Class: PageableMemStoreElement

DefaultDB.PageableMemStoreElement()

Some elements of the _storage_map are large enough that they should be stored on disk to keep RAM available. A PageableMemStoreElement instance is used as a standin for the actual data record. The total version of the object is to be placed in a file on disk. The larger fields are replaced in the object with a descriptor. The resulting smaller object is allowed to stay in memory the PageableMemStoreElement instance makes a reference to it via its _obj field. The PageableMemStoreElement instance retains information about the name of the file holding the complete object.

As the object refered to by the PageableMemStoreElement instance is used, the complete object may or may not reside in memory. The longer it is in memory without being used, the more likely the object will be reduced with the complete form being put out to disk. Several fields relate to the state of the objects storage and residence in memory.

  • unhooked -- the object has been stashed during the syncing interval.
  • saved -- true if the object data has been written to disk.
  • flat_object -- the string form of the storage whose length determines if the PageableMemStoreElement is appropriate
  • file -- where the object will be stored, which is the name of the _id field, the wide are id.