feat: add Java scalar UDF support#46

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andygrove wants to merge 13 commits into

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andygrove:feat/scalar-udf

Commits on May 13, 2026

feat(native): cache JavaVM in OnceLock via JNI_OnLoad
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committed

Commits on May 14, 2026

feat(udf): add ScalarUdf interface and Volatility enum
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feat(udf): add JniBridge trampoline for per-call UDF invocation
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feat(native): add JavaScalarUdf skeleton implementing ScalarUDFImpl
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feat(udf): register Java UDFs via SessionContext.registerUdf
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feat(udf): implement invoke_with_args via Arrow C Data Interface
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fix(udf): plug exception leak, add SAFETY comment, validate row count and zero-arg case
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test(udf): cover concat, square, and repeated invocations
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test(udf): cover null/wrong-rows/wrong-type/exception contract violations
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test(udf): cover multi-UDF, cross-session, and multi-row lifecycle
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test(udf): exercise all three Volatility kinds
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docs(udf): add user-guide page and runnable AddOne example
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refactor(udf): null-guard registerUdf arguments and drop dead assertion
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