MYSQL空间点在边界框中

我正在尝试测试边界框中的点。它总是返回null而不是0或1，我所做的有什么不对

SET @g1 = GEOMFROMTEXT('POLYGON(
        (-34.139468536232 18.303737037571,-34.139468536232 18.653342962429
        ,-33.849613463768 18.303737037571,-33.849613463768 18.653342962429))');

SET @g2 = GEOMFROMTEXT('POINT(-33.994541 18.478540)');

SELECT MBRCONTAINS(@g1,@g2);

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在多边形中，如果我在末端再次重复第一个点（以包围多边形），它将起作用：

看这把小提琴：

SET @g1 = GEOMFROMTEXT('POLYGON(
        (-34.139468536232 18.303737037571,-34.139468536232 18.653342962429
        ,-33.849613463768 18.303737037571,-33.849613463768 18.653342962429, -34.139468536232 18.303737037571))');

SET @g2 = GEOMFROMTEXT('POINT(-33.994541 18.478540)');

SELECT MBRCONTAINS(@g1,@g2);