[CI] PushQueriesIT testCaseInsensitiveEquality {KEYWORD} failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic-platform-support #8908 / rhel-7_platform-support-unix
• elasticsearch-intake #24271 / part3
• elasticsearch-pull-request #76245 / part-3
• elasticsearch-pull-request #76056 / part-3

Reproduction Line:

./gradlew ":x-pack:plugin:esql:qa:server:single-node:javaRestTest" --tests "org.elasticsearch.xpack.esql.qa.single_node.PushQueriesIT.testCaseInsensitiveEquality {KEYWORD}" -Dtests.seed=287F16CEF0622D1C -Dtests.locale=en-CH -Dtests.timezone=America/Bahia -Druntime.java=24

Applicable branches:
8.19

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: Expected a map containing
             operator: "LuceneSourceOperator[maxPageSize = 4854, remainingDocs = 999]"
               status: a map containing
      processed_queries: a list containing
                        0: expected ("CaseInsensitiveTermQuery{test:}") but was "test:"
       processed_slices: <1> unexpected but ok
       processed_shards: <[test:0]> unexpected but ok
           total_slices: <1> unexpected but ok
              slice_max: <0> unexpected but ok
                current: <2147483647> unexpected but ok
              slice_min: <0> unexpected but ok
           rows_emitted: <1> unexpected but ok
          pages_emitted: <1> unexpected but ok
partitioning_strategies: <{test:0=SHARD}> unexpected but ok
       processing_nanos: <315684> unexpected but ok
            slice_index: <0> unexpected but ok

Issue Reasons:

• [8.19] 4 failures in test testCaseInsensitiveEquality {KEYWORD} (0.8% fail rate in 533 executions)
• [8.19] 2 failures in step part-3 (2.7% fail rate in 73 executions)
• [8.19] 2 failures in pipeline elasticsearch-pull-request (2.8% fail rate in 72 executions)

Note:
This issue was created using new test triage automation. Please report issues or feedback to es-delivery.

[elasticsearchmachine]

This has been muted on branch main

Mute Reasons:

• [main] 2 failures in test testCaseInsensitiveEquality {KEYWORD} (1.3% fail rate in 154 executions)

Build Scans:

• elasticsearch-periodic-platform-support #8748 / rocky-8_platform-support-unix
• elasticsearch-pull-request #75558 / part-3

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[alex-spies]

Also had this in 8.19 on a PR. Buildscan

[luigidellaquila]

I have the feeling that it's something related to the test rather than to the functionality.
I'm labeling it as low risk for now.

[nik9000]

Fun:

                        0: expected ("CaseInsensitiveTermQuery{test:}") but was "test:"

Looks like a test bug indeed. Will reproduce.

[nik9000]

8.19 only it looks like

[nik9000]

Applicable branches: 8.19

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But muted on main?!