PDB

Summary

The Persistent DataBase (PDB) is a simple wrapper around a SQLite database present on the mx system. The user is free to access this database and store long term on it if necessary.

Using the PDB

As of the current version the PDB is only accessible via backends, using the C++ API. On the mulex::MxBackend context there is a pdb field to access a mulex::PdbAccessRemote class.

bool PdbAccess::createTable(const std::string& table, const std::initializer_list<std::string>& spec)

Create a table named table under the main database for the experiment. spec is a list of all the modifiers given to the database columns, i.e.:

// Within MxBackend context
pdb.createTable(
    "mytable",
    {
        "id INTEGER PRIMARY KEY AUTOINCREMENT",
        "value TEXT NOT NULL"
    }
);

template<PdbVariable... Vs> std::function<bool(const std::optional<Vs>&...)> getWriter(const std::string& table, const std::initializer_list<std::string>& names)

Returns a writter function for the given table, allowing the user to write to the database. Types need to be specified on the template when calling.

auto writer = pdb.getWriter<int, PdbString>("mytable", {"id", "value"});

// Now we can write in the table
// std::nullopt is the equivalent of NULL in SQL here and since id is AUTOINCREMENT
writer(std::nullopt, "mystring");
writer(std::nullopt, "another column");

template<PdbVariable... Vs> std::function<std::vector<std::tuple<Vs...>>(const std::string&)> getReader(const std::string& table, const std::initializer_list<std::string>& names)

Returns a reader function for the given table, allowing the user to read from the database. Types need to be specified on the template when calling.

auto reader = pdb.getReader<int, PdbString>("table0", {"id", "value"});

// Get id 3
auto values = reader("WHERE id = 3"); // The reader function accepts conditions formatted SQL style
auto [id, value] = values[0];

// Get all ids
auto avalues = reader();
auto [id0, value0] = avalues[0];
auto [id1, value1] = avalues[1];
// ...