Re: Next Steps with Hash Indexes

On Thu, Oct 14, 2021 at 12:48 AM Simon Riggs
<simon.riggs@enterprisedb.com> wrote:
> The hash index tuples are 20-bytes each. If that were rounded up to
> 8-byte alignment, then that would be 24 bytes.
>
> Using pageinspect, the max(live_items) on any data page (bucket or
> overflow) is 407 items, so they can't be 24 bytes long.

That's the same as an nbtree page, which confirms my suspicion. The 20
bytes consists of a 16 byte tuple, plus a 4 byte line pointer. The
tuple-level alignment overhead gets you from 12 bytes to 16 bytes with
a single int4 column. So the padding is there for the taking.

-- 
Peter Geoghegan