Submitted by: @livius2

Now when we try to create index on big e.g. VARCHAR(1000) field
we got an error
"key size too big for index XXX".

But this is not definitly true as it depend on page size.

Will be good if the message will be variable. It should depend of database page size.
As you know max index size depend on page size. This info should be included into error message.
If database page size is lower then FB max page size it should contain info like:

"key size too big for index XXX. Increase database page size to support bigger key sizes."

Now many users of Firebird use some tools which have default 4K page size. And they think that FB is so limited and they choose different database for use becaouse of such simple thing.
I know presonally 2 persons which was affected by this and i see also sample in FB tracker CORE2201 - "Vrinda Nayak 15/Nov/17 04:29 PM"