Bring CalcitePPLEnhancedCoalesceIT to parity on the analytics-engine route

[ahkcs]

Description

Brings CalcitePPLEnhancedCoalesceIT to parity on the analytics-engine route (:integ-test:integTestRemote -Dtests.analytics.parquet_indices=true): 4 failing → 0. coalesce itself computes correctly on the route (it's wired via STANDARD_PROJECT_OPS); every failure was a row-ordering or capability edge case, not a coalesce bug.

Where a sort makes the test deterministic, the test is fixed in place — not skipped. Only the cases a sort can't make correct on both routes are skipped, behind assumeNotAnalytics(...) + the gradle exclude list (the AnalyticsRouteLimitation registry / pattern from #5546).

Fixed in place with an explicit sort (no skip)

These used head N without a sort. On the analytics route the scan surfaces the raw-PUT docs (added in init()) ahead of the bulk-loaded docs, so head returned a different row set. Adding sort - age makes them deterministic with their original expectations unchanged, because the sort key is unique over the head window (or the tie projects identical values):

Test	Fix
testCoalesceNested (head 2)	sort - age — top-2 ages (70, 30) unique
testCoalesceEmptyFieldWithFallback (head 1)	sort - age — max age (70) unique
testCoalesceWithMultipleNonExistentFields (head 1)	sort - age — max age (70) unique
testCoalesceWithNullLiteralAndIntegerField (head 3)	sort - age — the age=25 tie projects identical [25, 25], so the expectation holds regardless of tie order

Skipped on the analytics route (a sort can't fix these)

Test(s)	Reason
testCoalesceBasic, testCoalesceWithMixedTypes (head 3)	The third row needs a nullable tiebreak: at the age=25 tie, the real doc (John) vs. a raw-PUT null-name doc. Null placement under sort diverges between the v2/Calcite and analytics routes, so no sort makes the expectation hold on both.
testCoalesceWithAllNonExistentFields	coalesce(field1, field2, field3) where every operand is untyped NULL is rejected by the analytics-engine capability registry: No backend supports scalar function [COALESCE] among [datafusion]. The v2/Calcite path returns an undefined-typed null instead (#5175). Genuine engine-side gap.

Pass rate

Route	Before	After
analytics-engine (:integTestRemote -Dtests.analytics.parquet_indices=true)	4 failing / 19	0 failing — 16 run, 3 excluded (stable across 3 reruns)
v2 (:integ-test:integTest, fresh cluster)	19 pass	19 pass, 0 skip

Note for reviewers

The skips are genuine route divergences (recorded as AnalyticsRouteLimitation constants): the COALESCE-over-all-null-operands one is an engine capability gap, and the head-without-stable-sort + nullable-tiebreak one is a route ordering difference that a test-side sort can't reconcile. The four sort fixes are pure determinism additions — expectations and the v2 path are unchanged.

Check List

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

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.