Hi hackers,
Currently, the COPY TO api does not support callback functions, while the COPY FROM api does. The COPY TO code does, however, include placeholders for supporting callbacks in the future.
Rounding out the support of callback functions to both could be very beneficial for extension development. In particular, supporting callbacks for COPY TO will allow developers to utilize the preexisting command in order to create tools that give users more support for moving data for storage, backup, analytics, etc.
We are aiming to get the support in core PostgreSQL and add COPY TO callback support in the next commitfest. The attached patch contains a change to COPY TO api to support callbacks.
Best,
Bilva