/*-------------------------------------------------------------------------
 *
 * nodeAppend.c--
 *	  routines to handle append nodes.
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeAppend.c,v 1.10 1997/12/27 06:40:50 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
/* INTERFACE ROUTINES
 *		ExecInitAppend	- initialize the append node
 *		ExecProcAppend	- retrieve the next tuple from the node
 *		ExecEndAppend	- shut down the append node
 *
 *	 NOTES
 *		Each append node contains a list of one or more subplans which
 *		must be iteratively processed (forwards or backwards).
 *		Tuples are retrieved by executing the 'whichplan'th subplan
 *		until the subplan stops returning tuples, at which point that
 *		plan is shut down and the next started up.
 *
 *		Append nodes don't make use of their left and right
 *		subtrees, rather they maintain a list of subplans so
 *		a typical append node looks like this in the plan tree:
 *
 *				   ...
 *				   /
 *				Append -------+------+------+--- nil
 *				/	\		  |		 |		|
 *			  nil	nil		 ...	...    ...
 *								 subplans
 *
 *		Append nodes are currently used to unions, and to support inheritance
 *		queries, where several relations need to be scanned.
 *		For example, in our standard person/student/employee/student-emp
 *		example, where student and employee inherit from person
 *		and student-emp inherits from student and employee, the
 *		query:
 *
 *				retrieve (e.name) from e in person*
 *
 *		generates the plan:
 *
 *				  |
 *				Append -------+-------+--------+--------+
 *				/	\		  |		  |		   |		|
 *			  nil	nil		 Scan	 Scan	  Scan	   Scan
 *							  |		  |		   |		|
 *							person employee student student-emp
 */
#include "postgres.h"


#include "access/heapam.h"
#include "executor/executor.h"
#include "executor/execdebug.h"
#include "executor/nodeAppend.h"
#include "executor/nodeIndexscan.h"
#include "utils/palloc.h"
#include "utils/mcxt.h"
#include "parser/parsetree.h"	/* for rt_store() macro */

static bool exec_append_initialize_next(Append *node);

/* ----------------------------------------------------------------
 *		exec-append-initialize-next
 *
 *		Sets up the append node state (i.e. the append state node)
 *		for the "next" scan.
 *
 *		Returns t iff there is a "next" scan to process.
 * ----------------------------------------------------------------
 */
static bool
exec_append_initialize_next(Append *node)
{
	EState	   *estate;
	AppendState *unionstate;
	TupleTableSlot *result_slot;
	List	   *rangeTable;

	int			whichplan;
	int			nplans;
	List	   *rts;
	List	   *rtentries;
	ResTarget  *rtentry;

	Index		unionrelid;

	/* ----------------
	 *	get information from the append node
	 * ----------------
	 */
	estate = node->plan.state;
	unionstate = node->unionstate;
	result_slot = unionstate->cstate.cs_ResultTupleSlot;
	rangeTable = estate->es_range_table;

	whichplan = unionstate->as_whichplan;
	nplans = unionstate->as_nplans;
	rts = node->unionrts;
	rtentries = node->unionrtentries;

	if (whichplan < 0)
	{
		/* ----------------
		 *		if scanning in reverse, we start at
		 *		the last scan in the list and then
		 *		proceed back to the first.. in any case
		 *		we inform ExecProcAppend that we are
		 *		at the end of the line by returning FALSE
		 * ----------------
		 */
		unionstate->as_whichplan = 0;
		return FALSE;

	}
	else if (whichplan >= nplans)
	{
		/* ----------------
		 *		as above, end the scan if we go beyond
		 *		the last scan in our list..
		 * ----------------
		 */
		unionstate->as_whichplan = nplans - 1;
		return FALSE;

	}
	else
	{
		/* ----------------
		 *		initialize the scan
		 *		(and update the range table appropriately)
		 *		  (doesn't this leave the range table hosed for anybody upstream
		 *		   of the Append node??? - jolly )
		 * ----------------
		 */
		if (node->unionrelid > 0)
		{
			rtentry = nth(whichplan, rtentries);
			Assert(rtentry != NULL);

			unionrelid = node->unionrelid;

			rt_store(unionrelid, rangeTable, rtentry);
		}
		else
			estate->es_range_table = nth(whichplan, rts);
		
		if (unionstate->as_junkFilter_list)
		{
			estate->es_junkFilter =
				(JunkFilter *) nth(whichplan,
								   unionstate->as_junkFilter_list);
		}
		if (unionstate->as_result_relation_info_list)
		{
			estate->es_result_relation_info =
				(RelationInfo *) nth(whichplan,
						   unionstate->as_result_relation_info_list);
		}
		result_slot->ttc_whichplan = whichplan;

		return TRUE;
	}
}

/* ----------------------------------------------------------------
 *		ExecInitAppend
 *
 *		Begins all of the subscans of the append node, storing the
 *		scan structures in the 'initialized' vector of the append-state
 *		structure.
 *
 *	   (This is potentially wasteful, since the entire result of the
 *		append node may not be scanned, but this way all of the
 *		structures get allocated in the executor's top level memory
 *		block instead of that of the call to ExecProcAppend.)
 *
 *		Returns the scan result of the first scan.
 * ----------------------------------------------------------------
 */
bool
ExecInitAppend(Append *node, EState *estate, Plan *parent)
{
	AppendState *unionstate;
	int			nplans;
	List	   *resultList = NULL;
	List	   *rtentries;
	List	   *unionplans;
	bool	   *initialized;
	int			i;
	Plan	   *initNode;
	List	   *junkList;
	RelationInfo *es_rri = estate->es_result_relation_info;

	/* ----------------
	 *	assign execution state to node and get information
	 *	for append state
	 * ----------------
	 */
	node->plan.state = estate;

	unionplans = node->unionplans;
	nplans = length(unionplans);
	rtentries = node->unionrtentries;

	CXT1_printf("ExecInitAppend: context is %d\n", CurrentMemoryContext);
	initialized = (bool *) palloc(nplans * sizeof(bool));

	/* ----------------
	 *	create new AppendState for our append node
	 * ----------------
	 */
	unionstate = makeNode(AppendState);
	unionstate->as_whichplan = 0;
	unionstate->as_nplans = nplans;
	unionstate->as_initialized = initialized;
	unionstate->as_rtentries = rtentries;

	node->unionstate = unionstate;

	/* ----------------
	 *	Miscellanious initialization
	 *
	 *		 +	assign node's base_id
	 *		 +	assign debugging hooks
	 *
	 *	Append plans don't have expression contexts because they
	 *	never call ExecQual or ExecTargetList.
	 * ----------------
	 */
	ExecAssignNodeBaseInfo(estate, &unionstate->cstate, parent);

#define APPEND_NSLOTS 1
	/* ----------------
	 *	append nodes still have Result slots, which hold pointers
	 *	to tuples, so we have to initialize them..
	 * ----------------
	 */
	ExecInitResultTupleSlot(estate, &unionstate->cstate);

	/*
	 * If the inherits rtentry is the result relation, we have to make a
	 * result relation info list for all inheritors so we can update their
	 * indices and put the result tuples in the right place etc.
	 *
	 * e.g. replace p (age = p.age + 1) from p in person*
	 */
	if ((es_rri != (RelationInfo *) NULL) &&
		(node->unionrelid == es_rri->ri_RangeTableIndex))
	{
		RelationInfo *rri;
		List	   *rtentryP;

		foreach(rtentryP, rtentries)
		{
			Oid			reloid;
			RangeTblEntry *rtentry = lfirst(rtentryP);

			reloid = rtentry->relid;
			rri = makeNode(RelationInfo);
			rri->ri_RangeTableIndex = es_rri->ri_RangeTableIndex;
			rri->ri_RelationDesc = heap_open(reloid);
			rri->ri_NumIndices = 0;
			rri->ri_IndexRelationDescs = NULL;	/* index descs */
			rri->ri_IndexRelationInfo = NULL;	/* index key info */

			resultList = lcons(rri, resultList);
			ExecOpenIndices(reloid, rri);
		}
		unionstate->as_result_relation_info_list = resultList;
	}
	/* ----------------
	 *	call ExecInitNode on each of the plans in our list
	 *	and save the results into the array "initialized"
	 * ----------------
	 */
	junkList = NIL;

	for (i = 0; i < nplans; i++)
	{
		JunkFilter *j;
		List	   *targetList;

		/* ----------------
		 *	NOTE: we first modify range table in
		 *		  exec_append_initialize_next() and
		 *		  then initialize the subnode,
		 *		  since it may use the range table.
		 * ----------------
		 */
		unionstate->as_whichplan = i;
		exec_append_initialize_next(node);

		initNode = (Plan *) nth(i, unionplans);
		initialized[i] = ExecInitNode(initNode, estate, (Plan *) node);

		/* ---------------
		 *	Each targetlist in the subplan may need its own junk filter
		 *
		 *	This is true only when the reln being replaced/deleted is
		 *	the one that we're looking at the subclasses of
		 * ---------------
		 */
		if ((es_rri != (RelationInfo *) NULL) &&
			(node->unionrelid == es_rri->ri_RangeTableIndex))
		{

			targetList = initNode->targetlist;
			j = (JunkFilter *) ExecInitJunkFilter(targetList);
			junkList = lappend(junkList, j);
		}

	}
	unionstate->as_junkFilter_list = junkList;
	if (junkList != NIL)
		estate->es_junkFilter = (JunkFilter *) lfirst(junkList);

	/* ----------------
	 *	initialize the return type from the appropriate subplan.
	 * ----------------
	 */
	initNode = (Plan *) nth(0, unionplans);
	ExecAssignResultType(&unionstate->cstate,
/*						 ExecGetExecTupDesc(initNode), */
						 ExecGetTupType(initNode));
	unionstate->cstate.cs_ProjInfo = NULL;

	/* ----------------
	 *	return the result from the first subplan's initialization
	 * ----------------
	 */
	unionstate->as_whichplan = 0;
	exec_append_initialize_next(node);
#if 0
	result = (List *) initialized[0];
#endif
	return TRUE;
}

int
ExecCountSlotsAppend(Append *node)
{
	List	   *plan;
	List	   *unionplans = node->unionplans;
	int			nSlots = 0;

	foreach(plan, unionplans)
	{
		nSlots += ExecCountSlotsNode((Plan *) lfirst(plan));
	}
	return nSlots + APPEND_NSLOTS;
}

/* ----------------------------------------------------------------
 *	   ExecProcAppend
 *
 *		Handles the iteration over the multiple scans.
 *
 *	   NOTE: Can't call this ExecAppend, that name is used in execMain.l
 * ----------------------------------------------------------------
 */
TupleTableSlot *
ExecProcAppend(Append *node)
{
	EState	   *estate;
	AppendState *unionstate;

	int			whichplan;
	List	   *unionplans;
	Plan	   *subnode;
	TupleTableSlot *result;
	TupleTableSlot *result_slot;
	ScanDirection direction;

	/* ----------------
	 *	get information from the node
	 * ----------------
	 */
	unionstate = node->unionstate;
	estate = node->plan.state;
	direction = estate->es_direction;

	unionplans = node->unionplans;
	whichplan = unionstate->as_whichplan;
	result_slot = unionstate->cstate.cs_ResultTupleSlot;

	/* ----------------
	 *	figure out which subplan we are currently processing
	 * ----------------
	 */
	subnode = (Plan *) nth(whichplan, unionplans);

	if (subnode == NULL)
		elog(DEBUG, "ExecProcAppend: subnode is NULL");

	/* ----------------
	 *	get a tuple from the subplan
	 * ----------------
	 */
	result = ExecProcNode(subnode, (Plan *) node);

	if (!TupIsNull(result))
	{
		/* ----------------
		 *	if the subplan gave us something then place a copy of
		 *	whatever we get into our result slot and return it, else..
		 * ----------------
		 */
		return ExecStoreTuple(result->val,
							  result_slot, result->ttc_buffer, false);

	}
	else
	{
		/* ----------------
		 *	.. go on to the "next" subplan in the appropriate
		 *	direction and try processing again (recursively)
		 * ----------------
		 */
		whichplan = unionstate->as_whichplan;

		if (ScanDirectionIsForward(direction))
		{
			unionstate->as_whichplan = whichplan + 1;
		}
		else
		{
			unionstate->as_whichplan = whichplan - 1;
		}

		/* ----------------
		 *	return something from next node or an empty slot
		 *	all of our subplans have been exhausted.
		 * ----------------
		 */
		if (exec_append_initialize_next(node))
		{
			ExecSetSlotDescriptorIsNew(result_slot, true);
			return ExecProcAppend(node);
		}
		else
			return ExecClearTuple(result_slot);
	}
}

/* ----------------------------------------------------------------
 *		ExecEndAppend
 *
 *		Shuts down the subscans of the append node.
 *
 *		Returns nothing of interest.
 * ----------------------------------------------------------------
 */
void
ExecEndAppend(Append *node)
{
	AppendState *unionstate;
	int			nplans;
	List	   *unionplans;
	bool	   *initialized;
	int			i;
	List	   *resultRelationInfoList;
	RelationInfo *resultRelationInfo;

	/* ----------------
	 *	get information from the node
	 * ----------------
	 */
	unionstate = node->unionstate;
	unionplans = node->unionplans;
	nplans = unionstate->as_nplans;
	initialized = unionstate->as_initialized;

	/* ----------------
	 *	shut down each of the subscans
	 * ----------------
	 */
	for (i = 0; i < nplans; i++)
	{
		if (initialized[i] == TRUE)
		{
			ExecEndNode((Plan *) nth(i, unionplans), (Plan *) node);
		}
	}

	/* ----------------
	 *	close out the different result relations
	 * ----------------
	 */
	resultRelationInfoList = unionstate->as_result_relation_info_list;
	while (resultRelationInfoList != NIL)
	{
		Relation	resultRelationDesc;

		resultRelationInfo = (RelationInfo *) lfirst(resultRelationInfoList);
		resultRelationDesc = resultRelationInfo->ri_RelationDesc;
		heap_close(resultRelationDesc);
		pfree(resultRelationInfo);
		resultRelationInfoList = lnext(resultRelationInfoList);
	}
	if (unionstate->as_result_relation_info_list)
		pfree(unionstate->as_result_relation_info_list);

	/*
	 * XXX should free unionstate->as_rtentries  and
	 * unionstate->as_junkfilter_list here
	 */
}
