trait Session[F[_]] extends AnyRef
Represents a live connection to a Postgres database. Operations provided here are safe to use
concurrently. Note that this is a lifetime-managed resource and as such is invalid outside the
scope of its owning Resource
, as are any streams constructed here. If you start
an operation
be sure to join
its Fiber
before releasing the resource.
See the companion object for information on obtaining a pooled or single-use instance.
- Source
- Session.scala
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-
abstract
def
channel(name: Identifier): Channel[F, String, String]
A named asynchronous channel that can be used for inter-process communication.
-
abstract
def
execute(command: Command[Void]): F[Completion]
Execute a non-parameterized command and yield a
Completion
.Execute a non-parameterized command and yield a
Completion
. If you have parameters useprepare
instead. -
abstract
def
execute[A](query: Query[Void, A]): F[List[A]]
Execute a non-parameterized query and yield all results.
Execute a non-parameterized query and yield all results. If you have parameters or wish to limit returned rows use
prepare
instead. -
abstract
def
option[A](query: Query[Void, A]): F[Option[A]]
Execute a non-parameterized query and yield at most one row, raising an exception if there are more.
Execute a non-parameterized query and yield at most one row, raising an exception if there are more. If you have parameters use
prepare
instead. -
abstract
def
parameter(key: String): Stream[F, String]
Stream (possibly empty) of discrete values for the specified key, via
parameters
. -
abstract
def
parameters: Signal[F, Map[String, String]]
Signal representing the current state of all Postgres configuration variables announced to this session.
Signal representing the current state of all Postgres configuration variables announced to this session. These are sent after authentication and are updated asynchronously if the runtime environment changes. The current keys are as follows (with example values), but these may change with future releases so you should be prepared to handle unexpected ones.
Map( "application_name" -> "", "client_encoding" -> "UTF8", "DateStyle" -> "ISO, MDY", "integer_datetimes" -> "on", // cannot change after startup "IntervalStyle" -> "postgres", "is_superuser" -> "on", "server_encoding" -> "UTF8", // cannot change after startup "server_version" -> "9.5.3", // cannot change after startup "session_authorization" -> "postgres", "standard_conforming_strings" -> "on", "TimeZone" -> "US/Pacific", )
-
abstract
def
prepare[A](command: Command[A]): Resource[F, PreparedCommand[F, A]]
Prepare an
INSERT
,UPDATE
, orDELETE
command that returns no rows.Prepare an
INSERT
,UPDATE
, orDELETE
command that returns no rows. The resultingPreparedCommand
can be executed multiple times with different arguments. -
abstract
def
prepare[A, B](query: Query[A, B]): Resource[F, PreparedQuery[F, A, B]]
Resource that prepares a query, yielding a
PreparedQuery
which can be executed multiple times with different arguments. -
abstract
def
transaction[A](isolationLevel: TransactionIsolationLevel, accessMode: TransactionAccessMode): Resource[F, Transaction[F]]
Resource that wraps a transaction block.
Resource that wraps a transaction block. It has the ability to specify a non-default isolation level and access mode.
- See also
Session#transaction for more information
-
abstract
def
transaction[A]: Resource[F, Transaction[F]]
Resource that wraps a transaction block.
Resource that wraps a transaction block. A transaction is begun before entering the
use
block, on success the block is executed, and on exit the following behavior holds.- If the block exits normally, and the session transaction status is
Active
, then the transaction will be committed.Idle
, then this means the user terminated the transaction explicitly inside the block and there is nothing to be done.Error
then this means the user encountered and handled an error but left the transaction in a failed state, and the transaction will be rolled back.
- If the block exits due to cancellation or an error and the session transaction status is
not
Idle
then the transaction will be rolled back and any error will be re-raised.
- If the block exits normally, and the session transaction status is
-
abstract
def
transactionStatus: Signal[F, TransactionStatus]
Signal representing the current transaction status.
- abstract def typer: Typer
-
abstract
def
unique[A](query: Query[Void, A]): F[A]
Execute a non-parameterized query and yield exactly one row, raising an exception if there are more or fewer.
Execute a non-parameterized query and yield exactly one row, raising an exception if there are more or fewer. If you have parameters use
prepare
instead.
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def
pipe[A](command: Command[A]): Pipe[F, A, Completion]
Transform a
Command
into aPipe
from inputs toCompletion
s. -
final
def
synchronized[T0](arg0: ⇒ T0): T0
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Inherited from AnyRef
Inherited from Any
Queries
A query is any SQL statement that returns rows; i.e., any SELECT
or
VALUES
query, or an INSERT
, UPDATE
, or DELETE
command that returns rows via RETURNING
.
Parameterized queries must first be prepared, then can be executed many times with different
arguments. Non-parameterized queries can be executed directly.
Commands
A command is any SQL statement that cannot return rows. Parameterized commands must first be prepared, then can be executed many times with different arguments. Commands without parameters can be executed directly.
Transactions
Users can manipulate transactions directly via commands like BEGIN
and
COMMIT
, but dealing with cancellation and error conditions can be complicated and repetitive.
Skunk provides managed transaction blocks to make this easier.
Channels
Session Environment
The Postgres session has a dynamic environment that includes a
configuration map with keys like TimeZone
and server_version
, as well as a current
TransactionStatus
. These can change asynchronously and are exposed as Signal
s. Note that
any Stream
based on these signals is only valid for the lifetime of the Session
.