conditions.  There are some pretty bogus heuristics in prepqual.c that
try to decide whether to output CNF or DNF format; they need to be replaced,
likely.  Right now the code is probably too willing to choose DNF form,
which might hurt performance in some cases that used to work OK.
But at least we have a foundation to build on.

Most parts of the planner should ignore, or indeed never even see, uplevel
Vars because they will be or have been replaced by Params.  There were a
couple of places that got it wrong though, probably my fault from recent
changes...

case where ORDER BY and GROUP BY request the same sort order.

and fix_opids processing to a single recursive pass over the plan tree
executed at the very tail end of planning, rather than haphazardly here
and there at different places.  Now that tlist Vars do not get modified
until the very end, it's possible to get rid of the klugy var_equal and
match_varid partial-matching routines, and just use plain equal()
throughout the optimizer.  This is a step towards allowing merge and
hash joins to be done on expressions instead of only Vars ...

sort order down into planner, instead of handling it only at the very top
level of the planner.  This fixes many things.  An explicit sort is now
avoided if there is a cheaper alternative (typically an indexscan) not
only for ORDER BY, but also for the internal sort of GROUP BY.  It works
even when there is no other reason (such as a WHERE condition) to consider
the indexscan.  It works for indexes on functions.  It works for indexes
on functions, backwards.  It's just so cool...

CAUTION: I have changed the representation of SortClause nodes, therefore
THIS UPDATE BREAKS STORED RULES.  You will need to initdb.

> >
> > was implemented by Jan Wieck.
> > His work is for ascending order cases.
> >
> > Here is a patch to prevent sorting also in descending
> > order cases.
> > Because I had already changed _bt_first() to position
> > backward correctly before v6.5,this patch would work.
> >
Hiroshi Inoue
Inoue@tpf.co.jp

sure if they are all fixed, because rewriter is now the stumbling block,
but at least some cases work that did not work before.

returned NULL, which it will do in some cases where an elog(ERROR) would
probably be more appropriate.  For the moment, generate a not-very-
informative error message rather than proceeding to certain coredump.
Probably ought to think about making query_planner elog instead of
returning NULL, but this is at least a safe change for now.

inheritance ... basically it was completely busted :-(

lists are now plain old garden-variety Lists, allocated with palloc,
rather than specialized expansible-array data allocated with malloc.
This substantially simplifies their handling and eliminates several
sources of memory leakage.
Several basic types of erroneous queries (syntax error, attempt to
insert a duplicate key into a unique index) now demonstrably leak
zero bytes per query.

in Resdom and GroupClause so changing of resno's doesn't confuse
the grouping any more.

Jan

real affect now.

nodes with HAVING qualifier of upper plan.  Have not seen any failures,
just being a little bit paranoid...

from EXCEPT/HAVING patch.  Cases involving nontrivial GROUP BY expressions
now work again.  Also, the code is at least somewhat better documented...

This fixes a few of the problems Hiroshi Inoue complained of, but
I have not touched the rewrite-related issues.

change functionality, but makes the code more ANSI C'ish.
My AIX xlc compiler barfs on all of these. Can someone please
review and apply to current.

 <<port.patch>>
Thanks
Andreas

From: Tatsuo Ishii <t-ishii@sra.co.jp>

Ok. I made patches replacing all of "#if FALSE" or "#if 0" to "#ifdef
NOT_USED" for current. I have tested these patches in that the
postgres binaries are identical.

allways present tuples in the requested order.

Jan

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

I will be cleaning this up more before the Oct 1 deadline.

David Hartwig.  AND/OR fix.

was tested with Linux/GCC.  I still have some issues with with the
snprintf() function.

David Hartwig

   now. Here some tested features, (examples included in the patch):

1.1) Subselects in the having clause 1.2) Double nested subselects
1.3) Subselects used in the where clause and in the having clause
     simultaneously 1.4) Union Selects using having 1.5) Indexes
on the base relations are used correctly 1.6) Unallowed Queries
are prevented (e.g. qualifications in the
     having clause that belong to the where clause) 1.7) Insert
into as select

2) Queries using the having clause on view relations also work
   but there are some restrictions:

2.1) Create View as Select ... Having ...; using base tables in
the select 2.1.1) The Query rewrite system:

2.1.2) Why are only simple queries allowed against a view from 2.1)
? 2.2) Select ... from testview1, testview2, ... having...; 3) Bug
in ExecMergeJoin ??


Regards Stefan