Use get_multi instead of get for datastore reads

[achals]

Signed-off-by: Achal Shah achals@gmail.com

What this PR does / why we need it:

get is a wrapper around get_multi, and get_multi reduces the network costs involved.

Which issue(s) this PR fixes:

Fixes #1759

Does this PR introduce a user-facing change?:

Use a batch lookup API for Google Datastore. Users should see lower latencies for `get_online_features` when using Datastore as the online store.

[codecov-commenter]

Codecov Report

Merging #1814 (3a53cfb) into master (5857a55) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1814      +/-   ##
==========================================
- Coverage   84.85%   84.84%   -0.01%     
==========================================
  Files          92       92              
  Lines        6828     6844      +16     
==========================================
+ Hits         5794     5807      +13     
- Misses       1034     1037       +3     

Flag	Coverage Δ
integrationtests	84.77% <100.00%> (-0.01%)	⬇️
unittests	63.90% <10.00%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
sdk/python/feast/infra/online_stores/datastore.py	93.49% <100.00%> (+0.39%)	⬆️
sdk/python/tests/doctest/test_all.py	92.72% <0.00%> (-3.20%)	⬇️
sdk/python/feast/infra/provider.py	88.49% <0.00%> (-0.60%)	⬇️

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[woop]

What is the performance difference between these two approaches? Have you run a benchmark?

[achals]

What is the performance difference between these two approaches? Have you run a benchmark?

retrieving 10 records, using pytest-benchmark. Single retreival seems to be strictly slower, which is not surprising since get is implemented as a wrapper over get_multi.

----------------------------------------------------------------------------------------- benchmark: 2 tests ----------------------------------------------------------------------------------------
Name (time in s)                              Min               Max              Mean            StdDev            Median               IQR            Outliers     OPS            Rounds  Iterations
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
test_online_retrieval_datastore_batch      2.8716 (1.0)      3.2226 (1.0)      2.9943 (1.0)      0.0986 (1.0)      2.9681 (1.0)      0.1220 (1.0)           8;0  0.3340 (1.0)          30           5
test_online_retrieval_datastore_single     4.0147 (1.40)     4.6170 (1.43)     4.2247 (1.41)     0.1446 (1.47)     4.2366 (1.43)     0.1492 (1.22)          9;3  0.2367 (0.71)         30           5
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

[felixwang9817]

/lgtm

[feast-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: achals, felixwang9817

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[feast-ci-bot]

New changes are detected. LGTM label has been removed.