Stabilize subquery PPL ITs on the analytics-engine route

[ahkcs]

Description

Brings CalcitePPLScalarSubqueryIT and CalcitePPLInSubqueryIT to parity on the analytics-engine route (-Dtests.analytics.parquet_indices=true), where every test-created index is composite/parquet-backed and PPL queries route through the analytics engine (DataFusion). Both ITs already pass on the v2/Calcite route; this change is test-only.

Root cause 1 — append-only accumulation (fixes 19 of 23 failures)

Both ITs seed an extra worker doc (_id 7, "Tommy") via an unconditional raw PUT in init(). init() runs as @Before, before every test method, and preserveClusterUponCompletion() keeps indices across methods. On the analytics-engine parquet-backed store a PUT with an existing _id appends a new row instead of replacing, so Tommy accumulated one duplicate per test method and inflated row counts across the suite (e.g. a 7-row expectation returned 20 = 6 bulk docs + 14 duplicate Tommys).

The bulk loadIndex(...) calls don't have this problem because they're already isIndexExist-guarded. Fix: capture isIndexExist(...) before loadIndex creates the index, then seed Tommy only on first creation. End state is identical on the v2/Calcite route.

Root cause 2 — two unsupported behaviors on the route (the remaining 4 failures)

These are genuine analytics-engine behaviors, not test bugs (each verified directly against the route). They're skipped via the assumeNotAnalytics(...) registry (AnalyticsRouteLimitation) introduced in #5551, plus matching excludeTestsMatching entries in integTestRemote so the skip set stays countable in one place. Two new AnalyticsRouteLimitation constants:

• TEXT_FIELD_EXACT_MATCH — exact equality (= / ==) on an explicitly text-mapped field (no .keyword sub-field) returns no rows on the DataFusion scan. The sibling of the existing DYNAMIC_STRING_NO_KEYWORD for fields mapped text on purpose rather than by dynamic mapping. Verified directly: where department = 'DATA' returns no rows, while like(department, 'DATA') and keyword-field equality both work. Covers testTwoUncorrelatedScalarSubqueriesInOr, testInSubqueryWithTableAlias, testInCorrelatedSubquery (each filters department/occupation with = in the subsearch).
• SUBSEARCH_MAXOUT_IN_SUBQUERY — the subsearch.maxout cap is lowered as a LIMIT on the right-hand side of the IN-subquery semi-join (LogicalSystemLimit(fetch=N, type=SUBSEARCH_MAXOUT)), which the route does not honor, so the subsearch returns all rows regardless of the cap. Verified: with subsearch.maxout=1 an id in [...] subquery still returns every matching row. Covers testSubsearchMaxOut.

Note on the text-equality root cause: an earlier revision of this PR described it as "text fields can't do exact match", which was too coarse — testSelfInSubquery filters a text field (country = 'USA') inside a self-index subquery and passes. Re-verified directly against the cluster: standalone text = returns no rows for every text field, keyword = works, and like() works; the three skipped tests all hinge on a text = filter in a cross-index subsearch. The gap is the analyzed-text exact-match scan limitation (same family as DYNAMIC_STRING_NO_KEYWORD), now captured precisely in TEXT_FIELD_EXACT_MATCH.

Results

Run via :integ-test:integTestRemote against an analytics :run cluster.

Test class	Analytics route — before	Analytics route — after	v2/Calcite route
CalcitePPLScalarSubqueryIT	2/14 pass, 12 fail	13/13 run, 0 fail (1 excluded)	14/14 pass
CalcitePPLInSubqueryIT	7/18 pass, 11 fail	14/15 run, 0 fail (3 excluded; 1 pre-existing @Ignore)	17/18 pass (1 @Ignore)

On the analytics route the skipped tests are removed by excludeTestsMatching so they don't run; each also carries an in-test assumeNotAnalytics(...) as a safety net. The v2/Calcite route runs all of them (the gradle excludes apply only to integTestRemote, and assumeNotAnalytics is a no-op when the analytics flag is off).

Check List

• New functionality includes testing.
• New functionality has been documented.
• Commits are signed per the DCO using --signoff.

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