Google: noindex meta tag does not help to save crawlingly budget
To detect the meta tag, Googlebot must crawl your page and, accordingly, to spend some knowledgewho budget. Thus, noindex prevents indexing of the page, but not scan.
— John (@JohnMu November 30, 2016
For most webmasters this is obvious, but the issues on this topic raised from time to time among industry professionals.
Regarding rel=canonical, Googlebot scans not only canonical, but also other pages. This is necessary in order to make sure they really are duplicates.
@bheligman probably not (or not much). we have to pick a canonical & have to crawl the dups to see that they're dups anyway.
— @JohnMu November 30, 2016
In October, Google spokesman Gary Illyes reminded that if the code page is specified, both the Directive and the noindex and index – it will be noindex.