Deserialize pickles in a asyncio executor + converted db functions reader() and IWriter.serialize() to async

[masipcat]

I measured that big objects >50kB take a lot of time to deserialize, about 50, 100, 200ms depending on the size.. This change avoids blocking all requests in the process during deserialization.

I'm not sure if we should consider this a breaking change or if it's ok as a patch version

[codecov-commenter]

Codecov Report

Merging #1171 (7c1b5d2) into master (ee38eea) will increase coverage by 0.1%. The diff coverage is 96.6%.

@@           Coverage Diff            @@
##           master   #1171     +/-   ##
========================================
+ Coverage    94.6%   94.6%   +0.1%     
========================================
  Files         377     377             
  Lines       32650   32658      +8     
========================================
+ Hits        30873   30881      +8     
  Misses       1777    1777             

Impacted Files	Coverage Δ
guillotina/_settings.py	100.0% <ø> (ø)
guillotina/db/transaction.py	89.8% <85.8%> (ø)
guillotina/db/reader.py	100.0% <100.0%> (ø)
guillotina/db/storages/cockroach.py	80.0% <100.0%> (ø)
guillotina/db/storages/dummy.py	94.0% <100.0%> (ø)
guillotina/db/storages/pg.py	85.9% <100.0%> (ø)
guillotina/db/writer.py	95.4% <100.0%> (ø)
guillotina/factory/content.py	83.3% <100.0%> (ø)
guillotina/tests/cache/test_cache_memory.py	100.0% <100.0%> (ø)
guillotina/tests/mocks.py	85.4% <100.0%> (ø)
... and 2 more

[masipcat]

IMO, this is a breaking change. Lots of interfaces that are potentially used.

OK, agree

We could make the interface optionally async. Use https://github.com/plone/guillotina/blob/master/guillotina/utils/misc.py#L126 to not cause breaking change

I'm ok with this change but third-party applications using the guillotina IWriter will still break so maybe we should update the minor version?

[vangheem]

maybe we should update the minor version

Yes, I agree.