Re: SELECT is faster on SQL Server

Frank Millman schrieb am 19.03.2021 um 09:52:
>>> I am writing a cross-platform accounting app, and I test using Sql
>>> Server on Windows 10 and PostgreSql on Fedora 31. Performance is
>>> usually very similar, with a slight edge to PostgreSql. Now I have a
>>> SELECT which runs over twice as fast on Sql Server compared to
>>> PostgreSql.
>>>
>> Can you change the SELECT statement?
>>
>> Very often "distinct on ()" is faster in Postgres compared to the equivalent solution using window functions
>
> Thanks, Thomas
>
> I tried that, and it ran about 10% faster. Every little helps, but SQL Server appears to have some secret sauce!

The two derived tables (cl_bal, op_bal) seem to be doing exactly the same thing - at least I can't spot a difference.

If that is correct, you can move them into a common table expression - maybe detecting that is SQL Server's secret sauce.

with totals as (
SELECT a.source_code_id, SUM(a.tran_tot) AS total
FROM (
SELECT distinct on (location_row_id, function_row_id, source_code_id) source_code_id, tran_tot
FROM prop.ar_totals
WHERE deleted_id = 0
AND tran_date <= '2018-03-31'
AND ledger_row_id = 1
ORDER BY location_row_id, function_row_id, source_code_id, tran_date DESC
) AS a
GROUP BY a.source_code_id
)
select
'2018-03-01' AS op_date, '2018-03-31' AS cl_date,
cl_bal.source_code_id, op_bal.total as op_tot, cl_bal.total.cl_tot
FROM totals as cl_bal
LEFT JOIN totals as op_bal ON op_bal.source_code_id = cl_bal.source_code_id;