select_object optimizations

[Geal]

Small optimizations when selecting entity types and keys for federated queries

Checklist

Complete the checklist (and note appropriate exceptions) before a final PR is raised.

• Changes are compatible[^1]
• Documentation[^2] completed
• Performance impact assessed and acceptable
• Tests added and passing[^3]
  • Unit Tests
  • Integration Tests
  • Manual Tests

Exceptions

Note any exceptions here

Notes

[^1]. It may be appropriate to bring upcoming changes to the attention of other (impacted) groups. Please endeavour to do this before seeking PR approval. The mechanism for doing this will vary considerably, so use your judgement as to how and when to do this.
[^2]. Configuration is an important part of many changes. Where applicable please try to document configuration examples.
[^3]. Tick whichever testing boxes are applicable. If you are adding Manual Tests:
- please document the manual testing (extensively) in the Exceptions.
- please raise a separate issue to automate the test and label it (or ask for it to be labeled) as manual test

[github-actions]

@Geal, please consider creating a changeset entry in /.changesets/. These instructions describe the process and tooling.

[Geal]

perf test please

[router-perf]

CI performance tests

• events_big_cap_high_rate - Stress test for events with a lot of users, deduplication enabled and high rate event with a big queue capacity
• events_without_dedup - Stress test for events with a lot of users and deduplication DISABLED
• events - Stress test for events with a lot of users and deduplication ENABLED
• large-request - Stress test with a 1 MB request payload
• step - Basic stress test that steps up the number of users over time
• xlarge-request - Stress test with 10 MB request payload
• reload - Reload test over a long period of time at a constant rate of users
• no-graphos - Basic stress test, no GraphOS.
• xxlarge-request - Stress test with 100 MB request payload
• step-jemalloc-tuning - Clone of the basic stress test for jemalloc tuning
• const - Basic stress test that runs with a constant number of users

[Geal]

The benchmark we use in CI has few entities but a lot of fields. Here I am testing with a lot of entities, so creating the representations for federated queries is heavier.

Router on dev (38be5e2), 2 cores, 200 clients:

Summary:
  Total:	30.2196 secs
  Slowest:	0.9184 secs
  Fastest:	0.0423 secs
  Average:	0.2310 secs
  Requests/sec:	862.7849
  

Response time histogram:
  0.042 [1]	|
  0.130 [223]	|■
  0.217 [11779]	|■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
  0.305 [12346]	|■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
  0.393 [1371]	|■■■■
  0.480 [94]	|
  0.568 [49]	|
  0.656 [40]	|
  0.743 [55]	|
  0.831 [29]	|
  0.918 [86]	|


Latency distribution:
  10% in 0.1787 secs
  25% in 0.1988 secs
  50% in 0.2209 secs
  75% in 0.2484 secs
  90% in 0.2856 secs
  95% in 0.3179 secs
  99% in 0.4792 secs

Details (average, fastest, slowest):
  DNS+dialup:	0.0002 secs, 0.0423 secs, 0.9184 secs
  DNS-lookup:	0.0002 secs, 0.0000 secs, 0.0871 secs
  req write:	0.0000 secs, 0.0000 secs, 0.0910 secs
  resp wait:	0.2304 secs, 0.0369 secs, 0.9180 secs
  resp read:	0.0001 secs, 0.0000 secs, 0.0164 secs

Status code distribution:
  [200]	26073 responses

This PR, 2 cores:

Summary:
  Total:	30.1998 secs
  Slowest:	0.4410 secs
  Fastest:	0.0681 secs
  Average:	0.2127 secs
  Requests/sec:	937.4899
  

Response time histogram:
  0.068 [1]	|
  0.105 [58]	|
  0.143 [454]	|■
  0.180 [3788]	|■■■■■■■■■■■■
  0.217 [12671]	|■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
  0.255 [8102]	|■■■■■■■■■■■■■■■■■■■■■■■■■■
  0.292 [2437]	|■■■■■■■■
  0.329 [627]	|■■
  0.366 [153]	|
  0.404 [17]	|
  0.441 [4]	|


Latency distribution:
  10% in 0.1727 secs
  25% in 0.1899 secs
  50% in 0.2090 secs
  75% in 0.2322 secs
  90% in 0.2585 secs
  95% in 0.2771 secs
  99% in 0.3186 secs

Details (average, fastest, slowest):
  DNS+dialup:	0.0002 secs, 0.0681 secs, 0.4410 secs
  DNS-lookup:	0.0002 secs, 0.0000 secs, 0.0664 secs
  req write:	0.0000 secs, 0.0000 secs, 0.0643 secs
  resp wait:	0.2122 secs, 0.0634 secs, 0.4409 secs
  resp read:	0.0001 secs, 0.0000 secs, 0.0283 secs

Status code distribution:
  [200]	28312 responses