On Fri, Jun 14, 2013 at 11:28 PM, Alvaro Herrera <alvhe...@2ndquadrant.com> wrote: > Re-summarization is relatively expensive, because the complete page range has > to be scanned.
That doesn't sound too bad to me. It just means there's a downside to having larger page ranges. I would expect the page ranges to be something in the ballpark of 32 pages -- scanning 32 pages to resummarize doesn't sound that painful but sounds like it's large enough that the resulting index would be a reasonable size. But I don't understand why an insert would invalid a tuple. An insert can just update the min and max incrementally. It's a delete that invalidates the range but as you note it doesn't really invalidate it, just mark it as needing a refresh -- and even then only if the value being deleted is equal to either the min or max. > Same-size page ranges? > Current related literature seems to consider that each "index entry" in a > minmax index must cover the same number of pages. There doesn't seem to be a I assume the reason for this in the literature is the need to quickly find the summary for a given page when you're handling an insert or delete. If you have some kind of meta data structure that lets you find it (which I gather is what the validity map is?) then you wouldn't need it. But that seems like a difficulty cost to justify compared to just having a 1:1 mapping from block to bitmap tuple. -- greg -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
