Is cache disable ???

I am working in one of the biggest bank in Poland. We trying to choose platform for one of datawarehouse apps. We're just decided to work with Linux, but we need good rdbms system.

1) We build db with amount of 100MB of data. It is one table with 4 fields: 3 numeric, 1 datetime. We've created indexes on all 4 fields and we trying with statement SELECT * from maindat WHERE knd01=1928372 AND org01=200 AND date=... etc.

We got about 5 times slower performance with compare to MS SQL 7.0.

What'a the reason I could not see much difference working with or without indexes.

2) After submiting the same statement (eg 10 times) there was no cache. What's the reason.

Thank you for your help...

Adam Michalunio
amichalu(at)poczta(dot)onet(dot)pl