PHOENIX-7902 SERVER ARRAY|JSON|BSON PROJECTION counted forms in EXPLAIN

[apurtell]

Replace the two opaque per-scan markers SERVER ARRAY ELEMENT PROJECTION and SERVER JSON FUNCTION PROJECTION with per-type clauses SERVER ARRAY PROJECTION <count>, SERVER JSON PROJECTION <count>, and SERVER BSON PROJECTION <count>, emitted only when at least one path expression of the corresponding type is pushed server side, and each followed by one indented detail line per expression via Expression.toString() indented to the next level.

ProjectionCompiler.compileSelectClause stashes the per-attribute expression buckets (the serverAttributeToFuncExpressionMap it already builds before scan serialization) on StatementContext as serverParsedProjections : Map<String, List<Expression>> keyed by scan attribute name. ExplainTable.explain(...) replaces the existing code with new code that processes "ARRAY", "JSON", and "BSON" buckets, emits the counted header, and the additional indented detail lines.

ExplainPlanAttributes retires the serverArrayElementProjection boolean and adds a serverParsedProjections: Map<String,List<String>> map, with up to three buckets ("ARRAY", "JSON", and "BSON" ) each holding a List<String>, with matching ExplainPlanTestUtil fluent assertion getters, setters, and testers.

Co-authored-by: Claude Opus 4.8[1m] noreply@anthropic.com

[Copilot]

Pull request overview

This PR updates Phoenix EXPLAIN output to replace the prior opaque server-side projection markers with per-type, counted SERVER ARRAY|JSON|BSON PROJECTION <count> clauses, and includes one additional indented line per pushed-down path expression. It also updates explain-plan attribute plumbing and tests accordingly.

Changes:

• Emit SERVER ARRAY|JSON|BSON PROJECTION <count> plus per-expression detail lines in ExplainTable.
• Plumb server-side parsed projection expressions through StatementContext and expose them via ExplainPlanAttributes as serverParsedProjections.
• Update unit/integration tests to assert the new explain text and attribute structure.

Reviewed changes

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Show a summary per file

File	Description
phoenix-core-client/src/main/java/org/apache/phoenix/iterate/ExplainTable.java	Replaces old per-scan markers with per-type counted projection clauses and detail lines; populates new explain attributes.
phoenix-core-client/src/main/java/org/apache/phoenix/compile/StatementContext.java	Adds storage for server-parsed projection expressions so EXPLAIN can render details.
phoenix-core-client/src/main/java/org/apache/phoenix/compile/ProjectionCompiler.java	Stashes per-attribute server-parsed function expression buckets onto the statement context during compilation.
phoenix-core-client/src/main/java/org/apache/phoenix/compile/ExplainPlanAttributes.java	Retires serverArrayElementProjection and adds serverParsedProjections with builder support and defensive copying.
phoenix-core/src/test/java/org/apache/phoenix/query/explain/ExplainPlanTestUtil.java	Adds fluent assertions for serverParsedProjections and removes old array-element boolean assertion usage.
phoenix-core/src/test/java/org/apache/phoenix/query/explain/ExplainPlanTest.java	Updates expected explain text and expected JSON attributes; adds JSON/BSON projection coverage.
phoenix-core/src/test/java/org/apache/phoenix/compile/QueryCompilerTest.java	Updates compilation-plan assertions to use serverParsedProjections APIs.
phoenix-core/src/it/java/org/apache/phoenix/end2end/ProjectArrayElemAfterHashJoinIT.java	Updates IT expectations to assert pushed-down array projection counts.
phoenix-core/src/it/java/org/apache/phoenix/end2end/json/JsonFunctionsIT.java	Updates IT string assertions for the new JSON projection explain marker.

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[apurtell]

Test Results

Suite	Tests run	Failures	Errors	Skipped	Result
Unit tests (full phoenix-core suite)	2539	0	0	9	PASS
Integration tests (impacted subset)	69	0	0	6	PASS

Unit tests

Result: Tests run: 2539, Failures: 0, Errors: 0, Skipped: 9 — BUILD SUCCESS.

The count rose from the previous baseline of 2537 to 2539 because two new connectionless cases were added to ExplainPlanTest:

• testJsonFunctionProjection — validates SERVER JSON PROJECTION 1 plus the JSON_VALUE(JSONCOL, '$.type') detail line.
• testBsonValueProjection — validates SERVER BSON PROJECTION 1 plus the BSON_VALUE(PAYLOAD, 'user.id', 'VARCHAR', ) detail line.

The pre-existing testArrayElementProjection covers SERVER ARRAY PROJECTION 1 plus ARRAY_ELEM(A_STRING_ARRAY, 1).

Directly relevant unit classes:

Class	Tests run	Result
org.apache.phoenix.query.explain.ExplainPlanTest	85	PASS
org.apache.phoenix.compile.QueryCompilerTest	(full class)	PASS

Integration tests

Result: BUILD SUCCESS. Per-class breakdown:

Class	Tests run	Failures	Errors	Skipped	Result
org.apache.phoenix.end2end.json.JsonFunctionsIT	15	0	0	0	PASS
org.apache.phoenix.end2end.ProjectArrayElemAfterHashJoinIT	2	0	0	0	PASS
org.apache.phoenix.end2end.Bson2IT	2	0	0	0	PASS
org.apache.phoenix.end2end.Bson3IT	16	0	0	0	PASS
org.apache.phoenix.end2end.Bson4IT	32	0	0	6	PASS
org.apache.phoenix.end2end.Bson5IT	2	0	0	0	PASS
Total	69	0	0	6	PASS

The behavior change touches three EXPLAIN code paths:

• SERVER ARRAY ELEMENT PROJECTION → SERVER ARRAY PROJECTION <n> + detail lines.
• SERVER JSON FUNCTION PROJECTION → SERVER JSON PROJECTION <n> + detail lines.
• BSON path projections now emit a new SERVER BSON PROJECTION <n> clause.

JsonFunctionsIT and ProjectArrayElemAfterHashJoinIT directly assert on the renamed JSON/array projection output and were migrated to the new serverParsedProjections API. The four Bson*IT suites assert table/iterator/scan-type attributes. Other explain-asserting ITs (e.g. ExplainPlanWithStatsEnabledIT) do not use array/JSON/BSON projections and were excluded.