Re: [HACKERS] WIP Patch: Pgbench Serialization and deadlock errors

On 12-08-2018 12:14, Fabien COELHO wrote:
> HEllo Marina,

Hello, Fabien!

>> v10-0003-Pgbench-errors-use-the-Variables-structure-for-c.patch
>> - a patch for the Variables structure (this is used to reset client
>> variables during the repeating of transactions after
>> serialization/deadlock failures).
>
> This patch adds an explicit structure to manage Variables, which is
> useful to reset these on pgbench script retries, which is the purpose
> of the whole patch series.
>
> About part 3:
>
> Patch applies cleanly,

On 12-08-2018 12:17, Fabien COELHO wrote:
>> About part 3:
>>
>> Patch applies cleanly,
>
> I forgot: compiles, global & local "make check" are ok.

I'm glad to hear it :-)

> * typo in comments: "varaibles"

I'm sorry, I'll fix it.

> * About enlargeVariables:
>
> multiple INT_MAX error handling looks strange, especially as this code
> can never be triggered because pgbench would be dead long before
> having allocated INT_MAX variables. So I would not bother to add such
> checks.
> ...
> I'm not sure that the size_t cast here and there are useful for any
> practical values likely to be encountered by pgbench.

Looking at the code of the functions, for example, ParseScript and
psql_scan_setup, where the integer variable is used for the size of the
entire script - ISTM that you are right.. Therefore size_t casts will
also be removed.

> ISTM that if something is amiss it will fail in pg_realloc anyway.

IIUC and physical RAM is not enough, this may depend on the size of the
swap.

> Also I do not like the ExpBuf stuff, as usual.

> The exponential allocation seems overkill. I'd simply add a constant
> number of slots, with a simple rule:
>
> /* reallocated with a margin */
> if (max_vars < needed) max_vars = needed + 8;
>
> So in the end the function should be much simpler.

Ok!

--
Marina Polyakova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company