Josh Berkus wrote:
> I agree with Jim that if we have a trustworthy Frozen Map, having a
> ReadOnly flag is of marginal value, unless such a ReadOnly flag allowed
> us to skip updating the individual row XIDs entirely. I can think of
> some ways to do that, but they have severe tradeoffs.
If you're thinking that the READ ONLY flag is only useful for freezing,
then yeah maybe it's of marginal value. But in the foreign key
constraint area, consider that you could have tables with
frequently-referenced PKs marked as READ ONLY -- then you don't need to
acquire row locks when inserting/updating rows in the referencing
tables. That might give you a good performance benefit that's not in
any way related to freezing, as well as reducing your multixact
consumption rate.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
