Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <

On Wed, Jun 15, 2016 at 1:54 PM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> Robert Haas wrote:

>> The expression index case is the one to worry about; if there is a
>> problem, that's where it is.  What bothers me is that a function used
>> in an expression index could do anything at all - it can read any
>> table in the database.
>
> Hmm, but if it does that, then the code that actually implements that
> query would run the STO checks, right?  The analyze code doesn't need
> to.

Right.  In the described case, you would get a "snapshot too old"
error inside the expression which is trying to generate the index
value.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company