Add new to_reg* functions for error-free OID lookups.

These functions won't throw an error if the object doesn't exist,
or if (for functions and operators) there's more than one matching
object.

Yugo Nagata and Nozomi Anzai, reviewed by Amit Khandekar, Marti
Raudsepp, Amit Kapila, and me.

1 files changed, 48 insertions, 0 deletions

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 6e2fbda6c23..33e093e2ab9 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15279,6 +15279,22 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
     <primary>collation for</primary>
    </indexterm>
 
+   <indexterm>
+    <primary>to_regclass</primary>
+   </indexterm>
+
+   <indexterm>
+    <primary>to_regproc</primary>
+   </indexterm>
+
+   <indexterm>
+    <primary>to_regoper</primary>
+   </indexterm>
+
+   <indexterm>
+    <primary>to_regtype</primary>
+   </indexterm>
+
   <para>
    <xref linkend="functions-info-catalog-table"> lists functions that
    extract information from the system catalogs.
@@ -15449,6 +15465,26 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
        <entry><type>text</type></entry>
        <entry>get the collation of the argument</entry>
       </row>
+      <row>
+       <entry><literal><function>to_regclass(<parameter>rel_name</parameter>)</function></literal></entry>
+       <entry><type>regclass</type></entry>
+       <entry>get the oid of the named relation</entry>
+      </row>
+      <row>
+       <entry><literal><function>to_regproc(<parameter>func_name</parameter>)</function></literal></entry>
+       <entry><type>regproc</type></entry>
+       <entry>get the oid of the named function</entry>
+      </row>
+      <row>
+       <entry><literal><function>to_regoper(<parameter>operator_name</parameter>)</function></literal></entry>
+       <entry><type>regoper</type></entry>
+       <entry>get the oid of the named operator</entry>
+      </row>
+      <row>
+       <entry><literal><function>to_regtype(<parameter>type_name</parameter>)</function></literal></entry>
+       <entry><type>regtype</type></entry>
+       <entry>get the oid of the named type</entry>
+      </row>
      </tbody>
     </tgroup>
    </table>
@@ -15614,6 +15650,18 @@ SELECT collation for ('foo' COLLATE "de_DE");
   is not of a collatable data type, then an error is raised.
   </para>
 
+  <para>
+   The <function>to_regclass</function>, <function>to_regproc</function>,
+   <function>to_regoper</function> and <function>to_regtype</function>
+   translate relation, function, operator, and type names to objects of
+   type <type>regclass</>, <type>regproc</>, <type>regoper</> and
+   <type>regtype</>, respectively.  These functions differ from a cast from
+   text in that they don't accept a numeric OID, and that they return null
+   rather than throwing an error if the name is not found (or, for
+   <function>to_regproc</function> and <function>to_regoper</function>, if
+   the given name matches multiple objects).
+  </para>
+
    <indexterm>
     <primary>col_description</primary>
    </indexterm>