always use source lookup in genericFunctionQuery

-> where substr(analyzed_text, 1,1) = 'x'

threw GroupByOnArrayUnsupported exception, now it works
correctly using source lookup
fixup! always use source lookup in genericFunctionQuery
fixup! fixup! always use source lookup in genericFunctionQuery
fixup! fixup! fixup! always use source lookup in genericFunctionQuery
fixup! fixup! fixup! fixup! always use source lookup in genericFunctionQuery