nodeagg.c

PostgreSQL7.4.6 for Linux

		MemoryContextSwitchTo(oldContext);
	}

	if (haveOldVal && !peraggstate->inputtypeByVal)
		pfree(DatumGetPointer(oldVal));

	tuplesort_end(peraggstate->sortstate);
	peraggstate->sortstate = NULL;
}

/*
 * Compute the final value of one aggregate.
 *
 * The finalfunction will be run, and the result delivered, in the
 * output-tuple context; caller's CurrentMemoryContext does not matter.
 */
static void
finalize_aggregate(AggState *aggstate,
				   AggStatePerAgg peraggstate,
				   AggStatePerGroup pergroupstate,
				   Datum *resultVal, bool *resultIsNull)
{
	MemoryContext oldContext;

	oldContext = MemoryContextSwitchTo(aggstate->ss.ps.ps_ExprContext->ecxt_per_tuple_memory);

	/*
	 * Apply the agg's finalfn if one is provided, else return transValue.
	 */
	if (OidIsValid(peraggstate->finalfn_oid))
	{
		FunctionCallInfoData fcinfo;

		MemSet(&fcinfo, 0, sizeof(fcinfo));
		fcinfo.flinfo = &peraggstate->finalfn;
		fcinfo.nargs = 1;
		fcinfo.arg[0] = pergroupstate->transValue;
		fcinfo.argnull[0] = pergroupstate->transValueIsNull;
		if (fcinfo.flinfo->fn_strict && pergroupstate->transValueIsNull)
		{
			/* don't call a strict function with NULL inputs */
			*resultVal = (Datum) 0;
			*resultIsNull = true;
		}
		else
		{
			*resultVal = FunctionCallInvoke(&fcinfo);
			*resultIsNull = fcinfo.isnull;
		}
	}
	else
	{
		*resultVal = pergroupstate->transValue;
		*resultIsNull = pergroupstate->transValueIsNull;
	}

	/*
	 * If result is pass-by-ref, make sure it is in the right context.
	 */
	if (!peraggstate->resulttypeByVal && !*resultIsNull &&
		!MemoryContextContains(CurrentMemoryContext,
							   DatumGetPointer(*resultVal)))
		*resultVal = datumCopy(*resultVal,
							   peraggstate->resulttypeByVal,
							   peraggstate->resulttypeLen);

	MemoryContextSwitchTo(oldContext);
}

/*
 * Initialize the hash table to empty.
 *
 * The hash table always lives in the aggcontext memory context.
 */
static void
build_hash_table(AggState *aggstate)
{
	Agg		   *node = (Agg *) aggstate->ss.ps.plan;
	MemoryContext tmpmem = aggstate->tmpcontext->ecxt_per_tuple_memory;
	Size		entrysize;

	Assert(node->aggstrategy == AGG_HASHED);
	Assert(node->numGroups > 0);

	entrysize = sizeof(AggHashEntryData) +
		(aggstate->numaggs - 1) *sizeof(AggStatePerGroupData);

	aggstate->hashtable = BuildTupleHashTable(node->numCols,
											  node->grpColIdx,
											  aggstate->eqfunctions,
											  aggstate->hashfunctions,
											  node->numGroups,
											  entrysize,
											  aggstate->aggcontext,
											  tmpmem);
}

/*
 * Find or create a hashtable entry for the tuple group containing the
 * given tuple.
 *
 * When called, CurrentMemoryContext should be the per-query context.
 */
static AggHashEntry
lookup_hash_entry(AggState *aggstate, TupleTableSlot *slot)
{
	AggHashEntry entry;
	bool		isnew;

	entry = (AggHashEntry) LookupTupleHashEntry(aggstate->hashtable,
												slot,
												&isnew);

	if (isnew)
	{
		/* initialize aggregates for new tuple group */
		initialize_aggregates(aggstate, aggstate->peragg, entry->pergroup);
	}

	return entry;
}

/*
 * ExecAgg -
 *
 *	  ExecAgg receives tuples from its outer subplan and aggregates over
 *	  the appropriate attribute for each aggregate function use (Aggref
 *	  node) appearing in the targetlist or qual of the node.  The number
 *	  of tuples to aggregate over depends on whether grouped or plain
 *	  aggregation is selected.	In grouped aggregation, we produce a result
 *	  row for each group; in plain aggregation there's a single result row
 *	  for the whole query.	In either case, the value of each aggregate is
 *	  stored in the expression context to be used when ExecProject evaluates
 *	  the result tuple.
 */
TupleTableSlot *
ExecAgg(AggState *node)
{
	if (node->agg_done)
		return NULL;

	if (((Agg *) node->ss.ps.plan)->aggstrategy == AGG_HASHED)
	{
		if (!node->table_filled)
			agg_fill_hash_table(node);
		return agg_retrieve_hash_table(node);
	}
	else
		return agg_retrieve_direct(node);
}

/*
 * ExecAgg for non-hashed case
 */
static TupleTableSlot *
agg_retrieve_direct(AggState *aggstate)
{
	Agg		   *node = (Agg *) aggstate->ss.ps.plan;
	PlanState  *outerPlan;
	ExprContext *econtext;
	ExprContext *tmpcontext;
	ProjectionInfo *projInfo;
	Datum	   *aggvalues;
	bool	   *aggnulls;
	AggStatePerAgg peragg;
	AggStatePerGroup pergroup;
	TupleTableSlot *outerslot;
	TupleTableSlot *firstSlot;
	int			aggno;

	/*
	 * get state info from node
	 */
	outerPlan = outerPlanState(aggstate);
	/* econtext is the per-output-tuple expression context */
	econtext = aggstate->ss.ps.ps_ExprContext;
	aggvalues = econtext->ecxt_aggvalues;
	aggnulls = econtext->ecxt_aggnulls;
	/* tmpcontext is the per-input-tuple expression context */
	tmpcontext = aggstate->tmpcontext;
	projInfo = aggstate->ss.ps.ps_ProjInfo;
	peragg = aggstate->peragg;
	pergroup = aggstate->pergroup;
	firstSlot = aggstate->ss.ss_ScanTupleSlot;

	/*
	 * We loop retrieving groups until we find one matching
	 * aggstate->ss.ps.qual
	 */
	while (!aggstate->agg_done)
	{
		/*
		 * If we don't already have the first tuple of the new group,
		 * fetch it from the outer plan.
		 */
		if (aggstate->grp_firstTuple == NULL)
		{
			outerslot = ExecProcNode(outerPlan);
			if (!TupIsNull(outerslot))
			{
				/*
				 * Make a copy of the first input tuple; we will use this
				 * for comparisons (in group mode) and for projection.
				 */
				aggstate->grp_firstTuple = heap_copytuple(outerslot->val);
			}
			else
			{
				/* outer plan produced no tuples at all */
				aggstate->agg_done = true;
				/* If we are grouping, we should produce no tuples too */
				if (node->aggstrategy != AGG_PLAIN)
					return NULL;
			}
		}

		/*
		 * Clear the per-output-tuple context for each group
		 */
		ResetExprContext(econtext);

		/*
		 * Initialize working state for a new input tuple group
		 */
		initialize_aggregates(aggstate, peragg, pergroup);

		if (aggstate->grp_firstTuple != NULL)
		{
			/*
			 * Store the copied first input tuple in the tuple table slot
			 * reserved for it.  The tuple will be deleted when it is
			 * cleared from the slot.
			 */
			ExecStoreTuple(aggstate->grp_firstTuple,
						   firstSlot,
						   InvalidBuffer,
						   true);
			aggstate->grp_firstTuple = NULL;	/* don't keep two pointers */

			/* set up for first advance_aggregates call */
			tmpcontext->ecxt_scantuple = firstSlot;

			/*
			 * Process each outer-plan tuple, and then fetch the next one,
			 * until we exhaust the outer plan or cross a group boundary.
			 */
			for (;;)
			{
				advance_aggregates(aggstate, pergroup);

				/* Reset per-input-tuple context after each tuple */
				ResetExprContext(tmpcontext);

				outerslot = ExecProcNode(outerPlan);
				if (TupIsNull(outerslot))
				{
					/* no more outer-plan tuples available */
					aggstate->agg_done = true;
					break;
				}
				/* set up for next advance_aggregates call */
				tmpcontext->ecxt_scantuple = outerslot;

				/*
				 * If we are grouping, check whether we've crossed a group
				 * boundary.
				 */
				if (node->aggstrategy == AGG_SORTED)
				{
					if (!execTuplesMatch(firstSlot->val,
										 outerslot->val,
										 firstSlot->ttc_tupleDescriptor,
										 node->numCols, node->grpColIdx,
										 aggstate->eqfunctions,
									  tmpcontext->ecxt_per_tuple_memory))
					{
						/*
						 * Save the first input tuple of the next group.
						 */
						aggstate->grp_firstTuple = heap_copytuple(outerslot->val);
						break;
					}
				}
			}
		}

		/*
		 * Done scanning input tuple group. Finalize each aggregate
		 * calculation, and stash results in the per-output-tuple context.
		 */
		for (aggno = 0; aggno < aggstate->numaggs; aggno++)
		{
			AggStatePerAgg peraggstate = &peragg[aggno];
			AggStatePerGroup pergroupstate = &pergroup[aggno];

			if (peraggstate->aggref->aggdistinct)
				process_sorted_aggregate(aggstate, peraggstate, pergroupstate);

			finalize_aggregate(aggstate, peraggstate, pergroupstate,
							   &aggvalues[aggno], &aggnulls[aggno]);
		}

		/*
		 * If we have no first tuple (ie, the outerPlan didn't return
		 * anything), create a dummy all-nulls input tuple for use by
		 * ExecQual/ExecProject. 99.44% of the time this is a waste of cycles,
		 * because ordinarily the projected output tuple's targetlist
		 * cannot contain any direct (non-aggregated) references to input
		 * columns, so the dummy tuple will not be referenced. However
		 * there are special cases where this isn't so --- in particular
		 * an UPDATE involving an aggregate will have a targetlist
		 * reference to ctid.  We need to return a null for ctid in that
		 * situation, not coredump.
		 *
		 * The values returned for the aggregates will be the initial values
		 * of the transition functions.
		 */
		if (TupIsNull(firstSlot))
		{
			TupleDesc	tupType;

			/* Should only happen in non-grouped mode */
			Assert(node->aggstrategy == AGG_PLAIN);
			Assert(aggstate->agg_done);

			tupType = firstSlot->ttc_tupleDescriptor;
			/* watch out for zero-column input tuples, though... */
			if (tupType && tupType->natts > 0)
			{
				HeapTuple	nullsTuple;
				Datum	   *dvalues;
				char	   *dnulls;

				dvalues = (Datum *) palloc0(sizeof(Datum) * tupType->natts);
				dnulls = (char *) palloc(sizeof(char) * tupType->natts);
				MemSet(dnulls, 'n', sizeof(char) * tupType->natts);
				nullsTuple = heap_formtuple(tupType, dvalues, dnulls);
				ExecStoreTuple(nullsTuple,
							   firstSlot,
							   InvalidBuffer,
							   true);
				pfree(dvalues);
				pfree(dnulls);
			}
		}

		/*
		 * Use the representative input tuple for any references to
		 * non-aggregated input columns in the qual and tlist.
		 */
		econtext->ecxt_scantuple = firstSlot;

		/*
		 * Check the qual (HAVING clause); if the group does not match,
		 * ignore it and loop back to try to process another group.
		 */
		if (ExecQual(aggstate->ss.ps.qual, econtext, false))
		{
			/*
			 * Form and return a projection tuple using the aggregate results
			 * and the representative input tuple.  Note we do not support
			 * aggregates returning sets ...
			 */
			return ExecProject(projInfo, NULL);
		}
	}

	/* No more groups */
	return NULL;
}

/*
 * ExecAgg for hashed case: phase 1, read input and build hash table
 */
static void
agg_fill_hash_table(AggState *aggstate)
{
	PlanState  *outerPlan;
	ExprContext *tmpcontext;
	AggHashEntry entry;
	TupleTableSlot *outerslot;

	/*
	 * get state info from node
	 */
	outerPlan = outerPlanState(aggstate);
	/* tmpcontext is the per-input-tuple expression context */
	tmpcontext = aggstate->tmpcontext;

	/*
	 * Process each outer-plan tuple, and then fetch the next one, until
	 * we exhaust the outer plan.
	 */
	for (;;)
	{
		outerslot = ExecProcNode(outerPlan);
		if (TupIsNull(outerslot))
			break;
		/* set up for advance_aggregates call */
		tmpcontext->ecxt_scantuple = outerslot;

		/* Find or build hashtable entry for this tuple's group */
		entry = lookup_hash_entry(aggstate, outerslot);

		/* Advance the aggregates */
		advance_aggregates(aggstate, entry->pergroup);

		/* Reset per-input-tuple context after each tuple */
		ResetExprContext(tmpcontext);
	}

	aggstate->table_filled = true;
	/* Initialize to walk the hash table */
	ResetTupleHashIterator(aggstate->hashtable, &aggstate->hashiter);
}

/*
 * ExecAgg for hashed case: phase 2, retrieving groups from hash table
 */
static TupleTableSlot *
agg_retrieve_hash_table(AggState *aggstate)
{
	ExprContext *econtext;
	ProjectionInfo *projInfo;
	Datum	   *aggvalues;
	bool	   *aggnulls;
	AggStatePerAgg peragg;
	AggStatePerGroup pergroup;
	AggHashEntry entry;
	TupleTableSlot *firstSlot;
	int			aggno;

	/*
	 * get state info from node
	 */
	/* econtext is the per-output-tuple expression context */
	econtext = aggstate->ss.ps.ps_ExprContext;
	aggvalues = econtext->ecxt_aggvalues;
	aggnulls = econtext->ecxt_aggnulls;
	projInfo = aggstate->ss.ps.ps_ProjInfo;
	peragg = aggstate->peragg;
	firstSlot = aggstate->ss.ss_ScanTupleSlot;

	/*
	 * We loop retrieving groups until we find one satisfying
	 * aggstate->ss.ps.qual
	 */
	while (!aggstate->agg_done)
	{
		/*
		 * Find the next entry in the hash table
		 */
		entry = (AggHashEntry) ScanTupleHashTable(&aggstate->hashiter);
		if (entry == NULL)
		{
			/* No more entries in hashtable, so done */
			aggstate->agg_done = TRUE;
			return NULL;
		}

		/*
		 * Clear the per-output-tuple context for each group
		 */
		ResetExprContext(econtext);

		/*
		 * Store the copied first input tuple in the tuple table slot
		 * reserved for it, so that it can be used in ExecProject.
		 */
		ExecStoreTuple(entry->shared.firstTuple,
					   firstSlot,
					   InvalidBuffer,
					   false);

		pergroup = entry->pergroup;

		/*
		 * Finalize each aggregate calculation, and stash results in the
		 * per-output-tuple context.
		 */
		for (aggno = 0; aggno < aggstate->numaggs; aggno++)
		{
			AggStatePerAgg peraggstate = &peragg[aggno];
			AggStatePerGroup pergroupstate = &pergroup[aggno];

			Assert(!peraggstate->aggref->aggdistinct);
			finalize_aggregate(aggstate, peraggstate, pergroupstate,
							   &aggvalues[aggno], &aggnulls[aggno]);
		}

		/*
		 * Use the representative input tuple for any references to
		 * non-aggregated input columns in the qual and tlist.
		 */
		econtext->ecxt_scantuple = firstSlot;

		/*
		 * Check the qual (HAVING clause); if the group does not match,
		 * ignore it and loop back to try to process another group.
		 */
		if (ExecQual(aggstate->ss.ps.qual, econtext, false))
		{
			/*
			 * Form and return a projection tuple using the aggregate results
			 * and the representative input tuple.  Note we do not support
			 * aggregates returning sets ...
			 */
			return ExecProject(projInfo, NULL);