I'm sorry if I missed something, but ISTM this is beginning to look a lot like GiST. This was pointed out by Robert Haas last year.
On Wed, Jun 18, 2014 at 12:09:42PM -0300, Claudio Freire wrote: > So, you have: > > An aggregate to generate a "compressed set" from several values Which GiST does by calling 'compress' on each value, and the 'unions' the results together. > A function which adds a new value to the "compressed set" and returns > the new "compressed set" Again, 'compress' + 'union' > A function which tests if a value is in a "compressed set" Which GiST does using 'compress' +'consistant' > A function which tests if a "compressed set" overlaps another > "compressed set" of equal type Which GiST calls 'consistant' So I'm wondering why you can't just reuse the btree_gist functions we already have in contrib. It seems to me that these MinMax indexes are in fact a variation on GiST that indexes the pages of a table based upon the 'union' of all the elements in a page. By reusing the GiST operator class you get support for many datatypes for free. > If you can define different compressed sets, you can use this to > generate both min/max indexes as well as bloom filter indexes. Whether > we'd want to have both is perhaps questionable, but having the ability > to is probably desirable. You could implement bloom filter in GiST too. It's been discussed before but I can't find any implementation. Probably because the filter needs to be parameterised and if you store the bloom filter for each element it gets expensive very quickly. However, hooked into a minmax structure which only indexes whole pages it could be quite efficient. > One problem with such a generalized implementation would be, that I'm > not sure in-place modification of the "compressed set" on-disk can be > assumed to be safe on all cases. Surely, for strictly-enlarging sets > it would, but while min/max and bloom filters both fit the bill, it's > not clear that one can assume this for all structures. I think GiST has already solved this problem. Have a nice day, -- Martijn van Oosterhout <klep...@svana.org> http://svana.org/kleptog/ > He who writes carelessly confesses thereby at the very outset that he does > not attach much importance to his own thoughts. -- Arthur Schopenhauer
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