Document that an SQL-standard-compliant query that expects a unique row

from information_schema.referential_constraints might return several in
Postgres because we allow duplicate-named constraints in the same
schema.

diff --git a/doc/src/sgml/information_schema.sgml b/doc/src/sgml/information_schema.sgml
index 52407a741fe8614656fa74cbac74b0acaa83f52e..91c2dd4d525f424f4370776bfd2c23482d4023ad 100644 (file)
--- a/doc/src/sgml/information_schema.sgml
+++ b/doc/src/sgml/information_schema.sgml
@@ -3211,6 +3211,19 @@ ORDER BY c.ordinal_position;
     
    
   
+
+  
+   
+    The SQL standard requires constraint names to be unique within a
+    schema;  PostgreSQL, however, does not
+    enforce this restriction.  If duplicate-named constraints are
+    stored in the same PostgreSQL schema, a
+    standard-compliant query that expects to return one row might
+    return several, one for each matching constraint stored in the
+    specified schema.
+   
+  
+