[CI] StoredFieldsSequentialIT testAggTenPercentConfiguredToTenPct failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic-platform-support #9329 / windows-2019_checkpart3_platform-support-windows
• elasticsearch-periodic-platform-support #9203 / windows-2022_checkpart3_platform-support-windows

Reproduction Line:

gradlew ":x-pack:plugin:esql:qa:server:single-node:javaRestTest" --tests "org.elasticsearch.xpack.esql.qa.single_node.StoredFieldsSequentialIT.testAggTenPercentConfiguredToTenPct" -Dtests.seed=BE499F7514B13CB2 -Dtests.locale=mn-MN -Dtests.timezone=America/Sao_Paulo -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: "ValuesSourceReaderOperator[fields = [test]]"
                                                      status: a map containing
                                                 readers_built: a map containing
 stored_fields[requires_source:true, fields:0, sequential: true]: expected a value equal to or greater than <1> but was <missing>
                                      test:column_at_a_time:null: <2> unexpected but ok
stored_fields[requires_source:true, fields:0, sequential: false]: <2> unexpected but ok
                         test:row_stride:BlockSourceReader.Bytes: <2> unexpected but ok
                                                  rows_emitted: <100> unexpected but ok
                                                 pages_emitted: <2> unexpected but ok
                                                 process_nanos: <54785900> unexpected but ok
                   
[truncated]

Issue Reasons:

• [8.19] 2 failures in test testAggTenPercentConfiguredToTenPct (0.3% fail rate in 665 executions)
• [8.19] 2 failures in pipeline elasticsearch-periodic-platform-support (10.5% fail rate in 19 executions)

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

[elasticsearchmachine]

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

[luigidellaquila]

sequential: true vs. sequential: false in ValuesSourceReaderOperator.
I'm not sure if it's due to a backport and to different expectations between main and 8.19.
I don't seem to be able to reproduce it locally.
Needs some more investigation, but I'll label it as low risk for now

[astefan]

Hi @nik9000,
This one seems to have been reported before and this test update we guessed should have double double checked that the index will have one segment in tests. Assigning this one to you to have a short look on whatever else might have gone wrong. I checked the CI report and I couldn't find artifacts (node logs) to look deeper into, but the same CI build did also have other failures (without logs I can't tell if something else messed up with this test or not).

I ran this test with the given seed multiple times locally and it doesn't repro, might be something completely unrelated to the test itself but nothing quickly jumps at me as to what that thing might be.

[julian-elastic]

I investigated the issue. It occurred on Jul 12th. Nick had a fix on main branch on Jul 11th. However the backport of the fix got merged to 8.19 on July 17th with #131117. So it did not have Nick's fix when the issue occurred.

The test case was never added to the muted tests, so it has been working ever since and the same error did not happen after the fix was merged.

Marking this is closed, it seems Nick's fix addressed the problem successfully.