SQLITE_FCNTL_PDB.

conn.go

@@ -68,7 +68,7 @@ func OpenFlags(filename string, flags OpenFlag) (*Conn, error) {
 	return newConn(context.Background(), filename, flags)
 }
 
-type connKey struct{}
+type connKey = util.ConnKey
 
 func newConn(ctx context.Context, filename string, flags OpenFlag) (res *Conn, _ error) {
 	err := ctx.Err()

internal/util/module.go

@@ -8,6 +8,8 @@ import (
 	"github.com/ncruces/go-sqlite3/internal/alloc"
 )
 
+type ConnKey struct{}
+
 type moduleKey struct{}
 type moduleState struct {
 	mmapState

vfs/api.go

@@ -191,3 +191,8 @@ type fileControl interface {
 	File
 	fileControl(ctx context.Context, mod api.Module, op _FcntlOpcode, pArg uint32) _ErrorCode
 }
+
+type filePDB interface {
+	File
+	SetDB(any)
+}

vfs/vfs.go

@@ -376,6 +376,12 @@ func vfsFileControlImpl(ctx context.Context, mod api.Module, file File, op _Fcnt
 				return _OK
 			}
 		}
+
+	case _FCNTL_PDB:
+		if file, ok := file.(filePDB); ok {
+			file.SetDB(ctx.Value(util.ConnKey{}))
+			return _OK
+		}
 	}
 
 	// Consider also implementing these opcodes (in use by SQLite):