searching tickets

Hi all,

used version: 1.9.12
I have some issues concerning the serach function:

- it seems that it is searched for whole keywords and not for substrings. Is that true?
- it seems that only keywords of a length that is at least 4 characters. Is that true?
- keywords are OR-combined in the search. Is it possible to combine them with AND?
- it is only serched for the full keywords. Is it possible to search for substrings?
- is it possible tor search for strings instead of keywords?

Thanks in advance!
brk