Documentation

Fields

• connPrepare :: Text -> IO Statement

  This function should prepare a Statement in the target database, which should allow for efficient query reuse.

• connInsertSql :: EntityDef -> [PersistValue] -> InsertSqlResult

  This function generates the SQL and values necessary for performing an insert against the database.

• connInsertManySql :: Maybe (EntityDef -> [[PersistValue]] -> InsertSqlResult)

  SQL for inserting many rows and returning their primary keys, for backends that support this functionality. If Nothing, rows will be inserted one-at-a-time using connInsertSql.

• connUpsertSql :: Maybe (EntityDef -> NonEmpty (FieldNameHS, FieldNameDB) -> Text -> Text)

  Some databases support performing UPSERT _and_ RETURN entity in a single call.

  This field when set will be used to generate the UPSERT+RETURN sql given * an entity definition * updates to be run on unique key(s) collision

  When left as Nothing, we find the unique key from entity def before * trying to fetch an entity by said key * perform an update when result found, else issue an insert * return new entity from db

  Since: 2.6

• connPutManySql :: Maybe (EntityDef -> Int -> Text)

  Some databases support performing bulk UPSERT, specifically "insert or replace many records" in a single call.

  This field when set, given * an entity definition * number of records to be inserted should produce a PUT MANY sql with placeholders for records

  When left as Nothing, we default to using defaultPutMany.

  Since: 2.8.1

• connStmtMap :: StatementCache

  A reference to the cache of statements. Statements are keyed by the Text queries that generated them.

• connClose :: IO ()

  Close the underlying connection.

• connMigrateSql :: [EntityDef] -> (Text -> IO Statement) -> EntityDef -> IO (Either [Text] [(Bool, Text)])

  This function returns the migrations required to include the EntityDef parameter in the [EntityDef] database. This might include creating a new table if the entity is not present, or altering an existing table if it is.

• connBegin :: (Text -> IO Statement) -> Maybe IsolationLevel -> IO ()

  A function to begin a transaction for the underlying database.

• connCommit :: (Text -> IO Statement) -> IO ()

  A function to commit a transaction to the underlying database.

• connRollback :: (Text -> IO Statement) -> IO ()

  A function to roll back a transaction on the underlying database.

• connEscapeFieldName :: FieldNameDB -> Text

  A function to extract and escape the name of the column corresponding to the provided field.

  Since: 2.12.0.0

• connEscapeTableName :: EntityDef -> Text

  A function to extract and escape the name of the table corresponding to the provided entity. PostgreSQL uses this to support schemas.

  Since: 2.12.0.0

• connEscapeRawName :: Text -> Text

  A function to escape raw DB identifiers. MySQL uses backticks, while PostgreSQL uses quotes, and so on.

  Since: 2.12.0.0

• connNoLimit :: Text
   
• connRDBMS :: Text

  A tag displaying what database the SqlBackend is for. Can be used to differentiate features in downstream libraries for different database backends.

• connLimitOffset :: (Int, Int) -> Text -> Text

  Attach a 'LIMIT/OFFSET' clause to a SQL query. Note that LIMIT/OFFSET is problematic for performance, and indexed range queries are the superior way to offer pagination.

• connLogFunc :: LogFunc

  A log function for the SqlBackend to use.

• connMaxParams :: Maybe Int

  Some databases (probably only Sqlite) have a limit on how many question-mark parameters may be used in a statement

  Since: 2.6.1

• connRepsertManySql :: Maybe (EntityDef -> Int -> Text)

  Some databases support performing bulk an atomic+bulk INSERT where constraint conflicting entities can replace existing entities.

  This field when set, given * an entity definition * number of records to be inserted should produce a INSERT sql with placeholders for primary+record fields

  When left as Nothing, we default to using defaultRepsertMany.

  Since: 2.9.0

• connVault :: Vault

  Carry arbitrary payloads for the connection that may be used to propagate information into hooks.

• connHooks :: SqlBackendHooks

  Instrumentation hooks that may be used to track the behaviour of a backend.

Fields

• hookGetStatement :: SqlBackend -> Text -> Statement -> IO Statement