Hi Bilva, Thank you for registering this patch!
I had a few suggestions: 1. Please run pg_indent[1] on your code. Make sure you add copy_data_destination_cb to src/tools/pgindent/typedefs.list. Please run pg_indent on only the files you changed (it will take files as command line args) 2. For features such as this, it is often helpful to find a use case within backend/utility/extension code that demonstrate thes callback and to include the code to exercise it with the patch. Refer how copy_read_data() is used as copy_data_source_cb, to copy the data from the query results from the WAL receiver (Refer: copy_table()). Finding a similar use case in the source tree will make a stronger case for this patch. 3. Wouldn't we want to return the number of bytes written from copy_data_destination_cb? (Similar to copy_data_source_cb) We should also think about how to represent failure. Looking at CopySendEndOfRow(), we should error out like we do for the other copy_dests after checking the return value for the callback invocation. 4. > bool pipe = (cstate->filename == NULL) && (cstate->data_destination_cb == > NULL); I think a similar change should also be applied to BeginCopyFrom() and CopyFrom(). Or even better, such code could be refactored to have a separate destination type COPY_PIPE. This of course, will be a separate patch. I think the above line is okay for this patch. Regards, Soumyadeep
