On 24-2-2018 11:40, antoedincharley@... [firebird-support] wrote:

> I am having a doubt that if Foreign Key reduces Query Performance Or not.
>
> My Environment is
>
> FirebirdCS2.6 :-
>
> Item Table :- 10 Records, PK - Itemcode Varchar(5);
>
> BillDetail Table :- 10 Million Records (FK Selectivity - 0.0076, PK
> Selectivity - 0.000000076)
>
>
> I am having FK between BillDetail.Itemcode And Item.Itemcode with FK
> every query is slow. but as i remove the FK and added Index with
> Itemcode&BillDetail_PK the queries are running lightning fast. But I
> prefer FK to be in Database with high performance queries.

It could mean the statistics on the index of the primary key or foreign
key are not up-to-date, so Firebird doesn't take the index into
consideration. Try updating the index statistics, see also
http://www.firebirdfaq.org/faq167/

If it still doesn't work, we need more information, like the full DDL,
the query and the execution plan in both situations.

Mark
--
Mark Rotteveel