plpgsql's exec_simple_cast_value() mistakenly supposed that it could bypass

casting effort whenever the input value was NULL.  However this prevents
application of not-null domain constraints in the cases that use this
function, as illustrated in bug #4741.  Since this function isn't meant
for use in performance-critical paths anyway, this certainly seems like
another case of "premature optimization is the root of all evil".

Back-patch as far as 8.2; older versions made no effort to enforce
domain constraints here anyway.

diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index ca4f33e103f37bdffdad2d78c6c39c7e065e4f3a..81c71e6c80679937e51ed098a94a19b8e34fe6fe 100644 (file)
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -4351,26 +4351,23 @@ exec_simple_cast_value(Datum value, Oid valtype,
                                           Oid reqtype, int32 reqtypmod,
                                           bool isnull)
 {
-       if (!isnull)
+       if (valtype != reqtype || reqtypmod != -1)
        {
-               if (valtype != reqtype || reqtypmod != -1)
-               {
-                       Oid                     typinput;
-                       Oid                     typioparam;
-                       FmgrInfo        finfo_input;
+               Oid                     typinput;
+               Oid                     typioparam;
+               FmgrInfo        finfo_input;
 
-                       getTypeInputInfo(reqtype, &typinput, &typioparam);
+               getTypeInputInfo(reqtype, &typinput, &typioparam);
 
-                       fmgr_info(typinput, &finfo_input);
+               fmgr_info(typinput, &finfo_input);
 
-                       value = exec_cast_value(value,
-                                                                       valtype,
-                                                                       reqtype,
-                                                                       &finfo_input,
-                                                                       typioparam,
-                                                                       reqtypmod,
-                                                                       isnull);
-               }
+               value = exec_cast_value(value,
+                                                               valtype,
+                                                               reqtype,
+                                                               &finfo_input,
+                                                               typioparam,
+                                                               reqtypmod,
+                                                               isnull);
        }
 
        return value;