Adopt appendcol, appendpipe, multisearch to spath

[ykmr1224]

Description

• Adopt appendcol, appendpipe, multisearch to spath
  • Fixed each command to adjust fields when used with spath command (dynamic fields)

Related Issues

#4984

Check List

• New functionality includes testing.
• New functionality has been documented.
• New functionality has javadoc added.
• New functionality has a user manual doc added.
• New PPL command checklist all confirmed.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff or -s.
• Public documentation issue/PR created.

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[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• New Features

  • The spath command now works with appendcol and multisearch commands (previously unsupported).

• Bug Fixes

  • Improved dynamic field handling in query processing to ensure consistent field adjustment across multiple inputs.

• Documentation

  • Updated spath command documentation to reflect expanded command compatibility.

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Walkthrough

This PR modifies field resolution and dynamic field handling to allow spath-related commands (appendcol, appendpipe, multisearch) to work with dynamic fields. The changes replace exception-throwing behavior with verification delegation to subqueries/subsearches, add bulk input alignment logic for dynamic fields, and extend test coverage. Documentation is updated to reflect that appendcol and multisearch are no longer restricted with spath.

Changes

Cohort / File(s)	Summary
Field Resolution Visitor Dispatch core/src/main/java/org/opensearch/sql/ast/analysis/FieldResolutionVisitor.java	Replaces exception-throwing for appendcol, appendpipe, and multisearch with verification-and-traversal pattern. New method visitAppendPipe added; visitMultisearch removed. Commands now delegate requirement checks to subsearches before continuing traversal instead of aborting.
Dynamic Field Input Alignment core/src/main/java/org/opensearch/sql/calcite/DynamicFieldsHelper.java	Adds three new methods: adjustInputsForDynamicFields (aligns multiple inputs together), getRequiredStaticFields (collects static fields across inputs with dynamic fields), and toSortedList (utility). Refactors join input handling to use bulk adjustment. Updates adjustFieldsForDynamicFields to use MAP_APPEND when merging with existing dynamic fields.
Dynamic Field Integration core/src/main/java/org/opensearch/sql/calcite/CalciteRelNodeVisitor.java	Adds single call to adjustInputsForDynamicFields for multisearch subquery inputs before schema unification and union.
Documentation & Tests docs/user/ppl/cmd/spath.md, integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalcitePPLSpathCommandIT.java, ppl/src/test/java/org/opensearch/sql/ppl/parser/FieldResolutionVisitorTest.java	Updates spath limitation docs to remove appendcol and multisearch restrictions. Adds 96 integration test lines for appendcol, appendpipe, multisearch scenarios with spath and dynamic fields. Adds 32 unit test lines covering field resolution for new append-style operators.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• Support spath with dynamic fields #5058: Directly related—both PRs modify the same visitor and helper classes (FieldResolutionVisitor, CalciteRelNodeVisitor, DynamicFieldsHelper) for dynamic field handling with spath commands.

Suggested reviewers

• LantaoJin
• ps48
• kavithacm
• joshuali925
• anirudha
• Swiddis
• qianheng-aws
• derek-ho

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 18.52% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adopting appendcol, appendpipe, and multisearch commands to work with spath.
Description check	✅ Passed	The description directly addresses the changeset by explaining that appendcol, appendpipe, and multisearch are being adopted to work with spath, with dynamic field adjustments.

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✨ Finishing touches

• 📝 Generate docstrings

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 ast-grep (0.40.5)

core/src/main/java/org/opensearch/sql/calcite/CalciteRelNodeVisitor.java

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