Call AggregateSeqFunction for empty input groups#390
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The per-group callback registered via CreateAggregateFunction was never invoked when a group had zero input rows, because the iter.Pull-backed coroutine only runs the user callback after the first Step. SQLite's xFinal contract calls for exactly one invocation per group, including the implicit single-group case of an ungrouped aggregate over an empty input. Track whether Step ran and, if not, invoke the user callback directly with an empty seq from Value. Fixes ncruces#389.
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Fixes #389.
CreateAggregateFunctionnever invokes the user'sAggregateSeqFunctionwhen a group has zero input rows, because theiter.Pullcoroutine only runs the callback after the firstStep. SQLite'sxFinalcontract calls for exactly one invocation per group, so an ungrouped custom aggregate over an empty input returnsNULLinstead of the documented value (e.g.0for a count).Track whether
Stepran on theaggregateFunc, and if not, invoke the user callback directly fromValuewith an emptyseq. The coroutine path is unchanged for the common case.Verified with the issue's repro:
Added
TestAggregateSeqFunction_EmptyInputwhich fails onmainand passes with the fix. Existinggo test -race ./...is green on.and./tests/....