On Fri, Apr 22, 2016 at 1:45 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
neha khatri <nehakhatri5@gmail.com> writes: > I have recently started working on Postgresql and I was looking in the the > pg_upgrade code. pg_upgrade checks index control data(max_index_keys) to be > equal in the old and new version.
> I would like to understand why the number of index columns should be equal > in new and old versions.
Because that changes the size of index tuple headers, see src/include/access/itup.h > Can the number of maximum index columns not be > changed from one release to another release.
Sure, as long as you don't care about on-disk database compatibility. The checks associated with pg_control are meant to ensure exactly that, though.