dbpath

dbpath is an R library for creating database connections via a single string (url).

Install

remotes::install_github("machow/dbpath")

Examples

library(dbpath)

sql_url <- dbpath("postgresql+RPostgres://some_user:some_password@localhost:5432")
sql_url

[1] "postgresql+RPostgres://some_user:****@localhost:5432"

You can use the dbpath output with either DBI::dbConnect, or dplyr::tbl to create a remote connection.

# get a database connection
con <- DBI::dbConnect(sql_url)

# get a database table called mtcars
tbl_mtcars <- dplyr::tbl(sql_url, "mtcars")
tbl_mtcars

URL Format

dbpath URLs follow the format below.

<dialect>+<driver>://<username>:<password>@<host>:<port>/<database>

Here's an example using mysql:

mysql_url <- "mysql+RMariaDB://root:some_password@localhost"

In this case, we're connecting to the mysql dialect, using R's MariaDB package as a driver.

The code below shows how it translates to making the connection manually.

# dbpath
DBI::dbConnect(mysql_url)

# manual
DBI::dbConnect(
  RMariaDB::MariaDB(),
  user = "root",
  password = "some_password",
  host = "localhost"
  )

Behind the scenes, dbpath uses driver hooks to know that if RMariaDB is the driver, then we need its MariaDB() object. Note that the RMariaDB in mysql+RMariaDB is optional!

Interoperability with Python

dbpath's approach is based on python's SQLAlchemy library. This means that you can use the same string across languages!

<!-- python example -->

# one string to rule them all
sql_url = "postgresql://user:password@localhost:port/dbname"

library(dbpath)
DBI::dbconnection(sql_url)

import sqlalchemy
sqlalchemy.create_engine(sql_url)

Configuring Driver Selection

The code below adds a custom driver for SQLite.

library(dbpath)

driver_registry$set(my_driver = function () RSQLite::SQLite)

# Note the 3 slashes, rather than two, meaning no user name, password, or host
sqlite_url <- "sqlite+my_driver:///:memory:"

sqlite_url

[1] "sqlite+my_driver://:****@/:memory:"

DBI::dbConnect(sqlite_url)

<SQLiteConnection>
  Path: :memory:
  Extensions: TRUE

Available Driver Hooks

# see available drivers
driver_registry$get()

# see defaults for when no driver is specified
driver_defaults$get()

Here are the current driver defaults:

 postgresql       mysql     mariadb 
"RPostgres"  "RMariaDB"  "RMariaDB" 

Configuring Driver Connections

dbpath uses an s3 method called dbpath_params to get a list of parameters to pass to DBI::dbConnect (or dplyr::tbl).

url <- dbpath("postgresql://a_user:a_password@localhost/dbname")

dbpath_params(url)

$drv
<PqDriver>

$user
[1] "a_user"

$password
[1] "a_password"

$host
[1] "localhost"

$port
[1] ""

$dbname
[1] "dbname"

In order to support a new driver type, you can register an s3 method for it. The function should return a list of parameters, whose names are the arguments that would be passed to DBI::dbConnect.

dbpath_params.PqDriver <- function(driver, url) {
  list(
    drv = driver
    user = url$user,
    password = url$password,
    host = url$host,
    port = url$port,
    
    # use PqDriver specific argument: dbname
    dbname = url$database
  )
}

You can get a specific drivers parameters by passing it as the first argument to dbpath_params:

driver <- RPostgres::Postgres()
class(driver)                        # <PqDriver>

dbpath_params(driver, url)