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!