Giorgi / DuckDB.NET / 38724654104

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push

github

Committed by Giorgi

Commit Message

Write a nullable result of a typed function as the type under it

A typed scalar function wrote its result with WriteValue<TResult>. For
a nullable result that went through WriteNullable, which is not
inlined and takes the value by reference. And when the JIT inlines the
user's lambda, it builds the int? on the stack with two narrow stores
and reads it back as one 8-byte value to pass it on, a load the
processor cannot forward from those stores. Together about 4 ns per
row on .NET 10: a function returning int? took twice the time of one
returning int.

The loops now test the result type, which the JIT folds, and write a
nullable result through WriteResult: one line per type a function can
return, the value taken out with a cast through object? (folded, no
box) and written as the type under it, or a NULL. Unsafe.As would take
the address of the result and bring the 8-byte load back. Any other
result goes straight to WriteValue as before: the .NET 8 JIT does not
inline the helper into the loops, and an int function routed through
it was 1.2 times slower there.

A million rows, .NET 10: int -> int? 0.46 of the time, int? -> int? with
NULLs 0.63, the int and double controls 0.97 and 0.99. .NET 8: no
change. A new test runs an identity function over all 21 nullable
types and a varargs function, with NULLs; it passes before and after.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TXdqHuNtM7YXS8B65qdfxX

Coverage Stats

2052 of 2285 branches covered (89.8%)

Branch coverage included in aggregate %.

40 of 42 new or added lines in 1 file covered. (95.24%)

7 existing lines in 1 file now uncovered.

3776 of 4012 relevant lines covered (94.12%)

1004586.64 hits per line