Re: [HACKERS] IS OF

Bruce Momjian wrote:
> Can someone suggest where to document IS OF, and either document it's
> non-standard behavior or supply patch?
>

Doc patch attached for IS OF. Please apply.

Thanks,

Joe


> ---------------------------------------------------------------------------
>
> Joe Conway wrote:
>
>>Gavin Sherry wrote:
>>
>>>8.14 <type predicate> to be exact.
>>>
>>
>>8.18 in SQL200x. I don't think the current implementation quite meets
>>the spec however:
>>
>>regression=# select f2 is null, f2 is of(int) from bar;
>>  ?column? | ?column?
>>----------+----------
>>  f        | t
>>  t        | t
>>(2 rows)
>>
>>If I read the spec correctly, the null value should return null, not 't'
>>in the above.
>>
>>General Rules
>>1) Let V be the result of evaluating the <row value predicand>.
>>2) Let ST be the set consisting of every type that is either some
>>    exclusively specified type, or a subtype of some inclusively
>>    specified type.
>>3) Let TPR be the result of evaluating the <type predicate>.
>>
>>Case:
>>a) If V is the null value, then TPR is Unknown.
>>b) If the most specific type of V is a member of ST, then TPR is True .
>>c) Otherwise, TPR is False
>>
Index: doc/src/sgml/reference.sgml
===================================================================
RCS file: /opt/src/cvs/pgsql-server/doc/src/sgml/reference.sgml,v
retrieving revision 1.45
diff -c -r1.45 reference.sgml
*** doc/src/sgml/reference.sgml    27 Jun 2003 14:45:25 -0000    1.45
--- doc/src/sgml/reference.sgml    8 Aug 2003 05:16:26 -0000
***************
*** 108,113 ****
--- 108,114 ----
     &fetch;
     &grant;
     &insert;
+    &isof;
     &listen;
     &load;
     &lock;
Index: doc/src/sgml/ref/allfiles.sgml
===================================================================
RCS file: /opt/src/cvs/pgsql-server/doc/src/sgml/ref/allfiles.sgml,v
retrieving revision 1.54
diff -c -r1.54 allfiles.sgml
*** doc/src/sgml/ref/allfiles.sgml    27 Jun 2003 14:45:25 -0000    1.54
--- doc/src/sgml/ref/allfiles.sgml    8 Aug 2003 04:45:35 -0000
***************
*** 76,81 ****
--- 76,82 ----
  <!entity fetch              system "fetch.sgml">
  <!entity grant              system "grant.sgml">
  <!entity insert             system "insert.sgml">
+ <!entity isof               system "isof.sgml">
  <!entity listen             system "listen.sgml">
  <!entity load               system "load.sgml">
  <!entity lock               system "lock.sgml">
Index: doc/src/sgml/ref/isof.sgml
===================================================================
RCS file: doc/src/sgml/ref/isof.sgml
diff -N doc/src/sgml/ref/isof.sgml
*** /dev/null    1 Jan 1970 00:00:00 -0000
--- doc/src/sgml/ref/isof.sgml    8 Aug 2003 05:20:46 -0000
***************
*** 0 ****
--- 1,84 ----
+ <refentry id="SQL-ISOF">
+  <refmeta>
+   <refentrytitle id="SQL-ISOF-TITLE">IS OF</refentrytitle>
+   <refmiscinfo>SQL - Language Statements</refmiscinfo>
+  </refmeta>
+
+  <refnamediv>
+   <refname>IS OF</refname>
+   <refpurpose>specify a type test</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+ <synopsis>
+ <replaceable class="parameter">expression</replaceable> IS [ NOT ] OF ( <replaceable
class="PARAMETER">typename</replaceable>[,... ] ) 
+ </synopsis>
+  </refsynopsisdiv>
+
+  <refsect1 id="sql-isof-description">
+   <title>Description</title>
+
+   <para>
+    This command allows an expression to be checked against a list
+    of data types. It returns TRUE if any data type in the list matches
+    that of the <replaceable class="parameter">expression</replaceable>,
+    FALSE otherwise.
+   </para>
+
+  </refsect1>
+
+  <refsect1>
+   <title>Examples</title>
+ <programlisting>
+ regression=# SELECT 1::int4 IS OF (int4, int8);
+  ?column?
+ ----------
+  t
+ (1 row)
+
+ regression=# SELECT 1::int4 IS OF (text);
+  ?column?
+ ----------
+  f
+ (1 row)
+
+ regression=# SELECT ARRAY['a'] IS OF (text[]);
+  ?column?
+ ----------
+  t
+ (1 row)
+ </programlisting>
+  </refsect1>
+
+  <refsect1 id="sql-isof-compat">
+   <title>Compatibility</title>
+
+   <para>
+    The SQL standard specifies that <literal>IS OF</literal>
+    must result in <literal>UNKNOWN</literal> if
+    <replaceable class="parameter">expression</replaceable> is
+    <literal>NULL</literal>. The <productname>PostgreSQL</productname>
+    implementation results in <literal>TRUE</literal> or <literal>FALSE</literal>
+    as appropriate based on the data type assigned by the planner.
+    Otherwise, this command is fully conforming.
+   </para>
+  </refsect1>
+
+ </refentry>
+
+ <!-- Keep this comment at the end of the file
+ Local variables:
+ mode: sgml
+ sgml-omittag:nil
+ sgml-shorttag:t
+ sgml-minimize-attributes:nil
+ sgml-always-quote-attributes:t
+ sgml-indent-step:1
+ sgml-indent-data:t
+ sgml-parent-document:nil
+ sgml-default-dtd-file:"../reference.ced"
+ sgml-exposed-tags:nil
+ sgml-local-catalogs:"/usr/lib/sgml/catalog"
+ sgml-local-ecat-files:nil
+ End:
+ -->