predmig.c

关系型数据库 Postgresql 6.5.2

{
	Stream		temp,
				parent;
	int			lowest = xfunc_num_relids((Stream) xfunc_get_upjoin(bottom));
	bool		progress;
	LispValue	primjoin;
	int			whichchild;

	if (!lowest)
		return;					/* no joins in stream, so no groups */

	/* initialize groups to be single nodes */
	for (temp = root;
		 temp != (Stream) NULL && temp != bottom;
		 temp = (Stream) get_downstream(temp))
	{
		/* if a Join node */
		if (!is_clause(temp))
		{
			if (get_pathptr((Stream) get_downstream(temp))
			== (pathPtr) get_outerjoinpath((JoinPath) get_pathptr(temp)))
				whichchild = OUTER;
			else
				whichchild = INNER;
			set_groupcost(temp,
						  xfunc_join_expense((JoinPath) get_pathptr(temp),
											 whichchild));
			if (primjoin = xfunc_primary_join((JoinPath) get_pathptr(temp)))
			{
				set_groupsel(temp,
							 compute_clause_selec(queryInfo,
												  primjoin, NIL));
			}
			else
				set_groupsel(temp, 1.0);
		}
		else
/* a restriction, or 2-ary join pred */
		{
			set_groupcost(temp,
						  xfunc_expense(queryInfo,
										get_clause(get_cinfo(temp))));
			set_groupsel(temp,
						 compute_clause_selec(queryInfo,
											  get_clause(get_cinfo(temp)),
											  NIL));
		}
		set_groupup(temp, false);
	}

	/* make passes upwards, forming groups */
	do
	{
		progress = false;
		for (temp = (Stream) get_upstream(bottom);
			 temp != (Stream) NULL;
			 temp = (Stream) get_upstream(temp))
		{
			/* check for grouping with node upstream */
			if (!get_groupup(temp) &&	/* not already grouped */
				(parent = (Stream) get_upstream(temp)) != (Stream) NULL &&
			/* temp is a join or temp is the top of a group */
				(is_join((Path) get_pathptr(temp)) ||
				 get_downstream(temp) &&
				 get_groupup((Stream) get_downstream(temp))) &&
				get_grouprank(parent) < get_grouprank(temp))
			{
				progress = true;/* we formed a new group */
				set_groupup(temp, true);
				set_groupcost(temp,
							  get_groupcost(temp) +
							  get_groupsel(temp) * get_groupcost(parent));
				set_groupsel(temp, get_groupsel(temp) * get_groupsel(parent));

				/* fix costs and sels of all members of group */
				xfunc_setup_group(temp, bottom);
			}
		}
	} while (progress);
}


/* -------------------					 UTILITY FUNCTIONS	   ------------------------- */

/*
 ** xfunc_free_stream
 **   walk down a stream and pfree it
 */
static void
xfunc_free_stream(Stream root)
{
	Stream		cur,
				next;

	Assert(xfunc_check_stream(root));

	if (root != (Stream) NULL)
		for (cur = root; cur != (Stream) NULL; cur = next)
		{
			next = (Stream) get_downstream(cur);
			pfree(cur);
		}
}

/*
 ** xfunc_add<_clauses
 **    find any clauses above current, and insert them into stream as
 ** appropriate.  Return uppermost clause inserted, or current if none.
 */
static Stream
xfunc_add_clauses(Stream current)
{
	Stream		topnode = current;
	LispValue	temp;
	LispValue	primjoin;

	/* first add in the local clauses */
	foreach(temp, get_loc_restrictinfo((Path) get_pathptr(current)))
	{
		topnode = xfunc_streaminsert((RestrictInfo) lfirst(temp), topnode,
									 XFUNC_LOCPRD);
	}

	/* and add in the join clauses */
	if (IsA(get_pathptr(current), JoinPath))
	{
		primjoin = xfunc_primary_join((JoinPath) get_pathptr(current));
		foreach(temp, get_pathrestrictinfo((JoinPath) get_pathptr(current)))
		{
			if (!equal(get_clause((RestrictInfo) lfirst(temp)), primjoin))
				topnode = xfunc_streaminsert((RestrictInfo) lfirst(temp), topnode,
											 XFUNC_JOINPRD);
		}
	}
	return topnode;
}


/*
 ** xfunc_setup_group
 **   find all elements of stream that are grouped with node and are above
 ** bottom, and set their groupcost and groupsel to be the same as node's.
 */
static void
xfunc_setup_group(Stream node, Stream bottom)
{
	Stream		temp;

	if (node != bottom)
		/* traverse downwards */
		for (temp = (Stream) get_downstream(node);
			 temp != (Stream) NULL && temp != bottom;
			 temp = (Stream) get_downstream(temp))
		{
			if (!get_groupup(temp))
				break;
			else
			{
				set_groupcost(temp, get_groupcost(node));
				set_groupsel(temp, get_groupsel(node));
			}
		}

	/* traverse upwards */
	for (temp = (Stream) get_upstream(node); temp != (Stream) NULL;
		 temp = (Stream) get_upstream(temp))
	{
		if (!get_groupup((Stream) get_downstream(temp)))
			break;
		else
		{
			set_groupcost(temp, get_groupcost(node));
			set_groupsel(temp, get_groupsel(node));
		}
	}
}


/*
 ** xfunc_streaminsert
 **    Make a new Stream node to hold clause, and insert it above current.
 ** Return new node.
 */
static Stream
xfunc_streaminsert(RestrictInfo restrictinfo,
				   Stream current,
				   int clausetype)		/* XFUNC_LOCPRD or XFUNC_JOINPRD */
{
	Stream		newstream = RMakeStream();

	set_upstream(newstream, get_upstream(current));
	if (get_upstream(current))
		set_downstream((Stream) (get_upstream(current)), (StreamPtr) newstream);
	set_upstream(current, (StreamPtr) newstream);
	set_downstream(newstream, (StreamPtr) current);
	set_pathptr(newstream, get_pathptr(current));
	set_cinfo(newstream, restrictinfo);
	set_clausetype(newstream, clausetype);
	return newstream;
}

/*
 ** Given a Stream node, find the number of relids referenced in the pathnode
 ** associated with the stream node.  The number of relids gives a unique
 ** ordering on the joins in a stream, which we use to compare the height of
 ** join nodes.
 */
static int
xfunc_num_relids(Stream node)
{
	if (!node || !IsA(get_pathptr(node), JoinPath))
		return 0;
	else
		return (length
				(get_relids(get_parent((JoinPath) get_pathptr(node)))));
}

/*
 ** xfunc_get_downjoin
 **    Given a stream node, find the next lowest node which points to a
 ** join predicate or a scan node.
 */
static StreamPtr
xfunc_get_downjoin(Stream node)
{
	Stream		temp;

	if (!is_clause(node))		/* if this is a join */
		node = (Stream) get_downstream(node);
	for (temp = node; temp && is_clause(temp);
		 temp = (Stream) get_downstream(temp))
		 /* empty body in for loop */ ;

	return (StreamPtr) temp;
}

/*
 ** xfunc_get_upjoin
 **   same as above, but upwards.
 */
static StreamPtr
xfunc_get_upjoin(Stream node)
{
	Stream		temp;

	if (!is_clause(node))		/* if this is a join */
		node = (Stream) get_upstream(node);
	for (temp = node; temp && is_clause(temp);
		 temp = (Stream) get_upstream(temp))
		 /* empty body in for loop */ ;

	return (StreamPtr) temp;
}

/*
 ** xfunc_stream_qsort
 **   Given a stream, sort by group rank the elements in the stream from the
 ** node "bottom" up.  DESTRUCTIVELY MODIFIES STREAM!  Returns new root.
 */
static Stream
xfunc_stream_qsort(Stream root, Stream bottom)
{
	int			i;
	size_t		num;
	Stream	   *nodearray,
				output;
	Stream		tmp;

	/* find size of list */
	for (num = 0, tmp = root; tmp != bottom;
		 tmp = (Stream) get_downstream(tmp))
		num++;
	if (num <= 1)
		return root;

	/* copy elements of the list into an array */
	nodearray = (Stream *) palloc(num * sizeof(Stream));

	for (tmp = root, i = 0; tmp != bottom;
		 tmp = (Stream) get_downstream(tmp), i++)
		nodearray[i] = tmp;

	/* sort the array */
	qsort(nodearray, num, sizeof(LispValue), xfunc_stream_compare);

	/* paste together the array elements */
	output = nodearray[num - 1];
	set_upstream(output, (StreamPtr) NULL);
	for (i = num - 2; i >= 0; i--)
	{
		set_downstream(nodearray[i + 1], (StreamPtr) nodearray[i]);
		set_upstream(nodearray[i], (StreamPtr) nodearray[i + 1]);
	}
	set_downstream(nodearray[0], (StreamPtr) bottom);
	if (bottom)
		set_upstream(bottom, (StreamPtr) nodearray[0]);

	Assert(xfunc_check_stream(output));
	return output;
}

/*
 ** xfunc_stream_compare
 **    comparison function for xfunc_stream_qsort.
 ** Compare nodes by group rank.  If group ranks are equal, ensure that
 ** join nodes appear in same order as in plan tree.
 */
static int
xfunc_stream_compare(void *arg1, void *arg2)
{
	Stream		stream1 = *(Stream *) arg1;
	Stream		stream2 = *(Stream *) arg2;
	Cost		rank1,
				rank2;

	rank1 = get_grouprank(stream1);
	rank2 = get_grouprank(stream2);

	if (rank1 > rank2)
		return 1;
	else if (rank1 < rank2)
		return -1;
	else
	{
		if (is_clause(stream1) && is_clause(stream2))
			return 0;			/* doesn't matter what order if both are
								 * restrictions */
		else if (!is_clause(stream1) && !is_clause(stream2))
		{
			if (xfunc_num_relids(stream1) < xfunc_num_relids(stream2))
				return -1;
			else
				return 1;
		}
		else if (is_clause(stream1) && !is_clause(stream2))
		{
			if (xfunc_num_relids(stream1) == xfunc_num_relids(stream2))
				/* stream1 is a restriction over stream2 */
				return 1;
			else
				return -1;
		}
		else if (!is_clause(stream1) && is_clause(stream2))
		{
			/* stream2 is a restriction over stream1: never push down */
			return -1;
		}
	}
}

/* ------------------  DEBUGGING ROUTINES ---------------------------- */

/*
 ** Make sure all pointers in stream make sense.  Make sure no joins are
 ** out of order.
 */
static bool
xfunc_check_stream(Stream node)
{
	Stream		temp;
	int			numrelids,
				tmp;

	/* set numrelids higher than max */
	if (!is_clause(node))
		numrelids = xfunc_num_relids(node) + 1;
	else if (xfunc_get_downjoin(node))
		numrelids = xfunc_num_relids((Stream) xfunc_get_downjoin(node)) + 1;
	else
		numrelids = 1;

	for (temp = node; get_downstream(temp); temp = (Stream) get_downstream(temp))
	{
		if ((Stream) get_upstream((Stream) get_downstream(temp)) != temp)
		{
			elog(ERROR, "bad pointers in stream");
			return false;
		}
		if (!is_clause(temp))
		{
			if ((tmp = xfunc_num_relids(temp)) >= numrelids)
			{
				elog(ERROR, "Joins got reordered!");
				return false;
			}
			numrelids = tmp;
		}
	}

	return true;
}

/*
 ** xfunc_in_stream
 **   check if node is in stream
 */
static bool
xfunc_in_stream(Stream node, Stream stream)
{
	Stream		temp;

	for (temp = stream; temp; temp = (Stream) get_downstream(temp))
		if (temp == node)
			return 1;
	return 0;
}