Doc: explain that the string types can't store \0 (ASCII NUL).

This restriction was mentioned in connection with string literals,
but it wasn't made clear that it's a general restriction not just
a syntactic limitation in query strings.

Per unsigned documentation comment.

Discussion: https://postgr.es/m/160720552914.710.16625261471128631268@wrigleys.postgresql.org

diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml
index 35b9161871aafbf6fd3b4846ea2a288cdfe058d3..483263997f14928b34388c33ed75d06ceb96ef73 100644 (file)
--- a/doc/src/sgml/datatype.sgml
+++ b/doc/src/sgml/datatype.sgml
@@ -1166,6 +1166,14 @@ SELECT '52093.89'::money::numeric::float8;
     regular expressions.
    
 
+   
+    The characters that can be stored in any of these data types are
+    determined by the database character set, which is selected when
+    the database is created.  Regardless of the specific character set,
+    the character with code zero (sometimes called NUL) cannot be stored.
+    For more information refer to .
+   
+
    
     The storage requirement for a short string (up to 126 bytes) is 1 byte
     plus the actual string, which includes the space padding in the case of
@@ -1203,10 +1211,7 @@ SELECT '52093.89'::money::numeric::float8;
    
     Refer to  for information about
     the syntax of string literals, and to 
-    for information about available operators and functions. The
-    database character set determines the character set used to store
-    textual values; for more information on character set support,
-    refer to .
+    for information about available operators and functions.