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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Database-PostgreSQL-Simple-Notification.html">Source</a></li><li><a href="index.html">Contents</a></li><li><a href="doc-index.html">Index</a></li></ul><p class="caption">postgresql-simple-0.5.3.0: Mid-Level PostgreSQL client library</p></div><div id="content"><div id="module-header"><table class="info"><tr><th valign="top">Copyright</th><td>(c) 2011-2015 Leon P Smith<br />(c) 2012 Joey Adams</td></tr><tr><th>License</th><td>BSD3</td></tr><tr><th>Maintainer</th><td>leon@melding-monads.com</td></tr><tr><th>Stability</th><td>experimental</td></tr><tr><th>Safe Haskell</th><td>None</td></tr><tr><th>Language</th><td>Haskell98</td></tr></table><p class="caption">Database.PostgreSQL.Simple.Notification</p></div><div id="description"><p class="caption">Description</p><div class="doc"><p>Support for receiving asynchronous notifications via PostgreSQL's
Listen/Notify mechanism. See
<a href="https://www.postgresql.org/docs/9.5/static/sql-notify.html">https://www.postgresql.org/docs/9.5/static/sql-notify.html</a> for more
information.</p><p>Note that on Windows, <code>getNotification</code> currently uses a polling loop
of 1 second to check for more notifications, due to some inadequacies
in GHC's IO implementation and interface on that platform. See GHC
issue #7353 for more information. While this workaround is less than
ideal, notifications are still better than polling the database directly.
Notifications do not create any extra work for the backend, and are
likely cheaper on the client side as well.</p><p><a href="https://hackage.haskell.org/trac/ghc/ticket/7353">https://hackage.haskell.org/trac/ghc/ticket/7353</a></p></div></div><div id="synopsis"><p id="control.syn" class="caption expander" onclick="toggleSection('syn')">Synopsis</p><ul id="section.syn" class="hide" onclick="toggleSection('syn')"><li class="src short"><span class="keyword">data</span> <a href="#t:Notification">Notification</a> = <a href="#v:Notification">Notification</a> {<ul class="subs"><li><a href="#v:notificationPid">notificationPid</a> :: !<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-Posix-Types.html#t:CPid">CPid</a></li><li><a href="#v:notificationChannel">notificationChannel</a> :: !<a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString.html#t:ByteString">ByteString</a></li><li><a href="#v:notificationData">notificationData</a> :: !<a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString.html#t:ByteString">ByteString</a></li></ul>}</li><li class="src short"><a href="#v:getNotification">getNotification</a> :: <a href="Database-PostgreSQL-Simple-Internal.html#t:Connection">Connection</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a></li><li class="src short"><a href="#v:getNotificationNonBlocking">getNotificationNonBlocking</a> :: <a href="Database-PostgreSQL-Simple-Internal.html#t:Connection">Connection</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a>)</li><li class="src short"><a href="#v:getBackendPID">getBackendPID</a> :: <a href="Database-PostgreSQL-Simple-Internal.html#t:Connection">Connection</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-Posix-Types.html#t:CPid">CPid</a></li></ul></div><div id="interface"><h1>Documentation</h1><div class="top"><p class="src"><span class="keyword">data</span> <a id="t:Notification" class="def">Notification</a> <a href="src/Database-PostgreSQL-Simple-Notification.html#Notification" class="link">Source</a> <a href="#t:Notification" class="selflink">#</a></p><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a id="v:Notification" class="def">Notification</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div class="subs fields"><p class="caption">Fields</p><ul><li><dfn class="src"><a id="v:notificationPid" class="def">notificationPid</a> :: !<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-Posix-Types.html#t:CPid">CPid</a></dfn><div class="doc empty"> </div></li><li><dfn class="src"><a id="v:notificationChannel" class="def">notificationChannel</a> :: !<a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString.html#t:ByteString">ByteString</a></dfn><div class="doc empty"> </div></li><li><dfn class="src"><a id="v:notificationData" class="def">notificationData</a> :: !<a href="file:///usr/share/doc/ghc-doc/html/libraries/bytestring-0.10.8.1/Data-ByteString.html#t:ByteString">ByteString</a></dfn><div class="doc empty"> </div></li></ul></div></td></tr></table></div><div class="subs instances"><p id="control.i:Notification" class="caption collapser" onclick="toggleSection('i:Notification')">Instances</p><div id="section.i:Notification" class="show"><table><tr><td class="src clearfix"><span class="inst-left"><span id="control.i:id:Notification:Eq:1" class="instance expander" onclick="toggleSection('i:id:Notification:Eq:1')"></span> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Eq.html#t:Eq">Eq</a> <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a></span> <a href="src/Database-PostgreSQL-Simple-Notification.html#line-61" class="link">Source</a> <a href="#t:Notification" class="selflink">#</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div id="section.i:id:Notification:Eq:1" class="inst-details hide"><div class="subs methods"><p class="caption">Methods</p><p class="src"><a href="#v:-61--61-">(==)</a> :: <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a> -> <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Bool.html#t:Bool">Bool</a> <a href="#v:-61--61-" class="selflink">#</a></p><p class="src"><a href="#v:-47--61-">(/=)</a> :: <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a> -> <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Bool.html#t:Bool">Bool</a> <a href="#v:-47--61-" class="selflink">#</a></p></div></div></td></tr><tr><td class="src clearfix"><span class="inst-left"><span id="control.i:id:Notification:Show:2" class="instance expander" onclick="toggleSection('i:id:Notification:Show:2')"></span> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-Show.html#t:Show">Show</a> <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a></span> <a href="src/Database-PostgreSQL-Simple-Notification.html#line-61" class="link">Source</a> <a href="#t:Notification" class="selflink">#</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div id="section.i:id:Notification:Show:2" class="inst-details hide"><div class="subs methods"><p class="caption">Methods</p><p class="src"><a href="#v:showsPrec">showsPrec</a> :: <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a> -> <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-Show.html#t:ShowS">ShowS</a> <a href="#v:showsPrec" class="selflink">#</a></p><p class="src"><a href="#v:show">show</a> :: <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-String.html#t:String">String</a> <a href="#v:show" class="selflink">#</a></p><p class="src"><a href="#v:showList">showList</a> :: [<a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a>] -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Text-Show.html#t:ShowS">ShowS</a> <a href="#v:showList" class="selflink">#</a></p></div></div></td></tr></table></div></div></div><div class="top"><p class="src"><a id="v:getNotification" class="def">getNotification</a> :: <a href="Database-PostgreSQL-Simple-Internal.html#t:Connection">Connection</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a> <a href="src/Database-PostgreSQL-Simple-Notification.html#getNotification" class="link">Source</a> <a href="#v:getNotification" class="selflink">#</a></p><div class="doc"><p>Returns a single notification. If no notifications are available,
<code><a href="Database-PostgreSQL-Simple-Notification.html#v:getNotification">getNotification</a></code> blocks until one arrives.</p><p>It is safe to call <code><a href="Database-PostgreSQL-Simple-Notification.html#v:getNotification">getNotification</a></code> on a connection that is concurrently
being used for other purposes, note however that PostgreSQL does not
deliver notifications while a connection is inside a transaction.</p></div></div><div class="top"><p class="src"><a id="v:getNotificationNonBlocking" class="def">getNotificationNonBlocking</a> :: <a href="Database-PostgreSQL-Simple-Internal.html#t:Connection">Connection</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#t:Maybe">Maybe</a> <a href="Database-PostgreSQL-Simple-Notification.html#t:Notification">Notification</a>) <a href="src/Database-PostgreSQL-Simple-Notification.html#getNotificationNonBlocking" class="link">Source</a> <a href="#v:getNotificationNonBlocking" class="selflink">#</a></p><div class="doc"><p>Non-blocking variant of <code><a href="Database-PostgreSQL-Simple-Notification.html#v:getNotification">getNotification</a></code>. Returns a single notification,
if available. If no notifications are available, returns <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Maybe.html#v:Nothing">Nothing</a></code>.</p></div></div><div class="top"><p class="src"><a id="v:getBackendPID" class="def">getBackendPID</a> :: <a href="Database-PostgreSQL-Simple-Internal.html#t:Connection">Connection</a> -> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-IO.html#t:IO">IO</a> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-Posix-Types.html#t:CPid">CPid</a> <a href="src/Database-PostgreSQL-Simple-Notification.html#getBackendPID" class="link">Source</a> <a href="#v:getBackendPID" class="selflink">#</a></p><div class="doc"><p>Returns the process <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/System-Posix-Types.html#t:CPid">CPid</a></code> of the backend server process
handling this connection.</p><p>The backend PID is useful for debugging purposes and for comparison
to NOTIFY messages (which include the PID of the notifying backend
process). Note that the PID belongs to a process executing on the
database server host, not the local host!</p></div></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.17.3</p></div></body></html>
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