Re: Predicate locking

Greg Smith <greg(at)2ndquadrant(dot)com> wrote:

> However, if I increase the generate_series to create 349 rows (or
> more) instead, it works.

> I don't fully understand why this attempt I tried to do that is
> working the way it does though.

Check where the plan goes from a table scan to an indexed access.
Also look at what is showing for SIRead locks in pg_locks as you go.
Between those two bits of information, it should become apparent.

> I don't think Vlad is being unreasonable here; he's provided a
> test case demonstrating the behavior he'd like to see, and shown
> it doesn't work as expected.

... on a toy table with contrived values. How different is this
from the often-asked question about why a query against a four-line
table is not using the index they expect, and how can we expect it
to scale if it doesn't? I agree that it's not unreasonable for
someone to ask either question. If my response falls short, I'm
game to try again.

-Kevin