nodesubplan.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

	/*
	 * 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...
	 */
	if (subplan->setParam != NIL)
	{
		ListCell   *lst;

		foreach(lst, subplan->setParam)
		{
			int			paramid = lfirst_int(lst);
			ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);

			prm->execPlan = node;
		}
	}

	/*
	 * If we are going to hash the subquery output, initialize relevant stuff.
	 * (We don't create the hashtable until needed, though.)
	 */
	if (subplan->useHashTable)
	{
		int			ncols,
					i;
		TupleDesc	tupDesc;
		TupleTable	tupTable;
		TupleTableSlot *slot;
		List	   *lefttlist,
				   *righttlist,
				   *leftptlist,
				   *rightptlist;
		ListCell   *lexpr;

		/* We need a memory context to hold the hash table(s) */
		node->tablecxt =
			AllocSetContextCreate(CurrentMemoryContext,
								  "Subplan HashTable Context",
								  ALLOCSET_DEFAULT_MINSIZE,
								  ALLOCSET_DEFAULT_INITSIZE,
								  ALLOCSET_DEFAULT_MAXSIZE);
		/* and a short-lived exprcontext for function evaluation */
		node->innerecontext = CreateExprContext(estate);
		/* Silly little array of column numbers 1..n */
		ncols = list_length(node->exprs);
		node->keyColIdx = (AttrNumber *) palloc(ncols * sizeof(AttrNumber));
		for (i = 0; i < ncols; i++)
			node->keyColIdx[i] = i + 1;

		/*
		 * We use ExecProject to evaluate the lefthand and righthand
		 * expression lists and form tuples.  (You might think that we could
		 * use the sub-select's output tuples directly, but that is not the
		 * case if we had to insert any run-time coercions of the sub-select's
		 * output datatypes; anyway this avoids storing any resjunk columns
		 * that might be in the sub-select's output.) Run through the
		 * combining expressions to build tlists for the lefthand and
		 * righthand sides.  We need both the ExprState list (for ExecProject)
		 * and the underlying parse Exprs (for ExecTypeFromTL).
		 *
		 * We also extract the combining operators themselves to initialize
		 * the equality and hashing functions for the hash tables.
		 */
		lefttlist = righttlist = NIL;
		leftptlist = rightptlist = NIL;
		node->eqfunctions = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
		node->hashfunctions = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
		i = 1;
		foreach(lexpr, node->exprs)
		{
			FuncExprState *fstate = (FuncExprState *) lfirst(lexpr);
			OpExpr	   *opexpr = (OpExpr *) fstate->xprstate.expr;
			ExprState  *exstate;
			Expr	   *expr;
			TargetEntry *tle;
			GenericExprState *tlestate;
			Oid			hashfn;

			Assert(IsA(fstate, FuncExprState));
			Assert(IsA(opexpr, OpExpr));
			Assert(list_length(fstate->args) == 2);

			/* Process lefthand argument */
			exstate = (ExprState *) linitial(fstate->args);
			expr = exstate->expr;
			tle = makeTargetEntry(expr,
								  i,
								  NULL,
								  false);
			tlestate = makeNode(GenericExprState);
			tlestate->xprstate.expr = (Expr *) tle;
			tlestate->xprstate.evalfunc = NULL;
			tlestate->arg = exstate;
			lefttlist = lappend(lefttlist, tlestate);
			leftptlist = lappend(leftptlist, tle);

			/* Process righthand argument */
			exstate = (ExprState *) lsecond(fstate->args);
			expr = exstate->expr;
			tle = makeTargetEntry(expr,
								  i,
								  NULL,
								  false);
			tlestate = makeNode(GenericExprState);
			tlestate->xprstate.expr = (Expr *) tle;
			tlestate->xprstate.evalfunc = NULL;
			tlestate->arg = exstate;
			righttlist = lappend(righttlist, tlestate);
			rightptlist = lappend(rightptlist, tle);

			/* Lookup the combining function */
			fmgr_info(opexpr->opfuncid, &node->eqfunctions[i - 1]);
			node->eqfunctions[i - 1].fn_expr = (Node *) opexpr;

			/* Lookup the associated hash function */
			hashfn = get_op_hash_function(opexpr->opno);
			if (!OidIsValid(hashfn))
				elog(ERROR, "could not find hash function for hash operator %u",
					 opexpr->opno);
			fmgr_info(hashfn, &node->hashfunctions[i - 1]);

			i++;
		}

		/*
		 * Create a tupletable to hold these tuples.  (Note: we never bother
		 * to free the tupletable explicitly; that's okay because it will
		 * never store raw disk tuples that might have associated buffer pins.
		 * The only resource involved is memory, which will be cleaned up by
		 * freeing the query context.)
		 */
		tupTable = ExecCreateTupleTable(2);

		/*
		 * Construct tupdescs, slots and projection nodes for left and right
		 * sides.  The lefthand expressions will be evaluated in the parent
		 * plan node's exprcontext, which we don't have access to here.
		 * Fortunately we can just pass NULL for now and fill it in later
		 * (hack alert!).  The righthand expressions will be evaluated in our
		 * own innerecontext.
		 */
		tupDesc = ExecTypeFromTL(leftptlist, false);
		slot = ExecAllocTableSlot(tupTable);
		ExecSetSlotDescriptor(slot, tupDesc, true);
		node->projLeft = ExecBuildProjectionInfo(lefttlist,
												 NULL,
												 slot);

		tupDesc = ExecTypeFromTL(rightptlist, false);
		slot = ExecAllocTableSlot(tupTable);
		ExecSetSlotDescriptor(slot, tupDesc, true);
		node->projRight = ExecBuildProjectionInfo(righttlist,
												  node->innerecontext,
												  slot);
	}
}

/* ----------------------------------------------------------------
 *		ExecSetParamPlan
 *
 *		Executes an InitPlan subplan and sets its output parameters.
 *
 * This is called from ExecEvalParam() when the value of a PARAM_EXEC
 * parameter is requested and the param's execPlan field is set (indicating
 * that the param has not yet been evaluated).	This allows lazy evaluation
 * of initplans: we don't run the subplan until/unless we need its output.
 * Note that this routine MUST clear the execPlan fields of the plan's
 * output parameters after evaluating them!
 * ----------------------------------------------------------------
 */
void
ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
{
	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
	PlanState  *planstate = node->planstate;
	SubLinkType subLinkType = subplan->subLinkType;
	MemoryContext oldcontext;
	TupleTableSlot *slot;
	ListCell   *l;
	bool		found = false;
	ArrayBuildState *astate = NULL;

	/*
	 * Must switch to child query's per-query memory context.
	 */
	oldcontext = MemoryContextSwitchTo(node->sub_estate->es_query_cxt);

	if (subLinkType == ANY_SUBLINK ||
		subLinkType == ALL_SUBLINK)
		elog(ERROR, "ANY/ALL subselect unsupported as initplan");

	if (planstate->chgParam != NULL)
		ExecReScan(planstate, NULL);

	for (slot = ExecProcNode(planstate);
		 !TupIsNull(slot);
		 slot = ExecProcNode(planstate))
	{
		TupleDesc	tdesc = slot->tts_tupleDescriptor;
		int			i = 1;

		if (subLinkType == EXISTS_SUBLINK)
		{
			/* There can be only one param... */
			int			paramid = linitial_int(subplan->setParam);
			ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);

			prm->execPlan = NULL;
			prm->value = BoolGetDatum(true);
			prm->isnull = false;
			found = true;
			break;
		}

		if (subLinkType == ARRAY_SUBLINK)
		{
			Datum		dvalue;
			bool		disnull;

			found = true;
			/* stash away current value */
			dvalue = slot_getattr(slot, 1, &disnull);
			astate = accumArrayResult(astate, dvalue, disnull,
									  tdesc->attrs[0]->atttypid,
									  oldcontext);
			/* keep scanning subplan to collect all values */
			continue;
		}

		if (found &&
			(subLinkType == EXPR_SUBLINK ||
			 subLinkType == MULTIEXPR_SUBLINK))
			ereport(ERROR,
					(errcode(ERRCODE_CARDINALITY_VIOLATION),
					 errmsg("more than one row returned by a subquery used as an expression")));

		found = true;

		/*
		 * We need to copy the subplan's tuple into our own context, in case
		 * any of the params are pass-by-ref type --- the pointers stored in
		 * the param structs will point at this copied tuple! node->curTuple
		 * keeps track of the copied tuple for eventual freeing.
		 */
		MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
		if (node->curTuple)
			heap_freetuple(node->curTuple);
		node->curTuple = ExecCopySlotTuple(slot);
		MemoryContextSwitchTo(node->sub_estate->es_query_cxt);

		/*
		 * Now set all the setParam params from the columns of the tuple
		 */
		foreach(l, subplan->setParam)
		{
			int			paramid = lfirst_int(l);
			ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);

			prm->execPlan = NULL;
			prm->value = heap_getattr(node->curTuple, i, tdesc,
									  &(prm->isnull));
			i++;
		}
	}

	if (!found)
	{
		if (subLinkType == EXISTS_SUBLINK)
		{
			/* There can be only one param... */
			int			paramid = linitial_int(subplan->setParam);
			ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);

			prm->execPlan = NULL;
			prm->value = BoolGetDatum(false);
			prm->isnull = false;
		}
		else
		{
			foreach(l, subplan->setParam)
			{
				int			paramid = lfirst_int(l);
				ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);

				prm->execPlan = NULL;
				prm->value = (Datum) 0;
				prm->isnull = true;
			}
		}
	}
	else if (subLinkType == ARRAY_SUBLINK)
	{
		/* There can be only one param... */
		int			paramid = linitial_int(subplan->setParam);
		ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);

		Assert(astate != NULL);
		prm->execPlan = NULL;
		/* We build the result in query context so it won't disappear */
		prm->value = makeArrayResult(astate, econtext->ecxt_per_query_memory);
		prm->isnull = false;
	}

	MemoryContextSwitchTo(oldcontext);
}

/* ----------------------------------------------------------------
 *		ExecEndSubPlan
 * ----------------------------------------------------------------
 */
void
ExecEndSubPlan(SubPlanState *node)
{
	if (node->needShutdown)
	{
		MemoryContext oldcontext;

		oldcontext = MemoryContextSwitchTo(node->sub_estate->es_query_cxt);
		ExecEndPlan(node->planstate, node->sub_estate);
		MemoryContextSwitchTo(oldcontext);
		FreeExecutorState(node->sub_estate);
		node->sub_estate = NULL;
		node->planstate = NULL;
		node->needShutdown = false;
	}
}

/*
 * Mark an initplan as needing recalculation
 */
void
ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent)
{
	PlanState  *planstate = node->planstate;
	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
	EState	   *estate = parent->state;
	ListCell   *l;

	/* sanity checks */
	if (subplan->parParam != NIL)
		elog(ERROR, "direct correlated subquery unsupported as initplan");
	if (subplan->setParam == NIL)
		elog(ERROR, "setParam list of initplan is empty");
	if (bms_is_empty(planstate->plan->extParam))
		elog(ERROR, "extParam set of initplan is empty");

	/*
	 * Don't actually re-scan: ExecSetParamPlan does it if needed.
	 */

	/*
	 * Mark this subplan's output parameters as needing recalculation
	 */
	foreach(l, subplan->setParam)
	{
		int			paramid = lfirst_int(l);
		ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);

		prm->execPlan = node;
		parent->chgParam = bms_add_member(parent->chgParam, paramid);
	}
}