Fix AggregateFinal behavior on window functions

CHANGELOG.md

@@ -5,7 +5,18 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-[Unreleased]: https://github.com/zombiezen/go-sqlite/compare/v0.10.0...main
+[Unreleased]: https://github.com/zombiezen/go-sqlite/compare/v0.10.1...main
+
+## [0.10.1][] - 2022-07-17
+
+Version 0.10.1 fixes a bug in user-defined window functions.
+Special thanks to Jan Mercl for assistance in debugging this issue.
+
+[0.10.1]: https://github.com/zombiezen/go-sqlite/releases/tag/v0.10.1
+
+### Fixed
+
+- `AggregateFinal` is now called correctly at the end of window functions' usages.
 
 ## [0.10.0][] - 2022-07-10
 

func.go

@@ -409,16 +409,28 @@ type FunctionImpl struct {
 
 	// AggregateStep is called for each row
 	// of an aggregate function's SQL invocation.
+	//
+	// Use closure variables to accumulate state between calls to AggregateStep.
 	AggregateStep func(ctx Context, rowArgs []Value) error
-	// AggregateFinal is called after all of the aggregate function's input rows
-	// have been stepped through to construct the result.
+	// AggregateFinal is called
+	// after all of the aggregate function's input rows have been stepped through.
+	// The AggregateFinal function should
+	// reset the state used in AggregateStep to its initial value.
+	// When using the function as a non-window aggregate,
+	// the returned value is used as the function's result.
+	// When using a function as window aggregate,
+	// the function will only receive a call to AggregateFinal
+	// when it processes one or more rows during its evaluation
+	// to reset state (the returned Value is ignored).
 	//
-	// Use closure variables to pass information between AggregateStep and
-	// AggregateFinal. The AggregateFinal function should also reset any shared
-	// variables to their initial states before returning.
+	// Use closure variables to pass information between AggregateStep and AggregateFinal.
 	AggregateFinal func(ctx Context) (Value, error)
 
-	// WindowValue is called to get the current value of a aggregate window function.
+	// WindowValue is called to get the current value of an aggregate window function.
+	// This function will not be called when using an aggregate window function
+	// as an ordinary aggregate function.
+	//
+	// Use closure variables to pass information between AggregateStep and WindowValue.
 	WindowValue func(ctx Context) (Value, error)
 	// WindowInverse is called to remove
 	// the oldest presently aggregated result of AggregateStep
@@ -608,6 +620,14 @@ func funcTrampoline(tls *libc.TLS, ctx uintptr, n int32, valarray uintptr) {
 }
 
 func stepTrampoline(tls *libc.TLS, ctx uintptr, n int32, valarray uintptr) {
+	f := getxfuncs(tls, ctx)
+	if f.xValue != nil {
+		// SQLite only calls xFinal on window functions
+		// when they have an aggregate context allocated.
+		// The actual data is unused, since the closures pass data out-of-band.
+		lib.Xsqlite3_aggregate_context(tls, ctx, 1)
+	}
+
 	vals := make([]Value, 0, int(n))
 	for ; len(vals) < cap(vals); valarray += uintptr(ptrSize) {
 		vals = append(vals, Value{
@@ -616,7 +636,7 @@ func stepTrampoline(tls *libc.TLS, ctx uintptr, n int32, valarray uintptr) {
 		})
 	}
 	goCtx := Context{tls: tls, ptr: ctx}
-	if err := getxfuncs(tls, ctx).xStep(goCtx, vals); err != nil {
+	if err := f.xStep(goCtx, vals); err != nil {
 		goCtx.resultError(err)
 	}
 }

func_test.go

@@ -102,6 +102,7 @@ func TestAggFunc(t *testing.T) {
 		}
 	}
 
+	finalCalled := false
 	sumintsImpl := &FunctionImpl{
 		NArgs:         1,
 		Deterministic: true,
@@ -114,6 +115,7 @@ func TestAggFunc(t *testing.T) {
 			return nil
 		}
 		sumintsImpl.AggregateFinal = func(ctx Context) (Value, error) {
+			finalCalled = true
 			result := IntegerValue(sum)
 			sum = 0
 			return result, nil
@@ -134,6 +136,9 @@ func TestAggFunc(t *testing.T) {
 	if got := stmt.ColumnInt(0); got != want {
 		t.Errorf("sum(c)=%d, want %d", got, want)
 	}
+	if !finalCalled {
+		t.Error("xFinal not called")
+	}
 }
 
 // Equivalent of https://www.sqlite.org/windowfunctions.html#user_defined_aggregate_window_functions
@@ -172,6 +177,7 @@ func TestWindowFunc(t *testing.T) {
 		t.Errorf("INSERT: %v", err)
 	}
 
+	finalCalled := false
 	sumintImpl := &FunctionImpl{
 		NArgs:         1,
 		Deterministic: true,
@@ -194,6 +200,7 @@ func TestWindowFunc(t *testing.T) {
 			return IntegerValue(sum), nil
 		}
 		sumintImpl.AggregateFinal = func(ctx Context) (Value, error) {
+			finalCalled = true
 			result := IntegerValue(sum)
 			sum = 0
 			return result, nil
@@ -240,6 +247,9 @@ func TestWindowFunc(t *testing.T) {
 	if diff := cmp.Diff(want, got, cmp.AllowUnexported(row{})); diff != "" {
 		t.Errorf("-want +got:\n%s", diff)
 	}
+	if !finalCalled {
+		t.Error("xFinal not called")
+	}
 }
 
 func TestCastTextToInteger(t *testing.T) {