Data load optimization with a target table that has indexes efficiently loads data pages while maintaining the index.
All rows are packed in a set of preallocated data pages and directly written to disk to improve data load performance. Recoverability is guaranteed.
When the target table defines indexes, the indexes are also maintained while writing data pages in bulk.
Slightly increased database space may be required when the existing pages are not full because insert...select when used with ins_by_bulk does not append rows to the existing pages, but allocates a new page when inserting the first rows.