diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/bki.sgml | 5 | ||||
| -rw-r--r-- | doc/src/sgml/datatype.sgml | 167 |
2 files changed, 163 insertions, 9 deletions
diff --git a/doc/src/sgml/bki.sgml b/doc/src/sgml/bki.sgml index 4ea0f5f92ba..36503de6590 100644 --- a/doc/src/sgml/bki.sgml +++ b/doc/src/sgml/bki.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/bki.sgml,v 1.10 2002/03/22 19:20:02 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/bki.sgml,v 1.11 2002/04/25 02:56:55 tgl Exp $ --> <chapter id="bki"> @@ -122,7 +122,8 @@ $Header: /cvsroot/pgsql/doc/src/sgml/bki.sgml,v 1.10 2002/03/22 19:20:02 petere storage. The following types are allowed: <type>bool</type>, <type>bytea</type>, <type>char</type> (1 byte), <type>name</type>, <type>int2</type>, <type>int2vector</type>, - <type>int4</type>, <type>regproc</type>, <type>text</type>, + <type>int4</type>, <type>regproc</type>, <type>regclass</type>, + <type>regtype</type>, <type>text</type>, <type>oid</type>, <type>tid</type>, <type>xid</type>, <type>cid</type>, <type>oidvector</type>, <type>smgr</type>, <type>_int4</type> (array), <type>_aclitem</type> (array). diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml index aef751cbc58..4f06cee5037 100644 --- a/doc/src/sgml/datatype.sgml +++ b/doc/src/sgml/datatype.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.89 2002/04/21 18:58:00 thomas Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.90 2002/04/25 02:56:55 tgl Exp $ --> <chapter id="datatype"> @@ -173,12 +173,6 @@ $Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.89 2002/04/21 18:58:00 th </row> <row> - <entry><type>oid</type></entry> - <entry></entry> - <entry>object identifier</entry> - </row> - - <row> <entry><type>path</type></entry> <entry></entry> <entry>open and closed geometric path in 2D plane</entry> @@ -2894,6 +2888,165 @@ SELECT SUBSTRING(b FROM 1 FOR 2) FROM test; </sect1> + <sect1 id="datatype-oid"> + <title>Object Identifier Types</title> + + <indexterm zone="datatype-oid"> + <primary>object identifier</primary> + <secondary>data type</secondary> + </indexterm> + + <indexterm zone="datatype-oid"> + <primary>oid</primary> + </indexterm> + + <indexterm zone="datatype-oid"> + <primary>regproc</primary> + </indexterm> + + <indexterm zone="datatype-oid"> + <primary>regprocedure</primary> + </indexterm> + + <indexterm zone="datatype-oid"> + <primary>regoper</primary> + </indexterm> + + <indexterm zone="datatype-oid"> + <primary>regoperator</primary> + </indexterm> + + <indexterm zone="datatype-oid"> + <primary>regclass</primary> + </indexterm> + + <indexterm zone="datatype-oid"> + <primary>regtype</primary> + </indexterm> + + <para> + Object identifiers (OIDs) are used internally by + <productname>PostgreSQL</productname> as primary keys for various system + tables. Also, an OID system column is added to user-created tables + (unless <literal>WITHOUT OIDS</> is specified at table creation time). + Type <type>oid</> represents an object identifier. There are also + several aliases for <type>oid</>: <type>regproc</>, <type>regprocedure</>, + <type>regoper</>, <type>regoperator</>, <type>regclass</>, + and <type>regtype</>. + </para> + + <para> + The <type>oid</> type is currently implemented as an unsigned four-byte + integer. + Therefore, it is not large enough to provide database-wide uniqueness + in large databases, or even in large individual tables. So, using a + user-created table's OID column as a primary key is discouraged. + OIDs are best used only for references to system tables. + </para> + + <para> + The <type>oid</> type itself has few operations beyond comparison + (which is implemented as unsigned comparison). It can be cast to + integer, however, and then manipulated using the standard integer + operators. (Beware of possible signed-versus-unsigned confusion + if you do this.) + </para> + + <para> + The <type>oid</> alias types have no operations of their own except + for specialized input and output routines. These routines are able + to accept and display symbolic names for system objects, rather than + the raw numeric value that type <type>oid</> would use. The alias + types allow simplified lookup of OID values for objects: for example, + one may write <literal>'mytable'::regclass</> to get the OID of table + <literal>mytable</>, rather than <literal>SELECT oid FROM pg_class WHERE + relname = 'mytable'</>. (In reality, a much more complicated SELECT would + be needed to deal with selecting the right OID when there are multiple + tables named <literal>mytable</> in different schemas.) + </para> + + <para> + <table tocentry="1"> + <title>Object Identifier Types</title> + <tgroup cols="4"> + <thead> + <row> + <entry>Type name</entry> + <entry>References</entry> + <entry>Description</entry> + <entry>Examples</entry> + </row> + </thead> + + <tbody> + + <row> + <entry><type>oid</></entry> + <entry>any</entry> + <entry>Numeric object identifier</entry> + <entry>564182</entry> + </row> + + <row> + <entry><type>regproc</></entry> + <entry>pg_proc</entry> + <entry>Function name</entry> + <entry>sum</entry> + </row> + + <row> + <entry><type>regprocedure</></entry> + <entry>pg_proc</entry> + <entry>Function with argument types</entry> + <entry>sum(int4)</entry> + </row> + + <row> + <entry><type>regoper</></entry> + <entry>pg_operator</entry> + <entry>Operator name</entry> + <entry>+</entry> + </row> + + <row> + <entry><type>regoperator</></entry> + <entry>pg_operator</entry> + <entry>Operator with argument types</entry> + <entry>*(integer,integer) -(NONE,integer)</entry> + </row> + + <row> + <entry><type>regclass</></entry> + <entry>pg_class</entry> + <entry>Relation name</entry> + <entry>pg_type</entry> + </row> + + <row> + <entry><type>regtype</></entry> + <entry>pg_type</entry> + <entry>Type name</entry> + <entry>integer</entry> + </row> + </tbody> + </tgroup> + </table> + </para> + + <para> + All of the alias types accept schema-qualified names, and will + display schema-qualified names on output if the object would not + be found in the current search path without being qualified. + The <type>regproc</> and <type>regoper</> alias types will only + accept input names that are unique (not overloaded), so they are + of limited use; for most uses <type>regprocedure</> or + <type>regoperator</> is more appropriate. For <type>regoperator</>, + unary operators are identified by writing NONE for the unused + operand. + </para> + + </sect1> + </chapter> <!-- Keep this comment at the end of the file |