On 12 September 2015 at 00:45, Anastasia Lubennikova < a.lubennik...@postgrespro.ru> wrote:
> I've started work on a patch that allows to combine covering and unique > functionality. > Great to hear someone is working on this! > Next issue is pg_index changes. > Now there's only a boolean flag > > - bool indisunique; /* is this a unique index? */ > > But new algorithm requires to store a single number > > - unit16 n_unique_columns; /* number of first columns of index which > has unique constrains. */ > > I think, that numbers of all attributes themselves are not needed. Is it > right? > > I think the total number of attributes is already in indnatts. I imagine you're planning to keep the indexed columns at the start of the indkey[] array, and just use n_unique_columns to mark how many of the indkey[] attributes to check as indexed columns. I'd imagine the change would be fairly simple from a planner point of view as you'd just need to check columns 1 to n_unique_columns instead of 1 to indnatts. Although I have a tendency to under estimate these things :( I imagine you don't want to name the new column n_unique_columns, since it does not fit too well with non-unique indexes. Perhaps just indindexedatts, or something slightly along those lines. But perhaps it would be a good idea to also rename "ncolumns" in code, to ensure that any non-updated code does not even compile. Perhaps including "tot" or "total" in there might help indicate it's new meaning. Regards David Rowley -- David Rowley http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Training & Services
