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<!--
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/odbc.sgml,v 1.30 2002/03/22 19:20:16 petere Exp $
-->
<chapter id="odbc">
<docinfo>
<authorgroup>
<author>
<firstname>Tim</firstname>
<surname>Goeke</surname>
</author>
<author>
<firstname>Thomas</firstname>
<surname>Lockhart</surname>
</author>
</authorgroup>
<date>1998-10-21</date>
</docinfo>
<title>ODBC Interface</title>
<indexterm zone="odbc">
<primary>ODBC</primary>
</indexterm>
<sect1 id="odbc-intro">
<title>Introduction</title>
<note>
<para>
Background information originally by Tim Goeke
(<email>tgoeke@xpressway.com</email>)
</para>
</note>
<para>
<acronym>ODBC</acronym> (Open Database Connectivity) is an abstract
<acronym>API</acronym>
that allows you to write applications that can interoperate
with various <acronym>RDBMS</acronym> servers.
<acronym>ODBC</acronym> provides a product-neutral interface
between frontend applications and database servers,
allowing a user or developer to write applications that are
portable between servers from different manufacturers..
</para>
<para>
The <acronym>ODBC</acronym> <acronym>API</acronym> matches up
on the backend to an <acronym>ODBC</acronym>-compatible data source.
This could be anything from a text file to an Oracle or
<productname>PostgreSQL</productname> <acronym>RDBMS</acronym>.
</para>
<para>
The backend access comes from <acronym>ODBC</acronym> drivers,
or vendor-specific drivers that
allow data access. <productname>psqlODBC</productname>, which is included in the <productname>PostgreSQL</> distribution, is such a driver,
along with others that are
available, such as the <productname>OpenLink</productname> <acronym>ODBC</acronym> drivers.
</para>
<para>
Once you write an <acronym>ODBC</acronym> application,
you <emphasis>should</emphasis> be able to connect to <emphasis>any</emphasis>
back-end database, regardless of the vendor, as long as the database schema
is the same.
</para>
<para>
For example. you could have <productname>MS SQL Server</productname>
and <productname>PostgreSQL</productname> servers that have
exactly the same data. Using <acronym>ODBC</acronym>,
your Windows application would make exactly the
same calls and the back-end data source would look the same (to the Windows
application).
</para>
</sect1>
<sect1 id="odbc-install">
<title>Installation</title>
<para>
In order to make use of an <acronym>ODBC</> driver there must
exist a <firstterm>driver manager</> on the system where the
<acronym>ODBC</> driver is to be used. There are two free
<acronym>ODBC</> driver managers for Unix-like operating systems
known to us: <indexterm><primary>iODBC</primary></indexterm>
<ulink url="http://www.iodbc.org"><productname>iODBC</></ulink>
and <indexterm><primary>unixODBC</primary></indexterm> <ulink
url="http://www.unixodbc.org"><productname>unixODBC</></ulink>.
Instructions for installing these driver managers are to be found
in the respective distribution. Software that provides database
access through <acronym>ODBC</acronym> should provide its own
driver manager (which may well be one of these two). Having said
that, any driver manager that you can find for your platform
should support the <productname>PostgreSQL</> <acronym>ODBC</>
driver, or any other <acronym>ODBC</> driver for that matter.
</para>
<note>
<para>
The <productname>unixODBC</> distribution ships with a
<productname>PostgreSQL</> <acronym>ODBC</> driver of its own,
which is similar to the one contained in the
<productname>PostgreSQL</> distribution. It is up to you which
one you want to use. We plan to coordinate the development of
both drivers better in the future.
</para>
</note>
<para>
To install the <acronym>ODBC</> you simply need to supply the
<option>--enable-odbc</> option to the <filename>configure</>
script when you are building the entire <productname>PostgreSQL</>
distribution. The library will then automatically be built and
installed with the rest of the programs. If you forget that option
or want to build the ODBC driver later you can change into the
directory <filename>src/interfaces/odbc</> and do <literal>make</>
and <literal>make install</> there.
</para>
<para>
It is also possible to build the driver to be specifically tuned
for use with <productname>iODBC</> or <productname>unixODBC</>.
This means in particular that the driver will use the driver
manager's routines to process the configuration files, which is
probably desirable since it creates a more consistent
<acronym>ODBC</> environment on your system. If you want to do
that, then supply the <filename>configure</> options
<option>--with-iodbc</> or <option>--with-unixodbc</> (but not
both).
</para>
<para>
If you build a <quote>stand-alone</quote> driver (not tied to
<productname>iODBC</> or <productname>unixODBC</>), then you can
specify where the driver should look for the configuration file
<filename>odbcinst.ini</>. By default it will be the directory
<filename>/usr/local/pgsql/etc/</>, or equivalent, depending on
what <option>--prefix</> and/or <option>--sysconfdir</> options
you supplied to <filename>configure</>. To select a specific
location outside the <productname>PostgreSQL</> installation
layout, use the <option>--with-odbcinst</> option. To be most
useful, it should be arranged that the driver and the driver
manager read the same configuration file.
</para>
<para>
<indexterm><primary>odbc.sql</></>
Additionally, you should install the ODBC catalog extensions. That will
provide a number of functions mandated by the ODBC standard that are not
supplied by <productname>PostgreSQL</> by default. The file
<filename>/usr/local/pgsql/share/odbc.sql</> (in the default installation layout)
contains the appropriate definitions, which you can install as follows:
<programlisting>
psql -d template1 -f <replaceable>LOCATION</>/odbc.sql
</programlisting>
where specifying <literal>template1</literal> as the target
database will ensure that all subsequent new databases will have
these same definitions. If for any reason you want to remove
these functions again, run the file
<filename>odbc-drop.sql</filename> through
<command>psql</command>.
</para>
</sect1>
<sect1 id="odbc-config">
<title>Configuration Files</title>
<indexterm zone="odbc-config"><primary>.odbc.ini</></>
<para>
<filename>~/.odbc.ini</filename> contains user-specified access information
for the <productname>psqlODBC</productname> driver.
The file uses conventions typical for <productname>Windows</productname>
Registry files.
</para>
<para>
The <filename>.odbc.ini</filename> file has three required sections.
The first is <literal>[ODBC Data Sources]</literal>
which is a list of arbitrary names and descriptions for each database
you wish to access. The second required section is the
Data Source Specification and there will be one of these sections
for each database.
Each section must be labeled with the name given in
<literal>[ODBC Data Sources]</literal> and must contain the following entries:
<programlisting>
Driver = <replaceable>prefix</replaceable>/lib/libpsqlodbc.so
Database = <replaceable>DatabaseName</replaceable>
Servername = localhost
Port = 5432
</programlisting>
<tip>
<para>
Remember that the <productname>PostgreSQL</productname> database name is
usually a single word, without path names of any sort.
The <productname>PostgreSQL</productname> server manages the actual access
to the database, and you need only specify the name from the client.
</para>
</tip>
Other entries may be inserted to control the format of the display.
The third required section is <literal>[ODBC]</literal>
which must contain the <literal>InstallDir</literal> keyword
and which may contain other options.
</para>
<para>
Here is an example <filename>.odbc.ini</filename> file,
showing access information for three databases:
<programlisting>
[ODBC Data Sources]
DataEntry = Read/Write Database
QueryOnly = Read-only Database
Test = Debugging Database
Default = Postgres Stripped
[DataEntry]
ReadOnly = 0
Servername = localhost
Database = Sales
[QueryOnly]
ReadOnly = 1
Servername = localhost
Database = Sales
[Test]
Debug = 1
CommLog = 1
ReadOnly = 0
Servername = localhost
Username = tgl
Password = "no$way"
Port = 5432
Database = test
[Default]
Servername = localhost
Database = tgl
Driver = /opt/postgres/current/lib/libpsqlodbc.so
[ODBC]
InstallDir = /opt/applix/axdata/axshlib
</programlisting>
</para>
</sect1>
<sect1 id="odbc-windows">
<title><productname>Windows</productname> Applications</title>
<para>
In the real world, differences in drivers and the level of
<acronym>ODBC</acronym> support
lessens the potential of <acronym>ODBC</acronym>:
<itemizedlist spacing="compact" mark="bullet">
<listitem>
<para>
Access, Delphi, and Visual Basic all support <acronym>ODBC</acronym> directly.
</para>
</listitem>
<listitem>
<para>
Under C++, such as Visual C++,
you can use the C++ <acronym>ODBC</acronym> <acronym>API</acronym>.
</para>
</listitem>
<listitem>
<para>
In Visual C++, you can use the <classname>CRecordSet</classname> class, which wraps the
<acronym>ODBC</acronym> <acronym>API</acronym>
set within an <application>MFC</application> 4.2 class. This is the easiest route if you are doing
Windows C++ development under Windows NT.
</para>
</listitem>
</itemizedlist>
</para>
<sect2>
<title>Writing Applications</title>
<para>
<quote>
If I write an application for <productname>PostgreSQL</productname>
can I write it using <acronym>ODBC</acronym> calls
to the <productname>PostgreSQL</productname> server,
or is that only when another database program
like MS SQL Server or Access needs to access the data?
</quote>
</para>
<para>
The <acronym>ODBC</acronym> <acronym>API</acronym>
is the way to go.
For <productname>Visual C++</productname> coding you can find out more at
Microsoft's web site or in your <productname>Visual C++</productname>
documentation.
</para>
<para>
Visual Basic and the other <acronym>RAD</acronym> tools have <classname>Recordset</classname> objects
that use <acronym>ODBC</acronym>
directly to access data. Using the data-aware controls, you can quickly
link to the <acronym>ODBC</acronym> back-end database
(<emphasis>very</emphasis> quickly).
</para>
<para>
Playing around with <productname>MS Access</> will help you sort this out. Try using
<menuchoice><guimenu>File</><guimenuitem>Get External Data</></menuchoice>.
</para>
<tip>
<para>
You'll have to set up a <acronym>DSN</acronym> first.
</para>
</tip>
</sect2>
</sect1>
<sect1 id="odbc-applixware">
<title><application>ApplixWare</application></title>
<indexterm zone="odbc-applixware">
<primary>Applixware</primary>
</indexterm>
<para>
<productname>Applixware</productname> has an
<acronym>ODBC</acronym> database interface
supported on at least some platforms.
<productname>Applixware</productname> 4.4.2 has been
demonstrated under Linux with <productname>PostgreSQL</productname> 7.0
using the <productname>psqlODBC</productname>
driver contained in the <productname>PostgreSQL</productname> distribution.
</para>
<sect2>
<title>Configuration</title>
<para>
<productname>Applixware</productname> must be configured correctly
in order for it to
be able to access the <productname>PostgreSQL</productname>
<acronym>ODBC</acronym> software drivers.
</para>
<procedure>
<title>Enabling <application>Applixware</application> Database Access</title>
<para>
These instructions are for the 4.4.2 release of
<productname>Applixware</productname> on <productname>Linux</productname>.
Refer to the <citetitle>Linux Sys Admin</citetitle> on-line book
for more detailed information.
</para>
<step performance="required">
<para>
You must modify <filename>axnet.cnf</filename> so that
<filename>elfodbc</filename> can
find <filename>libodbc.so</filename>
(the <acronym>ODBC</acronym> driver manager) shared library.
This library is included with the <application>Applixware</application> distribution,
but <filename>axnet.cnf</filename> needs to be modified to point to the
correct location.
</para>
<para>
As root, edit the file
<filename><replaceable>applixroot</replaceable>/applix/axdata/axnet.cnf</filename>.
</para>
<substeps>
<step performance="required">
<para>
At the bottom of <filename>axnet.cnf</filename>,
find the line that starts with
<programlisting>
#libFor elfodbc /ax/<replaceable>...</replaceable>
</programlisting>
</para>
</step>
<step performance="required">
<para>
Change line to read
<programlisting>
libFor elfodbc <replaceable>applixroot</replaceable>/applix/axdata/axshlib/lib
</programlisting>
which will tell <literal>elfodbc</literal> to look in this directory
for the <acronym>ODBC</acronym> support library.
Typically <productname>Applix</productname> is installed in
<filename>/opt</filename> so the full path would be
<filename>/opt/applix/axdata/axshlib/lib</filename>,
but if you have installed <productname>Applix</productname>
somewhere else then change the path accordingly.
</para>
</step>
</substeps>
</step>
<step performance="required">
<para>
Create <filename>.odbc.ini</filename> as
described in <xref linkend="odbc-config">. You may also want to add the flag
<programlisting>
TextAsLongVarchar=0
</programlisting>
to the database-specific portion of <filename>.odbc.ini</filename>
so that text fields will not be shown as <literal>**BLOB**</literal>.
</para>
</step>
</procedure>
<procedure>
<title>Testing <application>Applixware</application> ODBC Connections</title>
<step performance="required">
<para>
Bring up <application>Applix Data</application>
</para>
</step>
<step performance="required">
<para>
Select the <productname>PostgreSQL</productname> database of interest.
</para>
<substeps>
<step performance="required">
<para>
Select <menuchoice><guimenu>Query</guimenu><guimenuitem>Choose Server</guimenuitem></menuchoice>.
</para>
</step>
<step performance="required">
<para>
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 <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 <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 <guibutton>OK</guibutton>.
</para>
</step>
</substeps>
<para>
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.
</para>
</step>
<step performance="required">
<para>
The <quote>Ready</quote> message will appear in the lower left corner of the data
window. This indicates that you can now enter queries.
</para>
</step>
<step performance="required">
<para>
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>
</sect2>
<sect2>
<title>Common Problems</title>
<para>
The following messages can appear while trying to make an
<acronym>ODBC</acronym> connection through
<productname>Applix Data</productname>:
<variablelist>
<varlistentry>
<term>
<computeroutput>Cannot launch gateway on server</computeroutput>
</term>
<listitem>
<para>
<literal>elfodbc</literal> can't find <filename>libodbc.so</filename>.
Check your <filename>axnet.cnf</filename>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><computeroutput>
Error from ODBC Gateway:
IM003::[iODBC][Driver Manager]Specified driver could not be loaded</computeroutput>
</term>
<listitem>
<para>
<filename>libodbc.so</filename> cannot find the driver listed in
<filename>.odbc.ini</filename>. Verify the settings.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<computeroutput>Server: Broken Pipe</computeroutput>
</term>
<listitem>
<para>
The driver process has terminated due to some other
problem. You might not have an up-to-date version
of the <productname>PostgreSQL</productname>
<acronym>ODBC</acronym> package.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<computeroutput>setuid to 256: failed to launch gateway</computeroutput>
</term>
<listitem>
<para>
The September release of <application>Applixware</application> 4.4.1 (the first release with official
<acronym>ODBC</acronym> support under Linux) shows problems when user names
exceed eight (8) characters in length.
Problem description contributed by Steve Campbell
(<email>scampbell@lear.com</email>).
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
<note>
<title>Author</title>
<para>
Contributed by Steve Campbell (<email>scampbell@lear.com</email>),
1998-10-20
</para>
</note>
The <application>axnet</application> program's security system
seems a little suspect. <application>axnet</application> does things
on behalf of the user and on a true
multiuser system it really should be run with root security
(so it can read/write in each user's directory).
I would hesitate to recommend this, however, since we have no idea what
security holes this creates.
</para>
</sect2>
<sect2>
<title>Debugging <application>Applixware</application> ODBC Connections</title>
<para>
One good tool for debugging connection problems uses the Unix system
utility <application>strace</application>.
</para>
<procedure>
<title>Debugging with <command>strace</command></title>
<step performance="required">
<para>
Start <application>Applixware</application>.
</para>
</step>
<step performance="required">
<para>
Start an <application>strace</application> on
the <literal>axnet</literal> process. For example, if
<screen>
<prompt>$</prompt> <userinput>ps -aucx | grep ax</userinput>
</screen>
shows
<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
</screen>
</para>
<para>
Then run
<screen>
<prompt>$</prompt> <userinput>strace -f -s 1024 -p 10432</userinput>
</screen>
</para>
</step>
<step performance="required">
<para>
Check the <command>strace</command> output.
</para>
<note>
<title>Note from Cary</title>
<para>
Many of the error messages from <productname>Applixware</productname>
go to <filename>stderr</filename>,
but I'm not sure where <filename>stderr</filename>
is sent, so <command>strace</command> is the way to find out.
</para>
</note>
</step>
</procedure>
<para>
For example, after getting
a <errorname>Cannot launch gateway on server</errorname>,
I ran <command>strace</command> on <literal>axnet</literal> and got
<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)
</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>
</sect2>
<sect2>
<title>Running the <application>Applixware</application> Demo</title>
<comment>I think the condition this refers to is gone. -- petere 2002-01-07</comment>
<para>
In order to go through the
<citetitle>Applixware Data Tutorial</citetitle>, you need to create
the sample tables that the Tutorial refers to. The ELF Macro used to
create the tables tries to use a NULL condition
on many of the database columns,
and <productname>PostgreSQL</productname> does not currently allow this option.
</para>
<para>
To get around this problem, you can do the following:
</para>
<procedure>
<title>Modifying the <application>Applixware</application> Demo</title>
<step performance="required">
<para>
Copy <filename>/opt/applix/axdata/eng/Demos/sqldemo.am</filename>
to a local directory.
</para>
</step>
<step performance="required">
<para>
Edit this local copy of <filename>sqldemo.am</filename>:
</para>
<substeps>
<step performance="required">
<para>
Search for <literal>null_clause = "NULL"</literal>.
</para>
</step>
<step performance="required">
<para>
Change this to <literal>null_clause = ""</literal>.
</para>
</step>
</substeps>
</step>
<step performance="required">
<para>
Start <application>Applix Macro Editor</application>.
</para>
</step>
<step performance="required">
<para>
Open the <filename>sqldemo.am</filename> file from the <application>Macro Editor</application>.
</para>
</step>
<step performance="required">
<para>
Select <menuchoice><guimenu>File</><guimenuitem>Compile and Save</></menuchoice>.
</para>
</step>
<step performance="required">
<para>
Exit <application>Macro Editor</application>.
</para>
</step>
<step performance="required">
<para>
Start <application>Applix Data</application>.
</para>
</step>
<step performance="required">
<para>
Select <menuchoice><guimenu>*</><guimenuitem>Run Macro</guimenuitem></menuchoice>.
</para>
</step>
<step performance="required">
<para>
Enter the value <literal>sqldemo</literal>, then click <guibutton>OK</guibutton>.
</para>
<para>
You should see the progress in the status line of the data window
(in the lower left corner).
</para>
</step>
<step performance="required">
<para>
You should now be able to access the demo tables.
</para>
</step>
</procedure>
</sect2>
<sect2>
<title>Useful Macros</title>
<para>
You can add information about your
database login and password to the standard <application>Applix</application> start-up
macro file. This is an example
<filename>~/axhome/macros/login.am</filename> file:
<programlisting>
macro login
set_set_system_var@("sql_username@","tgl")
set_system_var@("sql_passwd@","no$way")
endmacro
</programlisting>
<caution>
<para>
You should be careful about the file protections on any file containing
user name and password information.
</para>
</caution>
</para>
</sect2>
</sect1>
</chapter>
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