txt: ## dist_zef-leont-Net-Postgres.md
  [![Actions Status](https://github.com/Leont/net-postgres/workflows/test/badge.svg)](https://github.com/Leont/net-postgres/actions)
  
  # Name
  
  Net::Postgres - an asynchronous postgresql client
  
  # Synopsis
  
  ```
  use v6.d;
  use Net::Postgres;
  
  my $client = await Net::Postgres::Connection.connect(:$host, :$port, :$user, :$password, :$database, :$tls);
  
  my $resultset = await $client.query('SELECT * FROM foo WHERE id = $1', 42);
  for $resultset.objects(Foo) -> $foo {
      do-something($foo);
  }
  await $client.transaction: {
      my $id = await $client.query('INSERT INTO foo(data) VALUES($1) RETURNING id', $data);
  }
  
  ```
  
  # Description
  
  Net::Postgres is asynchronous implementation of (the client side of) the postgresql protocol based on `Protocol::Postgres`. It is typically used through the `Net::Postgres::Connection` class.
  
  # Client
  
  `Net::Postgres::Client` has the following methods
  
  ## connect-tcp(--> Promise)
  
  This creates a promise to a new postgres client. It takes the following named arguments:
  
  * Str :$host = 'localhost'
  * Int :$port = 5432
  * Str :$user = ~$\*USER
  * Str :password
  * Str :$database
  * TypeMap :$typemap = Protocol::Postgres::TypeMap::JSON
  * Bool :$tls = False
  * :%tls-args = ()
  
  ## connect-local(--> Promise)
  
  * IO(Str) :$path = '/var/run/postgresql/'.IO
  * Int :$port = 5432
  * Str :$user = ~$\*USER
  * Str :password
  * Str :$database
  * TypeMap :$typemap = Protocol::Postgres::TypeMap::JSON
  
  ## connect(--> Promise)
  
  This takes the same arguments as `connect-local` and `connect-tcp`. It will call the former if the `$host` is localhost and the `$path` exists, otherwise it will call `connect-tcp`.
  
  ## query($query, @bind-values --> Promise)
  
  This will issue a query with the given bind values, and return a promise to the result.
  
  For fetching queries such as `SELECT` the result in the promise will be a `ResultSet` object, for manipulation (e.g. `INSERT`) and definition (e.g. `CREATE`) queries it will result a string describing the change (e.g. `DELETE 3`). For a `COPY TO` query it will `Supply` with the data stream, and for `COPY FROM` it will be a `Supplier`.
  
  Both the input types and the output types will be typemapped between Raku types and Postgres types using the typemapper.
  
  Not that this uses postgres-native placeholders (`$1, $2`), instead of DBI-style (`?, ?`).
  
  ## query-multiple($query --> Supply[ResultSet])
  
  This will issue a complex query that may contain multiple statements, but can not use bind values. It will return a `Supply` to the results of each query.
  
  ## prepare($query --> Promise[PreparedStatement])
  
  This prepares the query, and returns a Promise to the PreparedStatement object.
  
  ## transaction(&code)
  
  To use a transaction, one can use the `transaction` method. It's code reference will act as a wrapper for the transaction. If anything throws an exception out of the callback (e.g. a failed query method), a rollback will be attempted.
  
  ## add-enum-type(Str $name, ::Enum --> Promise)
  
  This looks up the `oid` of postgres enum `$name`, and adds an appriopriate `Type` object to the typemap to convert it from/to `Enum`.
  
  ## add-composite-type(Str $name, ::Composite, Bool :$positional --> Promise)
  
  This looks up the `oid` of the postgres composite type <$name>, and maps it to `Composite`; if `$positional` is set it will use positional constructor arguments, otherwise named ones are used.
  
  ## add-custom-type(Str $name, ::Custom, &from-string?, &to-string?)
  
  This adds a custom converter from postgres type `$name` from/to Raku type `Custom`. By default `&from-string` will do a coercion, and `&to-string` will do stringification.
  
  ## terminate(--> Nil)
  
  This sends a message to the server to terminate the connection
  
  ## listen(Str $channel-name --> Promise[Supply])
  
  This listens to notifications on the given channel. It returns a `Promise` to a `Supply` of `Notification`s.
  
  ## query-status(--> Protocol::Postgres::QueryStatus)
  
  This returns the query status as of the last finished query as a `enum Protocol::Postgres::QueryStatus` value: `Idle` (No transaction is active), `Transaction` (A transaction is currently in progress) or `Error` (The current transaction has failed and needs to be rolled back).
  
  # ResultSet
  
  A `Net::Postgres::ResultSet` represents the results of a query, if any. It defines the following methods:
  
  ## columns(--> List)
  
  This returns the column names for this resultset.
  
  ## rows(--> Supply[List])
  
  This returns a Supply of rows. Each row is a list of values.
  
  ## hash-rows(--> Supply[Hash])
  
  This returns a Supply of rows. Each row is a hash with the column names as keys and the row values as values.
  
  ## object-rows(::Class, Bool :$positional --> Supply[Class])
  
  This returns a Supply of objects of class `Class`, each object is constructed form the row hash unless positional is true in which case it's constructed from the row list.
  
  ## arrays
  
  This returns a sequence of arrays of results from all rows. This may `await`.
  
  ## array
  
  This returns a single array of results from one row. This may `await`.
  
  ## value
  
  This returns a single value from a single row. This may `await`.
  
  ## hashes
  
  This returns a sequence of hashes of the results from all rows. This may `await`.
  
  ## hash
  
  This returns a single hash of the results from one rows. This may `await`.
  
  ## objects(::Class, Bool :$positional)
  
  This returns a sequence of objects based on all the rows. This may `await`.
  
  ## object(:Class, Bool :$positional)
  
  This returns a single object based on a single row. This may `await`.
  
  # PreparedStatement
  
  A `Net::Postgres::PreparedStatement` represents a prepated statement. Its reason of existence is to call `execute` on it.
  
  ## execute(@arguments --> Promise)
  
  This runs the prepared statement, much like the `query` method would have done and with the same result values.
  
  ## close()
  
  This closes the prepared statement.
  
  ## columns()
  
  This returns the columns of the result once executed.
  
  # Notification
  
  `Net::Postgres::Notification` has the following methods:
  
  ## message(--> Str)
  
  This is the message of the notification. The notification will also stringify to this value.
  
  ## channel(--> Str)
  
  The channel of the notification.
  
  ## sender(--> Int)
  
  This is the process-id of the sender
  
  # Todo
  
  * Persistent connections
  * Connection pooling
  
  # Author
  
  Leon Timmermans [fawaka@gmail.com](mailto:fawaka@gmail.com)
  
  # Copyright and License
  
  Copyright 2022 Leon Timmermans
  
  This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.
  