Improved arg reuse.

const.go

@@ -11,10 +11,9 @@ const (
 	_ROW  = 100 /* sqlite3_step() has another row ready */
 	_DONE = 101 /* sqlite3_step() has finished executing */
 
-	_MAX_NAME         = 1e6 // Self-imposed limit for most NUL terminated strings.
-	_MAX_LENGTH       = 1e9
-	_MAX_SQL_LENGTH   = 1e9
-	_MAX_FUNCTION_ARG = 100
+	_MAX_NAME       = 1e6 // Self-imposed limit for most NUL terminated strings.
+	_MAX_LENGTH     = 1e9
+	_MAX_SQL_LENGTH = 1e9
 
 	ptrlen = util.PtrLen
 	intlen = util.IntLen

ext/bloom/bloom.go

@@ -268,13 +268,13 @@ func (b *bloom) Open() (sqlite3.VTabCursor, error) {
 
 type cursor struct {
 	*bloom
-	arg *sqlite3.Value
+	arg sqlite3.Value
 	eof bool
 }
 
 func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 	c.eof = false
-	c.arg = &arg[0]
+	c.arg = arg[0]
 	blob := arg[0].RawBlob()
 
 	f, err := c.db.OpenBlob(c.schema, c.storage, "data", 1, false)
@@ -312,7 +312,7 @@ func (c *cursor) Column(ctx sqlite3.Context, n int) error {
 	case 0:
 		ctx.ResultBool(true)
 	case 1:
-		ctx.ResultValue(*c.arg)
+		ctx.ResultValue(c.arg)
 	}
 	return nil
 }

ext/statement/stmt.go

@@ -159,8 +159,6 @@ func (c *cursor) Close() error {
 }
 
 func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
-	c.arg = arg
-	c.rowID = 0
 	err := errors.Join(
 		c.stmt.Reset(),
 		c.stmt.ClearBindings())
@@ -187,6 +185,8 @@ func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 			return err
 		}
 	}
+	c.arg = append(c.arg[:0], arg...)
+	c.rowID = 0
 	return c.Next()
 }
 

func.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"iter"
 	"sync"
+	"sync/atomic"
 
 	"github.com/tetratelabs/wazero/api"
 
@@ -196,21 +197,19 @@ func compareCallback(ctx context.Context, mod api.Module, pApp ptr_t, nKey1 int3
 }
 
 func funcCallback(ctx context.Context, mod api.Module, pCtx, pApp ptr_t, nArg int32, pArg ptr_t) {
-	args := getFuncArgs()
-	defer putFuncArgs(args)
 	db := ctx.Value(connKey{}).(*Conn)
+	args := callbackArgs(db, nArg, pArg)
+	defer returnArgs(args)
 	fn := util.GetHandle(db.ctx, pApp).(ScalarFunction)
-	callbackArgs(db, args[:nArg], pArg)
-	fn(Context{db, pCtx}, args[:nArg]...)
+	fn(Context{db, pCtx}, *args...)
 }
 
 func stepCallback(ctx context.Context, mod api.Module, pCtx, pAgg, pApp ptr_t, nArg int32, pArg ptr_t) {
-	args := getFuncArgs()
-	defer putFuncArgs(args)
 	db := ctx.Value(connKey{}).(*Conn)
-	callbackArgs(db, args[:nArg], pArg)
+	args := callbackArgs(db, nArg, pArg)
+	defer returnArgs(args)
 	fn, _ := callbackAggregate(db, pAgg, pApp)
-	fn.Step(Context{db, pCtx}, args[:nArg]...)
+	fn.Step(Context{db, pCtx}, *args...)
 }
 
 func valueCallback(ctx context.Context, mod api.Module, pCtx, pAgg, pApp ptr_t, final int32) {
@@ -234,12 +233,11 @@ func valueCallback(ctx context.Context, mod api.Module, pCtx, pAgg, pApp ptr_t,
 }
 
 func inverseCallback(ctx context.Context, mod api.Module, pCtx, pAgg ptr_t, nArg int32, pArg ptr_t) {
-	args := getFuncArgs()
-	defer putFuncArgs(args)
 	db := ctx.Value(connKey{}).(*Conn)
-	callbackArgs(db, args[:nArg], pArg)
+	args := callbackArgs(db, nArg, pArg)
+	defer returnArgs(args)
 	fn := util.GetHandle(db.ctx, pAgg).(WindowFunction)
-	fn.Inverse(Context{db, pCtx}, args[:nArg]...)
+	fn.Inverse(Context{db, pCtx}, *args...)
 }
 
 func callbackAggregate(db *Conn, pAgg, pApp ptr_t) (AggregateFunction, ptr_t) {
@@ -258,28 +256,31 @@ func callbackAggregate(db *Conn, pAgg, pApp ptr_t) (AggregateFunction, ptr_t) {
 	return fn, 0
 }
 
-func callbackArgs(db *Conn, arg []Value, pArg ptr_t) {
-	for i := range arg {
-		arg[i] = Value{
+var (
+	valueArgsPool sync.Pool
+	valueArgsLen  atomic.Int32
+)
+
+func callbackArgs(db *Conn, nArg int32, pArg ptr_t) *[]Value {
+	arg, ok := valueArgsPool.Get().(*[]Value)
+	if !ok || cap(*arg) < int(nArg) {
+		max := valueArgsLen.Or(nArg) | nArg
+		lst := make([]Value, max)
+		arg = &lst
+	}
+	lst := (*arg)[:nArg]
+	for i := range lst {
+		lst[i] = Value{
 			c:      db,
 			handle: util.Read32[ptr_t](db.mod, pArg+ptr_t(i)*ptrlen),
 		}
 	}
+	*arg = lst
+	return arg
 }
 
-var funcArgsPool sync.Pool
-
-func putFuncArgs(p *[_MAX_FUNCTION_ARG]Value) {
-	clear(p[:])
-	funcArgsPool.Put(p)
-}
-
-func getFuncArgs() *[_MAX_FUNCTION_ARG]Value {
-	if p := funcArgsPool.Get(); p == nil {
-		return new([_MAX_FUNCTION_ARG]Value)
-	} else {
-		return p.(*[_MAX_FUNCTION_ARG]Value)
-	}
+func returnArgs(p *[]Value) {
+	valueArgsPool.Put(p)
 }
 
 type aggregateFunc struct {
@@ -291,7 +292,7 @@ type aggregateFunc struct {
 
 func (a *aggregateFunc) Step(ctx Context, arg ...Value) {
 	a.ctx = ctx
-	a.arg = arg
+	a.arg = append(a.arg[:0], arg...)
 	if _, more := a.next(); !more {
 		a.stop()
 	}

vtab.go

@@ -162,6 +162,7 @@ type VTabDestroyer interface {
 }
 
 // A VTabUpdater allows a virtual table to be updated.
+// Implementations must not retain arg.
 type VTabUpdater interface {
 	VTab
 	// https://sqlite.org/vtab.html#xupdate
@@ -241,6 +242,7 @@ type VTabSavepointer interface {
 // to loop through the virtual table.
 // A VTabCursor may optionally implement
 // [io.Closer] to free resources.
+// Implementations of Filter must not retain arg.
 //
 // https://sqlite.org/c3ref/vtab_cursor.html
 type VTabCursor interface {
@@ -489,12 +491,12 @@ func vtabBestIndexCallback(ctx context.Context, mod api.Module, pVTab, pIdxInfo
 }
 
 func vtabUpdateCallback(ctx context.Context, mod api.Module, pVTab ptr_t, nArg int32, pArg, pRowID ptr_t) res_t {
-	vtab := vtabGetHandle(ctx, mod, pVTab).(VTabUpdater)
-
 	db := ctx.Value(connKey{}).(*Conn)
-	args := make([]Value, nArg)
-	callbackArgs(db, args, pArg)
-	rowID, err := vtab.Update(args...)
+	args := callbackArgs(db, nArg, pArg)
+	defer returnArgs(args)
+
+	vtab := vtabGetHandle(ctx, mod, pVTab).(VTabUpdater)
+	rowID, err := vtab.Update(*args...)
 	if err == nil {
 		util.Write64(mod, pRowID, rowID)
 	}
@@ -593,15 +595,17 @@ func cursorCloseCallback(ctx context.Context, mod api.Module, pCur ptr_t) res_t
 }
 
 func cursorFilterCallback(ctx context.Context, mod api.Module, pCur ptr_t, idxNum int32, idxStr ptr_t, nArg int32, pArg ptr_t) res_t {
-	cursor := vtabGetHandle(ctx, mod, pCur).(VTabCursor)
 	db := ctx.Value(connKey{}).(*Conn)
-	args := make([]Value, nArg)
-	callbackArgs(db, args, pArg)
+	args := callbackArgs(db, nArg, pArg)
+	defer returnArgs(args)
+
 	var idxName string
 	if idxStr != 0 {
 		idxName = util.ReadString(mod, idxStr, _MAX_LENGTH)
 	}
-	err := cursor.Filter(int(idxNum), idxName, args...)
+
+	cursor := vtabGetHandle(ctx, mod, pCur).(VTabCursor)
+	err := cursor.Filter(int(idxNum), idxName, *args...)
 	return vtabError(ctx, mod, pCur, _CURSOR_ERROR, err)
 }