App very unresponsive while performing simple update - Mailing list pgsql-performance

Is Postgres supposed to be able to handle concurrent requests while doing large updates?

This morning I was executing the following simple update statement that would affect 220,000 rows in my product table:

update product set is_hungry = 'true'  where date_modified > current_date - 10;

But the application that accesses the product table for reading became very unresponsive while the update was happening.

Is it just a matter of slow I/O? The CPU usage seemed very low (less than 5%) and iostat showed  less than 1 MB / sec throughput.

I was doing the update in psql.

Are there any settings that I could tweak that would help with this sort of thing?

Thanks,