prepunion.c

PostgreSQL7.4.6 for Linux

	 *
	 * 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 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
 * 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,
					 bool hack_constants,
					 List *input_tlist,
					 List *refnames_tlist)
{
	List	   *tlist = NIL;
	int			resno = 1;
	List	   *i;
	Resdom	   *resdom;
	Node	   *expr;

	foreach(i, colTypes)
	{
		Oid			colType = lfirsto(i);
		TargetEntry *inputtle = (TargetEntry *) lfirst(input_tlist);
		TargetEntry *reftle = (TargetEntry *) lfirst(refnames_tlist);
		int32		colTypmod;

		Assert(inputtle->resdom->resno == resno);
		Assert(reftle->resdom->resno == resno);
		Assert(!inputtle->resdom->resjunk);
		Assert(!reftle->resdom->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(0,
									inputtle->resdom->resno,
									inputtle->resdom->restype,
									inputtle->resdom->restypmod,
									0);
		if (inputtle->resdom->restype == colType)
		{
			/* no coercion needed, and believe the input typmod */
			colTypmod = inputtle->resdom->restypmod;
		}
		else
		{
			expr = coerce_to_common_type(NULL,	/* no UNKNOWNs here */
										 expr,
										 colType,
										 "UNION/INTERSECT/EXCEPT");
			colTypmod = -1;
		}
		resdom = makeResdom((AttrNumber) resno++,
							colType,
							colTypmod,
							pstrdup(reftle->resdom->resname),
							false);
		tlist = lappend(tlist, makeTargetEntry(resdom, (Expr *) expr));
		input_tlist = lnext(input_tlist);
		refnames_tlist = lnext(refnames_tlist);
	}

	if (flag >= 0)
	{
		/* Add a resjunk flag column */
		resdom = makeResdom((AttrNumber) resno++,
							INT4OID,
							-1,
							pstrdup("flag"),
							true);
		/* flag value is the given constant */
		expr = (Node *) makeConst(INT4OID,
								  sizeof(int4),
								  Int32GetDatum(flag),
								  false,
								  true);
		tlist = lappend(tlist, makeTargetEntry(resdom, (Expr *) expr));
	}

	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.
 */
static List *
generate_append_tlist(List *colTypes, bool flag,
					  List *input_plans,
					  List *refnames_tlist)
{
	List	   *tlist = NIL;
	int			resno = 1;
	List	   *curColType;
	int			colindex;
	Resdom	   *resdom;
	Node	   *expr;
	List	   *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(length(colTypes) * sizeof(int32));

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

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

			if (subtle->resdom->resjunk)
				continue;
			Assert(curColType != NIL);
			if (subtle->resdom->restype == lfirsto(curColType))
			{
				/* If first subplan, copy the typmod; else compare */
				if (planl == input_plans)
					colTypmods[colindex] = subtle->resdom->restypmod;
				else if (subtle->resdom->restypmod != colTypmods[colindex])
					colTypmods[colindex] = -1;
			}
			else
			{
				/* types disagree, so force typmod to -1 */
				colTypmods[colindex] = -1;
			}
			curColType = lnext(curColType);
			colindex++;
		}
		Assert(curColType == NIL);
	}

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

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

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

	pfree(colTypmods);

	return tlist;
}

/*
 * Does tlist have same datatypes as requested colTypes?
 *
 * Resjunk columns are ignored if junkOK is true; otherwise presence of
 * a resjunk column will always cause a 'false' result.
 */
static bool
tlist_same_datatypes(List *tlist, List *colTypes, bool junkOK)
{
	List	   *i;

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

		if (tle->resdom->resjunk)
		{
			if (!junkOK)
				return false;
		}
		else
		{
			if (colTypes == NIL)
				return false;
			if (tle->resdom->restype != lfirsto(colTypes))
				return false;
			colTypes = lnext(colTypes);
		}
	}
	if (colTypes != NIL)
		return false;
	return true;
}


/*
 * 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	   *examined_relids = NIL;
	List	   *unexamined_relids = makeListo1(parentrel);

	/*
	 * While the queue of unexamined relids is nonempty, remove the first
	 * element, mark it examined, and find its direct descendants. NB:
	 * cannot use foreach(), since we modify the queue inside loop.
	 */
	while (unexamined_relids != NIL)
	{
		Oid			currentrel = lfirsto(unexamined_relids);
		List	   *currentchildren;

		unexamined_relids = lnext(unexamined_relids);
		examined_relids = lappendo(examined_relids, currentrel);
		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.)
		 */
		currentchildren = set_differenceo(currentchildren, examined_relids);
		unexamined_relids = set_uniono(unexamined_relids, currentchildren);
	}

	return examined_relids;
}

/*
 * 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 return an integer list of RT indexes for the
 *		whole inheritance set (parent and children).
 *		If not, return NIL.
 *
 * When dup_parent is false, the initially given RT index is part of the
 * returned list (if any).	When dup_parent is true, the given RT index
 * is *not* in the returned list; a duplicate RTE will be made for the
 * parent table.
 *
 * A childless table is never considered to be an inheritance set; therefore
 * the result will never be a one-element list.  It'll be either empty
 * or have two or more elements.
 *
 * NOTE: after this routine executes, the specified RTE will always have
 * its inh flag cleared, whether or not there were any children.  This
 * ensures we won't expand the same RTE twice, which would otherwise occur
 * for the case of an inherited UPDATE/DELETE target relation.
 *
 * XXX probably should convert the result type to Relids?
 */
List *
expand_inherited_rtentry(Query *parse, Index rti, bool dup_parent)
{
	RangeTblEntry *rte = rt_fetch(rti, parse->rtable);
	Oid			parentOID;
	List	   *inhOIDs;
	List	   *inhRTIs;
	List	   *l;

	/* Does RT entry allow inheritance? */
	if (!rte->inh)
		return NIL;
	Assert(rte->rtekind == RTE_RELATION);
	/* Always clear the parent's inh flag, see above comments */
	rte->inh = false;
	/* Fast path for common case of childless table */
	parentOID = rte->relid;
	if (!has_subclass(parentOID))
		return NIL;
	/* 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 (lnext(inhOIDs) == NIL)
		return NIL;
	/* OK, it's an inheritance set; expand it */
	if (dup_parent)
		inhRTIs = NIL;
	else