source.mode "derived": union source "{label}" failed to read ({error}) and was skipped this pass.

Warnings reference › source.derived.union.failed.*

Identifier

source.derived.union.failed.*

Raised by

The grid (core)

Since

1.51.0

What happened

Reading one parent threw - usually in its map function, or in the parent grid itself - so that parent contributes no rows to this pass. The union still delivers the others, so the grid shows a partial set rather than nothing.

The fix

The error's message is quoted in the line. A map that assumes a field the parent does not always carry is the usual cause.

Reference

Covered in full at the API reference.