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

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 f82de5c46.  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
index cf0fc9d794d44329ffe977a634d5c76be6c0713f..cec80baceaf46f8fc5d301cb84f02abd7edade46 100644 (file)
--- a/src/backend/commands/copyfrom.c
+++ b/src/backend/commands/copyfrom.c
@@ -1485,6 +1485,12 @@ 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 */