Honestly, the reason is mainly because each line created will call self.getParentValue().recursiveReindexObject() which becomes incredibly slow when the balance transaction have more than REINDEX_SPLIT_COUNT sub objects.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@31875 20353a03-c40f-0410-a6d1-a30d3c3de9de