bq. The downside that I see, is the bucket_number that we have to
maintain both at time or reading/writing and update it in case of
cluster restructuring.
I agree that this maintenance can be painful. However, Phoenix
(https://github.com/forcedotcom/phoenix) now supports salting,
automating this maintenance. If you want to salt your table, just add a
SALT_BUCKETS = <n> property at the end of your DDL statement, where <n>
is the total number of buckets (up to a max of 256). For example:
CREATE TABLE t (date_time DATE NOT NULL, event_id CHAR(15) NOT NULL
CONSTRAINT pk PRIMARY KEY (date_time, event_id))
SALT_BUCKETS=10;
This will add one byte at the beginning of your row key whose value is
formed by hashing the row key and mod-ing with 10. This will
automatically be done for any upsert and queries will automatically be
distributed and the results combined as expected.
Thanks,
James
@JamesPlusPlus
http://phoenix-hbase.blogspot.com/
On 04/30/2013 09:17 AM, Shahab Yunus wrote:
Well those are *some* words :) Anyway, can you explain a bit in detail that
why you feel so strongly about this design/approach? The salting here is
not the only option mentioned and static hashing can be used as well. Plus
even in case of salting, wouldn't the distributed scan take care of it? The
downside that I see, is the bucket_number that we have to maintain both at
time or reading/writing and update it in case of cluster restructuring.
Thanks,
Shahab
On Tue, Apr 30, 2013 at 11:57 AM, Michael Segel
<[email protected]>wrote:
Geez that's a bad article.
Never salt.
And yes there's a difference between using a salt and using the first 2-4
bytes from your MD5 hash.
(Hint: Salts are random. Your hash isn't. )
Sorry to be-itch but its a bad idea and it shouldn't be propagated.
On Apr 29, 2013, at 10:17 AM, Shahab Yunus <[email protected]> wrote:
I think you cannot use the scanner simply to to a range scan here as your
keys are not monotonically increasing. You need to apply logic to
decode/reverse your mechanism that you have used to hash your keys at the
time of writing. You might want to check out the SemaText library which
does distributed scans and seem to handle the scenarios that you want to
implement.
http://blog.sematext.com/2012/04/09/hbasewd-avoid-regionserver-hotspotting-despite-writing-records-with-sequential-keys/
On Mon, Apr 29, 2013 at 11:03 AM, <[email protected]> wrote:
Hi,
I have a rowkey defined by :
getMD5AsHex(Bytes.toBytes(myObjectId)) + String.format("%19d\n",
(Long.MAX_VALUE - changeDate.getTime()));
How could I get the previous and next row for a given rowkey ?
For instance, I have the following ordered keys :
00003db1b6c1e7e7d2ece41ff2184f76*9223370673172227807
00003db1b6c1e7e7d2ece41ff2184f76*9223370674468022807
00003db1b6c1e7e7d2ece41ff2184f76*9223370674468862807
00003db1b6c1e7e7d2ece41ff2184f76*9223370674984237807
00003db1b6c1e7e7d2ece41ff2184f76*9223370674987271807
If I choose the rowkey :
00003db1b6c1e7e7d2ece41ff2184f76*9223370674468862807, what would be the
correct scan to get the previous and next key ?
Result would be :
00003db1b6c1e7e7d2ece41ff2184f76*9223370674468022807
00003db1b6c1e7e7d2ece41ff2184f76*9223370674984237807
Thank you !
R.
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