The default mechanism for creating search strings and for doing the
actual search related to a file link may not work correctly in all
cases. For example, BibTeX database files have many entries like
year="1993" which would not result in good search strings, because
the only unique identification for a BibTeX entry is the citation key.
If you come across such a problem, you can write custom functions to
set the right search string for a particular file type, and to do the
search for the string in the file. Using
add-hook, these functions
need to be added to the hook variables
org-execute-file-search-functions. See the docstring for these
variables for more information. Org actually uses this mechanism for
BibTeX database files, and you can use the corresponding code as an
implementation example. See the file ‘org-bibtex.el’.