<Para>

pgtcl is a tcl package for front-end programs to interface with <ProductName>Postgres</ProductName>

backends. pgtcl does not use the libpq library but communicates to

the backend directly via the frontend-backend protocol. Thus, it is

more efficient than previous postgres->tcl bindings which are layered

on top of libpq. In addition, pgtcl can handle multiple backend

connections from a single frontend application.

backends. It makes most of the functionality of libpq available to

tcl scripts.

</Para>

<Para>

<ENTRY>pg_disconnect</ENTRY>

<ENTRY>closes a connection</ENTRY>

</ROW>

<ROW>

<ENTRY>pg_conndefaults</ENTRY>

<ENTRY>get connection options and their defaults</ENTRY>

</ROW>

<ROW>

<ENTRY>pg_exec</ENTRY>

<ENTRY>send a query to the backend</ENTRY>

</ROW>

<ROW>

<ENTRY>pg_result</ENTRY>

<ENTRY>manipulate the results of a query</ENTRY>

</ROW>

<ROW>

<ENTRY>pg_select</ENTRY>

<ENTRY>loop over the result of a select statement</ENTRY>

</ROW>

<ROW>

<ENTRY>pg_result</ENTRY>

<ENTRY>manipulate the results of a query</ENTRY>

<ENTRY>pg_listen</ENTRY>

<ENTRY>establish a callback for NOTIFY messages</ENTRY>

</ROW>

<ROW>

</Para>

<Para>

Some commands equivalent to libpq commands are provided for connection

and query operations.

These commands are described further on subsequent pages.

</Para>

<Para>

</Sect1>

<Sect1>

<Title>Reference Information</Title>

<Title>pgtcl CommandReference Information</Title>

<REFENTRY ID="PGTCL-PGCONNECT-1">

<REFMETA>

<LISTITEM>

<PARA>

The return result is either an error message or a handle for a database

connection. Handles start with the prefix "pgp"

connection. Handles start with the prefix "pgsql"

</PARA>

</LISTITEM>

</VARLISTENTRY>

</TITLE>

<PARA>

<FUNCTION>pg_exec</FUNCTION> submits a query to the <ProductName>Postgres</ProductName> backend and returns a result.

Handles start with the prefix "pgp".

Query result handles start with the connection handle and add a period

and a result number.

</PARA>

</REFSECT1>

<REFENTRY ID="PGTCL-PGLISTEN-1">

<REFMETA>

<REFENTRYTITLE>pg_listen</REFENTRYTITLE>

<REFMISCINFO>PGTCL - Asynchronous Notify</REFMISCINFO>

</REFMETA>

<REFNAMEDIV>

<REFNAME>pg_listen

</REFNAME>

<REFPURPOSE>sets or changes a callback for asynchronous NOTIFY messages

</REFPURPOSE>

<INDEXTERM ID="IX-PGTCL-PGLISTEN-1"><PRIMARY>pgtcl</PRIMARY><SECONDARY>notify</SECONDARY></INDEXTERM>

<INDEXTERM ID="IX-PGTCL-PGLISTEN-2"><PRIMARY>notify</PRIMARY></INDEXTERM>

</REFNAMEDIV>

<REFSYNOPSISDIV>

<REFSYNOPSISDIVINFO>

<DATE>1998-5-22</DATE>

</REFSYNOPSISDIVINFO>

<SYNOPSIS>

pg_listen <REPLACEABLE CLASS="PARAMETER">dbHandle</REPLACEABLE> <REPLACEABLE CLASS="PARAMETER">notifyName</REPLACEABLE> <REPLACEABLE CLASS="PARAMETER">callbackCommand</REPLACEABLE>

</SYNOPSIS>

<REFSECT2 ID="R2-PGTCL-PGLISTEN-1">

<REFSECT2INFO>

<DATE>1998-5-22</DATE>

</REFSECT2INFO>

<TITLE>Inputs

</TITLE>

<VARIABLELIST>

<VARLISTENTRY>

<TERM>

<REPLACEABLE CLASS="PARAMETER">dbHandle</REPLACEABLE>

</TERM>

<LISTITEM>

<PARA>Specifies a valid database handle.

</PARA>

</LISTITEM>

</VARLISTENTRY>

<VARLISTENTRY>

<TERM>

<REPLACEABLE CLASS="PARAMETER">notifyName</REPLACEABLE>

</TERM>

<LISTITEM>

<PARA>Specifies the notification name to start or stop listening to.

</PARA>

</LISTITEM>

</VARLISTENTRY>

<VARLISTENTRY>

<TERM>

<REPLACEABLE CLASS="PARAMETER">callbackCommand</REPLACEABLE>

</TERM>

<LISTITEM>

<PARA>If present and not empty, provides the command string to execute

when a matching notification arrives.

</PARA>

</LISTITEM>

</VARLISTENTRY>

</VARIABLELIST>

</REFSECT2>

<REFSECT2 ID="R2-PGTCL-PGLISTEN-2">

<REFSECT2INFO>

<DATE>1998-5-22</DATE>

</REFSECT2INFO>

<TITLE>Outputs

</TITLE>

<VARIABLELIST>

<VARLISTENTRY>

<TERM>

None

</TERM>

<LISTITEM>

<PARA>

</PARA>

</LISTITEM>

</VARLISTENTRY>

</VARIABLELIST>

</REFSECT2>

</REFSYNOPSISDIV>

<REFSECT1 ID="R1-PGTCL-PGLISTEN-1">

<REFSECT1INFO>

<DATE>1998-5-22</DATE>

</REFSECT1INFO>

<TITLE>Description

</TITLE>

<PARA><FUNCTION>pg_listen</FUNCTION> creates, changes, or cancels a request

to listen for asynchronous NOTIFY messages from the

<ProductName>Postgres</ProductName> backend. With a callbackCommand

parameter, the request is established, or the command string of an already

existing request is replaced. With no callbackCommand parameter, a prior

request is canceled.

</PARA>

After a <PARA><FUNCTION>pg_listen</FUNCTION> request is established,

the specified command string is executed whenever a NOTIFY message bearing

the given name arrives from the backend. This occurs when any

<ProductName>Postgres</ProductName> client application issues a NOTIFY command

referencing that name. (Note that the name can be, but does not have to be,

that of an existing relation in the database.)

The command string is executed from the Tcl idle loop. That is the normal

idle state of an application written with Tk. In non-Tk Tcl shells, you can

execute <FUNCTION>update</FUNCTION> or <FUNCTION>vwait</FUNCTION> to cause

the idle loop to be entered.

</PARA>

</REFSECT1>

Pg_ConnType.getFileProc=PgGetFileProc;

Pg_listen,

(ClientData)NULL, (Tcl_CmdDeleteProc*)NULL);

Tcl_CreateCommand(interp,

"pg_notifies",

Pg_notifies,

(ClientData)NULL, (Tcl_CmdDeleteProc*)NULL);

Tcl_PkgProvide(interp,"Pgtcl","1.1");

Tcl_PkgProvide(interp,"Pgtcl","1.2");

returnTCL_OK;

}