## Problem
There are several problems with our current statically allocated
`BufferPool`.
1. You cannot open two databases in the same process with different page
sizes, because the `BufferPool`'s `Arena`s will be locked forever into
the page size of the first database. This is the case regardless of
whether the two `Database`s are open at the same time, or if the first
is closed before the second is opened.
2. It is impossible to even write Rust tests for different page sizes
because of this, assuming the test uses a single process.
## Solution
Make `Database` own `BufferPool` instead of it being statically
allocated, so this problem goes away.
Note that I didn't touch the still statically-allocated
`TEMP_BUFFER_CACHE`, because it should continue to work regardless of
this change. It should only be a problem if the user has two or more
databases with different page sizes open simultaneously, because
`TEMP_BUFFER_CACHE` will only support one pool of a given page size at a
time, so the rest of the allocations will go through the global
allocator instead.
## Notes
I extracted this change out from #2569, because I didn't want it to be
smuggled in without being reviewed as an individual piece.
Reviewed-by: Avinash Sajjanshetty (@avinassh)
Closes#2596
Problem
There are several problems with our current statically allocated
`BufferPool`.
1. You cannot open two databases in the same process with different
page sizes, because the `BufferPool`'s `Arena`s will be locked forever
into the page size of the first database. This is the case regardless
of whether the two `Database`s are open at the same time, or if the first
is closed before the second is opened.
2. It is impossible to even write Rust tests for different page sizes because
of this, assuming the test uses a single process.
Solution
Make `Database` own `BufferPool` instead of it being statically allocated, so this
problem goes away.
Note that I didn't touch the still statically-allocated `TEMP_BUFFER_CACHE`, because
it should continue to work regardless of this change. It should only be a problem if
the user has two or more databases with different page sizes open simultaneously, because
`TEMP_BUFFER_CACHE` will only support one pool of a given page size at a time, so the rest
of the allocations will go through the global allocator instead.
Notes
I extracted this change out from #2569, because I didn't want it to be smuggled in without
being reviewed as an individual piece.
