Re: Performance difference in accessing differrent columns in a Postgres Table

[Dinesh Kumar <dns98944@xxxxxxxxx>]

Hi All,

I was wondering whether the case is solved or still continuing. As a Postgres newbie, I can't understand any of the terms (JIT, tuple deformation) as you mentioned above. Please anyone let me know , what is the current scenario.

Thanks,

Dineshkumar.

On Wed, Aug 1, 2018 at 8:51 PM Jeff Janes <jeff.janes@xxxxxxxxx> wrote:

On Mon, Jul 30, 2018 at 3:02 PM, Andres Freund <andres@xxxxxxxxxxx> wrote:

Hi,

On 2018-07-30 13:31:33 -0400, Jeff Janes wrote:
> I don't know where the time is going with the as-committed JIT.  None of
> the JIT-specific timings reported by EXPLAIN (ANALYZE) add up to anything
> close to the slow-down I'm seeing.  Shouldn't compiling and optimization
> time show up there?

As my timings showed, I don't see the slowdown you're reporting. Could
you post a few EXPLAIN ANALYZEs?

I don't think you showed any timings where jit_above_cost < query cost < jit_optimize_above_cost, which is where I saw the slow down.  (That is also where things naturally land for me using default settings)

I've repeated my test case on a default build (./configure --with-llvm --prefix=....) and default postgresql.conf, using the post-11BETA2 commit 5a71d3e.

I've attached the full test case, and the full output.

Here are the last two executions, with jit=on and jit=off, respectively.  Doing it with TIMING OFF doesn't meaningfully change things, nor does increasing shared_buffers beyond the default.

                                                        QUERY PLAN

--------------------------------------------------------------------------------------------------------------------------

 Seq Scan on i200c200  (cost=0.00..233332.28 rows=9999828 width=16) (actual time=29.317..11966.291 rows=10000000 loops=1)

 Planning Time: 0.034 ms

 JIT:

   Functions: 2

   Generation Time: 1.589 ms

   Inlining: false

   Inlining Time: 0.000 ms

   Optimization: false

   Optimization Time: 9.002 ms

   Emission Time: 19.948 ms

 Execution Time: 12375.493 ms

(11 rows)

Time: 12376.281 ms (00:12.376)

SET

Time: 1.955 ms

                                                       QUERY PLAN

------------------------------------------------------------------------------------------------------------------------

 Seq Scan on i200c200  (cost=0.00..233332.28 rows=9999828 width=16) (actual time=0.063..3897.302 rows=10000000 loops=1)

 Planning Time: 0.037 ms

 Execution Time: 4292.400 ms

(3 rows)

Time: 4293.196 ms (00:04.293)

Cheers,

Jeff