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.

Since: 1.12.0.0

Constructors

DB

Fields

• dbResources :: Resources

  Temporary resources and the final Plan.

• 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

makeDataDirectoryPermanent :: 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 makeDataDirectoryPermanent start) (either mempty stop)

Since: 1.24.0.0

toTemporaryDirectory :: DB -> FilePath

Get the directory that is used to create other temporary directories

Since: 1.12.0.0

toPostgresqlConfigFile :: DB -> String

Get the final postgresql.conf

Since: 1.25.0.0

fastPostgresConfig :: [(String, String)]

The fastest config we can make.

shared_buffers = 12MB
fsync = off
synchronous_commit = off
full_page_writes = off
log_min_messages = PANIC
log_min_error_statement = PANIC
log_statement = none
client_min_messages = ERROR

Since: 1.21.0.0

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 and listen on 127.0.0.1 and ::1 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_messages = PANIC
log_min_error_statement = PANIC
log_statement = none
client_min_messages = ERROR
commit_delay = 100000
wal_level = minimal
archive_mode = off
max_wal_senders = 0

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 redirects all output to /dev/null. See verboseConfig for a version that logs more output.

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

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

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

Since: 1.21.0.0

defaultConfig_9_3_10 :: Config

Default configuration for PostgreSQL versions 9.3 and greater but less than 10.

If you get an error that "--no-sync" is an invalid parameter then you should use this config.

Since: 1.21.1.0

verbosePostgresConfig :: [(String, String)]

Default postgres options

Since: 1.21.0.0

verboseConfig :: Config

This is similar to defaultConfig but it logs as much as possible..

Since: 1.21.0.0

autoExplainPostgresConfig :: Int -> [(String, String)]

Useful options for configuring and loading auto_explain.

Since: 1.34.1.0

autoExplainConfig

Arguments

:: Int

Minimum number of milliseconds to log. Use 0 to log all queries.

-> Config

A config which loads and configures auto_explain. Useful for understanding slow queries plans.

Since: 1.34.1.0

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 socketDirectory a "postgresql.conf" is created with:

listen_addresses = '127.0.0.1, ::1'
unix_socket_directories = 'SOCKET_DIRECTORY'

Additionally the generated Config also:

• Sets a connectionTimeout of one minute.
• Redirects output to /dev/null.

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: 1.15.0.0

start :: IO (Either StartError DB)

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

Since: 1.21.0.0

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

stopPostgresGracefully :: DB -> IO ExitCode

Only stop the postgres process but leave any temporary resources. In contrast to stopPostgres this function makes sure postgres has time to properly write files to the data directory.

Since: 1.16.1.0

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

Restart the postgres from DB using the prior Config. This will also start an instance previously stoppped with stopPostgres.

Since: 1.12.0.0

withConfig

Arguments

:: Config

The 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: 1.21.0.0

with

Arguments

:: (DB -> IO a)

action continuation.

-> IO (Either StartError a)

Default expectation safe interface. Equivalent to

with = withConfig defaultConfig

Since: 1.21.0.0

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: 1.21.0.0

prettyPrintDB :: DB -> String

Display a DB.

Since: 1.12.0.0

data CacheConfig

Configuration for the initdb data directory cache.

Since: 1.25.0.0

Constructors

CacheConfig

Fields

• cacheTemporaryDirectory :: FilePath

  Root temporary directory used if cacheDirectoryType is set to Temporary. /tmp is a good default.

• cacheDirectoryType :: DirectoryType

  Used to specify is a Permanent or Temporary directory should be used. defaultCacheConfig uses Permanent ~/.tmp-postgres by default.

• cacheUseCopyOnWrite :: Bool

  Some operatoring system versions support flags for cp that allow "copy on write" which is about 2x faster. defaultCacheConfig attempts to determine if the cp on the path supports copy on write and sets this to True if it does.

data Cache

A handle to cache temporary resources and configuration.

Since: 1.25.0.0

Constructors

Cache

Fields

• cacheResourcesCow :: Bool
• cacheResourcesDirectory :: CompleteDirectoryType

Instances

Generic Cache

Defined in Database.Postgres.Temp.Internal

Associated Types

type Rep Cache :: Type -> Type

Methods

from :: Cache -> Rep Cache x

to :: Rep Cache x -> Cache

NFData Cache

Defined in Database.Postgres.Temp.Internal

Methods

rnf :: Cache -> ()

type Rep Cache

Defined in Database.Postgres.Temp.Internal

type Rep Cache = D1 (MetaData "Cache" "Database.Postgres.Temp.Internal" "tmp-postgres-1.34.1.0-DKDjvRpjblb7GUUaSbcxl6" False) (C1 (MetaCons "Cache" PrefixI True) (S1 (MetaSel (Just "cacheResourcesCow") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Bool) :*: S1 (MetaSel (Just "cacheResourcesDirectory") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 CompleteDirectoryType)))

cowCheck :: Bool

A bool that is True if the cp on the path supports "copy on write" flags.

defaultCacheConfig :: CacheConfig

defaultCacheConfig attempts to determine if the cp on the path supports "copy on write" flags and if it does, sets cacheUseCopyOnWrite to True.

It sets cacheDirectoryType to Permanent ~/.tmp-postgres and cacheTemporaryDirectory to /tmp (but this is not used when Permanent is set).

Since: 1.25.0.0

setupInitDbCache :: CacheConfig -> IO Cache

Setup the initdb cache folder.

Since: 1.25.0.0

cleanupInitDbCache :: Cache -> IO ()

Cleanup the cache directory if it was Temporary.

Since: 1.25.0.0

withDbCacheConfig

Arguments

:: CacheConfig

Configuration

-> (Cache -> IO a)

action for which caching is enabled

-> IO a

Enable initdb data directory caching. This can lead to a 4x speedup.

Exception safe version of setupInitDbCache. Equivalent to

withDbCacheConfig = bracket (setupInitDbCache config) cleanupInitDbCache

Since: 1.25.0.0

withDbCache :: (Cache -> IO a) -> IO a

Equivalent to withDbCacheConfig with the CacheConfig defaultCacheConfig makes.

Here is an example using caching:

withDbCache $ \cache -> do
  withConfig (cacheConfig cache) $ \db -> ...
  withConfig (cacheConfig cache) $ \db -> ...

Since: 1.25.0.0

cacheConfig :: Cache -> Config

Helper to make a Config out of caching info.

Since: 1.25.0.0

newtype Snapshot

A type to track a possibly temporary snapshot directory

Since: 1.20.0.0

Constructors

Snapshot

Fields

• unSnapshot :: CompleteDirectoryType

Instances

Generic Snapshot

Defined in Database.Postgres.Temp.Internal

Associated Types

type Rep Snapshot :: Type -> Type

Methods

from :: Snapshot -> Rep Snapshot x

to :: Rep Snapshot x -> Snapshot

NFData Snapshot

Defined in Database.Postgres.Temp.Internal

Methods

rnf :: Snapshot -> ()

type Rep Snapshot

Defined in Database.Postgres.Temp.Internal

type Rep Snapshot = D1 (MetaData "Snapshot" "Database.Postgres.Temp.Internal" "tmp-postgres-1.34.1.0-DKDjvRpjblb7GUUaSbcxl6" True) (C1 (MetaCons "Snapshot" PrefixI True) (S1 (MetaSel (Just "unSnapshot") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 CompleteDirectoryType)))

takeSnapshot

Arguments

:: DB

The handle. The postgres is shutdown and the data directory is copied.

-> IO (Either StartError Snapshot)

Shutdown the database and copy the directory to a folder.

Since: 1.29.0.0

cleanupSnapshot :: Snapshot -> IO ()

Cleanup any temporary resources used for the snapshot.

Since: 1.20.0.0

withSnapshot :: DB -> (Snapshot -> IO a) -> IO (Either StartError a)

Exception safe method for taking a file system level copy of the database cluster.

Snapshots are useful if you would like to start every test from a migrated database and the migration process is more time consuming then copying the additional data.

Here is an example with caching and snapshots:

withDbCache $ \cache -> withConfig (cacheConfig cache) $ \db ->
  migrate db
  withSnapshot Temporary db $ \snapshot -> do
    withConfig (snapshotConfig db) $ \migratedDb -> ...
    withConfig (snapshotConfig db) $ \migratedDb -> ...
    withConfig (snapshotConfig db) $ \migratedDb -> ...

The Snapshots are ephemeral. If you would like the Snapshots to persistent consider using cacheAction instead.

Since: 1.29.0.0

snapshotConfig :: Snapshot -> Config

Convert a snapshot into a Config that includes a copyConfig for copying the snapshot directory to a temporary directory.

Since: 1.20.0.0

cacheAction

Arguments

:: FilePath

Location of the data directory cache.

-> (DB -> IO ())

action to cache.

-> Config

initial Config.

-> IO (Either StartError Config)

Check to see if a cached data directory exists.

If the file path does not exist the initial config is used to start a postgres instance. After which the action is applied, the data directory is cached and postgres is shutdown.

cacheAction mappends a config to copy the cached data directory on startup onto the initial config and returns it. In other words:

initialConfig <> configFromCachePath

cacheAction can be used to create a snapshot of migrated database and not remigrate as long as the migration does not change. See withSnapshot for a ephemeral version of taking snapshots.

You can nest calls to cacheAction and safe to call it from several threads. However cacheAction uses locks internal to prevent multiple threads from stomping on each other.

If one makes a nested call and accidently uses the same cache directory in both calls the calls will deadlock. If this occurs on the same thread RTS will throw an exception. However do not rely on this and just be careful to not reuse the same cache path when nesting calls.

There is no good reuse the cache path when nesting so one is unlikely to run into this.

Since: 1.34.0.0