ESQL: Makes ENRICH scope local to subqueries

[ncordon]

Closes https://github.com/elastic/esql-planning/issues/997

Similar to what we did for LOOKUP JOIN, we scope ENRICH policy resolution to the part of the query that actually feeds that specific ENRICH (its own FROM-subquery branch or WHERE IN subquery), instead of resolving it against every cluster touched anywhere in the whole query.

For example, in this query:

  FROM remote-b:logs-*
  | WHERE v IN (
      FROM cluster-a:logs-*
      | WHERE v > 1 AND v < 7
      | ENRICH _remote:values_enrich_a ON v WITH enrich_name
      | KEEP v
    )
  | ENRICH _remote:values_enrich_b ON v WITH enrich_name
  | KEEP v

we only need values_enrich_a to exist on cluster-a and values_enrich_b to exist on remote-b — not on every cluster the query touches.

Implementation:

• EsqlSession resolves all the relevant clusters for each ENRICH policy in the query, reusing the same tree walk we did for LOOKUP JOIN
• EnrichPolicyResolver narrows each scope having into account the ENRICH mode.

[ncordon]

This file has been refactored moving relevant code for having ENRICH in a cluster setup into EnrichClusterPluginSupport so the CrossClusterInSubqueryIT and CrossClsuterSubqueryIT files don't have to repeat the same setup

[Copilot]

Pull request overview

This PR updates ES|QL cross-cluster ENRICH policy resolution so each ENRICH occurrence is validated only against the cluster(s) that actually feed rows into that ENRICH (including subquery branches and WHERE ... IN (subquery) shapes), similar to existing LOOKUP JOIN scoping.

Changes:

• Add per-ENRICH “feeding cluster scope” computation in EsqlSession and pass that scope into EnrichPolicyResolver.
• Key EnrichResolution by the originating Enrich node’s Source (instead of (policyName, mode)), enabling independent resolution of same-named policies across differently-scoped subqueries/views.
• Extend unit and internal cluster tests to cover ENRICH scoping across FROM-subqueries and WHERE-IN subqueries, and add shared ENRICH test-cluster setup helpers.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/telemetry/PlanExecutorMetricsTests.java	Updates resolver mocking to match new resolvePolicies signature.
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/session/EsqlSessionTests.java	Adds thorough unit tests for computeEnrichScope(s) across unions, ROW sources, FROM-subqueries, and WHERE-IN subqueries.
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/AbstractLocalPhysicalPlanOptimizerTests.java	Adapts test enrich resolution setup to Source-keyed EnrichResolution.
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/enrich/EnrichPolicyResolverTests.java	Updates tests to supply per-occurrence Source+scope and validate Source-keyed resolution/errors.
x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/session/EsqlSession.java	Introduces ENRICH feeding-scope computation and wires scopes into enrich resolution.
x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/enrich/EnrichPolicyResolver.java	Accepts per-ENRICH scopes, narrows target clusters per policy/mode, and stores results keyed by Source.
x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/analysis/EnrichResolution.java	Switches resolution/error maps to be keyed by Source.
x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/analysis/Analyzer.java	Consumes EnrichResolution by plan.source() instead of policy-name/mode.
x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/EnrichClusterPluginSupport.java	Adds reusable ENRICH plugin + policy setup helpers for CCS ITs.
x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClusterSubqueryIT.java	Enables ENRICH in CCS subquery ITs and adds coverage for ENRICH modes across FROM-subquery unions.
x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClusterInSubqueryIT.java	Enables ENRICH in CCS WHERE-IN ITs and adds extensive mode/scope coverage, including view/source collisions.
x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/AbstractEnrichBasedCrossClusterTestCase.java	Refactors plugin/settings wiring to share ENRICH cluster setup logic.
x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/TestAnalyzer.java	Adapts test fixtures to Source-keyed enrich resolution via deferred (pending) registrations.

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