Example:

$ hugo new post/fast_data_indexing.md

will create a new content in content/post/fast_data_indexing.md as expected, but "fast_data_indexing" will not appear in list of pages (i.e. in {{ range .Data.Pages }}) nor will it be processed and rendered into public/post/ folder.

$ hugo version
Hugo Static Site Generator v0.19 windows/amd64 BuildDate: 2017-03-03T15:33:06-06:00