Simplify and fix hyper

Hyper is powering our `_approx_count_distinct` reducer. The dependency isn't
updated much and there is an under-counting bug discussed in issue #5084.

There is a more active fork [1], but moving to it is not practical as the
context records are changed. Unfortunately for us, those are part of the
on-disk indexing data structures. If we change them we risk breaking users'
views.

Additionally, we're not using most of the hyper library functionality: we only
use one backend, one precision value (11), and only a few API functions.

In light of that it makes sense to simplify the library and remove all the
un-used stuff. Also, add 100% test coverage, and fix the bug found by the
LivewareProblems/hyper fork.

In order to ensure we don't inadvertently modify the on-disk records those are
marked with a comment, and there is unit test that would break if we change
them. The existing record structure is kept as-is for that exact reason
including the silly mention of the `{hyper_binary, ...}` atom in the registers
field, just to ensure there are no compatibility issues for our users' views.

Fix #5084

[1] LivewareProblems/hyper

.gitignore

@@ -58,7 +58,6 @@ src/fauxton/
 src/folsom/
 src/hackney/
 src/hqueue/
-src/hyper/
 src/ibrowse/
 src/idna/
 src/jiffy/

LICENSE

@@ -2362,3 +2362,27 @@ INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 POSSIBILITY OF SUCH DAMAGE.
+
+couch_hyper
+
+The MIT License (MIT)
+
+Copyright (c) 2014 Game Analytics ApS
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

Makefile

@@ -74,7 +74,7 @@ DESTDIR=
 
 # Rebar options
 apps=
-skip_deps=meck,mochiweb,triq,proper,snappy,hyper,ibrowse
+skip_deps=meck,mochiweb,triq,proper,snappy,ibrowse
 suites=
 tests=
 

Makefile.win

@@ -79,7 +79,7 @@ DESTDIR=
 
 # Rebar options
 apps=
-skip_deps=meck,mochiweb,triq,proper,snappy,hyper,ibrowse,local
+skip_deps=meck,mochiweb,triq,proper,snappy,ibrowse,local
 suites=
 tests=
 

mix.exs

@@ -153,7 +153,6 @@ defmodule CouchDBTest.Mixfile do
       "proper",
       "mochiweb",
       "meck",
-      "hyper",
       "fauxton"
     ]
 

rebar.config.script

@@ -157,8 +157,6 @@ DepDescs = [
 %% %% Non-Erlang deps
 {fauxton,          {url, "https://github.com/apache/couchdb-fauxton"},
                    {tag, "v1.3.1"}, [raw]},
-%% Third party deps
-{hyper,            "hyper",            {tag, "CouchDB-2.2.0-7"}},
 {ibrowse,          "ibrowse",          {tag, "CouchDB-4.4.2-6"}},
 {jiffy,            "jiffy",            {tag, "1.1.2"}},
 {mochiweb,         "mochiweb",         {tag, "v3.2.2"}},

rel/reltool.config

@@ -48,7 +48,6 @@
         ets_lru,
         fabric,
         global_changes,
-        hyper,
         ibrowse,
         ioq,
         jiffy,
@@ -112,7 +111,6 @@
     {app, ets_lru, [{incl_cond, include}]},
     {app, fabric, [{incl_cond, include}]},
     {app, global_changes, [{incl_cond, include}]},
-    {app, hyper, [{incl_cond, include}]},
     {app, ibrowse, [{incl_cond, include}]},
     {app, ioq, [{incl_cond, include}]},
     {app, jiffy, [{incl_cond, include}]},

src/couch/src/couch.app.src

@@ -48,7 +48,6 @@
         couch_event,
         ioq,
         couch_stats,
-        hyper,
         couch_dist,
         couch_quickjs
     ]},