To index your ports tree into a database in /usr/ports/INDEX.db, run:
./portindex -v
You may find bsdportsearch/doc.py interesting, to see what's going on under
the hood.
To search your constructed database (/usr/ports/INDEX.db), run:
./portsearch query_string
To get long-format output (similar to make search), use the -l option:
./portsearch -l '(bash OR ksh)' AND 'maintainer=obrien*'