Subject Composite Indices
Author rodbracher

From the good old days of Paradox we still have a lot of Composite
indices on our relations. (now using FB1.0.3 and IBO 4).

These were useful for setrange / findkey etc. Now that we have got
rid of this sort of code and are using queries - I have a few

1) The optimizer will ofter choose a composite index over a single
column index - e.d index(accnum) vs index(accnum,date). Is this a
problem, or in firebird has the index just build it's info on the
first column anyway?

(I will remove the composite indexes in time- but there may be some
legacy code hiding somewhere)

2) Is splitting a composite index into separate indices better ?

3) Is a FK constraint on a join table a better index than creating an
index on the join table ? (In terms of performance - not integrity)

4) the RDB$Selectivity column - I read a value of 1 or greater means
the index is inefficient - true / false - more info required ?