Change index persistence for series to not be accumulated in memory
before being written as one large batch. `Labels` and `ChunkMeta`
objects are reused.
This cuts down memory spikes during compaction of multiple blocks
significantly.
As part of the the Index{Reader,Writer} now have an explicit notion of
symbols and series must be inserted in order.
This adds a basic compactor that will merge two persisted blocks into
one. It simply fully rewrites the index and concatenates the chunk
lists.
It just writes into the current working dir and doesn't properly handle
which blocks to compact for now.
This replaces mutation of underlying bytes in the iterated slice
with a shift counter, which is used when reading the head byte.
This is avoids having to copy the entire slice for every new iterator.
xor encoding is fast enough for our purposes and provides
very good compression.
We remove all other ones that partially don't support floats
for the sake of simplicity.
Fabian Reinartz
Goutham Veeramachaneni
Julius Volz