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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >tcn</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.2.24 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Additional Supplied Modules" HREF="contrib.html"><LINK REL="PREVIOUS" TITLE="tablefunc" HREF="tablefunc.html"><LINK REL="NEXT" TITLE="test_parser" HREF="test-parser.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2017-11-06T22:43:11"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.2.24 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="tablefunc" HREF="tablefunc.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="contrib.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Appendix F. Additional Supplied Modules</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="test_parser" HREF="test-parser.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="TCN" >F.36. tcn</A ></H1 ><P > The <TT CLASS="FILENAME" >tcn</TT > module provides a trigger function that notifies listeners of changes to any table on which it is attached. It must be used as an <TT CLASS="LITERAL" >AFTER</TT > trigger <TT CLASS="LITERAL" >FOR EACH ROW</TT >. </P ><P > Only one parameter may be supplied to the function in a <TT CLASS="LITERAL" >CREATE TRIGGER</TT > statement, and that is optional. If supplied it will be used for the channel name for the notifications. If omitted <TT CLASS="LITERAL" >tcn</TT > will be used for the channel name. </P ><P > The payload of the notifications consists of the table name, a letter to indicate which type of operation was performed, and column name/value pairs for primary key columns. Each part is separated from the next by a comma. For ease of parsing using regular expressions, table and column names are always wrapped in double quotes, and data values are always wrapped in single quotes. Embedded quotes are doubled. </P ><P > A brief example of using the extension follows. </P><PRE CLASS="PROGRAMLISTING" >test=# create table tcndata test-# ( test(# a int not null, test(# b date not null, test(# c text, test(# primary key (a, b) test(# ); NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "tcndata_pkey" for table "tcndata" CREATE TABLE test=# create trigger tcndata_tcn_trigger test-# after insert or update or delete on tcndata test-# for each row execute procedure triggered_change_notification(); CREATE TRIGGER test=# listen tcn; LISTEN test=# insert into tcndata values (1, date '2012-12-22', 'one'), test-# (1, date '2012-12-23', 'another'), test-# (2, date '2012-12-23', 'two'); INSERT 0 3 Asynchronous notification "tcn" with payload ""tcndata",I,"a"='1',"b"='2012-12-22'" received from server process with PID 22770. Asynchronous notification "tcn" with payload ""tcndata",I,"a"='1',"b"='2012-12-23'" received from server process with PID 22770. Asynchronous notification "tcn" with payload ""tcndata",I,"a"='2',"b"='2012-12-23'" received from server process with PID 22770. test=# update tcndata set c = 'uno' where a = 1; UPDATE 2 Asynchronous notification "tcn" with payload ""tcndata",U,"a"='1',"b"='2012-12-22'" received from server process with PID 22770. Asynchronous notification "tcn" with payload ""tcndata",U,"a"='1',"b"='2012-12-23'" received from server process with PID 22770. test=# delete from tcndata where a = 1 and b = date '2012-12-22'; DELETE 1 Asynchronous notification "tcn" with payload ""tcndata",D,"a"='1',"b"='2012-12-22'" received from server process with PID 22770.</PRE ><P> </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="tablefunc.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="test-parser.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >tablefunc</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="contrib.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >test_parser</TD ></TR ></TABLE ></DIV ></BODY ></HTML >