database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-28 23:42:10 +03:00
Code Activity

Rearrange top-level rewrite operations so that EXPLAIN works

Browse Source 
on queries involving UNION, EXCEPT, INTERSECT.
This commit is contained in:
Tom Lane
1999-05-09 23:31:47 +00:00
parent 6458daa180
commit 0b69d8a27c
3 changed files with 125 additions and 106 deletions
Download Patch File Download Diff File Expand all files Collapse all files

63
src/backend/rewrite/rewriteHandler.c
View File

@ -6,7 +6,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.37 1999/02/22 05:26:46 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.38 1999/05/09 23:31:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -59,8 +59,6 @@ static void modifyAggrefChangeVarnodes(Node **nodePtr, int rt_index, int new_ind
static void modifyAggrefDropQual(Node **nodePtr, Node *orignode, Expr *expr);
static SubLink *modifyAggrefMakeSublink(Expr *origexp, Query *parsetree);
static void modifyAggrefQual(Node **nodePtr, Query *parsetree);
static Query *fireRIRrules(Query *parsetree);
@ -2634,12 +2632,12 @@ RewritePreprocessQuery(Query *parsetree)
/*
* QueryRewrite -
* BasicQueryRewrite -
* rewrite one query via query rewrite system, possibly returning 0
* or many queries
*/
List *
QueryRewrite(Query *parsetree)
static List *
BasicQueryRewrite(Query *parsetree)
{
List *querylist;
List *results = NIL;
@ -2672,10 +2670,57 @@ QueryRewrite(Query *parsetree)
}
return results;
}
/***S*I***/
/* This function takes two targetlists as arguments and checks if the targetlists are compatible
* (i.e. both select for the same number of attributes and the types are compatible
/*
* QueryRewrite -
* Primary entry point to the query rewriter.
* Rewrite one query via query rewrite system, possibly returning 0
* or many queries.
*
* NOTE: The code in QueryRewrite was formerly in pg_parse_and_plan(), and was
* moved here so that it would be invoked during EXPLAIN. The division of
* labor between this routine and BasicQueryRewrite is not obviously correct
* ... at least not to me ... tgl 5/99.
*/
List *
QueryRewrite(Query *parsetree)
{
List *rewritten,
*rewritten_item;
/***S*I***/
/* Rewrite Union, Intersect and Except Queries
* to normal Union Queries using IN and NOT IN subselects */
if (parsetree->intersectClause)
parsetree = Except_Intersect_Rewrite(parsetree);
/* Rewrite basic queries (retrieve, append, delete, replace) */
rewritten = BasicQueryRewrite(parsetree);
/*
* Rewrite the UNIONS.
*/
foreach (rewritten_item, rewritten)
{
Query *qry = (Query *) lfirst(rewritten_item);
List *union_result = NIL;
List *union_item;
foreach (union_item, qry->unionClause)
{
union_result = nconc(union_result,
BasicQueryRewrite((Query *) lfirst(union_item)));
}
qry->unionClause = union_result;
}
return rewritten;
}
/***S*I***/
/* This function takes two targetlists as arguments and checks if the
* targetlists are compatible (i.e. both select for the same number of
* attributes and the types are compatible */
void check_targetlists_are_compatible(List *prev_target, List *current_target)
{
List *next_target;