如何在数组属性上创建全文索引？

I'd like to create a fulltext index for an array attribute without needs to redundantly copy all its strings. I tried by defining an index for "attrib[*].string" but this does not work. Am I using the wrong syntax? If not, is it hard to support such an index scenario? For my naive understanding there might be no huge difference in function except the reading function while creating the index ... at least I hope this :-)I'd like to create a fulltext index for an arra