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 4d43ba0584a37ae217479065aa85b5858643ef67..b82cbea14ed4c9bd4b1a50f461af94d8f9e83a19 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -4159,7 +4159,23 @@ cast(-44 as bit(12))           111111010100
     !~~ and !~~* operators that
     represent NOT LIKE and NOT
     ILIKE, respectively.  All of these operators are
-    PostgreSQL-specific.
+    PostgreSQL-specific.  You may see these
+    operator names in EXPLAIN output and similar
+    places, since the parser actually translates LIKE
+    et al. to these operators.
+   
+
+   
+    The phrases LIKE, ILIKE,
+    NOT LIKE, and NOT ILIKE are
+    generally treated as operators
+    in PostgreSQL syntax; for example they can
+    be used in expression
+    operator ANY
+    (subquery) constructs, although
+    an ESCAPE clause cannot be included there.  In some
+    obscure cases it may be necessary to use the underlying operator names
+    instead.