Re: COPY ON_CONFLICT TABLE; save duplicated record to another table.

Hi.

The attached patch should address most, if not all, of the issues you
both raised.

As explained in [1], we can export ExecInsert to let it perform the
main insertion work.
To allow ExecInsert to handle the remaining tasks, we need to carefuly manage
the lifecycle of constructed CopyFromStateData->ModifyTableContext (including
ModifyTableContext->EState): populate it, use it, and then release it.

Since ExecInsert already contains the necessary infrastructure for INSERT ON
CONFLICT DO NOTHING/SELECT, exporting it avoids duplicating that logic in
src/backend/commands/copyfrom.c (which is what v1 of the patch did).

[1]: https://postgr.es/m/CACJufxH_NbPuA+O5YR7xP4xDZ+iHkO2VFkddhrhBz+4-EUTp7w@mail.gmail.com

The exclusion unique constraint issue is still not resolved.... but,
overall v2 is better than v1, IMHO.



--
jian
https://www.enterprisedb.com/