/*-------------------------------------------------------------------------
 *
 * prepunion.c
 *	  Routines to plan set-operation queries.  The filename is a leftover
 *	  from a time when only UNIONs were implemented.
 *
 * There are two code paths in the planner for set-operation queries.
 * If a subquery consists entirely of simple UNION ALL operations, it
 * is converted into an "append relation".	Otherwise, it is handled
 * by the general code in this module (plan_set_operations and its
 * subroutines).  There is some support code here for the append-relation
 * case, but most of the heavy lifting for that is done elsewhere,
 * notably in prepjointree.c and allpaths.c.
 *
 * There is also some code here to support planning of queries that use
 * inheritance (SELECT FROM foo*).	Inheritance trees are converted into
 * append relations, and thenceforth share code with the UNION ALL case.
 *
 *
 * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.134 2006/10/04 00:29:55 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"


#include "access/heapam.h"
#include "catalog/namespace.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/plancat.h"
#include "optimizer/planmain.h"
#include "optimizer/planner.h"
#include "optimizer/prep.h"
#include "optimizer/tlist.h"
#include "parser/parse_clause.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parsetree.h"
#include "utils/lsyscache.h"


static Plan *recurse_set_operations(Node *setOp, PlannerInfo *root,
					   double tuple_fraction,
					   List *colTypes, bool junkOK,
					   int flag, List *refnames_tlist,
					   List **sortClauses);
static Plan *generate_union_plan(SetOperationStmt *op, PlannerInfo *root,
					double tuple_fraction,
					List *refnames_tlist, List **sortClauses);
static Plan *generate_nonunion_plan(SetOperationStmt *op, PlannerInfo *root,
					   List *refnames_tlist, List **sortClauses);
static List *recurse_union_children(Node *setOp, PlannerInfo *root,
					   double tuple_fraction,
					   SetOperationStmt *top_union,
					   List *refnames_tlist);
static List *generate_setop_tlist(List *colTypes, int flag,
					 Index varno,
					 bool hack_constants,
					 List *input_tlist,
					 List *refnames_tlist);
static List *generate_append_tlist(List *colTypes, bool flag,
					  List *input_plans,
					  List *refnames_tlist);
static void expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte,
						 Index rti);
static void make_inh_translation_lists(Relation oldrelation,
						   Relation newrelation,
						   Index newvarno,
						   List **col_mappings,
						   List **translated_vars);
static Node *adjust_appendrel_attrs_mutator(Node *node,
							   AppendRelInfo *context);
static Relids adjust_relid_set(Relids relids, Index oldrelid, Index newrelid);
static List *adjust_inherited_tlist(List *tlist,
					   AppendRelInfo *context);


/*
 * plan_set_operations
 *
 *	  Plans the queries for a tree of set operations (UNION/INTERSECT/EXCEPT)
 *
 * This routine only deals with the setOperations tree of the given query.
 * Any top-level ORDER BY requested in root->parse->sortClause will be added
 * when we return to grouping_planner.
 *
 * tuple_fraction is the fraction of tuples we expect will be retrieved.
 * tuple_fraction is interpreted as for grouping_planner(); in particular,
 * zero means "all the tuples will be fetched".  Any LIMIT present at the
 * top level has already been factored into tuple_fraction.
 *
 * *sortClauses is an output argument: it is set to a list of SortClauses
 * representing the result ordering of the topmost set operation.
 */
Plan *
plan_set_operations(PlannerInfo *root, double tuple_fraction,
					List **sortClauses)
{
	Query	   *parse = root->parse;
	SetOperationStmt *topop = (SetOperationStmt *) parse->setOperations;
	Node	   *node;
	Query	   *leftmostQuery;

	Assert(topop && IsA(topop, SetOperationStmt));

	/* check for unsupported stuff */
	Assert(parse->utilityStmt == NULL);
	Assert(parse->jointree->fromlist == NIL);
	Assert(parse->jointree->quals == NULL);
	Assert(parse->groupClause == NIL);
	Assert(parse->havingQual == NULL);
	Assert(parse->distinctClause == NIL);

	/*
	 * Find the leftmost component Query.  We need to use its column names for
	 * all generated tlists (else SELECT INTO won't work right).
	 */
	node = topop->larg;
	while (node && IsA(node, SetOperationStmt))
		node = ((SetOperationStmt *) node)->larg;
	Assert(node && IsA(node, RangeTblRef));
	leftmostQuery = rt_fetch(((RangeTblRef *) node)->rtindex,
							 parse->rtable)->subquery;
	Assert(leftmostQuery != NULL);

	/*
	 * Recurse on setOperations tree to generate plans for set ops. The final
	 * output plan should have just the column types shown as the output from
	 * the top-level node, plus possibly resjunk working columns (we can rely
	 * on upper-level nodes to deal with that).
	 */
	return recurse_set_operations((Node *) topop, root, tuple_fraction,
								  topop->colTypes, true, -1,
								  leftmostQuery->targetList,
								  sortClauses);
}

/*
 * recurse_set_operations
 *	  Recursively handle one step in a tree of set operations
 *
 * tuple_fraction: fraction of tuples we expect to retrieve from node
 * colTypes: list of type OIDs of expected output columns
 * junkOK: if true, child resjunk columns may be left in the result
 * flag: if >= 0, add a resjunk output column indicating value of flag
 * refnames_tlist: targetlist to take column names from
 * *sortClauses: receives list of SortClauses for result plan, if any
 *
 * We don't have to care about typmods here: the only allowed difference
 * between set-op input and output typmods is input is a specific typmod
 * and output is -1, and that does not require a coercion.
 */
static Plan *
recurse_set_operations(Node *setOp, PlannerInfo *root,
					   double tuple_fraction,
					   List *colTypes, bool junkOK,
					   int flag, List *refnames_tlist,
					   List **sortClauses)
{
	if (IsA(setOp, RangeTblRef))
	{
		RangeTblRef *rtr = (RangeTblRef *) setOp;
		RangeTblEntry *rte = rt_fetch(rtr->rtindex, root->parse->rtable);
		Query	   *subquery = rte->subquery;
		Plan	   *subplan,
				   *plan;

		Assert(subquery != NULL);

		/*
		 * Generate plan for primitive subquery
		 */
		subplan = subquery_planner(subquery, tuple_fraction, NULL);

		/*
		 * Add a SubqueryScan with the caller-requested targetlist
		 */
		plan = (Plan *)
			make_subqueryscan(generate_setop_tlist(colTypes, flag,
												   rtr->rtindex,
												   true,
												   subplan->targetlist,
												   refnames_tlist),
							  NIL,
							  rtr->rtindex,
							  subplan);

		/*
		 * We don't bother to determine the subquery's output ordering since
		 * it won't be reflected in the set-op result anyhow.
		 */
		*sortClauses = NIL;

		return plan;
	}
	else if (IsA(setOp, SetOperationStmt))
	{
		SetOperationStmt *op = (SetOperationStmt *) setOp;
		Plan	   *plan;

		/* UNIONs are much different from INTERSECT/EXCEPT */
		if (op->op == SETOP_UNION)
			plan = generate_union_plan(op, root, tuple_fraction,
									   refnames_tlist,
									   sortClauses);
		else
			plan = generate_nonunion_plan(op, root,
										  refnames_tlist,
										  sortClauses);

		/*
		 * If necessary, add a Result node to project the caller-requested
		 * output columns.
		 *
		 * XXX you don't really want to know about this: setrefs.c will apply
		 * replace_vars_with_subplan_refs() to the Result node's tlist. This
		 * would fail if the Vars generated by generate_setop_tlist() were not
		 * exactly equal() to the corresponding tlist entries of the subplan.
		 * However, since the subplan was generated by generate_union_plan()
		 * or generate_nonunion_plan(), and hence its tlist was generated by
		 * generate_append_tlist(), this will work.  We just tell
		 * generate_setop_tlist() to use varno 0.
		 */
		if (flag >= 0 ||
			!tlist_same_datatypes(plan->targetlist, colTypes, junkOK))
		{
			plan = (Plan *)
				make_result(generate_setop_tlist(colTypes, flag,
												 0,
												 false,
												 plan->targetlist,
												 refnames_tlist),
							NULL,
							plan);
		}
		return plan;
	}
	else
	{
		elog(ERROR, "unrecognized node type: %d",
			 (int) nodeTag(setOp));
		return NULL;			/* keep compiler quiet */
	}
}

/*
 * 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;
}

/*
 * Generate plan for an INTERSECT, INTERSECT ALL, EXCEPT, or EXCEPT ALL node
 */
static Plan *
generate_nonunion_plan(SetOperationStmt *op, PlannerInfo *root,
					   List *refnames_tlist,
					   List **sortClauses)
{
	Plan	   *lplan,
			   *rplan,
			   *plan;
	List	   *tlist,
			   *sortList,
			   *planlist,
			   *child_sortclauses;
	SetOpCmd	cmd;

	/* Recurse on children, ensuring their outputs are marked */
	lplan = recurse_set_operations(op->larg, root,
								   0.0 /* all tuples needed */ ,
								   op->colTypes, false, 0,
								   refnames_tlist,
								   &child_sortclauses);
	rplan = recurse_set_operations(op->rarg, root,
								   0.0 /* all tuples needed */ ,
								   op->colTypes, false, 1,
								   refnames_tlist,
								   &child_sortclauses);
	planlist = list_make2(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.
	 */
	sortList = addAllTargetsToSortList(NULL, NIL, tlist, false);

	if (sortList == NIL)		/* nothing to sort on? */
	{
		*sortClauses = NIL;
		return plan;
	}

	plan = (Plan *) make_sort_from_sortclauses(root, sortList, plan);
	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, plan, sortList, list_length(op->colTypes) + 1);

	*sortClauses = 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));
}

/*
 * Generate targetlist for a set-operation plan node
 *
 * colTypes: column datatypes for non-junk columns
 * flag: -1 if no flag column needed, 0 or 1 to create a const flag column
 * varno: varno to use in generated Vars
 * hack_constants: true to copy up constants (see comments in code)
 * input_tlist: targetlist of this node's input node
 * refnames_tlist: targetlist to take column names from
 */
static List *
generate_setop_tlist(List *colTypes, int flag,
					 Index varno,
					 bool hack_constants,
					 List *input_tlist,
					 List *refnames_tlist)
{
	List	   *tlist = NIL;
	int			resno = 1;
	ListCell   *i,
			   *j,
			   *k;
	TargetEntry *tle;
	Node	   *expr;

	j = list_head(input_tlist);
	k = list_head(refnames_tlist);
	foreach(i, colTypes)
	{
		Oid			colType = lfirst_oid(i);
		TargetEntry *inputtle = (TargetEntry *) lfirst(j);
		TargetEntry *reftle = (TargetEntry *) lfirst(k);

		Assert(inputtle->resno == resno);
		Assert(reftle->resno == resno);
		Assert(!inputtle->resjunk);
		Assert(!reftle->resjunk);

		/*
		 * Generate columns referencing input columns and having appropriate
		 * data types and column names.  Insert datatype coercions where
		 * necessary.
		 *
		 * HACK: constants in the input's targetlist are copied up as-is
		 * rather than being referenced as subquery outputs.  This is mainly
		 * to ensure that when we try to coerce them to the output column's
		 * datatype, the right things happen for UNKNOWN constants.  But do
		 * this only at the first level of subquery-scan plans; we don't want
		 * phony constants appearing in the output tlists of upper-level
		 * nodes!
		 */
		if (hack_constants && inputtle->expr && IsA(inputtle->expr, Const))
			expr = (Node *) inputtle->expr;
		else
			expr = (Node *) makeVar(varno,
									inputtle->resno,
									exprType((Node *) inputtle->expr),
									exprTypmod((Node *) inputtle->expr),
									0);
		if (exprType(expr) != colType)
		{
			expr = coerce_to_common_type(NULL,	/* no UNKNOWNs here */
										 expr,
										 colType,
										 "UNION/INTERSECT/EXCEPT");
		}
		tle = makeTargetEntry((Expr *) expr,
							  (AttrNumber) resno++,
							  pstrdup(reftle->resname),
							  false);
		tlist = lappend(tlist, tle);

		j = lnext(j);
		k = lnext(k);
	}

	if (flag >= 0)
	{
		/* Add a resjunk flag column */
		/* flag value is the given constant */
		expr = (Node *) makeConst(INT4OID,
								  sizeof(int4),
								  Int32GetDatum(flag),
								  false,
								  true);
		tle = makeTargetEntry((Expr *) expr,
							  (AttrNumber) resno++,
							  pstrdup("flag"),
							  true);
		tlist = lappend(tlist, tle);
	}

	return tlist;
}

/*
 * Generate targetlist for a set-operation Append node
 *
 * colTypes: column datatypes for non-junk columns
 * flag: true to create a flag column copied up from subplans
 * input_plans: list of sub-plans of the Append
 * refnames_tlist: targetlist to take column names from
 *
 * The entries in the Append's targetlist should always be simple Vars;
 * we just have to make sure they have the right datatypes and typmods.
 * The Vars are always generated with varno 0.
 */
static List *
generate_append_tlist(List *colTypes, bool flag,
					  List *input_plans,
					  List *refnames_tlist)
{
	List	   *tlist = NIL;
	int			resno = 1;
	ListCell   *curColType;
	ListCell   *ref_tl_item;
	int			colindex;
	TargetEntry *tle;
	Node	   *expr;
	ListCell   *planl;
	int32	   *colTypmods;

	/*
	 * First extract typmods to use.
	 *
	 * If the inputs all agree on type and typmod of a particular column, use
	 * that typmod; else use -1.
	 */
	colTypmods = (int32 *) palloc(list_length(colTypes) * sizeof(int32));

	foreach(planl, input_plans)
	{
		Plan	   *subplan = (Plan *) lfirst(planl);
		ListCell   *subtlist;

		curColType = list_head(colTypes);
		colindex = 0;
		foreach(subtlist, subplan->targetlist)
		{
			TargetEntry *subtle = (TargetEntry *) lfirst(subtlist);

			if (subtle->resjunk)
				continue;
			Assert(curColType != NULL);
			if (exprType((Node *) subtle->expr) == lfirst_oid(curColType))
			{
				/* If first subplan, copy the typmod; else compare */
				int32		subtypmod = exprTypmod((Node *) subtle->expr);

				if (planl == list_head(input_plans))
					colTypmods[colindex] = subtypmod;
				else if (subtypmod != colTypmods[colindex])
					colTypmods[colindex] = -1;
			}
			else
			{
				/* types disagree, so force typmod to -1 */
				colTypmods[colindex] = -1;
			}
			curColType = lnext(curColType);
			colindex++;
		}
		Assert(curColType == NULL);
	}

	/*
	 * Now we can build the tlist for the Append.
	 */
	colindex = 0;
	forboth(curColType, colTypes, ref_tl_item, refnames_tlist)
	{
		Oid			colType = lfirst_oid(curColType);
		int32		colTypmod = colTypmods[colindex++];
		TargetEntry *reftle = (TargetEntry *) lfirst(ref_tl_item);

		Assert(reftle->resno == resno);
		Assert(!reftle->resjunk);
		expr = (Node *) makeVar(0,
								resno,
								colType,
								colTypmod,
								0);
		tle = makeTargetEntry((Expr *) expr,
							  (AttrNumber) resno++,
							  pstrdup(reftle->resname),
							  false);
		tlist = lappend(tlist, tle);
	}

	if (flag)
	{
		/* Add a resjunk flag column */
		/* flag value is shown as copied up from subplan */
		expr = (Node *) makeVar(0,
								resno,
								INT4OID,
								-1,
								0);
		tle = makeTargetEntry((Expr *) expr,
							  (AttrNumber) resno++,
							  pstrdup("flag"),
							  true);
		tlist = lappend(tlist, tle);
	}

	pfree(colTypmods);

	return tlist;
}


/*
 * find_all_inheritors -
 *		Returns a list of relation OIDs including the given rel plus
 *		all relations that inherit from it, directly or indirectly.
 */
List *
find_all_inheritors(Oid parentrel)
{
	List	   *rels_list;
	ListCell   *l;

	/*
	 * We build a list starting with the given rel and adding all direct and
	 * indirect children.  We can use a single list as both the record of
	 * already-found rels and the agenda of rels yet to be scanned for more
	 * children.  This is a bit tricky but works because the foreach() macro
	 * doesn't fetch the next list element until the bottom of the loop.
	 */
	rels_list = list_make1_oid(parentrel);

	foreach(l, rels_list)
	{
		Oid			currentrel = lfirst_oid(l);
		List	   *currentchildren;

		/* Get the direct children of this rel */
		currentchildren = find_inheritance_children(currentrel);

		/*
		 * Add to the queue only those children not already seen. This avoids
		 * making duplicate entries in case of multiple inheritance paths from
		 * the same parent.  (It'll also keep us from getting into an infinite
		 * loop, though theoretically there can't be any cycles in the
		 * inheritance graph anyway.)
		 */
		rels_list = list_concat_unique_oid(rels_list, currentchildren);
	}

	return rels_list;
}

/*
 * expand_inherited_tables
 *		Expand each rangetable entry that represents an inheritance set
 *		into an "append relation".	At the conclusion of this process,
 *		the "inh" flag is set in all and only those RTEs that are append
 *		relation parents.
 */
void
expand_inherited_tables(PlannerInfo *root)
{
	Index		nrtes;
	Index		rti;
	ListCell   *rl;

	/*
	 * expand_inherited_rtentry may add RTEs to parse->rtable; there is no
	 * need to scan them since they can't have inh=true.  So just scan as far
	 * as the original end of the rtable list.
	 */
	nrtes = list_length(root->parse->rtable);
	rl = list_head(root->parse->rtable);
	for (rti = 1; rti <= nrtes; rti++)
	{
		RangeTblEntry *rte = (RangeTblEntry *) lfirst(rl);

		expand_inherited_rtentry(root, rte, rti);
		rl = lnext(rl);
	}
}

/*
 * expand_inherited_rtentry
 *		Check whether a rangetable entry represents an inheritance set.
 *		If so, add entries for all the child tables to the query's
 *		rangetable, and build AppendRelInfo nodes for all the child tables
 *		and add them to root->append_rel_list.	If not, clear the entry's
 *		"inh" flag to prevent later code from looking for AppendRelInfos.
 *
 * Note that the original RTE is considered to represent the whole
 * inheritance set.  The first of the generated RTEs is an RTE for the same
 * table, but with inh = false, to represent the parent table in its role
 * as a simple member of the inheritance set.
 *
 * A childless table is never considered to be an inheritance set; therefore
 * a parent RTE must always have at least two associated AppendRelInfos.
 */
static void
expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
{
	Query	   *parse = root->parse;
	Oid			parentOID;
	Relation	oldrelation;
	LOCKMODE	lockmode;
	List	   *inhOIDs;
	List	   *appinfos;
	ListCell   *l;

	/* Does RT entry allow inheritance? */
	if (!rte->inh)
		return;
	/* Ignore any already-expanded UNION ALL nodes */
	if (rte->rtekind != RTE_RELATION)
	{
		Assert(rte->rtekind == RTE_SUBQUERY);
		return;
	}
	/* Fast path for common case of childless table */
	parentOID = rte->relid;
	if (!has_subclass(parentOID))
	{
		/* Clear flag before returning */
		rte->inh = false;
		return;
	}

	/* Scan for all members of inheritance set */
	inhOIDs = find_all_inheritors(parentOID);

	/*
	 * Check that there's at least one descendant, else treat as no-child
	 * case.  This could happen despite above has_subclass() check, if table
	 * once had a child but no longer does.
	 */
	if (list_length(inhOIDs) < 2)
	{
		/* Clear flag before returning */
		rte->inh = false;
		return;
	}

	/*
	 * Must open the parent relation to examine its tupdesc.  We need not lock
	 * it since the rewriter already obtained at least AccessShareLock on each
	 * relation used in the query.
	 */
	oldrelation = heap_open(parentOID, NoLock);

	/*
	 * However, for each child relation we add to the query, we must obtain an
	 * appropriate lock, because this will be the first use of those relations
	 * in the parse/rewrite/plan pipeline.
	 *
	 * If the parent relation is the query's result relation, then we need
	 * RowExclusiveLock.  Otherwise, check to see if the relation is accessed
	 * FOR UPDATE/SHARE or not.  We can't just grab AccessShareLock because
	 * then the executor would be trying to upgrade the lock, leading to
	 * possible deadlocks.	(This code should match the parser and rewriter.)
	 */
	if (rti == parse->resultRelation)
		lockmode = RowExclusiveLock;
	else if (get_rowmark(parse, rti))
		lockmode = RowShareLock;
	else
		lockmode = AccessShareLock;

	/* Scan the inheritance set and expand it */
	appinfos = NIL;
	foreach(l, inhOIDs)
	{
		Oid			childOID = lfirst_oid(l);
		Relation	newrelation;
		RangeTblEntry *childrte;
		Index		childRTindex;
		AppendRelInfo *appinfo;

		/*
		 * It is possible that the parent table has children that are temp
		 * tables of other backends.  We cannot safely access such tables
		 * (because of buffering issues), and the best thing to do seems to be
		 * to silently ignore them.
		 */
		if (childOID != parentOID &&
			isOtherTempNamespace(get_rel_namespace(childOID)))
			continue;

		/* Open rel, acquire the appropriate lock type */
		if (childOID != parentOID)
			newrelation = heap_open(childOID, lockmode);
		else
			newrelation = oldrelation;

		/*
		 * Build an RTE for the child, and attach to query's rangetable list.
		 * We copy most fields of the parent's RTE, but replace relation OID,
		 * and set inh = false.
		 */
		childrte = copyObject(rte);
		childrte->relid = childOID;
		childrte->inh = false;
		parse->rtable = lappend(parse->rtable, childrte);
		childRTindex = list_length(parse->rtable);

		/*
		 * Build an AppendRelInfo for this parent and child.
		 */
		appinfo = makeNode(AppendRelInfo);
		appinfo->parent_relid = rti;
		appinfo->child_relid = childRTindex;
		appinfo->parent_reltype = oldrelation->rd_rel->reltype;
		appinfo->child_reltype = newrelation->rd_rel->reltype;
		make_inh_translation_lists(oldrelation, newrelation, childRTindex,
								   &appinfo->col_mappings,
								   &appinfo->translated_vars);
		appinfo->parent_reloid = parentOID;
		appinfos = lappend(appinfos, appinfo);

		/* Close child relations, but keep locks */
		if (childOID != parentOID)
			heap_close(newrelation, NoLock);
	}

	heap_close(oldrelation, NoLock);

	/*
	 * If all the children were temp tables, pretend it's a non-inheritance
	 * situation.  The duplicate RTE we added for the parent table is
	 * harmless, so we don't bother to get rid of it.
	 */
	if (list_length(appinfos) < 2)
	{
		/* Clear flag before returning */
		rte->inh = false;
		return;
	}

	/* Otherwise, OK to add to root->append_rel_list */
	root->append_rel_list = list_concat(root->append_rel_list, appinfos);

	/*
	 * The executor will check the parent table's access permissions when it
	 * examines the parent's added RTE entry.  There's no need to check twice,
	 * so turn off access check bits in the original RTE.
	 */
	rte->requiredPerms = 0;
}

/*
 * make_inh_translation_lists
 *	  Build the lists of translations from parent Vars to child Vars for
 *	  an inheritance child.  We need both a column number mapping list
 *	  and a list of Vars representing the child columns.
 *
 * For paranoia's sake, we match type as well as attribute name.
 */
static void
make_inh_translation_lists(Relation oldrelation, Relation newrelation,
						   Index newvarno,
						   List **col_mappings, List **translated_vars)
{
	List	   *numbers = NIL;
	List	   *vars = NIL;
	TupleDesc	old_tupdesc = RelationGetDescr(oldrelation);
	TupleDesc	new_tupdesc = RelationGetDescr(newrelation);
	int			oldnatts = old_tupdesc->natts;
	int			newnatts = new_tupdesc->natts;
	int			old_attno;

	for (old_attno = 0; old_attno < oldnatts; old_attno++)
	{
		Form_pg_attribute att;
		char	   *attname;
		Oid			atttypid;
		int32		atttypmod;
		int			new_attno;

		att = old_tupdesc->attrs[old_attno];
		if (att->attisdropped)
		{
			/* Just put 0/NULL into this list entry */
			numbers = lappend_int(numbers, 0);
			vars = lappend(vars, NULL);
			continue;
		}
		attname = NameStr(att->attname);
		atttypid = att->atttypid;
		atttypmod = att->atttypmod;

		/*
		 * When we are generating the "translation list" for the parent table
		 * of an inheritance set, no need to search for matches.
		 */
		if (oldrelation == newrelation)
		{
			numbers = lappend_int(numbers, old_attno + 1);
			vars = lappend(vars, makeVar(newvarno,
										 (AttrNumber) (old_attno + 1),
										 atttypid,
										 atttypmod,
										 0));
			continue;
		}

		/*
		 * Otherwise we have to search for the matching column by name.
		 * There's no guarantee it'll have the same column position, because
		 * of cases like ALTER TABLE ADD COLUMN and multiple inheritance.
		 */
		for (new_attno = 0; new_attno < newnatts; new_attno++)
		{
			att = new_tupdesc->attrs[new_attno];
			if (att->attisdropped || att->attinhcount == 0)
				continue;
			if (strcmp(attname, NameStr(att->attname)) != 0)
				continue;
			/* Found it, check type */
			if (atttypid != att->atttypid || atttypmod != att->atttypmod)
				elog(ERROR, "attribute \"%s\" of relation \"%s\" does not match parent's type",
					 attname, RelationGetRelationName(newrelation));

			numbers = lappend_int(numbers, new_attno + 1);
			vars = lappend(vars, makeVar(newvarno,
										 (AttrNumber) (new_attno + 1),
										 atttypid,
										 atttypmod,
										 0));
			break;
		}

		if (new_attno >= newnatts)
			elog(ERROR, "could not find inherited attribute \"%s\" of relation \"%s\"",
				 attname, RelationGetRelationName(newrelation));
	}

	*col_mappings = numbers;
	*translated_vars = vars;
}

/*
 * adjust_appendrel_attrs
 *	  Copy the specified query or expression and translate Vars referring
 *	  to the parent rel of the specified AppendRelInfo to refer to the
 *	  child rel instead.  We also update rtindexes appearing outside Vars,
 *	  such as resultRelation and jointree relids.
 *
 * Note: this is only applied after conversion of sublinks to subplans,
 * so we don't need to cope with recursion into sub-queries.
 *
 * Note: this is not hugely different from what ResolveNew() does; maybe
 * we should try to fold the two routines together.
 */
Node *
adjust_appendrel_attrs(Node *node, AppendRelInfo *appinfo)
{
	Node	   *result;

	/*
	 * Must be prepared to start with a Query or a bare expression tree.
	 */
	if (node && IsA(node, Query))
	{
		Query	   *newnode;

		newnode = query_tree_mutator((Query *) node,
									 adjust_appendrel_attrs_mutator,
									 (void *) appinfo,
									 QTW_IGNORE_RT_SUBQUERIES);
		if (newnode->resultRelation == appinfo->parent_relid)
		{
			newnode->resultRelation = appinfo->child_relid;
			/* Fix tlist resnos too, if it's inherited UPDATE */
			if (newnode->commandType == CMD_UPDATE)
				newnode->targetList =
					adjust_inherited_tlist(newnode->targetList,
										   appinfo);
		}
		result = (Node *) newnode;
	}
	else
		result = adjust_appendrel_attrs_mutator(node, appinfo);

	return result;
}

static Node *
adjust_appendrel_attrs_mutator(Node *node, AppendRelInfo *context)
{
	if (node == NULL)
		return NULL;
	if (IsA(node, Var))
	{
		Var		   *var = (Var *) copyObject(node);

		if (var->varlevelsup == 0 &&
			var->varno == context->parent_relid)
		{
			var->varno = context->child_relid;
			var->varnoold = context->child_relid;
			if (var->varattno > 0)
			{
				Node	   *newnode;

				if (var->varattno > list_length(context->translated_vars))
					elog(ERROR, "attribute %d of relation \"%s\" does not exist",
						 var->varattno, get_rel_name(context->parent_reloid));
				newnode = copyObject(list_nth(context->translated_vars,
											  var->varattno - 1));
				if (newnode == NULL)
					elog(ERROR, "attribute %d of relation \"%s\" does not exist",
						 var->varattno, get_rel_name(context->parent_reloid));
				return newnode;
			}
			else if (var->varattno == 0)
			{
				/*
				 * Whole-row Var: if we are dealing with named rowtypes, we
				 * can use a whole-row Var for the child table plus a coercion
				 * step to convert the tuple layout to the parent's rowtype.
				 * Otherwise we have to generate a RowExpr.
				 */
				if (OidIsValid(context->child_reltype))
				{
					Assert(var->vartype == context->parent_reltype);
					if (context->parent_reltype != context->child_reltype)
					{
						ConvertRowtypeExpr *r = makeNode(ConvertRowtypeExpr);

						r->arg = (Expr *) var;
						r->resulttype = context->parent_reltype;
						r->convertformat = COERCE_IMPLICIT_CAST;
						/* Make sure the Var node has the right type ID, too */
						var->vartype = context->child_reltype;
						return (Node *) r;
					}
				}
				else
				{
					/*
					 * Build a RowExpr containing the translated variables.
					 */
					RowExpr    *rowexpr;
					List	   *fields;

					fields = (List *) copyObject(context->translated_vars);
					rowexpr = makeNode(RowExpr);
					rowexpr->args = fields;
					rowexpr->row_typeid = var->vartype;
					rowexpr->row_format = COERCE_IMPLICIT_CAST;
					return (Node *) rowexpr;
				}
			}
			/* system attributes don't need any other translation */
		}
		return (Node *) var;
	}
	if (IsA(node, RangeTblRef))
	{
		RangeTblRef *rtr = (RangeTblRef *) copyObject(node);

		if (rtr->rtindex == context->parent_relid)
			rtr->rtindex = context->child_relid;
		return (Node *) rtr;
	}
	if (IsA(node, JoinExpr))
	{
		/* Copy the JoinExpr node with correct mutation of subnodes */
		JoinExpr   *j;

		j = (JoinExpr *) expression_tree_mutator(node,
											  adjust_appendrel_attrs_mutator,
												 (void *) context);
		/* now fix JoinExpr's rtindex (probably never happens) */
		if (j->rtindex == context->parent_relid)
			j->rtindex = context->child_relid;
		return (Node *) j;
	}
	if (IsA(node, InClauseInfo))
	{
		/* Copy the InClauseInfo node with correct mutation of subnodes */
		InClauseInfo *ininfo;

		ininfo = (InClauseInfo *) expression_tree_mutator(node,
											  adjust_appendrel_attrs_mutator,
														  (void *) context);
		/* now fix InClauseInfo's relid sets */
		ininfo->lefthand = adjust_relid_set(ininfo->lefthand,
											context->parent_relid,
											context->child_relid);
		ininfo->righthand = adjust_relid_set(ininfo->righthand,
											 context->parent_relid,
											 context->child_relid);
		return (Node *) ininfo;
	}
	/* Shouldn't need to handle OuterJoinInfo or AppendRelInfo here */
	Assert(!IsA(node, OuterJoinInfo));
	Assert(!IsA(node, AppendRelInfo));

	/*
	 * We have to process RestrictInfo nodes specially.
	 */
	if (IsA(node, RestrictInfo))
	{
		RestrictInfo *oldinfo = (RestrictInfo *) node;
		RestrictInfo *newinfo = makeNode(RestrictInfo);

		/* Copy all flat-copiable fields */
		memcpy(newinfo, oldinfo, sizeof(RestrictInfo));

		/* Recursively fix the clause itself */
		newinfo->clause = (Expr *)
			adjust_appendrel_attrs_mutator((Node *) oldinfo->clause, context);

		/* and the modified version, if an OR clause */
		newinfo->orclause = (Expr *)
			adjust_appendrel_attrs_mutator((Node *) oldinfo->orclause, context);

		/* adjust relid sets too */
		newinfo->clause_relids = adjust_relid_set(oldinfo->clause_relids,
												  context->parent_relid,
												  context->child_relid);
		newinfo->required_relids = adjust_relid_set(oldinfo->required_relids,
													context->parent_relid,
													context->child_relid);
		newinfo->left_relids = adjust_relid_set(oldinfo->left_relids,
												context->parent_relid,
												context->child_relid);
		newinfo->right_relids = adjust_relid_set(oldinfo->right_relids,
												 context->parent_relid,
												 context->child_relid);

		/*
		 * Reset cached derivative fields, since these might need to have
		 * different values when considering the child relation.
		 */
		newinfo->eval_cost.startup = -1;
		newinfo->this_selec = -1;
		newinfo->left_pathkey = NIL;
		newinfo->right_pathkey = NIL;
		newinfo->left_mergescansel = -1;
		newinfo->right_mergescansel = -1;
		newinfo->left_bucketsize = -1;
		newinfo->right_bucketsize = -1;

		return (Node *) newinfo;
	}

	/*
	 * NOTE: we do not need to recurse into sublinks, because they should
	 * already have been converted to subplans before we see them.
	 */
	Assert(!IsA(node, SubLink));
	Assert(!IsA(node, Query));

	/*
	 * BUT: although we don't need to recurse into subplans, we do need to
	 * make sure that they are copied, not just referenced as
	 * expression_tree_mutator will do by default.	Otherwise we'll have the
	 * same subplan node referenced from each arm of the finished APPEND plan,
	 * which will cause trouble in the executor.  This is a kluge that should
	 * go away when we redesign querytrees.
	 */
	if (is_subplan(node))
	{
		SubPlan    *subplan;

		/* Copy the node and process subplan args */
		node = expression_tree_mutator(node, adjust_appendrel_attrs_mutator,
									   (void *) context);
		/* Make sure we have separate copies of subplan and its rtable */
		subplan = (SubPlan *) node;
		subplan->plan = copyObject(subplan->plan);
		subplan->rtable = copyObject(subplan->rtable);
		return node;
	}

	return expression_tree_mutator(node, adjust_appendrel_attrs_mutator,
								   (void *) context);
}

/*
 * Substitute newrelid for oldrelid in a Relid set
 */
static Relids
adjust_relid_set(Relids relids, Index oldrelid, Index newrelid)
{
	if (bms_is_member(oldrelid, relids))
	{
		/* Ensure we have a modifiable copy */
		relids = bms_copy(relids);
		/* Remove old, add new */
		relids = bms_del_member(relids, oldrelid);
		relids = bms_add_member(relids, newrelid);
	}
	return relids;
}

/*
 * adjust_appendrel_attr_needed
 *		Adjust an attr_needed[] array to reference a member rel instead of
 *		the original appendrel
 *
 * oldrel: source of data (we use the attr_needed, min_attr, max_attr fields)
 * appinfo: supplies parent_relid, child_relid, col_mappings
 * new_min_attr, new_max_attr: desired bounds of new attr_needed array
 *
 * The relid sets are adjusted by substituting child_relid for parent_relid.
 * (NOTE: oldrel is not necessarily the parent_relid relation!)  We are also
 * careful to map attribute numbers within the array properly.	User
 * attributes have to be mapped through col_mappings, but system attributes
 * and whole-row references always have the same attno.
 *
 * Returns a palloc'd array with the specified bounds
 */
Relids *
adjust_appendrel_attr_needed(RelOptInfo *oldrel, AppendRelInfo *appinfo,
							 AttrNumber new_min_attr, AttrNumber new_max_attr)
{
	Relids	   *new_attr_needed;
	Index		parent_relid = appinfo->parent_relid;
	Index		child_relid = appinfo->child_relid;
	int			parent_attr;
	ListCell   *lm;

	/* Create empty result array */
	Assert(new_min_attr <= oldrel->min_attr);
	Assert(new_max_attr >= oldrel->max_attr);
	new_attr_needed = (Relids *)
		palloc0((new_max_attr - new_min_attr + 1) * sizeof(Relids));
	/* Process user attributes, with appropriate attno mapping */
	parent_attr = 1;
	foreach(lm, appinfo->col_mappings)
	{
		int			child_attr = lfirst_int(lm);

		if (child_attr > 0)
		{
			Relids		attrneeded;

			Assert(parent_attr <= oldrel->max_attr);
			Assert(child_attr <= new_max_attr);
			attrneeded = oldrel->attr_needed[parent_attr - oldrel->min_attr];
			attrneeded = adjust_relid_set(attrneeded,
										  parent_relid, child_relid);
			new_attr_needed[child_attr - new_min_attr] = attrneeded;
		}
		parent_attr++;
	}
	/* Process system attributes, including whole-row references */
	for (parent_attr = oldrel->min_attr; parent_attr <= 0; parent_attr++)
	{
		Relids		attrneeded;

		attrneeded = oldrel->attr_needed[parent_attr - oldrel->min_attr];
		attrneeded = adjust_relid_set(attrneeded,
									  parent_relid, child_relid);
		new_attr_needed[parent_attr - new_min_attr] = attrneeded;
	}

	return new_attr_needed;
}

/*
 * Adjust the targetlist entries of an inherited UPDATE operation
 *
 * The expressions have already been fixed, but we have to make sure that
 * the target resnos match the child table (they may not, in the case of
 * a column that was added after-the-fact by ALTER TABLE).	In some cases
 * this can force us to re-order the tlist to preserve resno ordering.
 * (We do all this work in special cases so that preptlist.c is fast for
 * the typical case.)
 *
 * The given tlist has already been through expression_tree_mutator;
 * therefore the TargetEntry nodes are fresh copies that it's okay to
 * scribble on.
 *
 * Note that this is not needed for INSERT because INSERT isn't inheritable.
 */
static List *
adjust_inherited_tlist(List *tlist, AppendRelInfo *context)
{
	bool		changed_it = false;
	ListCell   *tl;
	List	   *new_tlist;
	bool		more;
	int			attrno;

	/* This should only happen for an inheritance case, not UNION ALL */
	Assert(OidIsValid(context->parent_reloid));

	/* Scan tlist and update resnos to match attnums of child rel */
	foreach(tl, tlist)
	{
		TargetEntry *tle = (TargetEntry *) lfirst(tl);
		int			newattno;

		if (tle->resjunk)
			continue;			/* ignore junk items */

		/* Look up the translation of this column */
		if (tle->resno <= 0 ||
			tle->resno > list_length(context->col_mappings))
			elog(ERROR, "attribute %d of relation \"%s\" does not exist",
				 tle->resno, get_rel_name(context->parent_reloid));
		newattno = list_nth_int(context->col_mappings, tle->resno - 1);
		if (newattno <= 0)
			elog(ERROR, "attribute %d of relation \"%s\" does not exist",
				 tle->resno, get_rel_name(context->parent_reloid));

		if (tle->resno != newattno)
		{
			tle->resno = newattno;
			changed_it = true;
		}
	}

	/*
	 * If we changed anything, re-sort the tlist by resno, and make sure
	 * resjunk entries have resnos above the last real resno.  The sort
	 * algorithm is a bit stupid, but for such a seldom-taken path, small is
	 * probably better than fast.
	 */
	if (!changed_it)
		return tlist;

	new_tlist = NIL;
	more = true;
	for (attrno = 1; more; attrno++)
	{
		more = false;
		foreach(tl, tlist)
		{
			TargetEntry *tle = (TargetEntry *) lfirst(tl);

			if (tle->resjunk)
				continue;		/* ignore junk items */

			if (tle->resno == attrno)
				new_tlist = lappend(new_tlist, tle);
			else if (tle->resno > attrno)
				more = true;
		}
	}

	foreach(tl, tlist)
	{
		TargetEntry *tle = (TargetEntry *) lfirst(tl);

		if (!tle->resjunk)
			continue;			/* here, ignore non-junk items */

		tle->resno = attrno;
		new_tlist = lappend(new_tlist, tle);
		attrno++;
	}

	return new_tlist;
}
