structname> catalogues tables and mostly
everything else that has columns or is otherwise similar to a
table. This includes indexes (but see
table. This includes indexes (but see also
<structname>pg_index</structname>), sequences, views, and some
kinds of special relation kinds. Below, when we mean all of these
kinds of special relation. Below, when we mean all of these
kinds of objects we speak of <quote>relations</quote>. Not all
fields are meaningful for all relation types.
</para>
@ -565,8 +565,8 @@
<entry><type>oid</type></entry>
<entry>pg_type.oid</entry>
<entry>
The data type that corresponds to this table (not functional,
only set for system tables)
The OID of the data type that corresponds to this table, if any
(zero for indexes, which have no pg_type entry)
</entry>
</row>
@ -631,14 +631,19 @@
<entry>reltoastidxid</entry>
<entry><type>oid</type></entry>
<entry>pg_class.oid</entry>
<entry>Oid of the index on the TOAST table for this table, 0 if none</entry>
<entry>
For a TOAST table, the OID of its index. 0 if not a TOAST table.
</entry>
</row>
<row>
<entry>relhasindex</entry>
<entry><type>bool</type></entry>
<entry></entry>
<entry>True if this is a table and it has at least one index</entry>
<entry>True if this is a table and it has (or recently had) any indexes.
This is set by CREATE INDEX, but not cleared immediately by DROP INDEX.
VACUUM clears relhasindex if it finds the table has no indexes.
</entry>
</row>
<row>
@ -664,7 +669,7 @@
<entry><type>int2</type></entry>
<entry></entry>
<entry>
Number of columns in the relation, besides system columns.
Number of user columns in the relation (system columns not counted).
There must be this many corresponding entries in
<structname>pg_attribute</structname>. See also
<structname>pg_attribute</structname>.<structfield>attnum</structfield>.
@ -695,14 +700,30 @@
<entry>relukeys</entry>
<entry><type>int2</type></entry>
<entry></entry>
<entry>unused (<emphasis>Not</emphasis> the number of unique keys or something.)</entry>
<entry>unused (<emphasis>Not</emphasis> the number of unique keys)</entry>
</row>
<row>
<entry>relfkeys</entry>
<entry><type>int2</type></entry>
<entry></entry>
<entry>Number foreign keys on the table</entry>
<entry>unused (<emphasis>Not</emphasis> the number of foreign keys on the table)</entry>
</row>
<row>
<entry>relrefs</entry>
<entry><type>int2</type></entry>
<entry></entry>
<entry>unused</entry>
</row>
<row>
<entry>relhasoids</entry>
<entry><type>bool</type></entry>
<entry></entry>
<entry>
True if we generate an OID for each row of the relation.
</entry>
</row>
<row>
@ -710,8 +731,7 @@
<entry><type>bool</type></entry>
<entry></entry>
<entry>
unused (No, this does not say whether the table has a primary
key. It's really unused.)
True if the table has (or once had) a primary key.
</entry>
</row>
@ -726,7 +746,7 @@
<entry>relhassubclass</entry>
<entry><type>bool</type></entry>
<entry></entry>
<entry>At least one table inherits this one</entry>
<entry>At least one table inherits from this one</entry>
</row>
<row>
@ -874,6 +894,23 @@
<entry>The oid of the object this description pertains to</entry>
</row>
<row>
<entry>classoid</entry>
<entry><type>oid</type></entry>
<entry>pg_class.oid</entry>
<entry>The oid of the system catalog this object appears in</entry>
</row>
<row>
<entry>objsubid</entry>
<entry><type>int4</type></entry>
<entry></entry>
<entry>For a comment on a table attribute, this is the attribute's
column number (the objoid and classoid refer to the table itself).
For all other object types, this field is presently zero.
</entry>
</row>
<row>
<entry>description</entry>
<entry><type>text</type></entry>

74
doc/src/sgml/ref/create_table.sgml
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@ -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> ]
@ -108,6 +109,18 @@ and <replaceable class="PARAMETER">table_constraint</replaceable> can be:
</listitem>
</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>
@ -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>

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>