Re: Hash join on int takes 8..114 seconds - Mailing list pgsql-performance

> log file seems that mostly only those queries are slow:
>
> SELECT ...
>    FROM dok JOIN rid USING (dokumnr)
>    JOIN ProductId USING (ProductId)
>    WHERE rid.ProductId LIKE :p1 || '%' AND dok.SaleDate>=:p2
>
> :p1 and :p2 are parameters different for different queries.
>
> dok contains several years of data. :p2 is usually only few previous
> months
> or last year ago.
> SELECT column list contains fixed list of known columns from all tables.
>
> How to create index or materialized view to optimize this types of
> queries ?
>

    I would remove some granularity, for instance create a summary table
(materialized view) by month :

- date (contains the first day of the month)
- product_id
- total quantity, total price sold in given month

    You get the idea.
    If your products belong to categories, and you make queries on all the
products in a category, it could be worth making a summary table for
categories also.