Hi Amit, Thanks for the review, On Mon, Mar 20, 2017 at 5:17 PM, Amit Kapila <amit.kapil...@gmail.com> wrote: > idea could be to make hashm_spares a two-dimensional array > hashm_spares[32][4] where the first dimension will indicate the split > point and second will indicate the sub-split number. I am not sure > whether it will be simpler or complex than the method used in the > proposed patch, but I think we should think a bit more to see if we > can come up with some simple technique to solve this problem.
I think making it a 2-dimensional array will not be any useful in fact we really treat the given array 2-dimensional elements now. The main concern of yours I think is the calculation steps to find the phase of the splitpoint group the bucket belongs to. + tbuckets = (1 << (splitpoint_group + 2)); + phases_beyond_bucket = + (tbuckets - num_bucket) / (1 << (splitpoint_group - 1)); + return (((splitpoint_group + 1) << 2) - phases_beyond_bucket) - 1; Quickly thinking further we allocate 2^x of buckets on each phase of any splitpoint group and we have 4 such phases in each group; At each splitpoint group again we allocate 2^y buckets, So buckets number have a pattern in their bitmap representation to find out which phase of allocation they belong to. As below =========== Group 0 -- bit 0, 1 define which phase of group each bucket belong to. 0 -- 00000000 1 -- 00000001 2 -- 00000010 3 -- 00000011 =========== Group 1 -- bit 0, 1 define which phase of group each bucket belong to. 4 -- 00000100 5 -- 00000101 6 -- 00000110 7 -- 00000111 =========== Group 2 -- bit 1, 2 define which phase of group each bucket belong to. 8 -- 00001000 9 -- 00001001 10 -- 00001010 11 -- 00001011 12 -- 00001100 13 -- 00001101 14 -- 00001110 15 -- 00001111 =========== Group 3 -- bit 2, 3 define which phase of group each bucket belong to. 16 -- 00010000 17 -- 00010001 18 -- 00010010 19 -- 00010011 20 -- 00010100 21 -- 00010101 22 -- 00010110 23 -- 00010111 24 -- 00011000 25 -- 00011001 26 -- 00011010 27 -- 00011011 28 -- 00011100 29 -- 00011101 30 -- 00011110 31 -- 00011111 ============ So we can say given a bucket x of group n > 0 bits (n-1, n) defines which phase of group they belong to. I see an opportunity here to completely simplify the above calculation into a simple bitwise anding the bucket number with (n-1,n) bitmask to get the phase of allocation of bucket x. Formula can be (x >> (splitpoint_group - 1)) & 0x3 = phase of bucket Does this satisfy your concern? -- Thanks and Regards Mithun C Y EnterpriseDB: http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
