/*
* Generate plan for a UNION or UNION ALL node
*/
static Plan *
generate_union_plan(SetOperationStmt *op, Query *parse,
List *refnames_tlist)
{
List *planlist;
List *tlist;
Plan *plan;
/*
* If any of my children are identical UNION nodes (same op, all-flag,
* and colTypes) then they can be merged into this node so that we
* generate only one Append and Sort for the lot. Recurse to find
* such nodes and compute their children's plans.
*/
planlist = nconc(recurse_union_children(op->larg, parse,
op, refnames_tlist),
recurse_union_children(op->rarg, parse,
op, refnames_tlist));
/*
* Generate tlist for Append plan node.
*
* The tlist for an Append plan isn't important as far as the Append is
* concerned, but we must make it look real anyway for the benefit of
* the next plan level up.
*/
tlist = generate_append_tlist(op->colTypes, false,
planlist, refnames_tlist);
/*
* Append the child results together.
*/
plan = (Plan *) make_append(planlist, false, tlist);
/*
* For UNION ALL, we just need the Append plan. For UNION, need to
* add Sort and Unique nodes to produce unique output.
*/
if (!op->all)
{
List *sortList;
tlist = copyObject(tlist);
sortList = addAllTargetsToSortList(NULL, NIL, tlist, false);
plan = (Plan *) make_sort_from_sortclauses(parse, tlist,
plan, sortList);
plan = (Plan *) make_unique(tlist, plan, sortList);
}
return plan;
}
/*
* Generate plan for an INTERSECT, INTERSECT ALL, EXCEPT, or EXCEPT ALL node
*/
static Plan *
generate_nonunion_plan(SetOperationStmt *op, Query *parse,
List *refnames_tlist)
{
Plan *lplan,
*rplan,
*plan;
List *tlist,
*sortList,
*planlist;
SetOpCmd cmd;
/* Recurse on children, ensuring their outputs are marked */
lplan = recurse_set_operations(op->larg, parse,
op->colTypes, false, 0,
refnames_tlist);
rplan = recurse_set_operations(op->rarg, parse,
op->colTypes, false, 1,
refnames_tlist);
planlist = makeList2(lplan, rplan);
/*
* Generate tlist for Append plan node.
*
* The tlist for an Append plan isn't important as far as the Append is
* concerned, but we must make it look real anyway for the benefit of
* the next plan level up. In fact, it has to be real enough that the
* flag column is shown as a variable not a constant, else setrefs.c
* will get confused.
*/
tlist = generate_append_tlist(op->colTypes, true,
planlist, refnames_tlist);
/*
* Append the child results together.
*/
plan = (Plan *) make_append(planlist, false, tlist);
/*
* Sort the child results, then add a SetOp plan node to generate the
* correct output.
*/
tlist = copyObject(tlist);
sortList = addAllTargetsToSortList(NULL, NIL, tlist, false);
plan = (Plan *) make_sort_from_sortclauses(parse, tlist, plan, sortList);
switch (op->op)
{
case SETOP_INTERSECT:
cmd = op->all ? SETOPCMD_INTERSECT_ALL : SETOPCMD_INTERSECT;
break;
case SETOP_EXCEPT:
cmd = op->all ? SETOPCMD_EXCEPT_ALL : SETOPCMD_EXCEPT;
break;
default:
elog(ERROR, "unrecognized set op: %d",
(int) op->op);
cmd = SETOPCMD_INTERSECT; /* keep compiler quiet */
break;
}
plan = (Plan *) make_setop(cmd, tlist, plan, sortList,
length(op->colTypes) + 1);
return plan;
}
/*
* Generate plan for a UNION or UNION ALL node
*/
static Plan *
generate_union_plan(SetOperationStmt *op, PlannerInfo *root,
double tuple_fraction,
List *refnames_tlist,
List **sortClauses)
{
List *planlist;
List *tlist;
Plan *plan;
/*
* If plain UNION, tell children to fetch all tuples.
*
* Note: in UNION ALL, we pass the top-level tuple_fraction unmodified to
* each arm of the UNION ALL. One could make a case for reducing the
* tuple fraction for later arms (discounting by the expected size of the
* earlier arms' results) but it seems not worth the trouble. The normal
* case where tuple_fraction isn't already zero is a LIMIT at top level,
* and passing it down as-is is usually enough to get the desired result
* of preferring fast-start plans.
*/
if (!op->all)
tuple_fraction = 0.0;
/*
* If any of my children are identical UNION nodes (same op, all-flag, and
* colTypes) then they can be merged into this node so that we generate
* only one Append and Sort for the lot. Recurse to find such nodes and
* compute their children's plans.
*/
planlist = list_concat(recurse_union_children(op->larg, root,
tuple_fraction,
op, refnames_tlist),
recurse_union_children(op->rarg, root,
tuple_fraction,
op, refnames_tlist));
/*
* Generate tlist for Append plan node.
*
* The tlist for an Append plan isn't important as far as the Append is
* concerned, but we must make it look real anyway for the benefit of the
* next plan level up.
*/
tlist = generate_append_tlist(op->colTypes, false,
planlist, refnames_tlist);
/*
* Append the child results together.
*/
plan = (Plan *) make_append(planlist, false, tlist);
/*
* For UNION ALL, we just need the Append plan. For UNION, need to add
* Sort and Unique nodes to produce unique output.
*/
if (!op->all)
{
List *sortList;
sortList = addAllTargetsToSortList(NULL, NIL, tlist, false);
if (sortList)
{
plan = (Plan *) make_sort_from_sortclauses(root, sortList, plan);
plan = (Plan *) make_unique(plan, sortList);
}
*sortClauses = sortList;
}
else
*sortClauses = NIL;
return plan;
}