fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph

Andrew Kryczka df74b775e6 Limit backups opened ... Summary: This was requested by a customer who wants to proactively monitor whether any valid backups are available. The existing performance was poor because Open() serially reads every small meta-file (one per backup), which was slow on HDFS. Now we only read the minimum number of meta-files to find `max_valid_backups_to_open` valid backups. The customer mentioned above can just set it to one. Closes https://github.com/facebook/rocksdb/pull/2151 Differential Revision: D4882564 Pulled By: ajkr fbshipit-source-id: cb0edf9e8ac693e4d5f24902e725a011ed8c0c2f		8 years ago
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backupable_db.cc	Limit backups opened	8 years ago
backupable_db_test.cc	Limit backups opened	8 years ago