On 2014-08-29 22:42:46 +0900, Michael Paquier wrote: > Hi all, > > Using a plugin producing binary output, I came across this error: > =# select data from pg_logical_slot_peek_changes('foo', NULL, NULL); > ERROR: 0A000: output plugin cannot produce binary output > LOCATION: pg_logical_slot_get_changes_guts, logicalfuncs.c:404 > > Shouldn't the error message be here something like "binary output plugin > cannot produce textual output"? The plugin used in my case produces binary > output, but what is requested from it with pg_logical_slot_peek_changes is > textual output.
I don't like the new message much. It's imo even more misleading than the old message. How about "output plugin produces binary output but the sink only accepts textual data"?
Sounds fine for me. I am sure that native English speakers will come up as well with additional suggestions.
Btw, I am having a hard time understanding in which case OUTPUT_PLUGIN_BINARY_OUTPUT is actually useful. Looking at the code it is only a subset of what OUTPUT_PLUGIN_TEXTUAL_OUTPUT can do as textual can generate both binary and textual output, while binary can only generate binary output. The only code path where a flag OUTPUT_PLUGIN_* is used is in this code path for this very specific error message. On top of that, a logical receiver receives data in textual form even if the decoder is marked as binary when getting a message with PQgetCopyData.
Perhaps I am missing something... But in this case I think that the documentation should have a more detailed explanation about the output format options. Currently only the option value is mentioned, and there is nothing about what they actually do. This is error-prone for the user.
