This affects TestTx_Remove, TestTx_DeallocateToFreeList, and
TestTx_RecreateBitmap, all of which were adding hundreds of thousands
of individual bits, or more, and all of which work just as well and
produce the same behavior using largeish containers.
This reduces race-detector-test runtime from about 20 minutes to
a couple.
The MultiTx test runs for a fairly long time but doesn't add much
value running that much longer, and there's no reason it should take
more than half the time we spend on this entire directory.
The Cursor datatype is quite large, and allocating them constantly for
ops is extremely expensive. To avoid this, we create a single stable cursor
that lives in the DB, and can be used for freelist modifications. Since the
freelist is only ever modified once at a time, this should be safe. We also
don't fully zero it between operations, we just reset the relevant parts.
Several changes. One is, we don't provide a `New` for pagePool, which
allows allocPage to check whether a page was returned, and thus, zero
pages which were found in the pool, or make new pages, but never zero
pages it just created with make. We then also make many more things
which were making pages use the pool.
Reuse the same page allocation for multiple header pages dumped into
the WAL; the bitmap header pages aren't stashed in our page map,
they're only written to the disk, so we don't need to make a new page
each time, we can just make one new page for the whole batch.
Internally in the pool, we pool pointers to [PageSize]byte, rather
than slices. sync.Pool needs pointer-like things. To store a pointer
to a slice, you have to heap-allocate the slice, also. So, instead
of heap-allocating copies of these slices, we just use pointers to
the raw data.
the shardwidth22 tests were broken client side, but we didn't realize
this because we weren't running the client side tests since moving the
client code into the main FB repo until recently (woops), and more
recently, we'd stopped running the shardwidth22 tests in the move to
Gitlab, so when we re-enabled them we finally noticed that they were
broken in the client.
All this change does is takes the shardWidth value from the core
featurebase package instead of using a hardcoded value in the client package.
