odbc.sgml

关系型数据库 Postgresql 6.5.2

The file uses conventions typical for <productname>Windows</productname> 
Registry files, but despite this restriction can be made to work.
</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>POSTGRESDIR</replaceable>/lib/libpsqlodbc.so
Database=<replaceable>DatabaseName</replaceable>
Servername=localhost
Port=5432
</programlisting>

<tip>
<para>
Remember that the <productname>Postgres</productname> database name is
usually a single word, without path names of any sort. 
The <productname>Postgres</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>
<title>ApplixWare</title>

<sect2>
<title>Configuration</title>

<para>
<productname>ApplixWare</productname> must be configured correctly
 in order for it to
be able to access the <productname>Postgres</productname>
 <acronym>ODBC</acronym> software drivers.
</Para>

<procedure>
<title>Enabling ApplixWare Database Access</title>

<para>
These instructions are for the 4.4.1 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 ApplixWare 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 elfodbc to look in this directory
for the <acronym>ODBC</acronym> support library.
If you have installed applix somewhere else,
change the path accordingly.
</Para>
</step>
</substeps>
</step>

<step performance="required">
<para>
Create <filename>.odbc.ini</filename> as 
described above.  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 ApplixWare ODBC Connections</title>

<step performance="required">
<para>
    Bring up <application>Applix Data</application>
</Para>
</step>

<step performance="required">
<para>
Select the <productname>Postgres</productname> database of interest.
</Para>

<substeps>

<step performance="required">
<para>
Select <command>Query->Choose Server</command>.  
</Para>
</step>
<step performance="required">
<para>
 Select <acronym>ODBC</acronym>, and click <command>Browse</command>.
The database you configured in <filename>.odbc.ini</filename>
    should be shown.  Make sure that the <option>Host: field</option>
 is empty (if it is not, axnet will try to contact 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>.
</Para>
</step>
<step performance="required">
<para>
Enter username and password in the login identification dialog,
 and click <command>OK</command>.
</Para>
</step>
</substeps>

<para>
    You should see <quote>Starting elfodbc server</quote>
 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 'Ready' 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 Query->Choose tables, and then select Query->Query
    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>
Cannot launch gateway on server
</term>
<listitem>
<para>
<literal>elfodbc</literal> can't find <filename>libodbc.so</filename>.  
Check your <filename>axnet.cnf</filename>.
</Para>
</listitem>
</varlistentry>

<varlistentry>
<term>
Error from ODBC Gateway:
IM003::[iODBC][Driver Manager]Specified driver could not be loaded
</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>
Server: Broken Pipe
</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>Postgres</productname>
<acronym>ODBC</acronym> package.
</Para>
</listitem>
</varlistentry>

<varlistentry>
<term>
setuid to 256: failed to launch gateway
</term>

<listitem>
<para>
The September release of ApplixWare v4.4.1 (the first release with official
<acronym>ODBC</acronym> support under Linux) shows problems when usernames
exceed eight (8) characters in length.
Problem description ontributed by 
<ulink url="mailto:[e-mail]">Steve Campbell</ulink>.
</Para>
</listitem>
</varlistentry>

</variablelist>
</para>

<para>
<note>
<title>Author</title>

<para>
Contributed by 
<ulink url="mailto:[e-mail]">Steve Campbell</ulink> on
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
 multiple user 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 ApplixWare ODBC Connections</title>

<para>
One good tool for debugging connection problems uses the Unix system
utility <application>strace</application>.
</para>
<procedure>
<title>Debugging with strace</title>

<step performance="required">
<para>
Start applixware.
</para>
</step>
<step performance="required">
<para>
Start an <application>strace</application> on
the axnet process.  For example, if

<programlisting>
ps -aucx | grep ax 
</programlisting>

shows

<programlisting>
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>
</para>

<para>
Then run

<programlisting>
   strace -f -s 1024 -p 10432 
</programlisting>
</para>
</step>

<step performance="required">
<para>
Check the strace 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 <application>strace</application> is the way to find out.
</para>
</note>
</step>
</procedure>

<para>
  For example, after getting
a <quote>Cannot launch gateway on server</quote>, 
I ran strace on axnet and got

<programlisting>
[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>  
So what is happening is that applix elfodbc is searching for libodbc.so, but it
can't find it.  That is why axnet.cnf needed to be changed.
</para>
</sect2>

<sect2>
<title>Running the ApplixWare Demo</title>

<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>Postgres</productname> does not currently allow this option.
</para>
<para>
To get around this problem, you can do the following:
</para>

<procedure>
<title>Modifying the ApplixWare 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 'null_clause = "NULL"
</para>
</step>

<step performance="required">
<para>
Change this to null_clause = ""
</para>
</step>

</substeps>
</step>
<step performance="required">
<para>
Start <application>Applix Macro Editor</application>.
</para>
</step>

<step performance="required">
<para>
Open the sqldemo.am file from the <application>Macro Editor</application>.
</para>
</step>

<step performance="required">
<para>
Select <command>File->Compile and Save</command>.
</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 <command>*->Run Macro</command>
</para>
</step>

<step performance="required">
<para>
Enter the value <quote>sqldemo</quote>, then click <command>OK</command>.
</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 Applix startup
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
username and password information.
</para>
</caution>
</para>
</sect2>
<sect2>
<title>Supported Platforms</title>

<para>
<productname>psqlODBC</productname> has been built and tested
on <productname>Linux</productname>. There have been reports of success
with FreeBSD and with Solaris. There are no known restrictions
on the basic code for other platforms which already support
<productname>Postgres</productname>.
</para>
</sect2>
</sect1>
</Chapter>

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