Re: Querying w/ join slow for large/many child tables

On 1/29/19 8:49 PM, Wells Oliver wrote:
> I have a primary parent table with a child table per week of the year for
> each week back through 2015. There are a lot of child tables. Each week's
> child table has maybe 80-110m rows.

A *partititioned* table?

>
> When I join to the parent table on a column, it's very slow, but when I
> manually specify the specific week's child table, it's quite fast, e.g.
>
> Slow:
> select * from foo
> join schema.mytable on foo.col = mytable.col
>
> vs. fast:
> select * from foo
> join schema.mytable_2015_wk33 as mytable on foo.col = mytable.col
>
> What's the resolution to make querying the table faster in terms of it
> finding the appropriate child table? Is it putting an index on `col` on
> each child table? Some other thing?

If it's a partitioned table, then yes, putting the appropriate indexes on
each child table as well as the empty parent table is what we do.

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