Re: IO related waits

On Thu, 19 Sept 2024 at 02:01, veem v <veema0000(at)gmail(dot)com> wrote:

>
> On Wed, 18 Sept 2024 at 05:07, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
> wrote:
>
>> On 9/17/24 12:34, veem v wrote:
>> >
>>
>> It does if autocommit is set in the client, that is common to other
>> databases also:
>>
>> https://dev.mysql.com/doc/refman/8.4/en/commit.html
>>
>>
>> https://docs.oracle.com/en/database/oracle/developer-tools-for-vscode/getting-started/disabling-and-enabling-auto-commit.html
>>
>>
>> https://learn.microsoft.com/en-us/sql/t-sql/statements/set-implicit-transactions-transact-sql?view=sql-server-ver16
>>
>> You probably need to take a closer look at the client/driver you are
>> using and the code that interacting with it.
>>
>> In fact I would say you need to review the entire data transfer process
>> to see if there are performance gains that can be obtained without
>> adding an entirely new async component.
>>
>>
>>
> You were spot on. When we turned off the "auto commit" we started seeing
> less number of commits as per the number of batches.
>
> However we also started seeing deadlock issues. We have foreign key
> relationships between the tables and during the batch we do insert into the
> parent first and then to the child , but this does happen from multiple
> sessions for different batches. So why do we see below error, as we
> ensure in each batch we first insert into parent and then into the child
> tables?
>
> caused by: org.postgresql.util.PSQLException: ERROR: deadlock detected
> Detail: Process 10443 waits for ShareLock on transaction 220972157;
> blocked by process 10454.
> Process 10454 waits for ShareLock on transaction 220972155; blocked by
> process 10443.
> Hint: See server log for query details.
> Where: while inserting index tuple (88736,28) in relation
> "TAB1_p2024_08_29"
>

As we are able to get hold of one session, we see "insert into <parent
partition table>" was blocked by "insert into <child partition table>". And
the "insert into <child partition table> " was experiencing a "client
read" wait event. Still unable to understand why it's happening and how to
fix it?