 <chapter id="regress">
  <title id="regress-title">Regression Test</title>

  <abstract>
   <para>
    Regression test instructions and analysis.
   </para>
  </abstract>

  <para>
   The PostgreSQL regression tests are a comprehensive set of tests for the
   SQL implementation embedded in PostgreSQL.  They test standard SQL
   operations as well as the extended capabilities of PostgreSQL.
  </para>

  <para>
   There are two different ways in which the regression tests can be run:
   the "sequential" method and the "parallel" method.  The sequential method
   runs each test script in turn, whereas the parallel method starts up
   multiple server processes to run groups of tests in parallel.  Parallel
   testing gives confidence that interprocess communication and locking
   are working correctly.  Another key difference is that the sequential
   test procedure uses an already-installed postmaster, whereas the
   parallel test procedure tests a system that has been built but not yet
   installed.  (The parallel test script actually does an installation into
   a temporary directory and fires up a private postmaster therein.)
  </para>

  <para>
   Some properly installed and fully functional PostgreSQL installations
   can "fail" some of these regression tests due to artifacts of floating point
   representation and time zone support. The tests are currently evaluated
   using a simple <application>diff</application> comparison against the
   outputs generated on a reference system, so the results are sensitive to
   small system differences.
   When a test is reported as "failed", always examine the differences
   between expected and actual results; you may well find that the differences
   are not significant.
  </para>

  <para>
   The regression tests were originally developed by Jolly Chen and Andrew Yu,
   and were extensively revised/repackaged by Marc Fournier and Thomas Lockhart.
   From <productname>PostgreSQL</productname> v6.1 onward
   the regression tests are current for every official release. 
  </para>

  <sect1>
   <title>Regression Environment</title>

   <para>
    The regression testing notes below assume the following (except where noted):
    <itemizedlist spacing="compact" mark="bullet">
     <listitem>
      <para>
       Commands are Unix-compatible. See note below.
      </para>
     </listitem>
     <listitem>
      <para>
       Defaults are used except where noted.
      </para>
     </listitem>
     <listitem>
      <para>
       User postgres is the <productname>Postgres</productname> superuser.
      </para>
     </listitem>
     <listitem>
      <para>
       The source path is /usr/src/pgsql (other paths are possible).
      </para>
     </listitem>
     <listitem>
      <para>
       The runtime path is /usr/local/pgsql (other paths are possible).
      </para>
     </listitem>
    </itemizedlist>
   </para>

   <para>
    Normally, the regression tests should be run as the postgres user since
    the 'src/test/regress' directory and sub-directories are owned by the
    postgres user. If you run the regression test as another user the
    'src/test/regress' directory tree must be writeable by that user.
   </para>

   <para>
    It was formerly necessary to run the postmaster with system time zone
    set to PST, but this is no longer required.  You can run the regression
    tests under your normal postmaster configuration.  The test script will
    set the PGTZ environment variable to ensure that timezone-dependent tests
    produce the expected results.  However, your system must provide
    library support for the PST8PDT time zone, or the timezone-dependent
    tests will fail.
    To verify that your machine does have this support, type
    the following:

    <programlisting>
setenv TZ PST8PDT
date
    </programlisting>
   </para>

   <para>
    The "date" command above should have returned the current system time
    in the PST8PDT time zone. If the PST8PDT database is not available, then
    your system may have returned the time in GMT. If the PST8PDT time zone
    is not available, you can set the time zone rules explicitly:
    <programlisting>
setenv PGTZ PST8PDT7,M04.01.0,M10.05.03
    </programlisting>
   </para>

   <para>
    The directory layout for the regression test area is:

    <table tocentry="1">
     <title>Directory Layout</title>

     <titleabbrev>Kerberos</titleabbrev>

     <tgroup cols="2">
      <thead>
       <row>
	<entry>Directory</entry>
	<entry>Description</entry>
       </row>
      </thead>
      <tbody>
       <row>
	<entry>Directory</entry>
	<entry>Description</entry>
       </row>
       <row>
	<entry>input</entry>
	<entry>
	 Source files that are converted using
	 <command>make all</command> into
	 some of the <filename>.sql</filename> files in the
	 <filename>sql</filename> subdirectory.
	</entry>
       </row>

       <row>
	<entry>output</entry>
	<entry>
	 Source files that are converted using
	 <command>make all</command> into
	 <filename>.out</filename> files in the
	 <filename>expected</filename> subdirectory.
	</entry>
       </row>

       <row>
	<entry>sql</entry>
	<entry>
	 <filename>.sql</filename> files used to perform the
	 regression tests.
	</entry>
       </row>

       <row>
	<entry>expected</entry>
	<entry>
	 <filename>.out</filename> files that represent what we
	 <emphasis>expect</emphasis> the results to
	 look like.
	</entry>
       </row>

       <row>
	<entry>results</entry>
	<entry>
	 <filename>.out</filename> files that contain what the results
	 <emphasis>actually</emphasis> look
	 like. Also used as temporary storage for table copy testing.
	</entry>
       </row>

       <row>
	<entry>tmp_check</entry>
	<entry>
	 Temporary installation created by parallel testing script.
	</entry>
       </row>
      </tbody>
     </tgroup>
    </table>
   </para>
  </sect1>
  
  <sect1>
    <title>Regression Test Procedure</title>
    
    <para>
      Commands were tested on RedHat Linux version 4.2 using the bash shell.
      Except where noted, they will probably work on most systems. Commands
      like <filename>ps</filename> and <filename>tar</filename> vary
    wildly on what options you should use on each
      platform. <emphasis>Use common sense</emphasis> before typing in these commands.
    </para>
    
    <procedure>
      <title><productname>Postgres</productname> Regression Test</title>
      
      <step performance="required">
	<para>
	  Prepare the files needed for the regression test with:
	  <programlisting>
	    cd /usr/src/pgsql/src/test/regress
	    gmake clean
	    gmake all
	  </programlisting>
	  You can skip "gmake clean" if this is the first time you
	  are running the tests.
	</para>
	<para>
	  This step compiles a <acronym>C</acronym>
	  program with PostgreSQL extension functions into a shared library.
	  Localized SQL scripts and output-comparison files are also created
	  for the tests that need them.  The localization replaces macros in
	  the source files with absolute pathnames and user names.
	</para>
      </step>

      <step performance="optional">
	<para>
	  If you intend to use the "sequential" test procedure, which tests
	  an already-installed postmaster, be sure that the postmaster
	  is running.  If it isn't already running,
	  start the postmaster in an available window by typing
	  <programlisting>
	    postmaster
	  </programlisting>
	  or start the postmaster daemon running in the background by typing
	  <programlisting>
	    cd
	    nohup postmaster > regress.log 2>&1 &
	  </programlisting>
	  The latter is probably preferable, since the regression test log
	  will be quite lengthy (60K or so, in
	  <productname>Postgres</productname> 7.0) and you might want to
	  review it for clues if things go wrong.
	  
	  <note>
	    <para>
	      Do not run <filename>postmaster</filename> from the root account.
	    </para>
	  </note>
	</para>
      </step>
      
      <step performance="required">
	<para>
	  Run the regression tests.  For a sequential test, type
	  <programlisting>
	    cd /usr/src/pgsql/src/test/regress
	    gmake runtest
	  </programlisting>
	  For a parallel test, type
	  <programlisting>
	    cd /usr/src/pgsql/src/test/regress
	    gmake runcheck
	  </programlisting>
	  The sequential test just runs the test scripts using your
	  already-running postmaster.
	  The parallel test will perform a complete installation of
	  <productname>Postgres</productname> into a temporary directory,
	  start a private postmaster therein, and then run the test scripts.
	  Finally it will kill the private postmaster (but the temporary
	  directory isn't removed automatically).
	</para>
      </step>
      
      <step performance="required">
	<para>
	  You should get on the screen (and also written to file ./regress.out)
	  a series of statements stating which tests passed and which tests
	  failed.  Please note that it can be normal for some of the tests to
	  "fail" due to platform-specific variations.  See the next section
	  for details on determining whether a "failure" is significant.
	</para>
	<para>
	  Some of the tests, notably "numeric", can take a while, especially
	  on slower platforms.  Have patience.
	</para>
      </step>
      
      <step performance="required">
	<para>
	  After running the tests and examining the results, type
	  <programlisting>
	    cd /usr/src/pgsql/src/test/regress
	    gmake clean
	  </programlisting>
	  to recover the temporary disk space used by the tests.
	  If you ran a sequential test, also type
	  <programlisting>
	    dropdb regression
	  </programlisting>
	</para>
      </step>
    </procedure>
  </sect1>
  
  <sect1>
    <title>Regression Analysis</title>

     <para>
       The actual outputs of the regression tests are in files in the
       <filename>./results</filename> directory. The test script
       uses <application>diff</application> to compare each output file
       against the reference outputs stored in the
       <filename>./expected</filename> directory.  Any differences are
       saved for your inspection in
       <filename>./regression.diffs</filename>.  (Or you can run
       <application>diff</application> yourself, if you prefer.)
     </para>

     <para>
       The files might not compare exactly.  The test script will report
       any difference as a "failure", but the difference might be due
       to small cross-system differences in error message wording,
       math library behavior, etc.
      "Failures" of this type do not indicate a problem with
      <productname>Postgres</productname>.
    </para>
    
    <para>
      Thus, it is necessary to examine the actual differences for each
      "failed" test to determine whether there is really a problem.
      The following paragraphs attempt to provide some guidance in
      determining whether a difference is significant or not.
    </para>
    
    <sect2>
      <title>Error message differences</title>
      
      <para>
	Some of the regression tests involve intentional invalid input values.
	Error messages can come from either the Postgres code or from the host
	platform system routines. In the latter case, the messages may vary
	between platforms, but should reflect similar information. These
	differences in messages will result in a "failed" regression test which
	can be validated by inspection.
      </para>
      
    </sect2>
    
    <sect2>
      <title>Date and time differences</title>
      
      <para>
  Most of the date and time results are dependent on timezone environment.
  The reference files are generated for timezone PST8PDT (Berkeley,
  California) and there will be apparent failures if the tests are not
  run with that timezone setting.  The regression test driver sets
  environment variable PGTZ to PST8PDT to ensure proper results.
      </para>

      <para>
       Some of the queries in the "timestamp" test will fail if you run
       the test on the day of a daylight-savings time changeover, or the
       day before or after one.  These queries assume that the intervals
       between midnight yesterday, midnight today and midnight tomorrow are
       exactly twenty-four hours ... which is wrong if daylight-savings time
       went into or out of effect meanwhile.
      </para>

      <para>
  There appear to be some systems which do not accept the recommended syntax
  for explicitly setting the local time zone rules; you may need to use
  a different PGTZ setting on such machines.
      </para>

      <para>
  Some systems using older timezone libraries fail to apply daylight-savings
  corrections to pre-1970 dates, causing pre-1970 PDT times to be displayed
  in PST instead.  This will result in localized differences in the test
  results.
      </para>
      
    </sect2>
    
    <sect2>
      <title>Floating point differences</title>
      
      <para>
	Some of the tests involve computing 64-bit (<type>float8</type>) numbers from table
	columns. Differences in results involving mathematical functions of
	<type>float8</type> columns have been observed.  The float8
	and geometry tests are particularly prone to small differences
	across platforms.
	Human eyeball comparison is needed to determine the real significance
	of these differences which are usually 10 places to the right of
	the decimal point.
      </para>

      <para>
	Some systems signal errors from pow() and exp() differently from
	the mechanism expected by the current Postgres code.
      </para>
      
    </sect2>
    
    <sect2>
      <title>Polygon differences</title>
      
      <para>
	Several of the tests involve operations on geographic date about the
	Oakland/Berkley CA street map. The map data is expressed as polygons
	whose vertices are represented as pairs of <type>float8</type> numbers (decimal
	latitude and longitude). Initially, some tables are created and
	loaded with geographic data, then some views are created which join
	two tables using the polygon intersection operator (##), then a select
	is done on the view. 
	
	When comparing the results from different platforms, differences occur
	in the 2nd or 3rd place to the right of the decimal point. The SQL
	statements where these problems occur are the following:
	
	<programlisting>
	  QUERY: SELECT * from street;
	  QUERY: SELECT * from iexit;
	</programlisting>
      </para>
      
    </sect2>
    
    <sect2>
      <title>Random differences</title>
      
      <para>
	There is at least one case in the "random" test script that is
	intended to produce
	random results. This causes random to fail the regression test
	once in a while (perhaps once in every five to ten trials).
	Typing
	<programlisting>
	  diff results/random.out expected/random.out
	</programlisting>
	should produce only one or a few lines of differences.  You need
	not worry unless the random test always fails in repeated attempts.
	(On the other hand, if the random test is <emphasis>never</emphasis>
	reported to fail even in many trials of the regress tests, you
	probably <emphasis>should</emphasis> worry.)
      </para>
      
    </sect2>
    
    <sect2>
      <title>The "expected" files</title>
      
      <para>
	The <filename>./expected/*.out</filename> files were adapted from the original monolithic
	<filename>expected.input</filename> file provided by Jolly Chen et al. Newer versions of these
	files generated on various development machines have been substituted after
	careful (?) inspection. Many of the development machines are running a
	Unix OS variant (FreeBSD, Linux, etc) on Ix86 hardware.
	
	The original <filename>expected.input</filename> file was created on a SPARC Solaris 2.4
	system using the <filename>postgres5-1.02a5.tar.gz</filename> source tree. It was compared
	with a file created on an I386 Solaris 2.4 system and the differences
	were only in the floating point polygons in the 3rd digit to the right
	of the decimal point.
	
	The original <filename>sample.regress.out</filename> file was from the postgres-1.01 release
	constructed by Jolly Chen. It may
	have been created on a DEC ALPHA machine as the <filename>Makefile.global</filename>
	in the postgres-1.01 release has PORTNAME=alpha.
      </para>
      
    </sect2>
    
  </sect1>

  <sect1>
    <title>Platform-specific comparison files</title>

     <para>
  Since some of the tests inherently produce platform-specific results,
  we have provided a way to supply platform-specific result comparison
  files.  Frequently, the same variation applies to multiple platforms;
  rather than supplying a separate comparison file for every platform,
  there is a mapping file that defines which comparison file to use.
  So, to eliminate bogus test "failures" for a particular platform,
  you must choose or make a variant result file, and then add a line
  to the mapping file, which is "resultmap".
     </para>

     <para>
  Each line in the mapping file is of the form
	<programlisting>
		testname/platformnamepattern=comparisonfilename
	</programlisting>
  The test name is just the name of the particular regression test module.
  The platform name pattern is a pattern in the style of expr(1) (that is,
  a regular expression with an implicit ^ anchor at the start).  It is matched
  against the platform name as printed by config.guess.  The comparison
  file name is the name of the substitute result comparison file.
     </para>

     <para>
  For example: the int2 regress test includes a deliberate entry of a value
  that is too large to fit in int2.  The specific error message that is
  produced is platform-dependent; our reference platform emits
	<programlisting>
    ERROR:  pg_atoi: error reading "100000": Numerical result out of range
	</programlisting>
  but a fair number of other Unix platforms emit
	<programlisting>
    ERROR:  pg_atoi: error reading "100000": Result too large
	</programlisting>
  Therefore, we provide a variant comparison file, int2-too-large.out,
  that includes this spelling of the error message.  To silence the
  bogus "failure" message on HPPA platforms,  resultmap includes
	<programlisting>
		int2/hppa=int2-too-large
	</programlisting>
  which will trigger on any machine for which config.guess's output
  begins with 'hppa'.  Other lines in resultmap select the variant
  comparison file for other platforms where it's appropriate.
     </para>
    
  </sect1>
  
</chapter>

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