In COPY FROM, fail cleanly when unsupported encoding conversion is needed.

tglsfdc · tglsfdc · commit ea0e7cd6b87f · 2023-10-01T12:09:26.000-04:00
In recent releases, such cases fail with "cache lookup failed for function 0" rather than complaining that the conversion function doesn't exist as prior versions did. Seems to be a consequence of sloppy refactoring in commit f82de5c. Add the missing error check. Per report from Pierre Fortin. Back-patch to v14 where the oversight crept in. Discussion: https://postgr.es/m/20230929163739.3bea46e5.pfortin@pfortin.com
diff --git a/src/backend/commands/copyfrom.c b/src/backend/commands/copyfrom.c
@@ -1481,6 +1481,12 @@ BeginCopyFrom(ParseState *pstate,
 		cstate->need_transcoding = true;
 		cstate->conversion_proc = FindDefaultConversionProc(cstate->file_encoding,
 															GetDatabaseEncoding());
+		if (!OidIsValid(cstate->conversion_proc))
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_FUNCTION),
+					 errmsg("default conversion function for encoding \"%s\" to \"%s\" does not exist",
+							pg_encoding_to_char(cstate->file_encoding),
+							pg_encoding_to_char(GetDatabaseEncoding()))));
 	}
 
 	cstate->copy_src = COPY_FILE;	/* default */
