On Wed, Mar 26, 2014 at 1:22 PM, Stephan Beal <[email protected]> wrote:
> Last summer i remember running some numbers on this in the tcl repo and > IIRC the biggest collision was 10 or 11. 12 seemed to be the magic point at > which all collisions disappear (IIRC). > It seems that in fossil the highest collision in fossil is 8 bytes long: sqlite> select substr(uuid,0,8) as short, count(*) from blob group by short having count(short)>1; b652b90|2 sqlite> select uuid from blob where uuid glob 'b652b90*'; b652b900e940c3bb5cbbfb2b0c4a98cb5edb1c90 # a ticket re. RSS feed b652b9088b0d9e9cc8c2fb4c153443d72429d7c9 # some old/replaced C file sqlite> select substr(uuid,0,9) as short, count(*) from blob group by short having count(short)>1; sqlite> select substr(uuid,0,10) as short, count(*) from blob group by short having count(short)>1; sqlite> select substr(uuid,0,11) as short, count(*) from blob group by short having count(short)>1; collisions start to become "common" at 7 bytes: sqlite> select substr(uuid,0,7) as short, count(*) from blob group by short having count(short)>1; 0830c3|2 6fdf52|2 8d712d|2 904ab4|2 927257|2 940431|2 b652b9|2 ba837f|2 bdbf14|2 be32eb|2 c1b1ba|2 c8735d|2 d07537|2 d43165|2 e980ba|2 ef17fb|2 f94f7e|2 -- ----- stephan beal http://wanderinghorse.net/home/stephan/ http://gplus.to/sgbeal "Freedom is sloppy. But since tyranny's the only guaranteed byproduct of those who insist on a perfect world, freedom will have to do." -- Bigby Wolf
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