firebird-support - Question about few Firebird details

Subject	Question about few Firebird details
Author	liviuslivius
Post date	2016-05-23T19:05:54Z

Hi,

https://ib-aid.com/en/articles/45-ways-to-speed-up-firebird-database/

i have few questions:

44. Use NO_AUTO_UNDO - what happend when i do rollback? I do not understand what really do this option..

30. Use derived tables to optimize SELECT with ORDER BY/GROUP BY -

SELECT T.FIELD_KEY, T.FIELD1, T.FIELD2, ... T.FIELD_N
FROM (SELECT FIELD_KEY FROM T ORDER BY FIELD2) T2
JOIN T ON T.FIELD_KEY = T2.FIELD_KEY

why this can be faster then?

SELECT FIELD_KEY, FIELD1, FIELD2, ... FIELD_N
FROM T
ORDER BY FIELD2

Firebird sort whole resultset of "sorted key - Field2" or do different work?

I see in FB3 plan sort width and it looks like not true but?

regards,

Karol Bieniaszewski