The header merge column width of the pivot plugin cannot cover the entire table

[CoderSxy]

Bug description

In the pivot viz plugin with a particularly large number of columns, the width of the header merged columns cannot cover the entire table

Screenshots/recordings

Superset version

master / latest-dev

Python version

3.9

Node version

18 or greater

Browser

Chrome

Additional context

No response

Checklist

• I have searched Superset docs and Slack and didn't find a solution to my problem.
• I have searched the GitHub issue tracker and didn't find a similar bug report.
• I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.

[dosubot]

This issue is likely related to how the pivot table plugin calculates and renders merged header columns when there are many columns. The merged header widths are determined by the colSpan logic in the React component (TableRenderer), and the overall table width is set in CSS to calc(100% - theme.sizeUnit px). If the table's content exceeds this width, merged headers may not visually cover the entire table, especially with wide or many columns. Recent PRs have addressed related header and layout issues, such as fixing column bleed and header alignment with scrollbars, which may help in some cases (PR #36134, PR #36190).

If you're still seeing the issue on the latest master, you might experiment with custom CSS to set the table width to 100% or auto, or adjust the overflow handling. The root cause is likely a mismatch between the calculated header spans and the actual rendered table width when there are many columns.

To reply, just mention @dosu.

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[CoderSxy]

I've found the reason