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Commitbd8ffc6

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Hi!
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 postscriptversion). I hope that you find something of it useful and would behappy if parts of it find their way into the PostgreSQL documentationproject (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 prepareand post a patch. Now I applied the changes to v6.4 to get Intersectand Except working with the new version. Chapter 3 of my documentationdeals with the changes against v6.3.2, so keep that in mind whencomparing the parts of the code printed there with the patched sourcesof v6.4.Here are some remarks on the patch. There are some things that havestill to be done but at the moment I don't have time to do themmyself. (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
1 parent52065cf commitbd8ffc6

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19 files changed

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19 files changed

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‎src/backend/executor/execAmi.c

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*
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* Copyright (c) 1994, Regents of the University of California
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*
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* $Id: execAmi.c,v 1.28 1998/12/14 08:11:02 scrappy Exp $
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* $Id: execAmi.c,v 1.29 1999/01/18 00:09:45 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include"executor/nodeNestloop.h"
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#include"executor/nodeHashjoin.h"
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#include"executor/nodeHash.h"
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/***S*I***/
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#include"executor/nodeGroup.h"
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#include"executor/nodeAgg.h"
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#include"executor/nodeGroup.h"
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#include"executor/nodeResult.h"

‎src/backend/executor/nodeAgg.c

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* As long as the retrieved group does not match the
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* qualifications it is ignored and the next group is fetched
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*/
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qual_result=ExecQual(fix_opids(node->plan.qual),econtext);
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if(node->plan.qual!=NULL){
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qual_result=ExecQual(fix_opids(node->plan.qual),econtext);
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}
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if (oneTuple)
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pfree(oneTuple);
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}

‎src/backend/nodes/outfuncs.c

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*
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* Copyright (c) 1994, Regents of the University of California
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*
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* $Id: outfuncs.c,v 1.58 1998/12/20 07:13:36 scrappy Exp $
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* $Id: outfuncs.c,v 1.59 1999/01/18 00:09:45 momjian Exp $
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*
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* NOTES
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* Every (plan) node in POSTGRES has an associated "out" routine which
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node->hasSubLinks ?"true" :"false");
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_outNode(str,node->unionClause);
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appendStringInfo(str," :intersectClause ");
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_outNode(str,node->intersectClause);
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appendStringInfo(str," :limitOffset ");
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_outNode(str,node->limitOffset);
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‎src/backend/nodes/readfuncs.c

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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/nodes/readfuncs.c,v 1.40 1998/12/14 00:01:47 thomas Exp $
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* $Header: /cvsroot/pgsql/src/backend/nodes/readfuncs.c,v 1.41 1999/01/18 00:09:46 momjian Exp $
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*
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* NOTES
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* Most of the read functions for plan nodes are tested. (In fact, they
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token=lsptok(NULL,&length);/* skip :unionClause */
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local_node->unionClause=nodeRead(true);
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/***S*I***/
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token=lsptok(NULL,&length);/* skip :intersectClause */
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local_node->intersectClause=nodeRead(true);
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token=lsptok(NULL,&length);/* skip :limitOffset */
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local_node->limitOffset=nodeRead(true);
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