In CREATE CONVERSION, test that the given function is a valid conversion

function for the specified source and destination encodings. We do that by
calling the function with an empty string. If it can't perform the requested
conversion, it will throw an error.

Backport to 7.4 - 8.3. Per bug report #4680 by Denis Afonin.

diff --git a/src/backend/commands/conversioncmds.c b/src/backend/commands/conversioncmds.c
index f067da298373f3fb1a2310f6739c1833f7c138f6..b716dd8e4f523fe87b446bab9df885d10505dffc 100644 (file)
--- a/src/backend/commands/conversioncmds.c
+++ b/src/backend/commands/conversioncmds.c
@@ -49,6 +49,7 @@ CreateConversionCommand(CreateConversionStmt *stmt)
        const char *to_encoding_name = stmt->to_encoding_name;
        List       *func_name = stmt->func_name;
        static Oid      funcargs[] = {INT4OID, INT4OID, CSTRINGOID, INTERNALOID, INT4OID};
+       char            result[1];
 
        /* Convert list of names to a name and namespace */
        namespaceId = QualifiedNameGetCreationNamespace(stmt->conversion_name,
@@ -95,6 +96,19 @@ CreateConversionCommand(CreateConversionStmt *stmt)
                aclcheck_error(aclresult, ACL_KIND_PROC,
                                           NameListToString(func_name));
 
+       /*
+        * Check that the conversion function is suitable for the requested
+        * source and target encodings. We do that by calling the function with
+        * an empty string; the conversion function should throw an error if it
+        * can't perform the requested conversion.
+        */
+       OidFunctionCall5(funcoid,
+                                        Int32GetDatum(from_encoding),
+                                        Int32GetDatum(to_encoding),
+                                        CStringGetDatum(""),
+                                        CStringGetDatum(result),
+                                        Int32GetDatum(0));
+
        /*
         * All seem ok, go ahead (possible failure would be a duplicate conversion
         * name)