The current SyncEvolution master is using a more efficient approach for the "is empty" check (point 2 from comment 3). I don't intend to implement point 3, because the current solution for CalDAV (a REPORT without item content) should already be comparable in performance to the simpler PROPFIND and adding a slower, more accurate approach is of little value (isEmpty() is allowed to err on the side of caution and report "not empty" for cases where the server has mixed content and only items which would get ignored during the sync). commit 75115022c525d21341be4113d789eccd6e23cca8 Author: Patrick Ohly <email@example.com> Date: Thu Feb 12 13:36:42 2015 +0100 CalDAV: more efficient "is empty" check (FDO #86335) Since 22.214.171.124, syncing WebDAV collections always checks first whether there are items in the collections. This was partly done for slow sync prevention (which is not necessary for empty collections), partly for the "is the datastore usable" check. However, this did not take into account that for CalDAV collections, the entire content gets downloaded for this check. That is because filtering by item type (VEVENT vs. VJOURNAL) is not implemented correctly by all servers. So now all CalDAV syncs, whether incremental or slow, always transfered all items, which is not the intention (incremental syncs should be fast and efficient). This commit adds a more efficient isEmpty() check: for simple CardDAV collections, only luid and etag get transferred, as in listAllItems(). This is the behavior from 1.5. For CalDAV, a report with a filter for the content type is used and the transfer gets aborted after the first item, without actually double-checking the content of the item. This is different from listAllItems(), which really transfers the content. This extra content check would only be needed for some old servers (Radical 0.7) and is not essential, because reporting "not empty" even when empty is safe.