On 12 June 2015 at 20:06, Tom Lane <t...@sss.pgh.pa.us> wrote: > Simon Riggs <si...@2ndquadrant.com> writes: > > On 11 June 2015 at 22:12, Shay Rojansky <r...@roji.org> wrote: > >> Just in case it's interesting to you... The reason we implemented things > >> this way is in order to avoid a deadlock situation - if we send two > queries > >> as P1/D1/B1/E1/P2/D2/B2/E2, and the first query has a large resultset, > >> PostgreSQL may block writing the resultset, since Npgsql isn't reading > it > >> at that point. Npgsql on its part may get stuck writing the second query > >> (if it's big enough) since PostgreSQL isn't reading on its end (thanks > to > >> Emil Lenngren for pointing this out originally). > > > That part does sound like a problem that we have no good answer to. > Sounds > > worth starting a new thread on that. > > I do not accept that the backend needs to deal with that; it's the > responsibility of the client side to manage buffering properly if it is > trying to overlap sending the next query with receipt of data from a > previous one. See commit 2a3f6e368 for a related issue in libpq. >
Then it's our responsibility to define what "manage buffering properly" means and document it. People should be able to talk to us without risk of deadlock. -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
