On Tue, Sep 21, 2021 at 8:58 AM Ajin Cherian <itsa...@gmail.com> wrote: > > I understand why this is done, but I have 2 concerns here 1) We are > > having extra deform and copying the field from new to old in case it > > is unchanged replica identity. 2) The same unchanged attribute values > > get qualified in the old tuple as well as in the new tuple. What > > exactly needs to be done is that the only updated field should be > > validated as part of the old as well as the new tuple, the unchanged > > field does not make sense to have redundant validation. For that we > > will have to change the filter for the old tuple to just validate the > > attributes which are actually modified and remaining unchanged and new > > values will anyway get validated in the new tuple. > > > But what if the filter expression depends on multiple columns, say (a+b) > 100 > where a is unchanged while b is changed. Then we will still need both > columns for applying
In such a case, we need to. > the filter even though one is unchanged. Also, I am not aware of any > mechanism by which > we can apply a filter expression on individual attributes. The current > mechanism does it > on a tuple. Do let me know if you have any ideas there? What I suggested is to modify the filter for the old tuple, e.g. filter is (a > 10 and b < 20 and c+d = 20), now only if a and c are modified then we can process the expression and we can transform this filter to (a > 10 and c+d=20). > > Even if it were done, there would still be the overhead of deforming the > tuple. Suppose filter is just (a > 10 and b < 20) and only if the a is updated, and if we are able to modify the filter for the oldtuple to be just (a>10) then also do we need to deform? Even if we have to we can save a lot on avoiding duplicate expression evaluation. > I will run some performance tests like Amit suggested and see what the > overhead is and > try to minimise it. It is good to know, I think you must try with some worst-case scenarios, e.g. we have 10 text column and 1 int column in the REPLICA IDENTITY and only the int column get updated and all the text column are not updated, and you have a filter on all the columns. Regards, Dilip Kumar EnterpriseDB: http://www.enterprisedb.com