Add isnotempty PPL function

[lucacavenaghi97]

Description

Adds isnotempty(field) to PPL. Returns true when a field is not null and not empty string — logical negation of isempty(field).

Resolves #5182

Changes

• Added ISNOTEMPTY token and parser rules in ppl, language-grammar, and async-query-core grammars
• Added IS_NOT_EMPTY enum constant to BuiltinFunctionName
• Registered Calcite implementation as NOT(IS_NULL(arg) OR IS_EMPTY(arg)) in PPLFuncImpTable
• Added testIsNotEmpty integration test
• Added docs

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PR Reviewer Guide 🔍

(Review updated until commit 0ecc7f1)

Here are some key observations to aid the review process:

🧪 PR contains tests

🔒 No security concerns identified

✅ No TODO sections

🔀 No multiple PR themes

⚡ Recommended focus areas for review Logic Duplication The implementation of IS_NOT_EMPTY wraps the entire IS_EMPTY logic in a NOT operator. Consider refactoring to reuse the IS_EMPTY implementation directly to avoid code duplication and improve maintainability. register( IS_NOT_EMPTY, (FunctionImp1) (builder, arg) -> builder.makeCall( SqlStdOperatorTable.NOT, builder.makeCall( SqlStdOperatorTable.OR, builder.makeCall(SqlStdOperatorTable.IS_NULL, arg), builder.makeCall(SqlStdOperatorTable.IS_EMPTY, arg))), PPLTypeChecker.family(SqlTypeFamily.ANY));

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PR Code Suggestions ✨

Latest suggestions up to 0ecc7f1
Explore these optional code suggestions:

Category	Suggestion	Impact
General	Extract duplicated IS_EMPTY logic The IS_NOT_EMPTY implementation duplicates the logic from IS_EMPTY. Consider extracting the IS_EMPTY logic into a reusable method and negating it, which would improve maintainability and reduce code duplication. This ensures both functions stay synchronized if the empty check logic needs to change. core/src/main/java/org/opensearch/sql/expression/function/PPLFuncImpTable.java [1256-1266] register( IS_NOT_EMPTY, (FunctionImp1) (builder, arg) -> builder.makeCall( SqlStdOperatorTable.NOT, - builder.makeCall( - SqlStdOperatorTable.OR, - builder.makeCall(SqlStdOperatorTable.IS_NULL, arg), - builder.makeCall(SqlStdOperatorTable.IS_EMPTY, arg))), + makeIsEmptyCall(builder, arg)), PPLTypeChecker.family(SqlTypeFamily.ANY)); Suggestion importance[1-10]: 5 __ Why: The suggestion correctly identifies code duplication between IS_NOT_EMPTY and IS_EMPTY implementations. However, the proposed makeIsEmptyCall method doesn't exist in the codebase, and the suggestion doesn't show how to implement it. While refactoring would improve maintainability, the current implementation is functionally correct and the improvement is moderate.	Low

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Previous suggestions

Suggestions up to commit 88cfad4

Category	Suggestion	Impact
General	Extract common expression to variable The isnotempty implementation duplicates the isempty logic inline. Consider extracting the common OR expression into a variable or reusing the existing IS_EMPTY registration to avoid code duplication and improve maintainability. core/src/main/java/org/opensearch/sql/expression/function/PPLFuncImpTable.java [1256-1266] register( IS_NOT_EMPTY, (FunctionImp1) - (builder, arg) -> - builder.makeCall( - SqlStdOperatorTable.NOT, - builder.makeCall( - SqlStdOperatorTable.OR, - builder.makeCall(SqlStdOperatorTable.IS_NULL, arg), - builder.makeCall(SqlStdOperatorTable.IS_EMPTY, arg))), + (builder, arg) -> { + RexNode isEmptyCall = builder.makeCall( + SqlStdOperatorTable.OR, + builder.makeCall(SqlStdOperatorTable.IS_NULL, arg), + builder.makeCall(SqlStdOperatorTable.IS_EMPTY, arg)); + return builder.makeCall(SqlStdOperatorTable.NOT, isEmptyCall); + }, PPLTypeChecker.family(SqlTypeFamily.ANY)); Suggestion importance[1-10]: 4 __ Why: While extracting the common OR expression into a variable improves readability slightly, the impact is minimal. The current implementation is already clear and the duplication is intentional for defining IS_NOT_EMPTY as the negation of IS_EMPTY. This is a minor style improvement rather than a functional or maintainability concern.	Low

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Persistent review updated to latest commit 0ecc7f1