Re: Pluggable Storage - Andres's take - Mailing list pgsql-hackers

On Thu, Oct 18, 2018 at 1:04 PM Haribabu Kommi <kommi.haribabu@gmail.com> wrote:

On Tue, Oct 9, 2018 at 1:46 PM Haribabu Kommi <kommi.haribabu@gmail.com> wrote:

I also observed the failure of aggregates.sql, will look into it.

The random failure of aggregates.sql is as follows

  SELECT avg(a) AS avg_32 FROM aggtest WHERE a < 100;

!        avg_32        

! ---------------------

!  32.6666666666666667

  (1 row)

  -- In 7.1, avg(float4) is computed using float8 arithmetic.

--- 8,16 ----

  (1 row)

  SELECT avg(a) AS avg_32 FROM aggtest WHERE a < 100;

!  avg_32 

! --------

!        

  (1 row)

Same NULL result for another aggregate query on column b.

The aggtest table is accessed by two tests that are running in parallel.

i.e aggregates.sql and transactions.sql, In transactions.sql, inside a transaction

all the records in the aggtest table are deleted and aborted the transaction,

I suspect that some visibility checks are having some race conditions that leads

to no records on the table aggtest, thus it returns NULL result.

If I try the scenario manually by opening a transaction and deleting the records, the

issue is not occurring.

I am yet to find the cause for this problem.

I am not yet able to generate a test case where the above issue can occur easily for

debugging, it is happening randomly. I will try to add some logs to find out the problem.