Thank you for your answer! As mentioned in the other reply,
de-normalization assigns the responsibility for consistent data to the
programmer.
Andrew Purtell schrieb:
> Hello,
>
>> From: Mork0075 <[EMAIL PROTECTED]>
>> Subject: Re: Why is scaling HBase much simpler then scaling a relational db?
>> To: hbase-user@hadoop.apache.org
>> Date: Wednesday, August 27, 2008, 12:57 AM
>>> Can you please provide an example of "good
>>> de-normalization" in HBase and how its held
>>> consistent
>
> I explain it to colleagues as "insert time joins". If
> your query is going to pull data items {x,y,z} then
> you should duplicate/store {x,y,z} next to each other
> such that they will all be pulled off of disk -- from
> one location only -- to satisfy the query. This could
> be either in the same row of the same table (good), or
> in the same column family of the same table (better).
>
> table t:
> column c:
>
> insert using qualifiers 'c:x', 'c:y', and 'c:z'
>
>> Our webapp doenst use joins at the moment anyway.
>
> So then I assume your schema is normalized, maybe even
> third normal form, and/or uses secondary indexes then,
> or tertiary indexes etc.?
>
>>> As you describe it, its a problem of implementation.
> [...]
>>> Could MySQL perhaps decide tomorrow to implement
>>> something similar or does the relational model
>>> avoids this?
>
> Bigtable (therefore HBase) is a response to the
> particulars of very very large databases, especially as
> relates to the capabilities and limitations of today's
> storage hardware. Sharding a relational database in
> comparison is a hack and has drawbacks already
> explained in this thread.
>
> With that said there is nothing that says that someone
> could not layer at least some subset of the relational
> model and SQL support on top of the bigtable storage
> model. I think Vertica does this. If MySQL decided to do
> this one day that would be great. However the work
> involved is substantial in my estimation. Vertica is not
> giving away free product after doing that hard work...
>
> Hope this helps,
>
> - Andy
>
>
>
>
>
