Google flabtbuffer How to put array in struct in fbs file - flatbuffers

Question

This is extension to the following question
Size of Serialized data is not reducing using flatbuffer
As mentioned in the answer to reduce space we should use Struct. But in my case I need to define an idl file for Polygon
Each polygon will have five or more points, And I will have another DS which will have
array of polygons
I have define my fbs file as follow
namespace MyFlat;
struct Vertices {
x : double;
y :double;
}
table Polygon {
polygons : [Vertices];
}
table Layer {
polygons : [Polygon];
}
root_type Layer;
As expected with this my serialized data size is coming quite large. Is there any way to optimize the padding in table to reduce the serialized buffer size

Answer 1

There's no need to further optimize the structure of your data here, since >90% of the size of these buffers will typically be taken up by Vertices.
One thing to consider is to use float for x and y, given that you're unlikely to need to extra resolution.. that would almost half the size of your buffer.

Answer 2

Thanks for your answer. But When I am trying to print the size of 100 polygons having vertices 5 , the size is coming around 10.24KB. Ideally size should be around 8000 bytes(8 KB)
b := flatbuffers.NewBuilder(0)
var polyoffset []flatbuffers.UOffsetT
size := 100
StartedAtMarshal := time.Now()
for k := 0; k < size; k++ {
MyFlat.PolygonStartPolygonsVector(b, 5)
for i := 0; i < 5; i++ {
MyFlat.CreateVertices(b, 2.0, 2.4)
}
vec := b.EndVector(5)
MyFlat.PolygonStart(b)
MyFlat.PolygonAddPolygons(b, vec)
polyoffset = append(polyoffset, MyFlat.PolygonEnd(b))
}
MyFlat.LayerStartPolygonsVector(b, size)
for _, offset := range polyoffset {
b.PrependUOffsetT(offset)
}
vec := b.EndVector(size)
MyFlat.LayerStart(b)
MyFlat.LayerAddPolygons(b, vec)
finalOffset := MyFlat.LayerEnd(b)
b.Finish(finalOffset)
EndedAtMarshal := time.Now()
fmt.Println("Elapes Time for Seri", EndedAtMarshal.Sub(StartedAtMarshal).String())
mybyte := b.FinishedBytes()
fmt.Println(len(mybyte))
Is it expected size or My implementation is wrong