INTERSECT and EXCEPT is available for postgresql-v6.4!
The patch against v6.4 is included at the end of the current text
(in uuencoded form!)
I also included the text of my Master's Thesis. (a postscript
version). I hope that you find something of it useful and would be
happy if parts of it find their way into the PostgreSQL documentation
project (If so, tell me, then I send the sources of the document!)
The contents of the document are:
-) The first chapter might be of less interest as it gives only an
overview on SQL.
-) The second chapter gives a description on much of PostgreSQL's
features (like user defined types etc. and how to use these features)
-) The third chapter starts with an overview of PostgreSQL's internal
structure with focus on the stages a query has to pass (i.e. parser,
planner/optimizer, executor). Then a detailed description of the
implementation of the Having clause and the Intersect/Except logic is
given.
Originally I worked on v6.3.2 but never found time enough to prepare
and post a patch. Now I applied the changes to v6.4 to get Intersect
and Except working with the new version. Chapter 3 of my documentation
deals with the changes against v6.3.2, so keep that in mind when
comparing the parts of the code printed there with the patched sources
of v6.4.
Here are some remarks on the patch. There are some things that have
still to be done but at the moment I don't have time to do them
myself. (I'm doing my military service at the moment) Sorry for that
:-(
-) I used a rewrite technique for the implementation of the Except/Intersect
logic which rewrites the query to a semantically equivalent query before
it is handed to the rewrite system (for views, rules etc.), planner,
executor etc.
-) In v6.3.2 the types of the attributes of two select statements
connected by the UNION keyword had to match 100%. In v6.4 the types
only need to be familiar (i.e. int and float can be mixed). Since this
feature did not exist when I worked on Intersect/Except it
does not work correctly for Except/Intersect queries WHEN USED IN
COMBINATION WITH UNIONS! (i.e. sometimes the wrong type is used for the
resulting table. This is because until now the types of the attributes of
the first select statement have been used for the resulting table.
When Intersects and/or Excepts are used in combination with Unions it
might happen, that the first select statement of the original query
appears at another position in the query which will be executed. The reason
for this is the technique used for the implementation of
Except/Intersect which does a query rewrite!)
NOTE: It is NOT broken for pure UNION queries and pure INTERSECT/EXCEPT
queries!!!
-) I had to add the field intersect_clause to some data structures
but did not find time to implement printfuncs for the new field.
This does NOT break the debug modes but when an Except/Intersect
is used the query debug output will be the already rewritten query.
-) Massive changes to the grammar rules for SELECT and INSERT statements
have been necessary (see comments in gram.y and documentation for
deatails) in order to be able to use mixed queries like
(SELECT ... UNION (SELECT ... EXCEPT SELECT)) INTERSECT SELECT...;
-) When using UNION/EXCEPT/INTERSECT you will get:
NOTICE: equal: "Don't know if nodes of type xxx are equal".
I did not have time to add comparsion support for all the needed nodes,
but the default behaviour of the function equal met my requirements.
I did not dare to supress this message!
That's the reason why the regression test for union will fail: These
messages are also included in the union.out file!
-) Somebody of you changed the union_planner() function for v6.4
(I copied the targetlist to new_tlist and that was removed and
replaced by a cleanup of the original targetlist). These chnages
violated some having queries executed against views so I changed
it back again. I did not have time to examine the differences between the
two versions but now it works :-)
If you want to find out, try the file queries/view_having.sql on
both versions and compare the results . Two queries won't produce a
correct result with your version.
regards
Stefan
seem to be portable (HPUX doesn't like it, anyway). Also, clean up
StreamConnection(), which was mis-coded to assume that the address
family field is already set when it's called.
Here's another patch for the libpq backend areas. This patch removes all
usage of "FILE *" on the communications channel. It also cleans up the
comments and headers in the pqcomm.c file - a lot of things were either
missing or incorrect. Finally, it removes a couple of unused functions
(leftovers from the time of shared code between the libpq backend and
frontend).
Here is a first patch to cleanup the backend side of libpq.
This patch removes all external dependencies on the "Pfin" and "Pfout" that
are declared in pqcomm.h. These variables are also changed to "static" to
make sure.
Almost all the change is in the handler of the "copy" command - most other
areas of the backend already used the correct functions.
This change will make the way for cleanup of the internal stuff there - now
that all the functions accessing the file descriptors are confined to a
single directory.
when deciding whether a field is a year field. Assume *anything* longer
than 2 digits (if it isn't a special-case doy) is a valid year.
This should fix the "Y1K" and "Y10K" problems
pointed out by Massimo recently.
Check usage of BC to require a positive-valued year; before just used it
to flip the sign of the year without checking. This led to problems
near year zero.
Allow a 5 digit "concatenated date" of 2 digit year plus day of year.
Do 2->4 digit year correction for 6 and 5 digit "concatenated dates".
Somehow forgot this originally. Guess not many folks use it...
I think NAN is already guaranteed to be there from Jan's work on NUMERIC,
but perhaps HUGE_VAL needs some #ifndef's in the same place.
Should also include "-Infinity" as -HUGE_VAL sometime; not there yet.
to give HAVE_TM_ZONE priority. This fixes glibc2 machines and any other
machine which passes both tests in configure.
Repair HAVE_TM_ZONE code which stuffs tm structure with date type values.
Same problems as were originally there before v6.1, but never noticed.
Thanks to Oleg for nagging :)
Nakajima. Since he is not subscribing the mailing list, I'm posting
his patches by his request. According to him, he has successfully
compiled and passed the regression test on Mac SE/30 running
NetBSD/m68k. Also, another person has reported that with the patches
PostgreSQL is working on NetBSD/sun3 too.
--
Tatsuo Ishii
6.4.1. Here is the list:
- The type int8 now works. In fact, the bug(s) were in
src/backend/port/snprintf.c, so int8 is probably broken in every platform
that hasn't a native snprintf/vsnprintf. The type itself worked as
expected, only the output was wrong. Anyway, this patch should be checked
in other platforms.
- The regression tests for int2 and int4, which were broken due to
differences in the error messages, are fixed.
- The regression test for float8, which was broken in the reference
platform, is also fixed. I don't know if the new file (float8-OSF1.out)
will work on other platforms, but it might be worth to try it.
- Two new template files are provided (alpha_cc, which includes
optimization, and alpha_gcc), and src/templates/.similar is updated
accordingly. src/templates/alpha should be removed from the distribution.
*IMPORTANT NOTE*: I don't know if you can use gcc to compile postgres;
I've written the alpha_gcc file because alpha_cc has some flags that are
specific to DEC C.
- There is a (very basic) Digital Unix specific FAQ in
doc/FAQ_DigitalUnix.
--
-------------------------------------------------------------------
Pedro José Lobo Perea Tel: +34 91 336 78 19
