prepunion.c

来自「PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统」· C语言 代码 · 共 1,246 行 · 第 1/3 页

	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;
}

/*
 * 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)
{
	ListCell   *l;
	ListCell   *curColType = list_head(colTypes);

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

		if (tle->resjunk)
		{
			if (!junkOK)
				return false;
		}
		else
		{
			if (curColType == NULL)
				return false;
			if (exprType((Node *) tle->expr) != lfirst_oid(curColType))
				return false;
			curColType = lnext(curColType);
		}
	}
	if (curColType != NULL)
		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	   *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_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.
 *
 * Note that the original RTE is considered to represent the whole
 * inheritance set.  The first member of the returned list 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 set.  The original RT index is
 * never a member of the returned list.
 *
 * 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: there are cases in which this routine will be invoked multiple
 * times on the same RTE.  We will generate a separate set of child RTEs
 * for each invocation.  This is somewhat wasteful but seems not worth
 * trying to avoid.
 */
List *
expand_inherited_rtentry(PlannerInfo *root, Index rti)
{
	Query	   *parse = root->parse;
	RangeTblEntry *rte = rt_fetch(rti, parse->rtable);
	Oid			parentOID;
	List	   *inhOIDs;
	List	   *inhRTIs;
	ListCell   *l;

	/* Does RT entry allow inheritance? */
	if (!rte->inh)
		return NIL;
	Assert(rte->rtekind == RTE_RELATION);
	/* Fast path for common case of childless table */
	parentOID = rte->relid;
	if (!has_subclass(parentOID))
	{
		/* Clear flag to save repeated tests if called again */
		rte->inh = false;
		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 (list_length(inhOIDs) < 2)
	{
		/* Clear flag to save repeated tests if called again */
		rte->inh = false;
		return NIL;
	}

	/* OK, it's an inheritance set; expand it */
	inhRTIs = NIL;
	foreach(l, inhOIDs)
	{
		Oid			childOID = lfirst_oid(l);
		RangeTblEntry *childrte;
		Index		childRTindex;

		/*
		 * 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;

		/*
		 * 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);
		inhRTIs = lappend_int(inhRTIs, childRTindex);
	}