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Restructure building of join relation targetlists so that a join plan

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node emits only those vars that are actually needed above it in the
plan tree.  (There were comments in the code suggesting that this was
done at some point in the dim past, but for a long time we have just
made join nodes emit everything that either input emitted.)  Aside from
being marginally more efficient, this fixes the problem noted by Peter
Eisentraut where a join above an IN-implemented-as-join might fail,
because the subplan targetlist constructed in the latter case didn't
meet the expectation of including everything.
Along the way, fix some places that were O(N^2) in the targetlist
length.  This is not all the trouble spots for wide queries by any
means, but it's a step forward.
This commit is contained in:
Tom Lane
2003-06-29 23:05:05 +00:00
parent cf883ea95c
commit 835bb975d8
16 changed files with 334 additions and 221 deletions
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35
src/backend/optimizer/path/allpaths.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.102 2003/04/24 23:43:09 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.103 2003/06/29 23:05:04 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -235,6 +235,9 @@ set_inherited_rel_pathlist(Query *root, RelOptInfo *rel,
RangeTblEntry *childrte;
Oid childOID;
RelOptInfo *childrel;
List *reltlist;
List *parentvars;
List *childvars;
childrte = rt_fetch(childRTindex, root->rtable);
childOID = childrte->relid;
@ -251,21 +254,24 @@ set_inherited_rel_pathlist(Query *root, RelOptInfo *rel,
* Copy the parent's targetlist and restriction quals to the
* child, with attribute-number adjustment as needed. We don't
* bother to copy the join quals, since we can't do any joining of
* the individual tables.
* the individual tables. Also, we just zap attr_needed rather
* than trying to adjust it; it won't be looked at in the child.
*/
childrel->targetlist = (List *)
adjust_inherited_attrs((Node *) rel->targetlist,
reltlist = FastListValue(&rel->reltargetlist);
reltlist = (List *)
adjust_inherited_attrs((Node *) reltlist,
parentRTindex,
parentOID,
childRTindex,
childOID);
FastListFromList(&childrel->reltargetlist, reltlist);
childrel->attr_needed = NULL;
childrel->baserestrictinfo = (List *)
adjust_inherited_attrs((Node *) rel->baserestrictinfo,
parentRTindex,
parentOID,
childRTindex,
childOID);
childrel->baserestrictcost = rel->baserestrictcost;
/*
* Now compute child access paths, and save the cheapest.
@ -274,10 +280,27 @@ set_inherited_rel_pathlist(Query *root, RelOptInfo *rel,
subpaths = lappend(subpaths, childrel->cheapest_total_path);
/* Also update total size estimates */
/*
* Propagate size information from the child back to the parent.
* For simplicity, we use the largest widths from any child as the
* parent estimates.
*/
rel->rows += childrel->rows;
if (childrel->width > rel->width)
rel->width = childrel->width;
childvars = FastListValue(&childrel->reltargetlist);
foreach(parentvars, FastListValue(&rel->reltargetlist))
{
Var *parentvar = (Var *) lfirst(parentvars);
Var *childvar = (Var *) lfirst(childvars);
int parentndx = parentvar->varattno - rel->min_attr;
int childndx = childvar->varattno - childrel->min_attr;
if (childrel->attr_widths[childndx] > rel->attr_widths[parentndx])
rel->attr_widths[parentndx] = childrel->attr_widths[childndx];
childvars = lnext(childvars);
}
}
/*