nodesubplan.c

PostgreSQL7.4.6 for Linux

			if (col == 1)
			{
				rowresult = expresult;
				rownull = expnull;
			}
			else if (useOr)
			{
				/* combine within row per OR semantics */
				if (expnull)
					rownull = true;
				else if (DatumGetBool(expresult))
				{
					rowresult = BoolGetDatum(true);
					rownull = false;
					break;		/* needn't look at any more columns */
				}
			}
			else
			{
				/* combine within row per AND semantics */
				if (expnull)
					rownull = true;
				else if (!DatumGetBool(expresult))
				{
					rowresult = BoolGetDatum(false);
					rownull = false;
					break;		/* needn't look at any more columns */
				}
			}

			plst = lnext(plst);
			col++;
		}

		if (subLinkType == ANY_SUBLINK)
		{
			/* combine across rows per OR semantics */
			if (rownull)
				*isNull = true;
			else if (DatumGetBool(rowresult))
			{
				result = BoolGetDatum(true);
				*isNull = false;
				break;			/* needn't look at any more rows */
			}
		}
		else if (subLinkType == ALL_SUBLINK)
		{
			/* combine across rows per AND semantics */
			if (rownull)
				*isNull = true;
			else if (!DatumGetBool(rowresult))
			{
				result = BoolGetDatum(false);
				*isNull = false;
				break;			/* needn't look at any more rows */
			}
		}
		else
		{
			/* must be MULTIEXPR_SUBLINK */
			result = rowresult;
			*isNull = rownull;
		}
	}

	if (!found)
	{
		/*
		 * deal with empty subplan result.	result/isNull were previously
		 * initialized correctly for all sublink types except EXPR, ARRAY,
		 * and MULTIEXPR; for those, return NULL.
		 */
		if (subLinkType == EXPR_SUBLINK ||
			subLinkType == ARRAY_SUBLINK ||
			subLinkType == MULTIEXPR_SUBLINK)
		{
			result = (Datum) 0;
			*isNull = true;
		}
	}
	else if (subLinkType == ARRAY_SUBLINK)
	{
		Assert(astate != NULL);
		/* We return the result in the caller's context */
		result = makeArrayResult(astate, oldcontext);
	}

	MemoryContextSwitchTo(oldcontext);

	return result;
}

/*
 * buildSubPlanHash: load hash table by scanning subplan output.
 */
static void
buildSubPlanHash(SubPlanState *node)
{
	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
	PlanState  *planstate = node->planstate;
	int			ncols = length(node->exprs);
	ExprContext *innerecontext = node->innerecontext;
	MemoryContext tempcxt = innerecontext->ecxt_per_tuple_memory;
	MemoryContext oldcontext;
	int			nbuckets;
	TupleTableSlot *slot;

	Assert(subplan->subLinkType == ANY_SUBLINK);
	Assert(!subplan->useOr);

	/*
	 * If we already had any hash tables, destroy 'em; then create empty
	 * hash table(s).
	 *
	 * If we need to distinguish accurately between FALSE and UNKNOWN (i.e.,
	 * NULL) results of the IN operation, then we have to store subplan
	 * output rows that are partly or wholly NULL.	We store such rows in
	 * a separate hash table that we expect will be much smaller than the
	 * main table.	(We can use hashing to eliminate partly-null rows that
	 * are not distinct.  We keep them separate to minimize the cost of
	 * the inevitable full-table searches; see findPartialMatch.)
	 *
	 * If it's not necessary to distinguish FALSE and UNKNOWN, then we don't
	 * need to store subplan output rows that contain NULL.
	 */
	MemoryContextReset(node->tablecxt);
	node->hashtable = NULL;
	node->hashnulls = NULL;
	node->havehashrows = false;
	node->havenullrows = false;

	nbuckets = (int) ceil(planstate->plan->plan_rows);
	if (nbuckets < 1)
		nbuckets = 1;

	node->hashtable = BuildTupleHashTable(ncols,
										  node->keyColIdx,
										  node->eqfunctions,
										  node->hashfunctions,
										  nbuckets,
										  sizeof(TupleHashEntryData),
										  node->tablecxt,
										  tempcxt);

	if (!subplan->unknownEqFalse)
	{
		if (ncols == 1)
			nbuckets = 1;		/* there can only be one entry */
		else
		{
			nbuckets /= 16;
			if (nbuckets < 1)
				nbuckets = 1;
		}
		node->hashnulls = BuildTupleHashTable(ncols,
											  node->keyColIdx,
											  node->eqfunctions,
											  node->hashfunctions,
											  nbuckets,
											  sizeof(TupleHashEntryData),
											  node->tablecxt,
											  tempcxt);
	}

	/*
	 * We are probably in a short-lived expression-evaluation context.
	 * Switch to the child plan's per-query context for calling
	 * ExecProcNode.
	 */
	oldcontext = MemoryContextSwitchTo(node->sub_estate->es_query_cxt);

	/*
	 * Reset subplan to start.
	 */
	ExecReScan(planstate, NULL);

	/*
	 * Scan the subplan and load the hash table(s).  Note that when there
	 * are duplicate rows coming out of the sub-select, only one copy is
	 * stored.
	 */
	for (slot = ExecProcNode(planstate);
		 !TupIsNull(slot);
		 slot = ExecProcNode(planstate))
	{
		HeapTuple	tup = slot->val;
		TupleDesc	tdesc = slot->ttc_tupleDescriptor;
		int			col = 1;
		List	   *plst;
		bool		isnew;

		/*
		 * Load up the Params representing the raw sub-select outputs,
		 * then form the projection tuple to store in the hashtable.
		 */
		foreach(plst, subplan->paramIds)
		{
			int			paramid = lfirsti(plst);
			ParamExecData *prmdata;

			prmdata = &(innerecontext->ecxt_param_exec_vals[paramid]);
			Assert(prmdata->execPlan == NULL);
			prmdata->value = heap_getattr(tup, col, tdesc,
										  &(prmdata->isnull));
			col++;
		}
		slot = ExecProject(node->projRight, NULL);
		tup = slot->val;

		/*
		 * If result contains any nulls, store separately or not at all.
		 * (Since we know the projection tuple has no junk columns, we can
		 * just look at the overall hasnull info bit, instead of groveling
		 * through the columns.)
		 */
		if (HeapTupleNoNulls(tup))
		{
			(void) LookupTupleHashEntry(node->hashtable, slot, &isnew);
			node->havehashrows = true;
		}
		else if (node->hashnulls)
		{
			(void) LookupTupleHashEntry(node->hashnulls, slot, &isnew);
			node->havenullrows = true;
		}

		/*
		 * Reset innerecontext after each inner tuple to free any memory
		 * used in hash computation or comparison routines.
		 */
		ResetExprContext(innerecontext);
	}

	/*
	 * Since the projected tuples are in the sub-query's context and not
	 * the main context, we'd better clear the tuple slot before there's
	 * any chance of a reset of the sub-query's context.  Else we will
	 * have the potential for a double free attempt.
	 */
	ExecClearTuple(node->projRight->pi_slot);

	MemoryContextSwitchTo(oldcontext);
}

/*
 * findPartialMatch: does the hashtable contain an entry that is not
 * provably distinct from the tuple?
 *
 * We have to scan the whole hashtable; we can't usefully use hashkeys
 * to guide probing, since we might get partial matches on tuples with
 * hashkeys quite unrelated to what we'd get from the given tuple.
 */
static bool
findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot)
{
	int			numCols = hashtable->numCols;
	AttrNumber *keyColIdx = hashtable->keyColIdx;
	HeapTuple	tuple = slot->val;
	TupleDesc	tupdesc = slot->ttc_tupleDescriptor;
	TupleHashIterator hashiter;
	TupleHashEntry entry;

	ResetTupleHashIterator(hashtable, &hashiter);
	while ((entry = ScanTupleHashTable(&hashiter)) != NULL)
	{
		if (!execTuplesUnequal(entry->firstTuple,
							   tuple,
							   tupdesc,
							   numCols, keyColIdx,
							   hashtable->eqfunctions,
							   hashtable->tempcxt))
			return true;
	}
	return false;
}

/*
 * tupleAllNulls: is the tuple completely NULL?
 */
static bool
tupleAllNulls(HeapTuple tuple)
{
	int			ncols = tuple->t_data->t_natts;
	int			i;

	for (i = 1; i <= ncols; i++)
	{
		if (!heap_attisnull(tuple, i))
			return false;
	}
	return true;
}

/* ----------------------------------------------------------------
 *		ExecInitSubPlan
 * ----------------------------------------------------------------
 */
void
ExecInitSubPlan(SubPlanState *node, EState *estate)
{
	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
	EState	   *sp_estate;
	MemoryContext oldcontext;

	/*
	 * Do access checking on the rangetable entries in the subquery. Here,
	 * we assume the subquery is a SELECT.
	 */
	ExecCheckRTPerms(subplan->rtable, CMD_SELECT);

	/*
	 * initialize my state
	 */
	node->needShutdown = false;
	node->curTuple = NULL;
	node->projLeft = NULL;
	node->projRight = NULL;
	node->hashtable = NULL;
	node->hashnulls = NULL;
	node->tablecxt = NULL;
	node->innerecontext = NULL;
	node->keyColIdx = NULL;
	node->eqfunctions = NULL;
	node->hashfunctions = NULL;

	/*
	 * create an EState for the subplan
	 *
	 * The subquery needs its own EState because it has its own rangetable.
	 * It shares our Param ID space, however.  XXX if rangetable access
	 * were done differently, the subquery could share our EState, which
	 * would eliminate some thrashing about in this module...
	 */
	sp_estate = CreateExecutorState();
	node->sub_estate = sp_estate;

	oldcontext = MemoryContextSwitchTo(sp_estate->es_query_cxt);

	sp_estate->es_range_table = subplan->rtable;
	sp_estate->es_param_list_info = estate->es_param_list_info;
	sp_estate->es_param_exec_vals = estate->es_param_exec_vals;
	sp_estate->es_tupleTable =
		ExecCreateTupleTable(ExecCountSlotsNode(subplan->plan) + 10);
	sp_estate->es_snapshot = estate->es_snapshot;
	sp_estate->es_crosscheck_snapshot = estate->es_crosscheck_snapshot;
	sp_estate->es_instrument = estate->es_instrument;

	/*
	 * Start up the subplan (this is a very cut-down form of InitPlan())
	 */
	node->planstate = ExecInitNode(subplan->plan, sp_estate);

	node->needShutdown = true;	/* now we need to shutdown the subplan */

	MemoryContextSwitchTo(oldcontext);

	/*
	 * If this plan is un-correlated or undirect correlated one and want
	 * to set params for parent plan then mark parameters as needing
	 * evaluation.
	 *
	 * Note that in the case of un-correlated subqueries we don't care about
	 * setting parent->chgParam here: indices take care about it, for
	 * others - it doesn't matter...
	 */