Re: Implement Join in Java: looking for ideas

From: David Baer (nospam_at_gmx.ch)
Date: 12/21/03 

Date: Sun, 21 Dec 2003 19:06:19 +0100

Hi Ruud,
The data is coming from different data sources (even allowing others types
than databases).

So I could put the data back into a database, just for the purpose of
joining it, where i could not benefit much from indices in the database.

I think it is better to do the joins myself, don't you think?

david

Ruud de Koter wrote:

> Hi David,
>
> You wrote:
>>
>> Hi, for a proto type i'm implementing a join-operation (as in relational
>> databases) on potentialy huge tables in java.
>>
>> if implemented naively, this takes at least size(Table1) * size(Table2).
>> my plan was to put the keys of the smaller table into a hashtable and
>> than iterate over the larger table.
>>
>> is there any comment on this, or you have ideas for better data
>> structures?
>
> Given the fact that most RDBMS manufacturers have (tens of) years of
> experience with joins, why would you want to implement that yourself? Or,
> more positively: are you sure you have good reason to assume you can do
> the joining better than the RDBMS will do it?
>
> Regards,
>
> Ruud.
>>
>> thank you!
>>
>> david
>

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