/*-------------------------------------------------------------------------
 *
 * nodeNestloop.c--
 *    routines to support nest-loop joins
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /cvsroot/pgsql/src/backend/executor/nodeNestloop.c,v 1.2 1996/10/31 10:12:14 scrappy Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 *   INTERFACE ROUTINES
 *   	ExecNestLoop	 - process a nestloop join of two plans
 *   	ExecInitNestLoop - initialize the join
 *   	ExecEndNestLoop	 - shut down the join
 */
#include "postgres.h"

#include "executor/executor.h"
#include "executor/nodeNestloop.h"
#include "executor/nodeIndexscan.h"

/* ----------------------------------------------------------------
 *   	ExecNestLoop(node)
 *
 * old comments
 *   	Returns the tuple joined from inner and outer tuples which 
 *   	satisfies the qualification clause.
 *
 *	It scans the inner relation to join with current outer tuple.
 *
 *	If none is found, next tuple form the outer relation is retrieved
 *	and the inner relation is scanned from the beginning again to join
 *	with the outer tuple.
 *
 *   	Nil is returned if all the remaining outer tuples are tried and
 *   	all fail to join with the inner tuples.
 *
 *   	Nil is also returned if there is no tuple from inner realtion.
 *   
 *   	Conditions:
 *   	  -- outerTuple contains current tuple from outer relation and
 *   	     the right son(inner realtion) maintains "cursor" at the tuple
 *   	     returned previously.
 *              This is achieved by maintaining a scan position on the outer
 *              relation.
 *   
 *   	Initial States:
 *   	  -- the outer child and the inner child 
 *             are prepared to return the first tuple.
 * ----------------------------------------------------------------
 */
TupleTableSlot *
ExecNestLoop(NestLoop *node, Plan* parent)
{
    NestLoopState 	*nlstate;
    Plan	  	*innerPlan;
    Plan	  	*outerPlan;
    bool 	  	needNewOuterTuple;

    TupleTableSlot  	*outerTupleSlot;
    TupleTableSlot  	*innerTupleSlot;

    List	  	*qual;
    bool	  	qualResult;
    ExprContext	  	*econtext;

    /* ----------------
     *	get information from the node
     * ----------------
     */
    ENL1_printf("getting info from node");

    nlstate =    node->nlstate;
    qual =       node->join.qual;
    outerPlan =  outerPlan(&node->join);
    innerPlan =  innerPlan(&node->join);

    /* ----------------
     *	initialize expression context
     * ----------------
     */
    econtext = nlstate->jstate.cs_ExprContext;

    /* ----------------     *	get the current outer tuple
     * ----------------
     */
    outerTupleSlot = nlstate->jstate.cs_OuterTupleSlot;
    econtext->ecxt_outertuple = outerTupleSlot;

    /* ----------------
     *  Ok, everything is setup for the join so now loop until
     *  we return a qualifying join tuple..
     * ----------------
     */

    if (nlstate->jstate.cs_TupFromTlist) {
	TupleTableSlot  *result;
	bool		isDone;

	result = ExecProject(nlstate->jstate.cs_ProjInfo, &isDone);
	if (!isDone)
	    return result;
    }

    ENL1_printf("entering main loop");
    for(;;) {
	/* ----------------
	 *  The essential idea now is to get the next inner tuple
	 *  and join it with the current outer tuple.
	 * ----------------
	 */
	needNewOuterTuple = false;
	
	/* ----------------
	 *  If outer tuple is not null then that means
	 *  we are in the middle of a scan and we should
	 *  restore our previously saved scan position.
	 * ----------------
	 */
	if (! TupIsNull(outerTupleSlot)) {	    
	    ENL1_printf("have outer tuple, restoring outer plan");
	    ExecRestrPos(outerPlan);
	} else {
	    ENL1_printf("outer tuple is nil, need new outer tuple");
	    needNewOuterTuple = true;
	}
	
	/* ----------------
	 *  if we have an outerTuple, try to get the next inner tuple.
	 * ----------------
	 */
	if (!needNewOuterTuple) {
	    ENL1_printf("getting new inner tuple");
	
	    innerTupleSlot = ExecProcNode(innerPlan, (Plan*)node);
	    econtext->ecxt_innertuple = innerTupleSlot;
	    
	    if (TupIsNull(innerTupleSlot)) {
		ENL1_printf("no inner tuple, need new outer tuple");
		needNewOuterTuple = true;
	    }
	}
	
	/* ----------------
	 *  loop until we have a new outer tuple and a new
	 *  inner tuple.
	 * ----------------
	 */
	while (needNewOuterTuple) {
	    /* ----------------
	     *	now try to get the next outer tuple
	     * ----------------
	     */
	    ENL1_printf("getting new outer tuple");
	    outerTupleSlot = ExecProcNode(outerPlan, (Plan*)node);
	    econtext->ecxt_outertuple = outerTupleSlot;
	    
	    /* ----------------
	     *  if there are no more outer tuples, then the join
	     *  is complete..
	     * ----------------
	     */
	    if (TupIsNull(outerTupleSlot)) {
		ENL1_printf("no outer tuple, ending join");
		return NULL;
	    }
	    
	    /* ----------------
	     *  we have a new outer tuple so we mark our position
	     *  in the outer scan and save the outer tuple in the
	     *  NestLoop state
	     * ----------------
	     */
	    ENL1_printf("saving new outer tuple information");
	    ExecMarkPos(outerPlan);
	    nlstate->jstate.cs_OuterTupleSlot = outerTupleSlot;
	    
	    /* ----------------
	     *	now rescan the inner plan and get a new inner tuple
	     * ----------------
	     */
	    
	    ENL1_printf("rescanning inner plan");
	    /* 
	     * The scan key of the inner plan might depend on the current
	     * outer tuple (e.g. in index scans), that's why we pass our
	     * expr context.
	     */
	    ExecReScan(innerPlan, econtext, parent);

	    ENL1_printf("getting new inner tuple");
	    
	    innerTupleSlot = ExecProcNode(innerPlan, (Plan*)node);
	    econtext->ecxt_innertuple = innerTupleSlot;
	    
	    if (TupIsNull(innerTupleSlot)) {
		ENL1_printf("couldn't get inner tuple - need new outer tuple");
	    } else {
		ENL1_printf("got inner and outer tuples");
		needNewOuterTuple = false;
	    }
	} /* while (needNewOuterTuple) */
	
	/* ----------------
	 *   at this point we have a new pair of inner and outer
	 *   tuples so we test the inner and outer tuples to see
	 *   if they satisify the node's qualification.
	 * ----------------
	 */
	ENL1_printf("testing qualification");
	qualResult = ExecQual((List*)qual, econtext);
	
	if (qualResult) {
	    /* ----------------
	     *  qualification was satisified so we project and
	     *  return the slot containing the result tuple
	     *  using ExecProject().
	     * ----------------
	     */
	    ProjectionInfo *projInfo;
	    TupleTableSlot *result;
	    bool           isDone;
	    
	    ENL1_printf("qualification succeeded, projecting tuple");
	    
	    projInfo = nlstate->jstate.cs_ProjInfo;
	    result = ExecProject(projInfo, &isDone);
	    nlstate->jstate.cs_TupFromTlist = !isDone;
	    return result;
	} 
	
	/* ----------------
	 *  qualification failed so we have to try again..
	 * ----------------
	 */
	ENL1_printf("qualification failed, looping");
    }
}

/* ----------------------------------------------------------------
 *   	ExecInitNestLoop
 *   
 *   	Creates the run-time state information for the nestloop node
 *   	produced by the planner and initailizes inner and outer relations 
 *   	(child nodes).
 * ----------------------------------------------------------------  	
 */
bool
ExecInitNestLoop(NestLoop *node, EState *estate, Plan *parent)
{
    NestLoopState   *nlstate;

    NL1_printf("ExecInitNestLoop: %s\n",
	       "initializing node");
	
    /* ----------------
     *	assign execution state to node
     * ----------------
     */
    node->join.state = estate;

    /* ----------------
     *    create new nest loop state
     * ----------------
     */
    nlstate = makeNode(NestLoopState);
    nlstate->nl_PortalFlag = false;
    node->nlstate = nlstate;

    /* ----------------
     *  Miscellanious initialization
     *
     *	     +	assign node's base_id
     *       +	assign debugging hooks and
     *       +	create expression context for node
     * ----------------
     */
    ExecAssignNodeBaseInfo(estate, &nlstate->jstate, parent);
    ExecAssignExprContext(estate, &nlstate->jstate);

#define NESTLOOP_NSLOTS 1
    /* ----------------
     *	tuple table initialization
     * ----------------
     */
    ExecInitResultTupleSlot(estate, &nlstate->jstate);

    /* ----------------
     *    now initialize children
     * ----------------
     */
    ExecInitNode(outerPlan((Plan*)node), estate, (Plan*)node);
    ExecInitNode(innerPlan((Plan*)node), estate, (Plan*)node);

    /* ----------------
     * 	initialize tuple type and projection info
     * ----------------
     */
    ExecAssignResultTypeFromTL((Plan *) node, &nlstate->jstate);
    ExecAssignProjectionInfo((Plan *) node, &nlstate->jstate);

    /* ----------------
     *  finally, wipe the current outer tuple clean.
     * ----------------
     */
    nlstate->jstate.cs_OuterTupleSlot = NULL;
    nlstate->jstate.cs_TupFromTlist = false;

    NL1_printf("ExecInitNestLoop: %s\n",
	       "node initialized");
    return TRUE;
}

int
ExecCountSlotsNestLoop(NestLoop *node)
{
    return ExecCountSlotsNode(outerPlan(node)) +
	   ExecCountSlotsNode(innerPlan(node)) +
	   NESTLOOP_NSLOTS;
}

/* ----------------------------------------------------------------
 *   	ExecEndNestLoop
 *   
 *   	closes down scans and frees allocated storage
 * ----------------------------------------------------------------
 */
void
ExecEndNestLoop(NestLoop *node)
{
    NestLoopState   *nlstate;

    NL1_printf("ExecEndNestLoop: %s\n",
	       "ending node processing");

    /* ----------------
     *	get info from the node
     * ----------------
     */
    nlstate =  node->nlstate;

    /* ----------------
     *	Free the projection info
     *
     *  Note: we don't ExecFreeResultType(nlstate) 
     *        because the rule manager depends on the tupType
     *	      returned by ExecMain().  So for now, this
     *	      is freed at end-transaction time.  -cim 6/2/91     
     * ----------------
     */    
    ExecFreeProjectionInfo(&nlstate->jstate);

    /* ----------------
     *	close down subplans
     * ----------------
     */
    ExecEndNode(outerPlan((Plan *) node), (Plan*)node);
    ExecEndNode(innerPlan((Plan *) node), (Plan*)node);

    /* ----------------
     *	clean out the tuple table 
     * ----------------
     */
    ExecClearTuple(nlstate->jstate.cs_ResultTupleSlot);

    NL1_printf("ExecEndNestLoop: %s\n",
	       "node processing ended");
}
