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From Alex Kozlov <ale...@cloudera.com>
Subject Re: Hive assert()?
Date Thu, 26 May 2011 21:18:22 GMT
1) Would `select count(1) from (query)` do the same thing?  I am a bit
confused what is the semantic of assert: is it just no rows or some kind of
syntax error check?
2) Hive is not an OLTP and is not optimized for single row inserts (or
updates for this matter).  In a trivial implementation one would just do
copy-on-write, i.e. overwrite the whole data file, or add a small file
containing one or a few rows.  I do not think indices have been implemented
yet either.
3) You can probably do what you want with HBase (if you explain what you
want to do in more detail)


On Thu, May 26, 2011 at 2:00 PM, Igor Tatarinov <igor@decide.com> wrote:

> I would like to implement some kind of assert functionality in Hive QL.
>
> Here is how I do it in MySQL. I can assert that a given query returns no
> (bad) rows by creating a table with one row containing '1' and a unique
> index. Then, I try to insert into that table select 1 from (query). If the
> query returns something, I have an assert failure. I've found such asserts
> very helpful in catching data bugs early.
>
> Can I do something similar in Hive? I suppose I could implement a UDF that
> fails if it gets executed. This way I can ensure there is no records
> matching a given query.
> That doesn't sound too bad but perhaps there is a cleaner solution.
>
> Thanks!
>
>
>
>
>

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