flatc JSON serialisation of sorted tables

[Jiboo]

Hi,

I think that the current implementation of Parser::ParseVector serializes tables with key in the order of the JSON file and don't sorts the element by their keys. I clearly don't know enough of the internals to know if I'm right, but it looks like it just PushElement offset to tables in the order of parsing, and don't arrange the entries before serializing the offsets.

Bye,
JB.

Yes, default is no-sorting. You need to call CreateVectorOfSortedTables instead to get the sort. See also "Storing maps / dictionaries in a FlatBuffer" in the C++ docs.

[Jiboo]

You need to call CreateVectorOfSortedTables instead to get the sort.

Sorry I wasn't clear, I'm not responsible for that call, I was talking about the JSON to binary feature in the flatc tool, and idl.h's Parser::Parse which in the c++ docs under "Text & schema parsing".
They will both in the end use Parser::ParseVector to serialize a vector, which don't check that the vector is a table with a key, and just calls CreateVector and PushElement offset to your entries in the order they were parsed.
If you confirm that this is a a bug, I could extract it from #187 and make a separate PR.

[neoblazes]

I tried to read json text as sorted array from C#. But the problems I got were 1) I sorted json string key from VB and convert it with flatc.exe. But the index was broken. 2) I read thr array from C# and tried to store back after sort. But there is no deep copy and I should manually copy all fields. How I guarantee that the json txt string sort order is identical to what did by C#?

[aardappel]

@neoblazes I am not entirely clear on what you're trying to do. What is the index, and how is it broken?

Sorting an existing FlatBuffer in-place, or generally modifying an existing FlatBuffer is difficult, you should want to sort it before creating it.

[whitecostume]

@neoblazes I am not entirely clear on what you're trying to do. What is the index, and how is it broken?我不太清楚你想做什么。索引是什么？它是怎么坏的？

Sorting an existing FlatBuffer in-place, or generally modifying an existing FlatBuffer is difficult, you should want to sort it before creating it.对现有的 FlatBuffer 进行排序或通常修改现有的 FlatBuffer 很困难，您应该在创建它之前对其进行排序。

What he meant is that a json file that has been sorted by key becomes an unordered file after being exported as a binary file by flatc, which means that SortedVector cannot be used to find the corresponding data (when the key is a string)

[whitecostume]

@neoblazes I am not entirely clear on what you're trying to do. What is the index, and how is it broken?我不太清楚你想做什么。索引是什么？它是怎么坏的？
Sorting an existing FlatBuffer in-place, or generally modifying an existing FlatBuffer is difficult, you should want to sort it before creating it.对现有的 FlatBuffer 进行排序或通常修改现有的 FlatBuffer 很困难，您应该在创建它之前对其进行排序。

What he meant is that a json file that has been sorted by key becomes an unordered file after being exported as a binary file by flatc, which means that SortedVector cannot be used to find the corresponding data (when the key is a string)

I found out that it was a problem with string.CompareTo #8547