Decrease test time for TestManyKnnDocs.testLargeSegment

[jdconrad]

This change adds an additional test codec allowing a configurable number for max connections per vector when building an hnsw index. By setting the number of connections to 128 as part of TestManyKnnDocs.testLargeSegment we can reduce the number of indexed vectors to 2088992 and still reproduce the test failure prior to the fix by @benwtrent in #11905.

This changed reduced the test time for me from ~90 minutes to ~3 minutes locally.

cc @rmuir

[rmuir]

we need to run a ./gradlew tidy and commit/push the results to fix formatting.

Very cool, will test on my 2-core. we may be able to upgrade from @Monster to @Nightly.

[jdconrad]

Updated with tidy! (Oops on failing precommit.)

[rmuir]

Works for me. I was able to now run this monster test in < 10 minutes time.

<===:lucene:core:test (SUCCESS): 1 test(s)
The slowest tests (exceeding 500 ms) during this run:
  527.29s TestManyKnnDocs.testLargeSegment (:lucene:core)
The slowest suites (exceeding 1s) during this run:
  527.61s TestManyKnnDocs (:lucene:core)

BUILD SUCCESSFUL in 9m 2s
19 actionable tasks: 5 executed, 14 up-to-date

[uschindler]

Very cool idea (although I have no idea wha this does because of my ignorance for KNN).

[rmuir]

This M is ... the length of the "postings list" for vector. This test codec allows using a larger value... so more data written per document, but less documents needed to trigger the overflow that we wanted to test for here.

[benwtrent]

awesome stuff @jdconrad!!!

[rmuir]

thanks @jdconrad !

[msokolov]

oh nice plan, thanks everyone