we do this for almost all our tables On May 5, 2015 11:05 AM, "jeremy p" <athomewithagroove...@gmail.com> wrote:
> Thank you for your response! > > So I guess 'salt' is a bit of a misnomer. What I used to do is this : > > 1) Say that my key value is something like '1234foobar' > 2) I obtain the hash of '1234foobar'. Let's say that's '54824923' > 3) I mod the hash by my number of regions. Let's say I have 2000 regions. > 54824923 % 2000 = 923 > 4) I prepend that value to my original key value, so my new key is > '923_1234foobar' > > Is this the same thing you were talking about? > > A couple questions : > > * Why would my regions only be 1/2 full? > * Why would I only use this for sequential keys? I would think this would > give better performance in any situation where I don't need range scans. > For example, let's say my key value is a person's last name. That will > naturally cluster around certain letters, giving me an uneven distribution. > > --Jeremy > > > > On Sun, May 3, 2015 at 11:46 AM, Michael Segel <michael_se...@hotmail.com> > wrote: > > > Yes, don’t use a salt. Salt implies that your seed is orthogonal (read > > random) to the base table row key. > > You’re better off using a truncated hash (md5 is fastest) so that at > least > > you can use a single get(). > > > > Common? > > > > Only if your row key is mostly sequential. > > > > Note that even with bucketing, you will still end up with regions only > 1/2 > > full with the only exception being the last region. > > > > > On May 1, 2015, at 11:09 AM, jeremy p <athomewithagroove...@gmail.com> > > wrote: > > > > > > Hello all, > > > > > > I've been out of the HBase world for a while, and I'm just now jumping > > back > > > in. > > > > > > As of HBase .94, it was still common to take a hash of your RowKey and > > use > > > that to "salt" the beginning of your RowKey to obtain an even > > distribution > > > among your region servers. Is this still a common practice, or is > there > > a > > > better way to do this in HBase 1.0? > > > > > > --Jeremy > > > > The opinions expressed here are mine, while they may reflect a cognitive > > thought, that is purely accidental. > > Use at your own risk. > > Michael Segel > > michael_segel (AT) hotmail.com > > > > > > > > > > > > >
