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  • package root
    Definition Classes
    root
  • package skunk

    Skunk is a functional data access layer for Postgres.

    Skunk is a functional data access layer for Postgres.

    Design principles:

    • Skunk doesn't use JDBC. It speaks the Postgres wire protocol. It will not work with any other database back end.
    • Skunk is asynchronous all the way down, via cats-effect, fs2, and ultimately nio. The high-level network layers (Protocol and Session) are safe to use concurrently.
    • Serialization to and from schema types is not typeclass-based, so there are no implicit derivations. Codecs are explicit, like parser combinators.
    • I'm not sweating arity abstraction that much. Pass a ~ b ~ c for three args and Void if there are no args. This may change in the future but it's fine for now.
    • Skunk uses Resource for lifetime-managed objects, which means it takes some discipline to avoid leaks, especially when working concurrently. May or may not end up being problematic.
    • I'm trying to write good Scaladoc this time.

    A minimal example follows. We construct a Resource that yields a Session, then use it.

    package example

import cats.effect._
import skunk._
import skunk.implicits._
import skunk.codec.numeric._

object Minimal extends IOApp {

  val session: Resource[IO, Session[IO]] =
    Session.single(
      host     = "localhost",
      port     = 5432,
      user     = "postgres",
      database = "world",
    )

  def run(args: List[String]): IO[ExitCode] =
    session.use { s =>
      for {
        n <- s.unique(sql"select 42".query(int4))
        _ <- IO(println(s"The answer is $n."))
      } yield ExitCode.Success
    }

}

    Continue reading for an overview of the library. It's pretty small.

    Definition Classes
    root
  • package codec
    Definition Classes
    skunk
  • package data
    Definition Classes
    skunk
  • package exception
    Definition Classes
    skunk
  • package net

    Skunk network stack, starting with BitVectorSocket at the bottom and ending with Protocol at the top (Session delegates all its work to Protocol).

    Skunk network stack, starting with BitVectorSocket at the bottom and ending with Protocol at the top (Session delegates all its work to Protocol). Everything is non-blocking.

    Definition Classes
    skunk
  • package syntax
    Definition Classes
    skunk
  • package util
    Definition Classes
    skunk
  • AppliedFragment
  • Channel
  • Codec
  • Command
  • Cursor
  • Decoder
  • Encoder
  • Fragment
  • PreparedCommand
  • PreparedQuery
  • Query
  • SSL
  • Session
  • SqlState
  • Statement
  • Transaction
  • Void
  • implicits
  • ~

trait PreparedQuery[F[_], A, B] extends AnyRef

A prepared query, valid for the life of its originating Session.

Source
PreparedQuery.scala
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Abstract Value Members

  1. abstract def cursor(args: A)(implicit or: Origin): Resource[F, Cursor[F, B]]

    Resource that binds the supplied arguments to this PreparedQuery, yielding a Cursor from which rows can be fetched.

    Resource that binds the supplied arguments to this PreparedQuery, yielding a Cursor from which rows can be fetched. Note that higher-level operations like stream, option, and unique are usually what you want.

  2. abstract def option(args: A)(implicit or: Origin): F[Option[B]]

    Fetch and return at most one row, raising an exception if more rows are available.

  3. abstract def stream(args: A, chunkSize: Int)(implicit or: Origin): Stream[F, B]

    Construct a Cursor-backed stream that calls fetch repeatedly and emits chunks until none remain.

    Construct a Cursor-backed stream that calls fetch repeatedly and emits chunks until none remain. Note that each chunk is read atomically while holding the session mutex, which means interleaved streams will achieve better fairness with smaller chunks but greater overall throughput with larger chunks. So it's important to consider the use case when specifying chunkSize.

  4. abstract def unique(args: A)(implicit or: Origin): F[B]

    Fetch and return exactly one row, raising an exception if there are more or fewer.

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  1. final def !=(arg0: Any): Boolean
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  15. def pipe(chunkSize: Int)(implicit or: Origin): Pipe[F, A, B]

    A Pipe that executes this PreparedQuery for each input value, concatenating the resulting streams.

    A Pipe that executes this PreparedQuery for each input value, concatenating the resulting streams. See stream for details on the chunkSize parameter.

  16. final def synchronized[T0](arg0: ⇒ T0): T0
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