RangeError (byteOffset): Index out of range: index should be less than 2048: 2048

[MinseokKang003]

I have Map<String, dynamic> flex property in the entity schema.

When I'm trying to save ~30 UUIDs in this flex field, I'm getting these error logs:

RangeError (byteOffset): Index out of range: index should be less than 2048: 2048
flutter: #0      _byteDataByteOffsetCheck (dart:typed_data-patch/typed_data_patch.dart:5419:5)
typed_data_patch.dart:5419
#1      _ByteDataView.setUint8 (dart:typed_data-patch/typed_data_patch.dart:5115:18)
typed_data_patch.dart:5115
#2      Builder._pushUInt (package:flat_buffers/src/builder.dart:533:17)
builder.dart:533
#3      Builder._writeUInt (package:flat_buffers/src/builder.dart:495:5)
builder.dart:495
#4      Builder._createVector (package:flat_buffers/src/builder.dart:368:9)
builder.dart:368
#5      Builder._endMap (package:flat_buffers/src/builder.dart:441:17)
builder.dart:441
#6      Builder._sortKeysAndEndMap (package:flat_buffers/src/builder.dart:424:5)
builder.dart:424
#7      Builder.end (package:flat_buffers/src/builder.dart:246:7)
builder.dart:246
#8      Builder._add (package:flat_buffers/src/builder.dart:62:7)
builder.dart:62
#9      Builder.buildFromObject (package:flat_buffers/src/builder.dart:30:13)
builder.dart:30
#10     toFlexBuffer (package:objectbox/src/native/bindings/flexbuffers.dart:13:31)
flexbuffers.dart:13
#11     getObjectBoxModel.<anonymous closure> (package:ssadavoca/infrastructure/db/objectbox.g.dart:2079:33)
objectbox.g.dart:2079
#12     Box._put (package:objectbox/src/native/box.dart:25<…>

This is causing severe problems in my production app. If there was a hard size limit on the flex property, the documentation should have stated this.

Is it correct that the flex field has a 2048B size limit? Or is it configurable? Any help would be greatly appreciated.

[greenrobot-team]

Thanks for reporting! This isn't intended behavior. There appears to be a bug in the flatbuffers package when increasing the size of its internal buffer.

We'll look into this.

[greenrobot-team]

A simple test to verify this:

    test('put with many entries', () {
      final testMap = <String, Object>{};
      for (var i = 0; i < 50; i++) {
        testMap['key$i'] = '00112233-4455-6677-8899-ccddeeffaabb$i';
      }
      final entity = FlexMapEntity(flexDynamic: testMap);
      box.put(entity);
    });

Fails with:

dart:typed_data                                               _IntListMixin.setAll
package:flat_buffers/src/builder.dart 548:34                  Builder._pushBuffer
package:flat_buffers/src/builder.dart 108:5                   Builder.addString
package:flat_buffers/src/builder.dart 49:7                    Builder._add
package:flat_buffers/src/builder.dart 60:9                    Builder._add.<fn>
dart:_compact_hash                                            _LinkedHashMapMixin.forEach
package:flat_buffers/src/builder.dart 58:13                   Builder._add
package:flat_buffers/src/builder.dart 30:13                   Builder.buildFromObject
package:objectbox/src/native/bindings/flexbuffers.dart 13:31  toFlexBuffer
test\objectbox.g.dart 2599:41                                 getObjectBoxModel.<fn>
package:objectbox/src/native/box.dart 259:32                  Box._put
package:objectbox/src/native/box.dart 107:14                  Box.put
test\flex_test.dart 46:11                                     main.<fn>.<fn>

RangeError (end): Invalid value: Not in inclusive range 2011..2048: 2049

It appears the issue is in /lib/src/builder.dart. A new buffer is created, but not used:

  int _newOffset(int newValueSize) {
    final newOffset = _offset + newValueSize;
    var size = _buffer.lengthInBytes;
    final prevSize = size;
    while (size < newOffset) {
      size <<= 1;
    }
    if (prevSize < size) {
      final newBuf = ByteData(size);
      newBuf.buffer.asUint8List().setAll(0, _buffer.buffer.asUint8List()); // <-- _buffer not replaced with newBuf
    }
    return newOffset;
  }

[NSHuman]

This appears to be what is holding up my project as well.
If I am understanding this thread correctly, the maxDataSizeInKB parameter in the openStore function is what should be used to raise this 2048 byte limit, but currently will not have any effect? Do I have that right?

[greenrobot-team]

No, this is an issue with the currently used flat_buffers (version 25.9.23) package. A fix was already accepted (google/flatbuffers#8935), but we are still waiting for a new release of the package that includes it.