The SVN repository at work is huge, and I don't have the disk space to checkout the whole thing with the branches and everything on my small (but very fast) laptop SSD. But I needed to search through the whole repo for a file, the following command line can help out.
svn list -R https://subversion-repo/subfolder | findstr filename
svn list -R file:///subversion-repo/subfolder | grep filename
These commands don't look through the history but will find things at the current HEAD of the repository.
If you want to look for a particular point in time you can specify the revision thus:
svn list -r 1234 -R https://subversion-repo/subfolder | findstr filename
where 1234 is the revision to search though.
If you want to search the entire history you could script the search to look though every revision from 1 to n and list the files that match the search at each revision, then remove duplicates to get a single list. How about getting even fancier by recording the revision the file was first found and the revision it was deleted at. I have no requirement to do this right now but sounds like an interesting little project to try.
If you want to search for text in files I find searching the diffs useful. Just pipe the following into a file and search that in your favorite editor (Sublime text :-)
svn log -r1234:HEAD --diff https://subversion-repo/subfolder
this can be rather verbose but with a bit of tweaking and targeting of the repo/folder you can get some accurate results on text search in history