simple
(field1,field2) (field2,field1)
1 1 1 1
2 x 1 4
3 x 1 8
4 1 x 2
5 x x 3
6 x x 5
7 x x 6
8 1 x 7
etc
select where field2=1
in one case value = 1 could also be the last field1
in the second case the search ends after the third element
there may be other elements





-------Messaggio originale-------

Da: brucedickinson@... [firebird-support]
Data: 20/07/2015 14.20.37
A: firebird-support@yahoogroups.com
Oggetto: Re: Rif: [firebird-support] Re: Is it possible to use only "part"
of the index?


So, if I change the order of fields in the index I can speed things up.
Could someone explain me why it works like it works? What are the internals
behind this?



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