/*
* 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;
}
/*
* Pull up children of a UNION node that are identically-propertied UNIONs.
*
* NOTE: we can also pull a UNION ALL up into a UNION, since the distinct
* output rows will be lost anyway.
*/
static List *
recurse_union_children(Node *setOp, PlannerInfo *root,
double tuple_fraction,
SetOperationStmt *top_union,
List *refnames_tlist)
{
List *child_sortclauses;
if (IsA(setOp, SetOperationStmt))
{
SetOperationStmt *op = (SetOperationStmt *) setOp;
if (op->op == top_union->op &&
(op->all == top_union->all || op->all) &&
equal(op->colTypes, top_union->colTypes))
{
/* Same UNION, so fold children into parent's subplan list */
return list_concat(recurse_union_children(op->larg, root,
tuple_fraction,
top_union,
refnames_tlist),
recurse_union_children(op->rarg, root,
tuple_fraction,
top_union,
refnames_tlist));
}
}
/*
* Not same, so plan this child separately.
*
* Note we disallow any resjunk columns in child results. This is
* necessary since the Append node that implements the union won't do any
* projection, and upper levels will get confused if some of our output
* tuples have junk and some don't. This case only arises when we have an
* EXCEPT or INTERSECT as child, else there won't be resjunk anyway.
*/
return list_make1(recurse_set_operations(setOp, root,
tuple_fraction,
top_union->colTypes, false,
-1, refnames_tlist,
&child_sortclauses));
}
/*
* Pull up children of a UNION node that are identically-propertied UNIONs.
*
* NOTE: we can also pull a UNION ALL up into a UNION, since the distinct
* output rows will be lost anyway.
*/
static List *
recurse_union_children(Node *setOp, Query *parse,
SetOperationStmt *top_union,
List *refnames_tlist)
{
if (IsA(setOp, SetOperationStmt))
{
SetOperationStmt *op = (SetOperationStmt *) setOp;
if (op->op == top_union->op &&
(op->all == top_union->all || op->all) &&
equalo(op->colTypes, top_union->colTypes))
{
/* Same UNION, so fold children into parent's subplan list */
return nconc(recurse_union_children(op->larg, parse,
top_union,
refnames_tlist),
recurse_union_children(op->rarg, parse,
top_union,
refnames_tlist));
}
}
/*
* Not same, so plan this child separately.
*
* Note we disallow any resjunk columns in child results. This is
* necessary since the Append node that implements the union won't do
* any projection, and upper levels will get confused if some of our
* output tuples have junk and some don't. This case only arises when
* we have an EXCEPT or INTERSECT as child, else there won't be
* resjunk anyway.
*/
return makeList1(recurse_set_operations(setOp, parse,
top_union->colTypes, false,
-1, refnames_tlist));
}
/*
* 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;
}