On Thu, Mar 21, 2024 at 9:44 AM Bharath Rupireddy
<bharath.rupireddyforpostgres@gmail.com> wrote:
>
> Yes, usingVirtualTupleTableSlot helps improve the performance a lot.
> Below are results from my testing. Note that CMV, RMV, CTAS stand for
> CREATE MATERIALIZED VIEW, REFRESH MATERIALIZED VIEW, CREATE TABLE AS
> respectively. These commands got faster by 62.54%, 68.87%, 74.31% or
> 2.67, 3.21, 3.89 times respectively. I've used the test case specified
> at [1].
>
> HEAD:
> CMV:
> Time: 6276.468 ms (00:06.276)
> CTAS:
> Time: 8141.632 ms (00:08.142)
> RMV:
> Time: 14747.139 ms (00:14.747)
>
> PATCHED:
> CMV:
> Time: 2350.282 ms (00:02.350)
> CTAS:
> Time: 2091.427 ms (00:02.091)
> RMV:
> Time: 4590.180 ms (00:04.590)
>
> I quickly looked at the description of what a "virtual" tuple is from
> src/include/executor/tuptable.h [2]. IIUC, it is invented for
> minimizing data copying, but it also says that it's the responsibility
> of the generating plan node to be sure these resources are not
> released for as long as the virtual tuple needs to be valid or is
> materialized. While it says this, as far as this patch is concerned,
> the virtual slot gets materialized when we copy the tuples from source
> slot (can be any type of slot) to destination slot (which is virtual
> slot). See ExecCopySlot->
> tts_virtual_copyslot->tts_virtual_materialize. This way,
> tts_virtual_copyslot ensures the tuples storage doesn't depend on
> external memory because all the datums that aren't passed by value are
> copied into the slot's memory context.
>
> With the above understanding, it looks safe to use virtual slots for
> the multi insert buffered slots. I'm not so sure if I'm missing
> anything here.
I'm attaching the v13 patches using virtual tuple slots for buffered
tuples for multi inserts.
--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
