Reentrant arenas.

backup.go

@@ -62,7 +62,7 @@ func (src *Conn) BackupInit(srcDB, dstURI string) (*Backup, error) {
 }
 
 func (c *Conn) backupInit(dst uint32, dstName string, src uint32, srcName string) (*Backup, error) {
-	defer c.arena.reset()
+	defer c.arena.mark()()
 	dstPtr := c.arena.string(dstName)
 	srcPtr := c.arena.string(srcName)
 

blob.go

@@ -30,7 +30,7 @@ var _ io.ReadWriteSeeker = &Blob{}
 // https://sqlite.org/c3ref/blob_open.html
 func (c *Conn) OpenBlob(db, table, column string, row int64, write bool) (*Blob, error) {
 	c.checkInterrupt()
-	defer c.arena.reset()
+	defer c.arena.mark()()
 	blobPtr := c.arena.new(ptrlen)
 	dbPtr := c.arena.string(db)
 	tablePtr := c.arena.string(table)
@@ -92,8 +92,8 @@ func (b *Blob) Read(p []byte) (n int, err error) {
 		want = avail
 	}
 
-	ptr := b.c.new(uint64(want))
+	defer b.c.arena.mark()()
-	defer b.c.free(ptr)
+	ptr := b.c.arena.new(uint64(want))
 
 	r := b.c.call(b.c.api.blobRead, uint64(b.handle),
 		uint64(ptr), uint64(want), uint64(b.offset))
@@ -124,8 +124,8 @@ func (b *Blob) WriteTo(w io.Writer) (n int64, err error) {
 		want = avail
 	}
 
-	ptr := b.c.new(uint64(want))
+	defer b.c.arena.mark()()
-	defer b.c.free(ptr)
+	ptr := b.c.arena.new(uint64(want))
 
 	for want > 0 {
 		r := b.c.call(b.c.api.blobRead, uint64(b.handle),
@@ -158,8 +158,8 @@ func (b *Blob) WriteTo(w io.Writer) (n int64, err error) {
 //
 // https://sqlite.org/c3ref/blob_write.html
 func (b *Blob) Write(p []byte) (n int, err error) {
-	ptr := b.c.newBytes(p)
+	defer b.c.arena.mark()()
-	defer b.c.free(ptr)
+	ptr := b.c.arena.bytes(p)
 
 	r := b.c.call(b.c.api.blobWrite, uint64(b.handle),
 		uint64(ptr), uint64(len(p)), uint64(b.offset))
@@ -187,8 +187,8 @@ func (b *Blob) ReadFrom(r io.Reader) (n int64, err error) {
 		want = 1
 	}
 
-	ptr := b.c.new(uint64(want))
+	defer b.c.arena.mark()()
-	defer b.c.free(ptr)
+	ptr := b.c.arena.new(uint64(want))
 
 	for {
 		mem := util.View(b.c.mod, ptr, uint64(want))

conn.go

@@ -72,7 +72,7 @@ func newConn(filename string, flags OpenFlag) (conn *Conn, err error) {
 }
 
 func (c *Conn) openDB(filename string, flags OpenFlag) (uint32, error) {
-	defer c.arena.reset()
+	defer c.arena.mark()()
 	connPtr := c.arena.new(ptrlen)
 	namePtr := c.arena.string(filename)
 
@@ -96,7 +96,6 @@ func (c *Conn) openDB(filename string, flags OpenFlag) (uint32, error) {
 			}
 		}
 
-		c.arena.reset()
 		pragmaPtr := c.arena.string(pragmas.String())
 		r := c.call(c.api.exec, uint64(handle), uint64(pragmaPtr), 0, 0, 0)
 		if err := c.sqlite.error(r, handle, pragmas.String()); err != nil {
@@ -151,11 +150,11 @@ func (c *Conn) Close() error {
 // https://sqlite.org/c3ref/exec.html
 func (c *Conn) Exec(sql string) error {
 	c.checkInterrupt()
-	defer c.arena.reset()
+	defer c.arena.mark()()
 	sqlPtr := c.arena.string(sql)
 
 	r := c.call(c.api.exec, uint64(c.handle), uint64(sqlPtr), 0, 0, 0)
-	return c.error(r)
+	return c.error(r, sql)
 }
 
 // Prepare calls [Conn.PrepareFlags] with no flags.
@@ -177,7 +176,7 @@ func (c *Conn) PrepareFlags(sql string, flags PrepareFlag) (stmt *Stmt, tail str
 		return nil, "", nil
 	}
 
-	defer c.arena.reset()
+	defer c.arena.mark()()
 	stmtPtr := c.arena.new(ptrlen)
 	tailPtr := c.arena.new(ptrlen)
 	sqlPtr := c.arena.string(sql)

context.go

@@ -208,10 +208,10 @@ func (ctx Context) ResultError(err error) {
 
 	msg, code := errorCode(err, _OK)
 	if msg != "" {
-		ptr := ctx.c.newString(msg)
+		defer ctx.c.arena.mark()()
+		ptr := ctx.c.arena.string(msg)
 		ctx.c.call(ctx.c.api.resultError,
 			uint64(ctx.handle), uint64(ptr), uint64(len(msg)))
-		ctx.c.free(ptr)
 	}
 	if code != _OK {
 		ctx.c.call(ctx.c.api.resultErrorCode,

func.go

@@ -21,7 +21,7 @@ func (c *Conn) AnyCollationNeeded() {
 //
 // https://sqlite.org/c3ref/create_collation.html
 func (c *Conn) CreateCollation(name string, fn func(a, b []byte) int) error {
-	defer c.arena.reset()
+	defer c.arena.mark()()
 	namePtr := c.arena.string(name)
 	funcPtr := util.AddHandle(c.ctx, fn)
 	r := c.call(c.api.createCollation,
@@ -33,7 +33,7 @@ func (c *Conn) CreateCollation(name string, fn func(a, b []byte) int) error {
 //
 // https://sqlite.org/c3ref/create_function.html
 func (c *Conn) CreateFunction(name string, nArg int, flag FunctionFlag, fn func(ctx Context, arg ...Value)) error {
-	defer c.arena.reset()
+	defer c.arena.mark()()
 	namePtr := c.arena.string(name)
 	funcPtr := util.AddHandle(c.ctx, fn)
 	r := c.call(c.api.createFunction,
@@ -48,7 +48,7 @@ func (c *Conn) CreateFunction(name string, nArg int, flag FunctionFlag, fn func(
 //
 // https://sqlite.org/c3ref/create_function.html
 func (c *Conn) CreateWindowFunction(name string, nArg int, flag FunctionFlag, fn func() AggregateFunction) error {
-	defer c.arena.reset()
+	defer c.arena.mark()()
 	call := c.api.createAggregate
 	namePtr := c.arena.string(name)
 	funcPtr := util.AddHandle(c.ctx, fn)

sqlite.go

@@ -294,17 +294,23 @@ func (a *arena) free() {
 	if a.sqlt == nil {
 		return
 	}
-	a.reset()
+	for _, ptr := range a.ptrs {
+		a.sqlt.free(ptr)
+	}
 	a.sqlt.free(a.base)
 	a.sqlt = nil
 }
 
-func (a *arena) reset() {
+func (a *arena) mark() (reset func()) {
-	for _, ptr := range a.ptrs {
+	ptrs := len(a.ptrs)
-		a.sqlt.free(ptr)
+	next := a.next
+	return func() {
+		for _, ptr := range a.ptrs[ptrs:] {
+			a.sqlt.free(ptr)
+		}
+		a.ptrs = a.ptrs[:ptrs]
+		a.next = next
 	}
-	a.ptrs = nil
-	a.next = 0
 }
 
 func (a *arena) new(size uint64) uint32 {

stmt.go

@@ -104,7 +104,7 @@ func (s *Stmt) BindCount() int {
 //
 // https://sqlite.org/c3ref/bind_parameter_index.html
 func (s *Stmt) BindIndex(name string) int {
-	defer s.c.arena.reset()
+	defer s.c.arena.mark()()
 	namePtr := s.c.arena.string(name)
 	r := s.c.call(s.c.api.bindIndex,
 		uint64(s.handle), uint64(namePtr))

vtab.go

@@ -53,7 +53,7 @@ func CreateModule[T VTab](db *Conn, name string, create, connect VTabConstructor
 		flags |= VTAB_SAVEPOINTER
 	}
 
-	defer db.arena.reset()
+	defer db.arena.mark()()
 	namePtr := db.arena.string(name)
 	modulePtr := util.AddHandle(db.ctx, module[T]{create, connect})
 	r := db.call(db.api.createModule, uint64(db.handle),
@@ -70,7 +70,7 @@ func implements[T any](typ reflect.Type) bool {
 //
 // https://sqlite.org/c3ref/declare_vtab.html
 func (c *Conn) DeclareVtab(sql string) error {
-	// The arena will be cleared by the prepare or exec method.
+	defer c.arena.mark()()
 	sqlPtr := c.arena.string(sql)
 	r := c.call(c.api.declareVTab, uint64(c.handle), uint64(sqlPtr))
 	return c.error(r)
@@ -255,7 +255,7 @@ type IndexConstraintUsage struct {
 //
 // https://sqlite.org/c3ref/vtab_rhs_value.html
 func (idx *IndexInfo) RHSValue(column int) (*Value, error) {
-	// The arena will be cleared by the prepare or exec method.
+	defer idx.c.arena.mark()()
 	valPtr := idx.c.arena.new(ptrlen)
 	r := idx.c.call(idx.c.api.vtabRHSValue,
 		uint64(idx.handle), uint64(column), uint64(valPtr))
@@ -318,7 +318,7 @@ func (idx *IndexInfo) save() {
 	util.WriteUint32(mod, ptr+20, uint32(idx.IdxNum))
 	if idx.IdxStr != "" {
 		util.WriteUint32(mod, ptr+24, idx.c.newString(idx.IdxStr))
-		util.WriteUint32(mod, ptr+28, 1)
+		util.WriteUint32(mod, ptr+28, 1) // needToFreeIdxStr
 	}
 	if idx.OrderByConsumed {
 		util.WriteUint32(mod, ptr+32, 1)
@@ -567,11 +567,14 @@ func vtabError(ctx context.Context, mod api.Module, ptr, kind uint32, err error)
 	if msg != "" && ptr != 0 {
 		switch kind {
 		case _VTAB_ERROR:
-			ptr = ptr + 8
+			ptr = ptr + 8 // zErrMsg
 		case _CURSOR_ERROR:
-			ptr = util.ReadUint32(mod, ptr) + 8
+			ptr = util.ReadUint32(mod, ptr) + 8 // pVtab->zErrMsg
 		}
 		db := ctx.Value(connKey{}).(*Conn)
+		if ptr := util.ReadUint32(mod, ptr); ptr != 0 {
+			db.free(ptr)
+		}
 		util.WriteUint32(mod, ptr, db.newString(msg))
 	}
 	return code