Regression Test
Regression test instructions and analysis.
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.
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 PostgreSQL v6.1 onward
the regression tests are current for every official release.
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.
The regression testing notes below assume the following (except where noted):
Commands are Unix-compatible. See note below.
Defaults are used except where noted.
User postgres is the Postgres superuser.
The source path is /usr/src/pgsql (other paths are possible).
The runtime path is /usr/local/pgsql (other paths are possible).
Regression Environment
The regression test is invoked by the make command which compiles
a C 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
./expected/*.out files. The localization replaces macros in the source
files with absolute pathnames and user names.
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.
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:
setenv TZ PST8PDT
date
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:
setenv PGTZ PST8PDT7,M04.01.0,M10.05.03
Directory Layout
This should become a table in the previous section.
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.
Regression Test Procedure
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 ps and tar vary wildly on what options you should use on each
platform. Use common sense before typing in these commands.
For a fresh install or upgrading from previous releases of
Postgres:
Postgres Regression Configuration
The file /usr/src/pgsql/src/test/regress/README has detailed
instructions for running and interpreting the regression tests.
A short version follows here:
If the postmaster is not already running, start the postmaster on an
available window by typing
postmaster
or start the postmaster daemon running in the background by typing
cd
nohup postmaster > regress.log 2>&1 &
Run postmaster from your Postgres super user account (typically
account postgres).
Do not run postmaster from the root account.
If you have previously invoked the regression test, clean up the
working directory with:
cd /usr/src/pgsql/src/test/regress
gmake clean
You do not need to type "gmake clean" if this is the first time you
are running the tests.
Build the regression test. Type
cd /usr/src/pgsql/src/test/regress
gmake all
Run the regression tests. Type
cd /usr/src/pgsql/src/test/regress
gmake runtest
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:
cd /usr/src/pgsql/src/test/regress
diff -w expected/float8.out results
After running the tests and examining the results, type
dropdb regression
cd /usr/src/pgsql/src/test/regress
gmake clean
to recover the temporary disk space used by the tests.
Regression Analysis
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.)
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
Postgres.
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.
Error message differences
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.
OID differences
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.
Date and time differences
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.
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.
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.
Floating point differences
Some of the tests involve computing 64-bit (float8) numbers from table
columns. Differences in results involving mathematical functions of
float8 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.
Some systems signal errors from pow() and exp() differently from
the mechanism expected by the current Postgres code.
Polygon differences
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 float8 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:
QUERY: SELECT * from street;
QUERY: SELECT * from iexit;
Random differences
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
diff results/random.out expected/random.out
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.
The expected
files
The ./expected/*.out files were adapted from the original monolithic
expected.input 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 expected.input file was created on a SPARC Solaris 2.4
system using the postgres5-1.02a5.tar.gz 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 sample.regress.out 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 Makefile.global
in the postgres-1.01 release has PORTNAME=alpha.