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 de42788a91283dbce790f5a32714dea4d1351741..28c4fe1b17ccafa3360e11dfd4b76a8d334b7840 100644 (file)
--- a/src/backend/commands/conversioncmds.c
+++ b/src/backend/commands/conversioncmds.c
@@ -47,6 +47,7 @@ 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,
@@ -86,6 +87,19 @@ 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)