Обсуждение: Question about indexes on tables with inherited children
Hello,
A quick question (I think).
If I have Table_A with id integer, val text - and no data.
Table_B inherits from Table_A and has a bunch of data.
Table_C inherits from Table_A and has some data.
Table_X has id integer, someValue integer
If I do select * from Table_A a, Table_X x where a.id = x.id
and it only returns 1 or a few rows, should it use an index if I have an index built on Table_A using id?
Or do I need an index individually on B & C?
I thought having the index on A would be used, but in an analyze it was scanning the table until I created indexes on B & C.
If it should have worked, the only thing that I can think of was that the stats on the tables were maybe out of date? This is on 8.4.3.
Thanks,
Bryan.
A quick question (I think).
If I have Table_A with id integer, val text - and no data.
Table_B inherits from Table_A and has a bunch of data.
Table_C inherits from Table_A and has some data.
Table_X has id integer, someValue integer
If I do select * from Table_A a, Table_X x where a.id = x.id
and it only returns 1 or a few rows, should it use an index if I have an index built on Table_A using id?
Or do I need an index individually on B & C?
I thought having the index on A would be used, but in an analyze it was scanning the table until I created indexes on B & C.
If it should have worked, the only thing that I can think of was that the stats on the tables were maybe out of date? This is on 8.4.3.
Thanks,
Bryan.
On 16 June 2010 19:07, Bryan Montgomery <monty@english.net> wrote: > If I do select * from Table_A a, Table_X x where a.id = x.id > and it only returns 1 or a few rows, should it use an index if I have an > index built on Table_A using id? It should because it scans Table_A too. > Or do I need an index individually on B & C? Yes. Indexes are not inherited. -- Sergey Konoplev Blog: http://gray-hemp.blogspot.com / Linkedin: http://ru.linkedin.com/in/grayhemp / JID/GTalk: gray.ru@gmail.com / Skype: gray-hemp / ICQ: 29353802