Subject Page size vs. index depth?
Author Kjell Rilbe

I'm in the process of migrating a database from Firebird 2.5 to 3.0.
Since this requires a backup restore cycle, I thought I'd take the
opportunity to investigate an increased page size to achieve lower index

The database is ~170 Gbyte and a couple of tables contain ~300 million
records. Those tables do reach a high index depth unfortunately.

Now, I'm wondering if it's worthwhile to increase the page size from 8k
to 16k.

The index depth distribution with 8k page size is:
Depth 1: 353 indices
Depth 2: 533 indices
Depth 3: 146 indices
Depth 4: 8 indices

And for 16k page size (after backup/restore to FB 3):
Depth 1: 383 indices
Depth 2: 586 indices
Depth 3: 67 indices
Depth 4: 1 index

There is an improvement obviously. But I assume a larger page size has
other drawbacks?

So, would you recommend 8k or 16k in this case? Why? What would you need
to know about my usage pattern to be able to make a recommendation?

The large tables are mostly written to but they are also heavily queried
sometimes, and always using some index (too slow otherwise).


Kjell Rilbe
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