* BlobDB no longer updates the SST to blob file mapping upon failed compactions.
* Fix a bug in which a snapshot read through an iterator could be affected by a DeleteRange after the snapshot (#6062).
* Fixed a bug where BlobDB was comparing the `ColumnFamilyHandle` pointers themselves instead of only the column family IDs when checking whether an API call uses the default column family or not.
+* Delete superversions in BackgroundCallPurge.
+* Fix use-after-free and double-deleting files in BackgroundCallPurge().
## 6.6.0 (11/25/2019)
### Bug Fixes