database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-30 21:42:05 +03:00
Code Activity

Redesign DISTINCT ON as discussed in pgsql-sql 1/25/00: syntax is now

Browse Source 
SELECT DISTINCT ON (expr [, expr ...]) targetlist ...
and there is a check to make sure that the user didn't specify an ORDER BY
that's incompatible with the DISTINCT operation.
Reimplement nodeUnique and nodeGroup to use the proper datatype-specific
equality function for each column being compared --- they used to do
bitwise comparisons or convert the data to text strings and strcmp().
(To add insult to injury, they'd look up the conversion functions once
for each tuple...)  Parse/plan representation of DISTINCT is now a list
of SortClause nodes.
initdb forced by querytree change...
This commit is contained in:
Tom Lane
2000-01-27 18:11:50 +00:00
parent 3f0074e403
commit dd979f66be
32 changed files with 638 additions and 576 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
src/backend/optimizer/plan/createplan.c
View File

@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.81 2000/01/26 05:56:37 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.82 2000/01/27 18:11:30 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1342,16 +1342,19 @@ make_group(List *tlist,
}
/*
* The uniqueAttr argument must be a null-terminated string,
* either the name of the attribute to select unique on
* or "*"
* distinctList is a list of SortClauses, identifying the targetlist items
* that should be considered by the Unique filter.
*/
Unique *
make_unique(List *tlist, Plan *lefttree, char *uniqueAttr)
make_unique(List *tlist, Plan *lefttree, List *distinctList)
{
Unique *node = makeNode(Unique);
Plan *plan = &node->plan;
int numCols = length(distinctList);
int keyno = 0;
AttrNumber *uniqColIdx;
List *slitem;
copy_plan_costsize(plan, lefttree);
plan->state = (EState *) NULL;
@ -1361,10 +1364,22 @@ make_unique(List *tlist, Plan *lefttree, char *uniqueAttr)
plan->righttree = NULL;
node->nonameid = _NONAME_RELATION_ID_;
node->keycount = 0;
if (strcmp(uniqueAttr, "*") == 0)
node->uniqueAttr = NULL;
else
node->uniqueAttr = pstrdup(uniqueAttr);
/* convert SortClause list into array of attr indexes, as wanted by exec */
Assert(numCols > 0);
uniqColIdx = (AttrNumber *) palloc(sizeof(AttrNumber) * numCols);
foreach(slitem, distinctList)
{
SortClause *sortcl = (SortClause *) lfirst(slitem);
TargetEntry *tle = get_sortgroupclause_tle(sortcl, tlist);
uniqColIdx[keyno++] = tle->resdom->resno;
}
node->numCols = numCols;
node->uniqColIdx = uniqColIdx;
return node;
}