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lmdb

  • Testing out lmdb

Dependencies

  • bison
  • flex
  • googletest
  • lmdb
  • lmdbxx
  • hsql-parser

Notes

  • Ran into an issue 'llmdb.so could not be opened' -> add $LD_LIBRARY_PATH
  • Ran into an issue with MDB_val constructor, it seems like the function signatures are switched?
  • lmdb forces transactions
    • BDB doesn't require transactions to be used
    • db handle creation must take place in a transaction
  • lmdb has only one access method: key-value store
    • unlike BDB where we have multiple access methods, e.g. RECNO
  • lmdb uses B+ tree data structure
    • which means we can only implement a BTree internal representation
  • lmdb does not want you to modify the memory inside MDB_val's data
    • copy the data and modify it, then put it into the DB.

Minor Notes

  • call mdb_env_set_mapsize after calling mdb_env_create and before mdb_env_open
  • we get bt_ndata stat in the BDB version even though we are using a BTree access method because it has stores the amount of records in the DB if it was set with RECNO access method
  • view snippets of the C API being used in this repo
  • using MDB_APPEND will cause duplicate blocks to exist in your DB!