srcr (version 1.1.1)

srcr: Connect to database using config file

Description

Set up a or DBI or legacy dplyr database connection using information from a JSON configuration file, and return the connection.

Connecting to databases requires boilerplate code to specify connection parameters and to set up sessions properly with the DBMS. This package provides a simple tool to fill two purposes: abstracting connection details, including secret credentials, out of your source code and managing configuration for frequently-used database connections in a persistent and flexible way, while minimizing requirements on the runtime environment.

Usage

srcr(
  basenames = NA,
  dirs = NA,
  suffices = NA,
  paths = NA,
  config = NA,
  allow_post_connect = getOption("srcr.allow_post_connect", c())
)

Value

A database connection. The specific class of the object is determined by the src_name in the configuration data.

Arguments

basenames

A vector of file names (without directory or file type) to use in searching for configuration files.

dirs

A vector of directory names to use in searching for configuration files.

suffices

A vector of suffices (file "type"s) to use in searching for the configuration file.

paths

A vector of full path names for the configuration file. If present, only these paths are checked; find_config_files() is not called.

config

A list containing the configuration data, to be used instead of reading a configuration file, should you wish to skip that step.

allow_post_connect

A vector specifying what session setup you will permit after the connection is established. If any element of the vector is sql, then the post_connect_sql section of the configuration file is executed. Similarly, if any element is fun, then the post_connect_fun section of the config file is executed (after post_connect_sql, if both are present and allowed).

Author

Maintainer: Charles Bailey

Authors:

• Hanieh Razzaghi

Details

The configuration file must provide all of the information necessary to set up the DBI connection or dplyr src. Given the variety of ways a data source can be specified, the JSON must be a hash containing at least two elements:

• The src_name key points to a string containing name of a DBI driver method (e.g. SQLite), as one might pass to DBI::dbDriver(), or an old-style dplyr function that sets up the data source (e.g. dplyr::src_postgres(). If the value associated with src_name begins with 'src_', it is taken as the latter, otherwise it is taken as the former. In this case, an attempt will be made to load the appropriate DBI-compliant database library (e.g. RSQLite for the above example) if it hasn't already been loaded.

• The src_args key points to a nested hash, whose keys are the arguments to that function, and whose values are the argument values.

To locate the necessary configuration file, you can use all of the arguments taken by find_config_files(), but remember that the contents of the file must be JSON, regardless of the file's name. Alternatively, if paths is present, only the specified paths are checked. The first file that exists, is readable, and evaluates as legal JSON is used as the source of configuration data.

If your deployment strategy does not make use of configuration files (e.g. you access configuration data via a web service or similar API), you may also pass a list containing the configuration data directly via the config parameter. In this case, no configuration files are used.

Once the connection is established, the post_connect_sql and post_connect_fun elements of the configuration data can be used to perform additional processing to set session characteristics, roles, etc. However, because this entails the configuration file providing code that you won't see prior to runtime, you need to opt in to these features. You can make this choice globally by setting the srcr.allow_post_connect option via base::options().

See Also

Useful links:

• https://github.com/baileych/srcr

• Report bugs at https://github.com/baileych/srcr/issues

Examples

if (FALSE) {
# Search all the (filename-based) defaults
srcr()

# "The usual"
srcr('myproj_prod')

# Look around
srcr(dirs = c(Sys.getenv('PROJ_CONF_DIR'), 'var/lib', getwd()),
     basenames = c('myproj', Sys.getenv('PROJ_NAME')) )

# No defaults
srcr(paths = c('/path/to/known/config.json'))
srcr(config =
       list(src_name = 'Postgres',
            src_args = list(host = 'my.host', dbname = 'my_db', user = 'me'),
            post_connect_sql = 'set role project_role;'))
}