There are a couple of options - since it's not indexed, it may or not be
any faster.
a.) If your DB has a jdbc driver, use a linked table, query the linked
table and do the group/order by with H2.
b.) If you don't have a jdbc driver, you can treat CSVREAD() _as_ a table
without re-persisting it.
ex: given a csv like:
COMMON,DIFF
"a",1
"a",2
"b",3
"b",4
In h2, this works fine:
select common,count(diff) from CSVREAD('test.csv') group by common order by
common;
-Brian
On Friday, July 27, 2012 3:36:30 AM UTC-7, bharath phatak wrote:
>
> I am totally new to H2 database and have been following your posts in
> learning H2 database and working with it.
> I am stuck with a problem and need your advice .
>
> We treat H2 database as a tmpDB for running the query which are not
> supported by our underlying DB. Ex: Order by and Group By are not supported
> by our DB.
> To get this done we can use normal way like running the basic query on our
> DB ,storing the results in csv format and bulk insert into H2(CSVREAD) and
> run the query once again on H2 to get the final results.
>
> The problem with above approach is that it includes double I/O . The data
> can include million records.
>
> What we think:
>
>
> - Understand CSVREAD code and customize it to our needs.
> - The data keeps coming-in in buffer .
> - Without manipulating it,directly insert into H2 like CSVREAD.
> - Assuming that CSVREAD reads data and stores in a buffer before
> inserting into data, we need to implement CSVREAD code for inserting the
> data from buffer.
>
>
> Please advice on how to proceed further. It will be very helpful if you
> could provide point us to the CSVREAD code.
>
>
> Also please let us know if you have any better approach for bulk insert of
> data into H2 for buffer.
>
> Thanks in advance.
>
> Regards,
> Bharath
>
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