This allows encoders to be re-used and maintained in a pool to
avoid allocating new ones on every compactions and write of an encoded
block. The pool used is not a sync.Pool to ensure that the encoders
will not be garbage collected.
This commit makes a number of performance improvements to
reduce allocations during query execution. Several objects
and buffers are now reused across the components to avoid
allocations.
Previously a simple `count(value)` query across 1M points
would require 26,000+ allocations. After the changes in
this commit that number has been reduced to 88.
Will make it less error-prone to add new encodings int the future
since each encoder has it's set of constants. There are some placeholder
contants for uncompressed encodings which are not in all encoder currently.
Jason Wilder
Mark Rushakoff
Ben Johnson
Paul Dix