On Wed, Sep 30, 2020 at 01:48:12PM +0500, Andrey V. Lepikhov wrote: > Your code almost exactly the same as proposed in [1] as part of 'Fast COPY > FROM' command. But it seems there are differences. > > [1] > https://www.postgresql.org/message-id/flat/3d0909dc-3691-a576-208a-90986e55489f%40postgrespro.ru
I have been looking at what you have here while reviewing the contents of this thread, and it seems to me that you should basically be able to achieve the row-level control that your patch is doing with the callback to do the per-row processing posted here. The main difference, though, is that you want to have more control at the beginning and the end of the COPY TO processing which explains the split of DoCopyTo(). I am a bit surprised to see this much footprint in the backend code once there are two FDW callbacks to control the beginning and the end of the COPY TO, to be honest, sacrifying a lot the existing symmetry between the COPY TO and COPY FROM code paths where there is currently a strict control on the pre-row and post-row processing like the per-row memory context. -- Michael
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