Auto-folding¶

A technique for populating recursive hierarchies during dup-select, where the import process attempts to create a maximally-nested hierarchy for every row, but for rows that have fewer than the maximum # of levels, the extra levels are auto-folded together as a result of unique constraint collisions in dup-select. For the auto-folded rows, this requires the same unique constraint values to be explicitly populated for each level in the hierarchy, so that the collisions happen properly.

It is often easier to leave the unique constraint columns blank rather than copying them over to each level. To handle this case, use auto-forwarding (which requires some schema/mappings configuration).

This technique is used to populate the VegCore/VegBIEN sampling event hierarchy for VegBank/CVS, where a nested stratum event is sometimes needed but should collapse to the parent event when there is no stratum.