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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="REGRESS-EVALUATION"
>30.2. Test Evaluation</A
></H1
><P
> Some properly installed and fully functional
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> installations can
<SPAN
CLASS="QUOTE"
>"fail"</SPAN
> some of these regression tests due to
platform-specific artifacts such as varying floating-point representation
and message wording. The tests are currently evaluated using a simple
<TT
CLASS="COMMAND"
>diff</TT
> comparison against the outputs
generated on a reference system, so the results are sensitive to
small system differences. When a test is reported as
<SPAN
CLASS="QUOTE"
>"failed"</SPAN
>, always examine the differences between
expected and actual results; you might find that the
differences are not significant. Nonetheless, we still strive to
maintain accurate reference files across all supported platforms,
so it can be expected that all tests pass.
</P
><P
> The actual outputs of the regression tests are in files in the
<TT
CLASS="FILENAME"
>src/test/regress/results</TT
> directory. The test
script uses <TT
CLASS="COMMAND"
>diff</TT
> to compare each output
file against the reference outputs stored in the
<TT
CLASS="FILENAME"
>src/test/regress/expected</TT
> directory. Any
differences are saved for your inspection in
<TT
CLASS="FILENAME"
>src/test/regress/regression.diffs</TT
>.
(When running a test suite other than the core tests, these files
of course appear in the relevant subdirectory,
not <TT
CLASS="FILENAME"
>src/test/regress</TT
>.)
</P
><P
> If for some reason a particular platform generates a <SPAN
CLASS="QUOTE"
>"failure"</SPAN
>
for a given test, but inspection of the output convinces you that
the result is valid, you can add a new comparison file to silence
the failure report in future test runs. See
<A
HREF="regress-variant.html"
>Section 30.3</A
> for details.
</P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN38129"
>30.2.1. Error Message Differences</A
></H2
><P
> Some of the regression tests involve intentional invalid input
values. Error messages can come from either the
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> code or from the host
platform system routines. In the latter case, the messages can
vary between platforms, but should reflect similar
information. These differences in messages will result in a
<SPAN
CLASS="QUOTE"
>"failed"</SPAN
> regression test that can be validated by
inspection.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN38134"
>30.2.2. Locale Differences</A
></H2
><P
> If you run the tests against a server that was
initialized with a collation-order locale other than C, then
there might be differences due to sort order and subsequent
failures. The regression test suite is set up to handle this
problem by providing alternate result files that together are
known to handle a large number of locales.
</P
><P
> To run the tests in a different locale when using the
temporary-installation method, pass the appropriate
locale-related environment variables on
the <TT
CLASS="COMMAND"
>gmake</TT
> command line, for example:
</P><PRE
CLASS="PROGRAMLISTING"
>gmake check LANG=de_DE.utf8</PRE
><P>
(The regression test driver unsets <TT
CLASS="ENVAR"
>LC_ALL</TT
>, so it
does not work to choose the locale using that variable.) To use
no locale, either unset all locale-related environment variables
(or set them to <TT
CLASS="LITERAL"
>C</TT
>) or use the following
special invocation:
</P><PRE
CLASS="PROGRAMLISTING"
>gmake check NO_LOCALE=1</PRE
><P>
When running the tests against an existing installation, the
locale setup is determined by the existing installation. To
change it, initialize the database cluster with a different
locale by passing the appropriate options
to <TT
CLASS="COMMAND"
>initdb</TT
>.
</P
><P
> In general, it is advisable to try to run the
regression tests in the locale setup that is wanted for
production use, as this will exercise the locale- and
encoding-related code portions that will actually be used in
production. Depending on the operating system environment, you
might get failures, but then you will at least know what
locale-specific behaviors to expect when running real
applications.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN38145"
>30.2.3. Date and Time Differences</A
></H2
><P
> Most of the date and time results are dependent on the time zone
environment. The reference files are generated for time zone
<TT
CLASS="LITERAL"
>PST8PDT</TT
> (Berkeley, California), and there will be
apparent failures if the tests are not run with that time zone setting.
The regression test driver sets environment variable
<TT
CLASS="ENVAR"
>PGTZ</TT
> to <TT
CLASS="LITERAL"
>PST8PDT</TT
>, which normally
ensures proper results.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN38151"
>30.2.4. Floating-Point Differences</A
></H2
><P
> Some of the tests involve computing 64-bit floating-point numbers (<TT
CLASS="TYPE"
>double
precision</TT
>) from table columns. Differences in
results involving mathematical functions of <TT
CLASS="TYPE"
>double
precision</TT
> columns have been observed. The <TT
CLASS="LITERAL"
>float8</TT
> and
<TT
CLASS="LITERAL"
>geometry</TT
> tests are particularly prone to small differences
across platforms, or even with different compiler optimization settings.
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.
</P
><P
> Some systems display minus zero as <TT
CLASS="LITERAL"
>-0</TT
>, while others
just show <TT
CLASS="LITERAL"
>0</TT
>.
</P
><P
> Some systems signal errors from <CODE
CLASS="FUNCTION"
>pow()</CODE
> and
<CODE
CLASS="FUNCTION"
>exp()</CODE
> differently from the mechanism
expected by the current <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>
code.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN38165"
>30.2.5. Row Ordering Differences</A
></H2
><P
>You might see differences in which the same rows are output in a
different order than what appears in the expected file. In most cases
this is not, strictly speaking, a bug. Most of the regression test
scripts are not so pedantic as to use an <TT
CLASS="LITERAL"
>ORDER BY</TT
> for every single
<TT
CLASS="LITERAL"
>SELECT</TT
>, and so their result row orderings are not well-defined
according to the SQL specification. In practice, since we are
looking at the same queries being executed on the same data by the same
software, we usually get the same result ordering on all platforms,
so the lack of <TT
CLASS="LITERAL"
>ORDER BY</TT
> is not a problem. Some queries do exhibit
cross-platform ordering differences, however. When testing against an
already-installed server, ordering differences can also be caused by
non-C locale settings or non-default parameter settings, such as custom values
of <TT
CLASS="VARNAME"
>work_mem</TT
> or the planner cost parameters.
</P
><P
>Therefore, if you see an ordering difference, it's not something to
worry about, unless the query does have an <TT
CLASS="LITERAL"
>ORDER BY</TT
> that your
result is violating. However, please report it anyway, so that we can add an
<TT
CLASS="LITERAL"
>ORDER BY</TT
> to that particular query to eliminate the bogus
<SPAN
CLASS="QUOTE"
>"failure"</SPAN
> in future releases.
</P
><P
>You might wonder why we don't order all the regression test queries explicitly
to get rid of this issue once and for all. The reason is that that would
make the regression tests less useful, not more, since they'd tend
to exercise query plan types that produce ordered results to the
exclusion of those that don't.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN38177"
>30.2.6. Insufficient Stack Depth</A
></H2
><P
> If the <TT
CLASS="LITERAL"
>errors</TT
> test results in a server crash
at the <TT
CLASS="LITERAL"
>select infinite_recurse()</TT
> command, it means that
the platform's limit on process stack size is smaller than the
<A
HREF="runtime-config-resource.html#GUC-MAX-STACK-DEPTH"
>max_stack_depth</A
> parameter indicates. This
can be fixed by running the server under a higher stack
size limit (4MB is recommended with the default value of
<TT
CLASS="VARNAME"
>max_stack_depth</TT
>). If you are unable to do that, an
alternative is to reduce the value of <TT
CLASS="VARNAME"
>max_stack_depth</TT
>.
</P
><P
> On platforms supporting <CODE
CLASS="FUNCTION"
>getrlimit()</CODE
>, the server should
automatically choose a safe value of <TT
CLASS="VARNAME"
>max_stack_depth</TT
>;
so unless you've manually overridden this setting, a failure of this
kind is a reportable bug.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN38188"
>30.2.7. The <SPAN
CLASS="QUOTE"
>"random"</SPAN
> Test</A
></H2
><P
> The <TT
CLASS="LITERAL"
>random</TT
> test script is intended to produce
random results. In very rare cases, this causes that regression
test to fail. Typing:
</P><PRE
CLASS="PROGRAMLISTING"
>diff results/random.out expected/random.out</PRE
><P>
should produce only one or a few lines of differences. You need
not worry unless the random test fails repeatedly.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN38194"
>30.2.8. Configuration Parameters</A
></H2
><P
> When running the tests against an existing installation, some non-default
parameter settings could cause the tests to fail. For example, changing
parameters such as <TT
CLASS="VARNAME"
>enable_seqscan</TT
> or
<TT
CLASS="VARNAME"
>enable_indexscan</TT
> could cause plan changes that would
affect the results of tests that use <TT
CLASS="COMMAND"
>EXPLAIN</TT
>.
</P
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