| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | Chapman Flack <chap(at)anastigmatix(dot)net> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: lazy detoasting |
| Date: | 2018-04-11 13:28:18 |
| Message-ID: | CAA4eK1J3acTsfmf8Ufyw0C_rN0OdSo07HnOixKbna+z2YKn7RA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Apr 11, 2018 at 2:34 AM, Chapman Flack <chap(at)anastigmatix(dot)net> wrote:
> On 04/10/2018 04:03 PM, Robert Haas wrote:
>
>> I suspect you want, or maybe need, to use the same snapshot as the
>> scan that retrieved the tuple containing the toasted datum.
>
> I'm sure it's worth more than that, but I don't know if it's
> implementable.
>
> If I'm a function, and the datum came to me as a parameter, I may
> have no way to determine what snapshot the enclosing query used to
> obtain the thing passed to me.
>
Before query execution, we push the active snapshot, so any time
during execution, if you get the active snapshot via
GetActiveSnapshot(), you can access it. So, I think during a function
execution, if you use GetActiveSnapshot, you should get the snapshot
used by enclosing query.
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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