fix: Show x values in data order when grouping enabled

[nekketsuuu]

If the following conditions are met:

• Grouping is enabled,
• Values of x axis are not sorted by Plotly, and
• Some y value of some group is missing on some x value,

then the order of x values is broken because missing values are processed afterward.

This patch completely rewrote the way to pack values with grouping, and fixed the problem above by filling the missing values with null.

Screenshots

Details

An example query:

select '2026/01/01' as sold_date, 'A' as item_name, 100 as sold_count
union all
select '2026/01/01', 'B', 200
union all
select '2026/01/02', 'B', 100
union all
select '2026/01/03', 'A', 200
union all
select '2026/01/03', 'B', 300

Without Grouping

Charts are not changed with this patch.

Before	After

With Grouping

Every chart type except for pie chart is broken with the conditions above. "2026/01/02" is not located between "2026/01/01" and "2026/01/03". Pie chart doesn't have the grouping option.

Type	Before	After
Bar
Line
Scatter
Area
Pie

It seems that Plotly automatically sorts x values (so it hasn't been broken), for example, when they are formatted like "2026-01-01".

Grouping	Before	After
Disabled
Enabled