Re: [HACKERS] PATCH: Batch/pipelining support for libpq

Kyotaro HORIGUCHI wrote:

> A disucssion on psql batch mode was held in another branch of
> this thread. How do we treat that?

There's a batch mode for pgbench in a patch posted in [1],
with \beginbatch and \endbatch commands, but nothing
for psql AFAICS.
psql is more complicated because currently it uses a
blocking PQexec() call at its core. Craig mentioned psql
integration in [2] and [3].
Also a script can have inter-query dependencies such as in
insert into table(...) returning id \gset
update othertable set col= :id where ...;
which is a problem in batch mode, as we don't want
to send the update before the right value for :id is
known. Whether we want to support these dependencies
and how needs discussion.
For instance we might not support them at all, or
create a synchronization command that collects
all results of queries sent so far, or do it implicitly
when a variable is injected into a query...
This looks like substantial work that might be best
done separately from the libpq patch.

[1]
https://www.postgresql.org/message-id/b4e34135-2bd9-4b8a-94ca-27d760da26d7@manitou-mail.org
[2]
https://www.postgresql.org/message-id/CAMsr+YGLhaDkjymLuNVQy4MrSKQoA=F1vO=aN8XQf30N=aQuVA@mail.gmail.com
[3]
https://www.postgresql.org/message-id/CAMsr+YE6BK4iAaQz=nY3xDnbLhnNZ_4tp-PTJqbNNpsZMgoo8Q@mail.gmail.com

Best regards,
--
Daniel Vérité
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Twitter: @DanielVerite