Use overflow-safe size arithmetic in the Index[Only]Scan and parallel
instrumentation functions, consistent with other executor nodes (Hash,
Sort, Agg, Memoize). This was an oversight in dd78e69cfc.
Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Tomas Vondra <tomas@vondra.me>
Reviewed-by: Lukas Fittl <lukas@fittl.com>
Discussion: https://postgr.es/m/flat/a177a6dd-240b-455a-8f25-aca0b1c08c6e%40vondra.me
884f9b3c76