David Rowley <david.rowley@2ndquadrant.com> writes: > On 29 July 2018 at 17:38, Dinesh Kumar <dns98944@gmail.com> wrote: >> I found performance variance between accessing int1 and int200 column which >> is quite large.
> Have a look at slot_deform_tuple and heap_deform_tuple. You'll see > that tuples are deformed starting at the first attribute. If you ask > for attribute 200 then it must deform 1-199 first.
Note that that can be optimized away in some cases, though evidently not the one the OP is testing. From memory, you need a tuple that contains no nulls, and all the columns to the left of the target column have to be fixed-width datatypes. Otherwise, the offset to the target column is uncertain, and we have to search for it.
