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$Header: /cvsroot/pgsql/doc/src/sgml/libpq.sgml,v 1.74 2001/10/31 20:39:30 petere Exp $

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<chapter id="libpq">

complete examples of <filename>libpq</filename> applications in the

following directories:

<programlisting>

../src/test/regress

../src/test/examples

../src/bin/psql

</programlisting>

<simplelist>

<member><filename>src/test/examples</filename></member>

<member><filename>src/bin/psql</filename></member>

</simplelist>

</para>

<para>

particular order, or at all, or on the status always being one of these

documented values. An application may do something like this:

<programlisting>

switch(PQstatus(conn))

{

case CONNECTION_STARTED:

feedback = "Connecting...";

break;

switch(PQstatus(conn))

{

case CONNECTION_STARTED:

feedback = "Connecting...";

break;

case CONNECTION_MADE:

feedback = "Connected to server...";

break;

case CONNECTION_MADE:

feedback = "Connected to server...";

break;

.

.

.

default:

feedback = "Connecting...";

}

default:

feedback = "Connecting...";

}

</programlisting>

</para>

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<chapter id="odbc">

At the bottom of <filename>axnet.cnf</filename>,

find the line that starts with

<programlisting>

<programlisting>

#libFor elfodbc /ax/<replaceable>...</replaceable>

</programlisting>

</programlisting>

</para>

</step>

<step performance="required">

<para>

Change line to read

<programlisting>

<programlisting>

libFor elfodbc <replaceable>applixroot</replaceable>/applix/axdata/axshlib/lib

</programlisting>

</programlisting>

which will tell <literal>elfodbc</literal> to look in this directory

for the <acronym>ODBC</acronym> support library.

Create <filename>.odbc.ini</filename> as

described above. You may also want to add the flag

<programlisting>

<programlisting>

TextAsLongVarchar=0

</programlisting>

</programlisting>

to the database-specific portion of <filename>.odbc.ini</filename>

so that text fields will not be shown as <literal>**BLOB**</literal>.

<step performance="required">

<para>

Select <command>Query->Choose Server</command>.

Select <menuchoice><guimenu>Query</guimenu><guimenuitem>Choose Server</guimenuitem></menuchoice>.

</para>

</step>

<step performance="required">

<para>

Select <acronym>ODBC</acronym>, and click <command>Browse</command>.

Select <guimenuitem>ODBC</guimenuitem>, and click <guibutton>Browse</guibutton>.

The database you configured in <filename>.odbc.ini</filename>

should be shown. Make sure that the <option>Host: field</option>

should be shown. Make sure that the <guilabel>Host:</guilabel> field

is empty (if it is not, <literal>axnet</> will try to contact <literal>axnet</> on another machine

to look for the database).

</para>

</step>

<step performance="required">

<para>

Select the database in the box that was launched by <command>Browse</command>,

then click <command>OK</command>.

Select the database in the box that was launched by <guibutton>Browse</guibutton>,

then click <guibutton>OK</guibutton>.

</para>

</step>

<step performance="required">

<para>

Enter user name and password in the login identification dialog,

and click <command>OK</command>.

and click <guibutton>OK</guibutton>.

</para>

</step>

</substeps>

<para>

You should see <literal>Starting elfodbc server</literal>

You should see <guilabel>Starting elfodbc server</guilabel>

in the lower left corner of the

data window. If you get an error dialog box, see the debugging section

below.

</step>

<step performance="required">

<para>

Select a table from Query->Choose tables, and then select Query->Query

to access the database. The first 50 or so rows from the table should

appear.

Select a table from

<menuchoice><guimenu>Query</><guimenuitem>Choose

tables</></menuchoice>, and then select

<menuchoice><guimenu>Query</><guimenuitem>Query</></menuchoice>

to access the database. The first 50 or so rows from the table

should appear.

</para>

</step>

</procedure>

<para>

The driver process has terminated due to some other

problem. You might not have an up-to-date version

of the <productname>Postgres</productname>

of the <productname>PostgreSQL</productname>

<acronym>ODBC</acronym> package.

</para>

</listitem>

Start an <application>strace</application> on

the <literal>axnet</literal> process. For example, if

<programlisting>

%ps -aucx | grep ax

</programlisting>

<screen>

<prompt>$</prompt> <userinput>ps -aucx | grep ax</userinput>

</screen>

shows

<programlisting>

<screen>

cary 10432 0.0 2.6 1740 392 ? S Oct 9 0:00 axnet

cary 27883 0.9 31.0 12692 4596 ? S 10:24 0:04 axmain

</programlisting>

</screen>

</para>

<para>

Then run

<programlisting>

%strace -f -s 1024 -p 10432

</programlisting>

<screen>

<prompt>$</prompt> <userinput>strace -f -s 1024 -p 10432</userinput>

</screen>

</para>

</step>

a <literal>Cannot launch gateway on server</literal>,

I ran <command>strace</command> on <literal>axnet</literal> and got

<programlisting>

<screen>

[pid 27947] open("/usr/lib/libodbc.so", O_RDONLY) = -1 ENOENT

(No such file or directory)

[pid 27947] open("/lib/libodbc.so", O_RDONLY) = -1 ENOENT

(No such file or directory)

[pid 27947] write(2, "/usr2/applix/axdata/elfodbc:

can't load library 'libodbc.so'\n", 61) = -1 EIO (I/O error)

</programlisting>

</screen>

So what is happening is that <literal>applix elfodbc</literal> is searching for <filename>libodbc.so</filename>, but it

cannot find it. That is why <filename>axnet.cnf</filename> needed to be changed.

</para>

Now, compile and create the function:

<ProgramListing>

CREATE FUNCTION execq (TEXT, INT4) RETURNS INT4 AS '...path_to_so' LANGUAGE 'c';

CREATE FUNCTION execq (text, integer) RETURNS integer

AS '...path_to_so'

LANGUAGE C;

</ProgramListing>

<ProgramListing>

vac=> SELECT execq('CREATE TABLE a (xINT4)', 0);

vac=> SELECT execq('CREATE TABLE a (xINTEGER)', 0);

execq

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