Database.Postgres.Temp.Internal

This module provides the high level functions that are re-exported by Database.Postgres.Temp. Additionally it includes some identifiers that are used for testing but are not exported.

Documentation

data DB

Handle for holding temporary resources, the postgres process handle and postgres connection information. The DB also includes the final plan used to start initdb, createdb and postgres. See toConnectionString or toConnectionOptions for converting a DB to postgresql connection string.

Since: 1.12.0.0

Constructors

DB

Fields

• dbResources :: Resources

  Temporary resources and the final CompletePlan.

• dbPostgresProcess :: PostgresProcess

  postgres process handle and the connection options.

Instances

Pretty DB

Defined in Database.Postgres.Temp.Internal

Methods

pretty :: DB -> Doc

prettyList :: [DB] -> Doc

toConnectionString :: DB -> ByteString

Convert a DB to a connection string. Alternatively one can access the Options using toConnectionOptions.

Since: 1.12.0.0

toConnectionOptions :: DB -> Options

Convert a DB to a connection Options type.

Since: 1.12.0.0

toDataDirectory :: DB -> FilePath

Access the data directory. This was either generated or specified explicitly when creating the Config

Since: 1.12.0.0

makeDataDirPermanent :: DB -> DB

Make the data directory permanent. Useful for debugging. If you are using with or withConfig this function will not modify the DB that is passed for cleanup. You will need to setup your own bracket like

   bracket (fmap makeDataDirPermanent start) (either mempty stop)

Since: 1.12.0.0

toTemporaryDirectory :: DB -> FilePath

Get the directory that is used to create other temporary directories

Since: 1.12.0.0

defaultPostgresConfig :: [String]

Default postgres options

Since: 1.12.0.0

defaultConfig :: Config

The default configuration. This will create a database called "postgres" via initdb (it's default behavior). It will create a temporary directory for the data and a temporary directory for a unix socket on a random port. Additionally it will use the following "postgresql.conf" which is optimized for performance.

   shared_buffers = 12MB
   fsync = off
   synchronous_commit = off
   full_page_writes = off
   log_min_duration_statement = 0
   log_connections = on
   log_disconnections = on
   client_min_messages = ERROR

defaultConfig also passes the --no-sync flag to initdb.

If you would like to customize this behavior you can start with the defaultConfig and overwrite fields or combine a defaultConfig with another Config using <> (mappend).

Alternatively you can eschew defaultConfig altogether, however your postgres might start and run faster if you use defaultConfig.

The defaultConfig also disables the logging of internal Events.

To append additional lines to "postgresql.conf" file create a custom Config like the following.

 custom = defaultConfig <> mempty
   { plan = mempty
     { postgresConfigFile =
         [ "wal_level = replica"
         , "archive_mode = on"
         , "max_wal_senders = 2"
         , "fsync = on"
         , "synchronous_commit = on"
         ]
     }
   }

Or using the provided lenses and your favorite lens library:

 custom = defaultConfig & planL . postgresConfigFile <>~
   [ "wal_level = replica"
   , "archive_mode = on"
   , "max_wal_senders = 2"
   , "fsync = on"
   , "synchronous_commit = on"
   ]

This is common enough there is defaultPostgresConf which is a helper to do this.

As an alternative to using defaultConfig one could create a config from connections parameters using optionsToDefaultConfig.

Since: 1.12.0.0

defaultPostgresConf :: [String] -> Config

mappend the defaultConfig with a Config that provides additional "postgresql.conf" lines. Equivalent to:

defaultPostgresConf extra = defaultConfig <> mempty
  { plan = mempty
    { postgresConfigFile = extra
    }
  }

or with lenses:

defaultPostgresConf extra = defaultConfig & planL . postgresConfigFile <>~ extra

Since: 1.12.0.0

silentConfig :: Config

The same as defaultConfig but all the handles are set to devnull. See silentProcessConfig as well.

Since: 1.12.0.0

startConfig

Arguments

:: Config

extra configuration that is mappended last to the generated Config. generated <> extra.

-> IO (Either StartError DB)

Create zero or more temporary resources and use them to make a Config.

The passed in config is inspected and a generated config is created. The final config is built by

  generated <> extra

Based on the value of socketClass a "postgresql.conf" is created with:

  listen_addresses = 'IP_ADDRESS'

if it is IpSocket. If is UnixSocket then the lines:

  listen_addresses = ''
  unix_socket_directories = 'SOCKET_DIRECTORY'

are added.

Additionally the generated Config also does the following:

• Sets a connectionTimeout of one minute.
• Logs internal Events.
• Sets the processes to use the standard input and output handles.
• Sets the dataDirectoryString to file path generated from dataDirectory.

All of these values can be overrided by the extra config.

The returned DB requires cleanup. startConfig should be used with a bracket and stop, e.g.

  withConfig :: Config -> (DB -> IO a) -> IO (Either StartError a)
  withConfig plan f = bracket (startConfig plan) (either mempty stop) $
     either (pure . Left) (fmap Right . f)

or just use withConfig. If you are calling startConfig you probably want withConfig anyway.

Since: 1.12.0.0

start :: IO (Either StartError DB)

Default start behavior. Equivalent to calling startConfig with the defaultConfig.

Since: 1.12.0.0

stop :: DB -> IO ()

Stop the postgres process and cleanup any temporary resources that might have been created.

Since: 1.12.0.0

stopPostgres :: DB -> IO ExitCode

Only stop the postgres process but leave any temporary resources. Useful for testing backup strategies when used in conjunction with restart or withRestart.

Since: 1.12.0.0

restart :: DB -> IO (Either StartError DB)

Restart the postgres from DB using the prior Plan.

Since: 1.12.0.0

reloadConfig :: DB -> IO ()

Reload the configuration file without shutting down. Calls pg_reload_conf().

Since: 1.12.0.0

withConfig

Arguments

:: Config

extra. Config combined with the generated Config. See startConfig for more info.

-> (DB -> IO a)

action continuation.

-> IO (Either StartError a)

Exception safe database create with options. See startConfig for more details. Calls stop even in the face of exceptions.

Since: 1.12.0.0

with

Arguments

:: (DB -> IO a)

action continuation.

-> IO (Either StartError a)

Default expectation safe interface. Equivalent to

  with = withConfig defaultConfig

Since: 1.12.0.0

withRestart :: DB -> (DB -> IO a) -> IO (Either StartError a)

Exception safe version of restart.

Since: 1.12.0.0

optionsToDefaultConfig :: Options -> Config

Attempt to create a Config from a Options. Useful if you want to create a database owned by a specific user you will also login with among other use cases.

Since: 1.12.0.0

prettyPrintDB :: DB -> String

Display a DB.

Since: 1.12.0.0

dropDbIfExists :: Options -> String -> IO ()

Drop the db if it exists. Terminates all connections to the db first.

Since: 1.12.0.0

withNewDb

Arguments

:: DB

The original DB handle. The database name specified in the connection options is used as the template for the generated ProcessConfig

-> (DB -> IO a)

The modified DB handle that has the new database name in it's connection options.

-> IO (Either StartError a)

Use the current database as a template and make a copy. Give the copy a random name.

Equivalent to:

 withNewDb = withNewDbConfig mempty

See startNewDbConfig for more details.

Since: 1.12.0.0

withNewDbConfig

Arguments

:: ProcessConfig

extra createdb ProcessConfig.

-> DB

The original DB handle. The database name specified in the connection options is used as the template for the generated ProcessConfig.

-> (DB -> IO a)

The modified DB handle that has the new database name in it's connection options.

-> IO (Either StartError a)

Exception safe version of startNewDbConfig. Creates a temporary database using the current database as a template.

See startNewDbConfig for more details.

Since: 1.12.0.0

startNewDb

Arguments

:: DB

The original DB handle. The database name specified in the connection options is used as the template for the generated ProcessConfig.

-> IO (Either StartError DB)

Use the current database as a template and make a copy. Give the copy a random name.

Equivalent to:

 startNewDb = startNewDbConfig mempty

See startNewDbConfig for more details.

Since: 1.13.0.0

startNewDbConfig

Arguments

:: ProcessConfig

extra createdb ProcessConfig.

-> DB

The original DB handle. The database name specified in the connection options is used as the template for the generated ProcessConfig.

-> IO (Either StartError DB)

Use the current database as a template and make a copy. Give the copy a random name.

Copying a database from a template can be faster than creating a new postgres and migrating a database from scratch. In artifical benchmarks it appears to be about 2x faster.

To use the current database as a template all connections to the database must be terminated first.

To override the arguments passed to createdb one can pass in extra ProcessConfig. The combined process is created by mappended the generated with the extra ProcessConfig, e.g.

   combined = generated <> extra

The current implementation has a few known issues.

If a connection is made between the termination command and the createdb call the createdb call will fail.

Additionally the generated name is 32 character random name of characters "a" to "z". It is possible, although unlikeily that a duplicate database name could be generated and this would also cause a failure.

startNewDbConfig requires cleanup so it best to use a bracket along with stopNewDb. This is equivalient to withNewDbConfig.

The only reason to use startNewDbConfig over withNewDbConfig is if you are unable to use withNewDbConfig for some reason.

Since: 1.13.0.0

stopNewDb :: DB -> IO ()

Cleanup the temporary database created by startNewDbConfig or startNewDb.

Since: 1.13.0.0