This commit changes the underlying storage for `Bitmap` from a
red-black tree to a roaring bitmap. It also removes bitmaps from
the cache and only stores the bitmap count.
This commit refactors the anti-entropy system to fetch data from
all replicated blocks and only set/clear bits which deviate from
the consensus between all blocks.
An example of this is if 3 nodes had the following bits set for
a single bitmap:
Node A: 1 2 3
Node B: 2 4
Node C: 1 2 4
Then only bits which are set on a majority will be set. In this
case bits 1, 2, & 4 are set but 3 only exists on a single node.
The node performing the merge would then determine the following
set/clear diffs for each node:
Node A: clear(3), set(4)
Node B: set(1)
Node C: none
Once the merge is performed and all nodes receive their diff
instructions then the nodes will be in sync:
Node A: 1 2 4
Node B: 1 2 4
Node C: 1 2 4
There still exists situations where bits can be reset. If Node A
is up and Node B & C are down then Node A's bits will be reset
once B & C come back online. We should add write consistency
settings for incoming writes so that we can ensure that a quorum
is written to before returning a success. This is outside the
scope of this commit though.
This commit changes the `pql.Query` so that it can accept one or more
top-level calls instead of only one.
The query request format change because a query with a single call is
still valid. However, the result format now returns a `results` field
that has one result for each top-level call. The `profiles` field is
still the same, however, it combines all profiles from all bitmap
responses into one return so that there's not duplicate attributes.
Fixes#59
This commit refactors the roaring bitmaps to use uint64 values
instead of uint32 values. This is required for the size of
values we need in pilosa.
This change is not backwards compatible with the previous data
format so any existing data directories need to be removed before
using this code.
This commit adds an implementation of roaring bitmaps that can be
used with mmap files and also allow for delta changes that are
appended to the end of the file as a write-head log.
