Does index be used when doing "join" operation between a big table and a small table?

[孙而焓]

hello，

I have 2 tables need to do "join" operation by their primary key, the primary key of these 2 tables are both type "String".

There are 200 million pieces of data in the big table and only 20 throusand pieces of data in the small table.

This join operation is quite slow.
I want to know does index be used when doing "join" operation between a big table and a small table?

And how to confirm whether index be used?





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[Liang Chen]

If the index be used,  the number of tasks would be less.

Can you share your script (create table script and query script), let us
check if you created the effective index for filter columns.

Regards
Liang



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[Liang Chen]

Hi

If the index be used for filtering data, the number of tasks would be more
less.
Can you share the script(create table and query), let us check if created
the effective index for filter columns.  

Regards
Liang


Mic Sun wrote

> hello，
>
> I have 2 tables need to do "join" operation by their primary key, the
> primary key of these 2 tables are both type "String".
>
> There are 200 million pieces of data in the big table and only 20
> throusand pieces of data in the small table.
>
> This join operation is quite slow.
> I want to know does index be used when doing "join" operation between a
> big table and a small table?
>
> And how to confirm whether index be used?
>
>
>
>

> sunerhan1992@





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[孙而焓]

Except the number of tasks, can we confirm whether to use index from the log
file?
Such as something like keyword for us to search in the log file directly.



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