Not Supporting UNION in MapD


#1

Hi,

select name from a union select name from b;
Exception: Node LogicalUnion not supported yet

I was trying to use UNION But I am getting exception that “NOT SUPPORTED YET”.

In MapD, UNION is not there?

Thanks


#2

Hi @Ishika

Unfortunately, we don’t support union yet but can you try getting to your desired query result using a join. Using a join, you have to provide proper equijoin condition something like table1.id = table2.id. To get unique values, you should GROUP BY on that column.

Regards,
Veda


#3

Hi,

Thanks for reply @veda.

By using join, not getting expected result because using sum aggregate function in query.

Could you please tell me UNION will come in which release of MapD and when?

Thanks


#4

Hi @Ishika

It is likely that we will add the UNION ALL operator in the relatively near future. The base implementation of that is fairly trivial, its always been a question of whether, in the case that the constituent tables were small, we’d want to execute across as many tables at once as possible across multiple GPUs/CPU cores.

UNION, on the other hand, is not on our near-term roadmap. Do you need the de-duping of UNION or could you use UNION ALL?

Regards