> On Thu, Oct 8, 2015 at 9:39 PM, Robert Haas <robertmh...@gmail.com> wrote: > >> >> In the interest of full disclosure, I asked Ashutosh to work on this >> patch and have discussed the design with him several times. I believe >> that this is a good direction for PostgreSQL to be going. It's >> trivially easy right now to write a query against an FDW that performs >> needlessly easy, because a join, or a sort, or an aggregate is >> performed on the local server rather than the remote one. I, and >> EnterpriseDB, want that to get fixed. However, we also want it to get >> fixed in the best possible way, and not to do anything unless there is >> consensus on it. So, if anyone has opinions on this topic, please >> jump in. >> >
Are we planning to push sorting on foreign server with parametrized foreign path? We might get a parametrized path when local table is small enough and foreign table is bigger, like, for this query SELECT big_ft.x FROM big_ft, small_lt WHERE big_ft.x = small_lt.y; we might end up getting parametrized foreign path with remote query like: SELECT big_ft.x FROM big_ft WHERE big_ft.x = $1; And with this, if we have an ORDER BY clause like "ORDER BY big_ft.x" we will get remote query like: SELECT big_ft.x FROM big_ft WHERE big_ft.x = $1 ORDER BY big_ft.x; Is this possible??? If yes, then don't we need to sort again on local server? Assume each row on local server matches three rows from foreign table, then for each $1, we will have 3 rows returned from the foreign server, of-course sorted. But then all these fetched rows in batch of 3, needs to be re-sorted on local server, isn't it? If yes, this will be much more costly than fetching unsorted rows and sorting then locally only once. Or am I missing something here? -- Jeevan B Chalke Principal Software Engineer, Product Development EnterpriseDB Corporation The Enterprise PostgreSQL Company
