enable parallel query by default?

Hi,

One of the questions I have about parallel query is whether it should
be enabled by default.  That is, should we make the default value of
max_parallel_degree to a value higher than 0?  Perhaps 1, say?

There are some good reasons why this might be a bad idea, such as:

- As discussed on a nearby thread, there is every possibility of nasty bugs.
- Parallel query uses substantially more resources than a regular
query, which might overload your system.

On the other hand:

- Features that are on by default get more testing and thus might get
less buggy more quickly.
- A lot of people don't change the default configuration and thus
wouldn't get any benefit from the feature if it's not on by default.

Thoughts?

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company