Doc: explain that LIKE et al can be used in ANY (sub-select) etc.

This wasn't stated anywhere, and it's perhaps not that obvious,
since we get questions about it from time to time.  Also undocumented
was that the parser actually translates these into operators.

Discussion: https://postgr.es/m/CAFj8pRBkvZ71BqGKZnBBG4=0cKG+s50Dy+DYmrizUKEpAtdc+w@mail.gmail.com

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index cbc1aac6af80f86f850df9175b82e55b7698e2b7..43f0bf39f493802a499386f4354ed8d515b8036f 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -3945,7 +3945,23 @@ cast(-44 as bit(12))           <lineannotation>111111010100</lineannotation>
     <literal>!~~</literal> and <literal>!~~*</literal> operators that
     represent <function>NOT LIKE</function> and <function>NOT
     ILIKE</function>, respectively.  All of these operators are
-    <productname>PostgreSQL</productname>-specific.
+    <productname>PostgreSQL</productname>-specific.  You may see these
+    operator names in <command>EXPLAIN</command> output and similar
+    places, since the parser actually translates <function>LIKE</function>
+    et al. to these operators.
+   </para>
+
+   <para>
+    The phrases <function>LIKE</function>, <function>ILIKE</function>,
+    <function>NOT LIKE</function>, and <function>NOT ILIKE</function> are
+    generally treated as operators
+    in <productname>PostgreSQL</productname> syntax; for example they can
+    be used in <replaceable>expression</replaceable>
+    <replaceable>operator</replaceable> ANY
+    (<replaceable>subquery</replaceable>) constructs, although
+    an <literal>ESCAPE</literal> clause cannot be included there.  In some
+    obscure cases it may be necessary to use the underlying operator names
+    instead.
    </para>
   </sect2>