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Development Team/Datastore Rewrite (view source)
Revision as of 07:54, 23 September 2008
, 07:54, 23 September 2008no edit summary
== Design ==
== Design ==
=== Filesystem knows which entries are stored ===
By examining the directory structure, we know where is localized the data related to each entry. We don't depend any more on a binary structure that could become corrupted and unusable as a whole.
=== Metadata is stored as a single file for each entry ===
Each entry has its metadata stored in a single file, so that if corruption happened on one of those, the rest of the entries would be unaffected. The format in which metadata is stored even allows to recover from a malformed property by just dropping it.
=== Queries are accelerated with a disposable database ===
This allows us to efficiently query the stored entries, but as we only use the database to accelerate queries, we can drop and recreate it in case of corruption or update to an incompatible database format.
=== Detect identical files and hard-link them ===
This improves storage efficiency in general, but in our case is more important because we wish to record in the journal several interactions that refer to the same file. For example, "Downloaded lesson3.pdf", "Read lesson3.pdf", "Sent lesson3.pdf to Juan" would all refer to the same file and we need to only store it once.