On Fri, Mar 11, 2022 at 9:57 AM Tomas Vondra <tomas.von...@enterprisedb.com> wrote: > Hi Tomas, Thanks for your patches.
On Mon, Mar 9, 2022 at 9:53 PM Tomas Vondra <tomas.von...@enterprisedb.com> wrote: >On Wed, Mar 9, 2022 at 6:04 PM Amit Kapila <amit.kapil...@gmail.com> wrote: >>On Mon, Mar 7, 2022 at 11:18 PM Tomas Vondra <tomas.von...@enterprisedb.com> >>wrote: >>>On Fri, Mar 4, 2022 at 6:43 PM Amit Kapila <amit.kapil...@gmail.com> wrote: > >>> Fetching column filter info in tablesync.c is quite expensive. It > >>> seems to be using four round-trips to get the complete info whereas > >>> for row-filter we use just one round trip. I think we should try to > >>> get both row filter and column filter info in just one round trip. > >>> > >> > >> Maybe, but I really don't think this is an issue. > >> > > > > I am not sure but it might matter for small tables. Leaving aside the > > performance issue, I think the current way will get the wrong column > > list in many cases: (a) The ALL TABLES IN SCHEMA case handling won't > > work for partitioned tables when the partitioned table is part of one > > schema and partition table is part of another schema. (b) The handling > > of partition tables in other cases will fetch incorrect lists as it > > tries to fetch the column list of all the partitions in the hierarchy. > > > > One of my colleagues has even tested these cases both for column > > filters and row filters and we find the behavior of row filter is okay > > whereas for column filter it uses the wrong column list. We will share > > the tests and results with you in a later email. We are trying to > > unify the column filter queries with row filter to make their behavior > > the same and will share the findings once it is done. I hope if we are > > able to achieve this that we will reduce the chances of bugs in this > > area. > > > > OK, I'll take a look at that email. I tried to get both the column filters and the row filters with one SQL, but it failed because I think the result is not easy to parse. I noted that we use two SQLs to get column filters in the latest patches(20220311). I think maybe we could use one SQL to get column filters to reduce network cost. Like the SQL in the attachment. Regards, Wang wei
0001-Try-to-get-column-filters-with-one-SQL.patch
Description: 0001-Try-to-get-column-filters-with-one-SQL.patch
