regress.sgml

<Chapter 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 developed by Jolly Chen and
  Andrew Yu. It tests standard SQL operations as well as the extended
  capabilities of PostgreSQL.
</Para>

<Para>
  These tests have recently been revised by Marc Fournier and Thomas Lockhart
and are now packaged as
  functional units which should make them easier to run and easier to interpret.
From <ProductName>PostgreSQL</ProductName> v6.1 onward
 the regression tests are current for every official release. 
</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 current tests are evaluated
  using a simple "diff" algorithm, and are sensitive to small system
  differences. For apparently failed tests, examining the differences
  may reveal that the differences are not significant.
</Para>

<Para>
The regression testing notes below assume the following (except where noted):
<ItemizedList Mark="bullet" Spacing="compact">
<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>

<Sect1>
<Title>Regression Environment</Title>

<Para>
  The regression test is invoked by the <Command>make</Command> command which compiles
  a <Acronym>C</Acronym> program into a shared library
  in the current directory.  Localized shell scripts are also created in
  the current directory. The output file templates are massaged into the
  <FileName>./expected/*.out</FileName> files.  The localization replaces macros in the source
  files with absolute pathnames and user names.
</Para>

<Para>
  Normally, the regression test should be run as the pg_superuser since
  the 'src/test/regress' directory and sub-directories are owned by the
  pg_superuser. If you run the regression test as another user the
  'src/test/regress' directory tree should be writeable to 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>
  </sect1>
  
  <Sect1>
    <Title>Directory Layout</Title>
    
    <Para>
      <Note>
	<Para>
	  This should become a table in the previous section.
	</Para>
      </Note>
    </Para>
    
    <Para>
      <ProgramListing>
  input/ .... .source files that are converted using 'make all' into
              some of the .sql files in the 'sql' subdirectory

  output/ ... .source files that are converted using 'make all' into
              .out files in the 'expected' subdirectory

  sql/ ...... .sql files used to perform the regression tests

  expected/ . .out files that represent what we *expect* the results to
              look like

  results/ .. .out files that represent what the results *actually* look
              like. Also used as temporary storage for table copy testing.
      </ProgramListing>
    </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>
      
      <Para>
	For a fresh install or upgrading from previous releases of
	<ProductName>Postgres</ProductName>:
      </Para>
    
    <Procedure>
      <Title><ProductName>Postgres</ProductName> Regression Configuration</Title>

      <Step Performance="required">
	<Para>
	  The file /usr/src/pgsql/src/test/regress/README has detailed
	  instructions for running and interpreting the regression tests.
	  A short version follows here:
	</Para>
	
	<Para>
	  If the postmaster is not already running, start the postmaster on 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>
	</Para>
	
	<Para>
	  Run postmaster from your <ProductName>Postgres</ProductName> super user account (typically
	  account postgres).
	  
	  <Note>
	    <Para>
	      Do not run <FileName>postmaster</FileName> from the root account.
	    </Para>
	  </Note>
	</Para>
      </Step>
      
      <Step Performance="optional">
	<Para>
	  If you have previously invoked the regression test, clean up the
	  working directory with:
	  
	  <ProgramListing>
	    cd /usr/src/pgsql/src/test/regress
	    gmake clean
	  </ProgramListing>
	</para>
	<Para>
	  You do not need to type "gmake clean" if this is the first time you
	  are running the tests.
	</Para>
      </step>

      
      <Step Performance="required">
	<Para>
	  Build the regression test. Type
	  <ProgramListing>
	    cd /usr/src/pgsql/src/test/regress
	    gmake all
	  </ProgramListing>
	</Para>
      </Step>
      
      <Step Performance="required">
	<Para>
	  Run the regression tests.  Type
	  <ProgramListing>
	    cd /usr/src/pgsql/src/test/regress
	    gmake runtest
	  </ProgramListing>
	</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".  For the failed tests, use diff to compare the files in
	  directories ./results and ./expected.  If float8 failed, type
	  something like:
	  <ProgramListing>
	    cd /usr/src/pgsql/src/test/regress
	    diff -w expected/float8.out results
	  </ProgramListing>
	</Para>
      </Step>
      
      <Step Performance="required">
	<Para>
	  After running the tests and examining the results, type
	  <ProgramListing>
	    dropdb regression
	    cd /usr/src/pgsql/src/test/regress
	    gmake clean
	  </ProgramListing>
	  to recover the temporary disk space used by the tests.
	</Para>
      </Step>
    </procedure>
  </Sect1>
  
  <Sect1>
    <Title>Regression Analysis</Title>

     <Para>
       The results are in files in the ./results directory. These results
       can be compared with results in the ./expected directory using 'diff'.
       (The test script does this for you, and leaves the differences
       in ./regression.diffs.)
     </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>OID differences</Title>
      
      <Para>
	There are several places where PostgreSQL OID (object identifiers) appear
	in 'regress.out'. OID's are unique 32-bit integers which are generated
	by the PostgreSQL backend whenever a table row is inserted or updated.
	If you run the regression test on a non-virgin database or run it multiple
	times, the OID's reported will have different values. 
	
	The following SQL statements in 'misc.out' have shown this behavior:
	
	QUERY: SELECT user_relns() AS user_relns ORDER BY user_relns;
	
	The 'a,523676' row is composed from an OID.
      </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>
  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 folowing:
	
	<ProgramListing>
	  QUERY: SELECT * from street;
	  QUERY: SELECT * from iexit;
	</ProgramListing>
      </Para>
      
    </Sect2>
    
    <Sect2>
      <Title>Random differences</Title>
      
      <Para>
	There is at least one test case in random.out which is intended to produce
	random results. This causes random to fail the regression testing
	once in a while.
	Typing
	<ProgramListing>
	  diff results/random.out expected/random.out
	</ProgramListing>
	
	should produce only
	one or a few lines of differences for this reason, but other floating
	point differences on dissimilar architectures might cause many more
	differences. See the release notes below.
      </Para>
      
    </Sect2>
    
    <Sect2>
      <Title>The <Quote>expected</Quote> 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. (see below)
	
	The original <FileName>sample.regress.out</FileName> file was from the postgres-1.01 release
	constructed by Jolly Chen and is included here for reference. 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>
  
</Chapter>