Given these constraints, is it worthwhile to allow this operation, or
should we just disallow new indexing to be configured at runtime?
Per se I think it is a Good Thing. In relation with operating a DSA, it
depends if one can live with the constraints of:
a) do not allow modifications while reindexing
b) do not use the (new) indices until reindexing done
I note that (a) is equivalent to the (current) procedure of stopping
slapd, restarting it in readOnly mode, run slapindex on a copy of the
database, then replace the old with the new, re-indexed database and
restart slapd once more; except that slapd is never stopped, which is the
most significant advantage. As a consequence, I see an improvement from
the current status; if the constraint can be localized even further, the
improvement could be even greater.
(b) is also equivalent to this, unless it implies that indices cannot be
used entirely. For example: "cn" is indexed for "exact"; I need to change
it to "exact,substring". If until it's done I cannot even use "exact",
that's a loss of functionality with respect to the procedure described for
(a). I don't think this is desirable.