exectuples.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

 *			Obtain a copy of a slot's physical tuple.  The copy is
 *			palloc'd in the current memory context.
 *
 *		This works even if the slot contains a virtual tuple;
 *		however the "system columns" of the result will not be meaningful.
 * --------------------------------
 */
HeapTuple
ExecCopySlotTuple(TupleTableSlot *slot)
{
	/*
	 * sanity checks
	 */
	Assert(slot != NULL);
	Assert(!slot->tts_isempty);

	/*
	 * If we have a physical tuple then just copy it.
	 */
	if (slot->tts_tuple)
		return heap_copytuple(slot->tts_tuple);

	/*
	 * Otherwise we need to build a tuple from the Datum array.
	 */
	return heap_form_tuple(slot->tts_tupleDescriptor,
						   slot->tts_values,
						   slot->tts_isnull);
}

/* --------------------------------
 *		ExecFetchSlotTuple
 *			Fetch the slot's physical tuple.
 *
 *		If the slot contains a virtual tuple, we convert it to physical
 *		form.  The slot retains ownership of the physical tuple.
 *
 * The difference between this and ExecMaterializeSlot() is that this
 * does not guarantee that the contained tuple is local storage.
 * Hence, the result must be treated as read-only.
 * --------------------------------
 */
HeapTuple
ExecFetchSlotTuple(TupleTableSlot *slot)
{
	/*
	 * sanity checks
	 */
	Assert(slot != NULL);
	Assert(!slot->tts_isempty);

	/*
	 * If we have a physical tuple then just return it.
	 */
	if (slot->tts_tuple)
		return slot->tts_tuple;

	/*
	 * Otherwise materialize the slot...
	 */
	return ExecMaterializeSlot(slot);
}

/* --------------------------------
 *		ExecMaterializeSlot
 *			Force a slot into the "materialized" state.
 *
 *		This causes the slot's tuple to be a local copy not dependent on
 *		any external storage.  A pointer to the contained tuple is returned.
 *
 *		A typical use for this operation is to prepare a computed tuple
 *		for being stored on disk.  The original data may or may not be
 *		virtual, but in any case we need a private copy for heap_insert
 *		to scribble on.
 * --------------------------------
 */
HeapTuple
ExecMaterializeSlot(TupleTableSlot *slot)
{
	HeapTuple	newTuple;
	MemoryContext oldContext;

	/*
	 * sanity checks
	 */
	Assert(slot != NULL);
	Assert(!slot->tts_isempty);

	/*
	 * If we have a physical tuple, and it's locally palloc'd, we have nothing
	 * to do.
	 */
	if (slot->tts_tuple && slot->tts_shouldFree)
		return slot->tts_tuple;

	/*
	 * Otherwise, copy or build a tuple, and then store it as the new slot
	 * value.  (Note: tts_nvalid will be reset to zero here.  There are cases
	 * in which this could be optimized but it's probably not worth worrying
	 * about.)
	 *
	 * We may be called in a context that is shorter-lived than the tuple
	 * slot, but we have to ensure that the materialized tuple will survive
	 * anyway.
	 */
	oldContext = MemoryContextSwitchTo(slot->tts_mcxt);
	newTuple = ExecCopySlotTuple(slot);
	MemoryContextSwitchTo(oldContext);

	ExecStoreTuple(newTuple, slot, InvalidBuffer, true);

	return slot->tts_tuple;
}

/* --------------------------------
 *		ExecCopySlot
 *			Copy the source slot's contents into the destination slot.
 *
 *		The destination acquires a private copy that will not go away
 *		if the source is cleared.
 *
 *		The caller must ensure the slots have compatible tupdescs.
 * --------------------------------
 */
TupleTableSlot *
ExecCopySlot(TupleTableSlot *dstslot, TupleTableSlot *srcslot)
{
	HeapTuple	newTuple;
	MemoryContext oldContext;

	/*
	 * There might be ways to optimize this when the source is virtual, but
	 * for now just always build a physical copy.  Make sure it is in the
	 * right context.
	 */
	oldContext = MemoryContextSwitchTo(dstslot->tts_mcxt);
	newTuple = ExecCopySlotTuple(srcslot);
	MemoryContextSwitchTo(oldContext);

	return ExecStoreTuple(newTuple, dstslot, InvalidBuffer, true);
}


/* ----------------------------------------------------------------
 *				convenience initialization routines
 * ----------------------------------------------------------------
 */

/* --------------------------------
 *		ExecInit{Result,Scan,Extra}TupleSlot
 *
 *		These are convenience routines to initialize the specified slot
 *		in nodes inheriting the appropriate state.	ExecInitExtraTupleSlot
 *		is used for initializing special-purpose slots.
 * --------------------------------
 */

/* ----------------
 *		ExecInitResultTupleSlot
 * ----------------
 */
void
ExecInitResultTupleSlot(EState *estate, PlanState *planstate)
{
	planstate->ps_ResultTupleSlot = ExecAllocTableSlot(estate->es_tupleTable);
}

/* ----------------
 *		ExecInitScanTupleSlot
 * ----------------
 */
void
ExecInitScanTupleSlot(EState *estate, ScanState *scanstate)
{
	scanstate->ss_ScanTupleSlot = ExecAllocTableSlot(estate->es_tupleTable);
}

/* ----------------
 *		ExecInitExtraTupleSlot
 * ----------------
 */
TupleTableSlot *
ExecInitExtraTupleSlot(EState *estate)
{
	return ExecAllocTableSlot(estate->es_tupleTable);
}

/* ----------------
 *		ExecInitNullTupleSlot
 *
 * Build a slot containing an all-nulls tuple of the given type.
 * This is used as a substitute for an input tuple when performing an
 * outer join.
 * ----------------
 */
TupleTableSlot *
ExecInitNullTupleSlot(EState *estate, TupleDesc tupType)
{
	TupleTableSlot *slot = ExecInitExtraTupleSlot(estate);

	ExecSetSlotDescriptor(slot, tupType, false);

	return ExecStoreAllNullTuple(slot);
}

/* ----------------------------------------------------------------
 *		ExecTypeFromTL
 *
 *		Generate a tuple descriptor for the result tuple of a targetlist.
 *		(A parse/plan tlist must be passed, not an ExprState tlist.)
 *		Note that resjunk columns, if any, are included in the result.
 *
 *		Currently there are about 4 different places where we create
 *		TupleDescriptors.  They should all be merged, or perhaps
 *		be rewritten to call BuildDesc().
 * ----------------------------------------------------------------
 */
TupleDesc
ExecTypeFromTL(List *targetList, bool hasoid)
{
	return ExecTypeFromTLInternal(targetList, hasoid, false);
}

/* ----------------------------------------------------------------
 *		ExecCleanTypeFromTL
 *
 *		Same as above, but resjunk columns are omitted from the result.
 * ----------------------------------------------------------------
 */
TupleDesc
ExecCleanTypeFromTL(List *targetList, bool hasoid)
{
	return ExecTypeFromTLInternal(targetList, hasoid, true);
}

static TupleDesc
ExecTypeFromTLInternal(List *targetList, bool hasoid, bool skipjunk)
{
	TupleDesc	typeInfo;
	ListCell   *l;
	int			len;
	int			cur_resno = 1;

	if (skipjunk)
		len = ExecCleanTargetListLength(targetList);
	else
		len = ExecTargetListLength(targetList);
	typeInfo = CreateTemplateTupleDesc(len, hasoid);

	foreach(l, targetList)
	{
		TargetEntry *tle = lfirst(l);

		if (skipjunk && tle->resjunk)
			continue;
		TupleDescInitEntry(typeInfo,
						   cur_resno++,
						   tle->resname,
						   exprType((Node *) tle->expr),
						   exprTypmod((Node *) tle->expr),
						   0);
	}

	return typeInfo;
}

/*
 * ExecTypeFromExprList - build a tuple descriptor from a list of Exprs
 *
 * Here we must make up an arbitrary set of field names.
 */
TupleDesc
ExecTypeFromExprList(List *exprList)
{
	TupleDesc	typeInfo;
	ListCell   *l;
	int			cur_resno = 1;
	char		fldname[NAMEDATALEN];

	typeInfo = CreateTemplateTupleDesc(list_length(exprList), false);

	foreach(l, exprList)
	{
		Node	   *e = lfirst(l);

		sprintf(fldname, "f%d", cur_resno);

		TupleDescInitEntry(typeInfo,
						   cur_resno++,
						   fldname,
						   exprType(e),
						   exprTypmod(e),
						   0);
	}

	return typeInfo;
}

/*
 * BlessTupleDesc - make a completed tuple descriptor useful for SRFs
 *
 * Rowtype Datums returned by a function must contain valid type information.
 * This happens "for free" if the tupdesc came from a relcache entry, but
 * not if we have manufactured a tupdesc for a transient RECORD datatype.
 * In that case we have to notify typcache.c of the existence of the type.
 */
TupleDesc
BlessTupleDesc(TupleDesc tupdesc)
{
	if (tupdesc->tdtypeid == RECORDOID &&
		tupdesc->tdtypmod < 0)
		assign_record_type_typmod(tupdesc);

	return tupdesc;				/* just for notational convenience */
}

/*
 * TupleDescGetSlot - Initialize a slot based on the supplied tupledesc
 *
 * Note: this is obsolete; it is sufficient to call BlessTupleDesc on
 * the tupdesc.  We keep it around just for backwards compatibility with
 * existing user-written SRFs.
 */
TupleTableSlot *
TupleDescGetSlot(TupleDesc tupdesc)
{
	TupleTableSlot *slot;

	/* The useful work is here */
	BlessTupleDesc(tupdesc);

	/* Make a standalone slot */
	slot = MakeSingleTupleTableSlot(tupdesc);

	/* Return the slot */
	return slot;
}

/*
 * TupleDescGetAttInMetadata - Build an AttInMetadata structure based on the
 * supplied TupleDesc. AttInMetadata can be used in conjunction with C strings
 * to produce a properly formed tuple.
 */
AttInMetadata *
TupleDescGetAttInMetadata(TupleDesc tupdesc)
{
	int			natts = tupdesc->natts;
	int			i;
	Oid			atttypeid;
	Oid			attinfuncid;
	FmgrInfo   *attinfuncinfo;
	Oid		   *attioparams;
	int32	   *atttypmods;
	AttInMetadata *attinmeta;

	attinmeta = (AttInMetadata *) palloc(sizeof(AttInMetadata));

	/* "Bless" the tupledesc so that we can make rowtype datums with it */
	attinmeta->tupdesc = BlessTupleDesc(tupdesc);

	/*
	 * Gather info needed later to call the "in" function for each attribute
	 */
	attinfuncinfo = (FmgrInfo *) palloc0(natts * sizeof(FmgrInfo));
	attioparams = (Oid *) palloc0(natts * sizeof(Oid));
	atttypmods = (int32 *) palloc0(natts * sizeof(int32));

	for (i = 0; i < natts; i++)
	{
		/* Ignore dropped attributes */
		if (!tupdesc->attrs[i]->attisdropped)
		{
			atttypeid = tupdesc->attrs[i]->atttypid;
			getTypeInputInfo(atttypeid, &attinfuncid, &attioparams[i]);
			fmgr_info(attinfuncid, &attinfuncinfo[i]);
			atttypmods[i] = tupdesc->attrs[i]->atttypmod;
		}
	}
	attinmeta->attinfuncs = attinfuncinfo;
	attinmeta->attioparams = attioparams;
	attinmeta->atttypmods = atttypmods;

	return attinmeta;
}

/*
 * BuildTupleFromCStrings - build a HeapTuple given user data in C string form.
 * values is an array of C strings, one for each attribute of the return tuple.
 */
HeapTuple
BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)
{
	TupleDesc	tupdesc = attinmeta->tupdesc;
	int			natts = tupdesc->natts;
	Datum	   *dvalues;
	char	   *nulls;
	int			i;
	Oid			attioparam;
	int32		atttypmod;
	HeapTuple	tuple;

	dvalues = (Datum *) palloc(natts * sizeof(Datum));
	nulls = (char *) palloc(natts * sizeof(char));

	/* Call the "in" function for each non-null, non-dropped attribute */
	for (i = 0; i < natts; i++)
	{
		if (!tupdesc->attrs[i]->attisdropped)
		{
			/* Non-dropped attributes */
			if (values[i] != NULL)
			{
				attioparam = attinmeta->attioparams[i];
				atttypmod = attinmeta->atttypmods[i];

				dvalues[i] = FunctionCall3(&attinmeta->attinfuncs[i],
										   CStringGetDatum(values[i]),
										   ObjectIdGetDatum(attioparam),
										   Int32GetDatum(atttypmod));
				nulls[i] = ' ';
			}
			else
			{
				dvalues[i] = (Datum) 0;
				nulls[i] = 'n';
			}
		}
		else
		{
			/* Handle dropped attributes by setting to NULL */
			dvalues[i] = (Datum) 0;
			nulls[i] = 'n';
		}
	}

	/*
	 * Form a tuple
	 */
	tuple = heap_formtuple(tupdesc, dvalues, nulls);

	/*
	 * Release locally palloc'd space.  XXX would probably be good to pfree
	 * values of pass-by-reference datums, as well.
	 */
	pfree(dvalues);
	pfree(nulls);

	return tuple;
}

/*
 * Functions for sending tuples to the frontend (or other specified destination)
 * as though it is a SELECT result. These are used by utility commands that
 * need to project directly to the destination and don't need or want full
 * Table Function capability. Currently used by EXPLAIN and SHOW ALL
 */
TupOutputState *
begin_tup_output_tupdesc(DestReceiver *dest, TupleDesc tupdesc)
{
	TupOutputState *tstate;

	tstate = (TupOutputState *) palloc(sizeof(TupOutputState));

	tstate->metadata = TupleDescGetAttInMetadata(tupdesc);
	tstate->slot = MakeSingleTupleTableSlot(tupdesc);
	tstate->dest = dest;

	(*tstate->dest->rStartup) (tstate->dest, (int) CMD_SELECT, tupdesc);

	return tstate;
}

/*
 * write a single tuple
 *
 * values is a list of the external C string representations of the values
 * to be projected.
 *
 * XXX This could be made more efficient, since in reality we probably only
 * need a virtual tuple.
 */
void
do_tup_output(TupOutputState *tstate, char **values)
{
	/* build a tuple from the input strings using the tupdesc */
	HeapTuple	tuple = BuildTupleFromCStrings(tstate->metadata, values);

	/* put it in a slot */
	ExecStoreTuple(tuple, tstate->slot, InvalidBuffer, true);

	/* send the tuple to the receiver */
	(*tstate->dest->receiveSlot) (tstate->slot, tstate->dest);

	/* clean up */
	ExecClearTuple(tstate->slot);
}

/*
 * write a chunk of text, breaking at newline characters
 *
 * NB: scribbles on its input!
 *
 * Should only be used with a single-TEXT-attribute tupdesc.
 */
void
do_text_output_multiline(TupOutputState *tstate, char *text)
{
	while (*text)
	{
		char	   *eol;

		eol = strchr(text, '\n');
		if (eol)
			*eol++ = '\0';
		else
			eol = text +strlen(text);

		do_tup_output(tstate, &text);
		text = eol;
	}
}

void
end_tup_output(TupOutputState *tstate)
{
	(*tstate->dest->rShutdown) (tstate->dest);
	/* note that destroying the dest is not ours to do */
	ExecDropSingleTupleTableSlot(tstate->slot);
	/* XXX worth cleaning up the attinmetadata? */
	pfree(tstate);
}