postgresql/src/backend/executor/nodeHashjoin.c

/*-------------------------------------------------------------------------
 *
 * nodeHashjoin.c--
 *	  Routines to handle hash join nodes
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeHashjoin.c,v 1.9 1998/01/13 04:03:58 scrappy Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <sys/types.h>
#include <string.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <fcntl.h>

#include "postgres.h"

#include "executor/execdebug.h"
#include "executor/executor.h"
#include "executor/nodeHash.h"
#include "executor/nodeHashjoin.h"
#include "optimizer/clauses.h"	/* for get_leftop */

static TupleTableSlot *
			ExecHashJoinOuterGetTuple(Plan *node, Plan *parent, HashJoinState *hjstate);

static TupleTableSlot *
ExecHashJoinGetSavedTuple(HashJoinState *hjstate, char *buffer,
	  File file, TupleTableSlot *tupleSlot, int *block, char **position);

static int
ExecHashJoinGetBatch(int bucketno, HashJoinTable hashtable,
					 int nbatch);

static int	ExecHashJoinNewBatch(HashJoinState *hjstate);



/* ----------------------------------------------------------------
 *		ExecHashJoin
 *
 *		This function implements the Hybrid Hashjoin algorithm.
 *		recursive partitioning remains to be added.
 *		Note: the relation we build hash table on is the inner
 *			  the other one is outer.
 * ----------------------------------------------------------------
 */
TupleTableSlot *				/* return: a tuple or NULL */
ExecHashJoin(HashJoin *node)
{
	HashJoinState *hjstate;
	EState	   *estate;
	Plan	   *outerNode;
	Hash	   *hashNode;
	List	   *hjclauses;
	Expr	   *clause;
	List	   *qual;
	ScanDirection dir;
	TupleTableSlot *inntuple;
	Var		   *outerVar;
	ExprContext *econtext;

	HashJoinTable hashtable;
	int			bucketno;
	HashBucket	bucket;
	HeapTuple	curtuple;

	bool		qualResult;

	TupleTableSlot *outerTupleSlot;
	TupleTableSlot *innerTupleSlot;
	int			nbatch;
	int			curbatch;
	File	   *outerbatches;
	RelativeAddr *outerbatchNames;
	RelativeAddr *outerbatchPos;
	Var		   *innerhashkey;
	int			batch;
	int			batchno;
	char	   *buffer;
	int			i;
	bool		hashPhaseDone;
	char	   *pos;

	/* ----------------
	 *	get information from HashJoin node
	 * ----------------
	 */
	hjstate = node->hashjoinstate;
	hjclauses = node->hashclauses;
	clause = lfirst(hjclauses);
	estate = node->join.state;
	qual = node->join.qual;
	hashNode = (Hash *) innerPlan(node);
	outerNode = outerPlan(node);
	hashPhaseDone = node->hashdone;

	dir = estate->es_direction;

	/* -----------------
	 * get information from HashJoin state
	 * -----------------
	 */
	hashtable = hjstate->hj_HashTable;
	bucket = hjstate->hj_CurBucket;
	curtuple = hjstate->hj_CurTuple;

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

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

		result = ExecProject(hjstate->jstate.cs_ProjInfo, &isDone);
		if (!isDone)
			return result;
	}
	/* ----------------
	 *	if this is the first call, build the hash table for inner relation
	 * ----------------
	 */
	if (!hashPhaseDone)
	{							/* if the hash phase not completed */
		hashtable = node->hashjointable;
		if (hashtable == NULL)
		{						/* if the hash table has not been created */
			/* ----------------
			 * create the hash table
			 * ----------------
			 */
			hashtable = ExecHashTableCreate(hashNode);
			hjstate->hj_HashTable = hashtable;
			innerhashkey = hashNode->hashkey;
			hjstate->hj_InnerHashKey = innerhashkey;

			/* ----------------
			 * execute the Hash node, to build the hash table
			 * ----------------
			 */
			hashNode->hashtable = hashtable;
			innerTupleSlot = ExecProcNode((Plan *) hashNode, (Plan *) node);
		}
		bucket = NULL;
		curtuple = NULL;
		curbatch = 0;
		node->hashdone = true;
	}
	nbatch = hashtable->nbatch;
	outerbatches = hjstate->hj_OuterBatches;
	if (nbatch > 0 && outerbatches == NULL)
	{							/* if needs hash partition */
		/* -----------------
		 *	allocate space for file descriptors of outer batch files
		 *	then open the batch files in the current process
		 * -----------------
		 */
		innerhashkey = hashNode->hashkey;
		hjstate->hj_InnerHashKey = innerhashkey;
		outerbatchNames = (RelativeAddr *)
			ABSADDR(hashtable->outerbatchNames);
		outerbatches = (File *)
			palloc(nbatch * sizeof(File));
		for (i = 0; i < nbatch; i++)
		{
			outerbatches[i] = FileNameOpenFile(
											 ABSADDR(outerbatchNames[i]),
											   O_CREAT | O_RDWR, 0600);
		}
		hjstate->hj_OuterBatches = outerbatches;

		/* ------------------
		 *	get the inner batch file descriptors from the
		 *	hash node
		 * ------------------
		 */
		hjstate->hj_InnerBatches =
			hashNode->hashstate->hashBatches;
	}
	outerbatchPos = (RelativeAddr *) ABSADDR(hashtable->outerbatchPos);
	curbatch = hashtable->curbatch;
	outerbatchNames = (RelativeAddr *) ABSADDR(hashtable->outerbatchNames);

	/* ----------------
	 *	Now get an outer tuple and probe into the hash table for matches
	 * ----------------
	 */
	outerTupleSlot = hjstate->jstate.cs_OuterTupleSlot;
	outerVar = get_leftop(clause);

	bucketno = -1;				/* if bucketno remains -1, means use old
								 * outer tuple */
	if (TupIsNull(outerTupleSlot))
	{

		/*
		 * if the current outer tuple is nil, get a new one
		 */
		outerTupleSlot = (TupleTableSlot *)
			ExecHashJoinOuterGetTuple(outerNode, (Plan *) node, hjstate);

		while (curbatch <= nbatch && TupIsNull(outerTupleSlot))
		{

			/*
			 * if the current batch runs out, switch to new batch
			 */
			curbatch = ExecHashJoinNewBatch(hjstate);
			if (curbatch > nbatch)
			{

				/*
				 * when the last batch runs out, clean up
				 */
				ExecHashTableDestroy(hashtable);
				hjstate->hj_HashTable = NULL;
				return NULL;
			}
			else
				outerTupleSlot = (TupleTableSlot *)
					ExecHashJoinOuterGetTuple(outerNode, (Plan *) node, hjstate);
		}

		/*
		 * now we get an outer tuple, find the corresponding bucket for
		 * this tuple from the hash table
		 */
		econtext->ecxt_outertuple = outerTupleSlot;

#ifdef HJDEBUG
		printf("Probing ");
#endif
		bucketno = ExecHashGetBucket(hashtable, econtext, outerVar);
		bucket = (HashBucket) (ABSADDR(hashtable->top)
							   + bucketno * hashtable->bucketsize);
	}

	for (;;)
	{
		/* ----------------
		 *		Now we've got an outer tuple and the corresponding hash bucket,
		 *	but this tuple may not belong to the current batch.
		 * ----------------
		 */
		if (curbatch == 0 && bucketno != -1)	/* if this is the first
												 * pass */
			batch = ExecHashJoinGetBatch(bucketno, hashtable, nbatch);
		else
			batch = 0;
		if (batch > 0)
		{

			/*
			 * if the current outer tuple does not belong to the current
			 * batch, save to the tmp file for the corresponding batch.
			 */
			buffer = ABSADDR(hashtable->batch) + (batch - 1) * BLCKSZ;
			batchno = batch - 1;
			pos = ExecHashJoinSaveTuple(outerTupleSlot->val,
										buffer,
										outerbatches[batchno],
										ABSADDR(outerbatchPos[batchno]));

			outerbatchPos[batchno] = RELADDR(pos);
		}
		else if (bucket != NULL)
		{
			do
			{

				/*
				 * scan the hash bucket for matches
				 */
				curtuple = ExecScanHashBucket(hjstate,
											  bucket,
											  curtuple,
											  hjclauses,
											  econtext);

				if (curtuple != NULL)
				{

					/*
					 * we've got a match, but still need to test qpqual
					 */
					inntuple = ExecStoreTuple(curtuple,
											  hjstate->hj_HashTupleSlot,
											  InvalidBuffer,
											  false);	/* don't pfree this
														 * tuple */

					econtext->ecxt_innertuple = inntuple;

					/* ----------------
					 * test to see if we pass the qualification
					 * ----------------
					 */
					qualResult = ExecQual((List *) qual, econtext);

					/* ----------------
					 * if we pass the qual, then save state for next call and
					 * have ExecProject form the projection, store it
					 * in the tuple table, and return the slot.
					 * ----------------
					 */
					if (qualResult)
					{
						ProjectionInfo *projInfo;
						TupleTableSlot *result;
						bool		isDone;

						hjstate->hj_CurBucket = bucket;
						hjstate->hj_CurTuple = curtuple;
						hashtable->curbatch = curbatch;
						hjstate->jstate.cs_OuterTupleSlot = outerTupleSlot;

						projInfo = hjstate->jstate.cs_ProjInfo;
						result = ExecProject(projInfo, &isDone);
						hjstate->jstate.cs_TupFromTlist = !isDone;
						return result;
					}
				}
			}
			while (curtuple != NULL);
		}

		/* ----------------
		 *	 Now the current outer tuple has run out of matches,
		 *	 so we free it and get a new outer tuple.
		 * ----------------
		 */
		outerTupleSlot = (TupleTableSlot *)
			ExecHashJoinOuterGetTuple(outerNode, (Plan *) node, hjstate);

		while (curbatch <= nbatch && TupIsNull(outerTupleSlot))
		{

			/*
			 * if the current batch runs out, switch to new batch
			 */
			curbatch = ExecHashJoinNewBatch(hjstate);
			if (curbatch > nbatch)
			{

				/*
				 * when the last batch runs out, clean up
				 */
				ExecHashTableDestroy(hashtable);
				hjstate->hj_HashTable = NULL;
				return NULL;
			}
			else
				outerTupleSlot = (TupleTableSlot *)
					ExecHashJoinOuterGetTuple(outerNode, (Plan *) node, hjstate);
		}

		/* ----------------
		 *	 Now get the corresponding hash bucket for the new
		 *	 outer tuple.
		 * ----------------
		 */
		econtext->ecxt_outertuple = outerTupleSlot;
#ifdef HJDEBUG
		printf("Probing ");
#endif
		bucketno = ExecHashGetBucket(hashtable, econtext, outerVar);
		bucket = (HashBucket) (ABSADDR(hashtable->top)
							   + bucketno * hashtable->bucketsize);
		curtuple = NULL;
	}
}

/* ----------------------------------------------------------------
 *		ExecInitHashJoin
 *
 *		Init routine for HashJoin node.
 * ----------------------------------------------------------------
 */
bool							/* return: initialization status */
ExecInitHashJoin(HashJoin *node, EState *estate, Plan *parent)
{
	HashJoinState *hjstate;
	Plan	   *outerNode;
	Hash	   *hashNode;

	/* ----------------
	 *	assign the node's execution state
	 * ----------------
	 */
	node->join.state = estate;

	/* ----------------
	 * create state structure
	 * ----------------
	 */
	hjstate = makeNode(HashJoinState);

	node->hashjoinstate = hjstate;

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

#define HASHJOIN_NSLOTS 2
	/* ----------------
	 *	tuple table initialization
	 * ----------------
	 */
	ExecInitResultTupleSlot(estate, &hjstate->jstate);
	ExecInitOuterTupleSlot(estate, hjstate);

	/* ----------------
	 * initializes child nodes
	 * ----------------
	 */
	outerNode = outerPlan((Plan *) node);
	hashNode = (Hash *) innerPlan((Plan *) node);

	ExecInitNode(outerNode, estate, (Plan *) node);
	ExecInitNode((Plan *) hashNode, estate, (Plan *) node);

	/* ----------------
	 *	now for some voodoo.  our temporary tuple slot
	 *	is actually the result tuple slot of the Hash node
	 *	(which is our inner plan).	we do this because Hash
	 *	nodes don't return tuples via ExecProcNode() -- instead
	 *	the hash join node uses ExecScanHashBucket() to get
	 *	at the contents of the hash table.	-cim 6/9/91
	 * ----------------
	 */
	{
		HashState  *hashstate = hashNode->hashstate;
		TupleTableSlot *slot =
		hashstate->cstate.cs_ResultTupleSlot;

		hjstate->hj_HashTupleSlot = slot;
	}
	hjstate->hj_OuterTupleSlot->ttc_tupleDescriptor =
		ExecGetTupType(outerNode);

/*
	hjstate->hj_OuterTupleSlot->ttc_execTupDescriptor =
							  ExecGetExecTupDesc(outerNode);
*/

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

	/* ----------------
	 *	XXX comment me
	 * ----------------
	 */

	node->hashdone = false;

	hjstate->hj_HashTable = (HashJoinTable) NULL;
	hjstate->hj_HashTableShmId = (IpcMemoryId) 0;
	hjstate->hj_CurBucket = (HashBucket) NULL;
	hjstate->hj_CurTuple = (HeapTuple) NULL;
	hjstate->hj_CurOTuple = (OverflowTuple) NULL;
	hjstate->hj_InnerHashKey = (Var *) NULL;
	hjstate->hj_OuterBatches = (File *) NULL;
	hjstate->hj_InnerBatches = (File *) NULL;
	hjstate->hj_OuterReadPos = (char *) NULL;
	hjstate->hj_OuterReadBlk = (int) 0;

	hjstate->jstate.cs_OuterTupleSlot = (TupleTableSlot *) NULL;
	hjstate->jstate.cs_TupFromTlist = (bool) false;

	return TRUE;
}

int
ExecCountSlotsHashJoin(HashJoin *node)
{
	return ExecCountSlotsNode(outerPlan(node)) +
	ExecCountSlotsNode(innerPlan(node)) +
	HASHJOIN_NSLOTS;
}

/* ----------------------------------------------------------------
 *		ExecEndHashJoin
 *
 *		clean up routine for HashJoin node
 * ----------------------------------------------------------------
 */
void
ExecEndHashJoin(HashJoin *node)
{
	HashJoinState *hjstate;

	/* ----------------
	 *	get info from the HashJoin state
	 * ----------------
	 */
	hjstate = node->hashjoinstate;

	/* ----------------
	 * free hash table in case we end plan before all tuples are retrieved
	 * ---------------
	 */
	if (hjstate->hj_HashTable)
	{
		ExecHashTableDestroy(hjstate->hj_HashTable);
		hjstate->hj_HashTable = NULL;
	}

	/* ----------------
	 *	Free the projection info and the scan attribute info
	 *
	 *	Note: we don't ExecFreeResultType(hjstate)
	 *		  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(&hjstate->jstate);

	/* ----------------
	 * clean up subtrees
	 * ----------------
	 */
	ExecEndNode(outerPlan((Plan *) node), (Plan *) node);
	ExecEndNode(innerPlan((Plan *) node), (Plan *) node);

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

}

/* ----------------------------------------------------------------
 *		ExecHashJoinOuterGetTuple
 *
 *		get the next outer tuple for hashjoin: either by
 *		executing a plan node as in the first pass, or from
 *		the tmp files for the hashjoin batches.
 * ----------------------------------------------------------------
 */

static TupleTableSlot *
ExecHashJoinOuterGetTuple(Plan *node, Plan *parent, HashJoinState *hjstate)
{
	TupleTableSlot *slot;
	HashJoinTable hashtable;
	int			curbatch;
	File	   *outerbatches;
	char	   *outerreadPos;
	int			batchno;
	char	   *outerreadBuf;
	int			outerreadBlk;

	hashtable = hjstate->hj_HashTable;
	curbatch = hashtable->curbatch;

	if (curbatch == 0)
	{							/* if it is the first pass */
		slot = ExecProcNode(node, parent);
		return slot;
	}

	/*
	 * otherwise, read from the tmp files
	 */
	outerbatches = hjstate->hj_OuterBatches;
	outerreadPos = hjstate->hj_OuterReadPos;
	outerreadBlk = hjstate->hj_OuterReadBlk;
	outerreadBuf = ABSADDR(hashtable->readbuf);
	batchno = curbatch - 1;

	slot = ExecHashJoinGetSavedTuple(hjstate,
									 outerreadBuf,
									 outerbatches[batchno],
									 hjstate->hj_OuterTupleSlot,
									 &outerreadBlk,
									 &outerreadPos);

	hjstate->hj_OuterReadPos = outerreadPos;
	hjstate->hj_OuterReadBlk = outerreadBlk;

	return slot;
}

/* ----------------------------------------------------------------
 *		ExecHashJoinGetSavedTuple
 *
 *		read the next tuple from a tmp file using a certain buffer
 * ----------------------------------------------------------------
 */

static TupleTableSlot *
ExecHashJoinGetSavedTuple(HashJoinState *hjstate,
						  char *buffer,
						  File file,
						  TupleTableSlot *tupleSlot,
						  int *block,	/* return parameter */
						  char **position)		/* return parameter */
{
	char	   *bufstart;
	char	   *bufend;
	int			cc;
	HeapTuple	heapTuple;
	HashJoinTable hashtable;

	hashtable = hjstate->hj_HashTable;
	bufend = buffer + *(long *) buffer;
	bufstart = (char *) (buffer + sizeof(long));
	if ((*position == NULL) || (*position >= bufend))
	{
		if (*position == NULL)
			(*block) = 0;
		else
			(*block)++;
		FileSeek(file, *block * BLCKSZ, SEEK_SET);
		cc = FileRead(file, buffer, BLCKSZ);
		NDirectFileRead++;
		if (cc < 0)
			perror("FileRead");
		if (cc == 0)			/* end of file */
			return NULL;
		else
			(*position) = bufstart;
	}
	heapTuple = (HeapTuple) (*position);
	(*position) = (char *) LONGALIGN(*position + heapTuple->t_len);

	return ExecStoreTuple(heapTuple, tupleSlot, InvalidBuffer, false);
}

/* ----------------------------------------------------------------
 *		ExecHashJoinNewBatch
 *
 *		switch to a new hashjoin batch
 * ----------------------------------------------------------------
 */
static int
ExecHashJoinNewBatch(HashJoinState *hjstate)
{
	File	   *innerBatches;
	File	   *outerBatches;
	int		   *innerBatchSizes;
	Var		   *innerhashkey;
	HashJoinTable hashtable;
	int			nbatch;
	char	   *readPos;
	int			readBlk;
	char	   *readBuf;
	TupleTableSlot *slot;
	ExprContext *econtext;
	int			i;
	int			cc;
	int			newbatch;

	hashtable = hjstate->hj_HashTable;
	outerBatches = hjstate->hj_OuterBatches;
	innerBatches = hjstate->hj_InnerBatches;
	nbatch = hashtable->nbatch;
	newbatch = hashtable->curbatch + 1;

	/* ------------------
	 *	this is the last process, so it will do the cleanup and
	 *	batch-switching.
	 * ------------------
	 */
	if (newbatch == 1)
	{

		/*
		 * if it is end of the first pass, flush all the last pages for
		 * the batches.
		 */
		outerBatches = hjstate->hj_OuterBatches;
		for (i = 0; i < nbatch; i++)
		{
			cc = FileSeek(outerBatches[i], 0L, SEEK_END);
			if (cc < 0)
				perror("FileSeek");
			cc = FileWrite(outerBatches[i],
						 ABSADDR(hashtable->batch) + i * BLCKSZ, BLCKSZ);
			NDirectFileWrite++;
			if (cc < 0)
				perror("FileWrite");
		}
	}
	if (newbatch > 1)
	{

		/*
		 * remove the previous outer batch
		 */
		FileUnlink(outerBatches[newbatch - 2]);
	}

	/*
	 * rebuild the hash table for the new inner batch
	 */
	innerBatchSizes = (int *) ABSADDR(hashtable->innerbatchSizes);
	/* --------------
	 *	skip over empty inner batches
	 * --------------
	 */
	while (newbatch <= nbatch && innerBatchSizes[newbatch - 1] == 0)
	{
		FileUnlink(outerBatches[newbatch - 1]);
		FileUnlink(innerBatches[newbatch - 1]);
		newbatch++;
	}
	if (newbatch > nbatch)
	{
		hashtable->pcount = hashtable->nprocess;

		return newbatch;
	}
	ExecHashTableReset(hashtable, innerBatchSizes[newbatch - 1]);


	econtext = hjstate->jstate.cs_ExprContext;
	innerhashkey = hjstate->hj_InnerHashKey;
	readPos = NULL;
	readBlk = 0;
	readBuf = ABSADDR(hashtable->readbuf);

	while ((slot = ExecHashJoinGetSavedTuple(hjstate,
											 readBuf,
											 innerBatches[newbatch - 1],
											 hjstate->hj_HashTupleSlot,
											 &readBlk,
											 &readPos))
		   && !TupIsNull(slot))
	{
		econtext->ecxt_innertuple = slot;
		ExecHashTableInsert(hashtable, econtext, innerhashkey, NULL);
		/* possible bug - glass */
	}


	/* -----------------
	 *	only the last process comes to this branch
	 *	now all the processes have finished the build phase
	 * ----------------
	 */

	/*
	 * after we build the hash table, the inner batch is no longer needed
	 */
	FileUnlink(innerBatches[newbatch - 1]);
	hjstate->hj_OuterReadPos = NULL;
	hashtable->pcount = hashtable->nprocess;

	hashtable->curbatch = newbatch;
	return newbatch;
}

/* ----------------------------------------------------------------
 *		ExecHashJoinGetBatch
 *
 *		determine the batch number for a bucketno
 *		+----------------+-------+-------+ ... +-------+
 *		0			  nbuckets						 totalbuckets
 * batch		 0			 1		 2	   ...
 * ----------------------------------------------------------------
 */
static int
ExecHashJoinGetBatch(int bucketno, HashJoinTable hashtable, int nbatch)
{
	int			b;

	if (bucketno < hashtable->nbuckets || nbatch == 0)
		return 0;

	b = (float) (bucketno - hashtable->nbuckets) /
		(float) (hashtable->totalbuckets - hashtable->nbuckets) *
		nbatch;
	return b + 1;
}

/* ----------------------------------------------------------------
 *		ExecHashJoinSaveTuple
 *
 *		save a tuple to a tmp file using a buffer.
 *		the first few bytes in a page is an offset to the end
 *		of the page.
 * ----------------------------------------------------------------
 */

char	   *
ExecHashJoinSaveTuple(HeapTuple heapTuple,
					  char *buffer,
					  File file,
					  char *position)
{
	long	   *pageend;
	char	   *pagestart;
	char	   *pagebound;
	int			cc;

	pageend = (long *) buffer;
	pagestart = (char *) (buffer + sizeof(long));
	pagebound = buffer + BLCKSZ;
	if (position == NULL)
		position = pagestart;

	if (position + heapTuple->t_len >= pagebound)
	{
		cc = FileSeek(file, 0L, SEEK_END);
		if (cc < 0)
			perror("FileSeek");
		cc = FileWrite(file, buffer, BLCKSZ);
		NDirectFileWrite++;
		if (cc < 0)
			perror("FileWrite");
		position = pagestart;
		*pageend = 0;
	}
	memmove(position, heapTuple, heapTuple->t_len);
	position = (char *) LONGALIGN(position + heapTuple->t_len);
	*pageend = position - buffer;

	return position;
}