user: Question: What was the surface for the May 10, 2009 tournament?
Columns: ['Date', 'Tournament', 'Surface', 'Partner', 'Opponents', 'Score']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['March 25, 2007', 'Canada F3, Rock Forest', 'Hard (i)', 'Érik Chvojka', 'Christophe Palmanshofer Jason Zimmermann', '7–5, 6–3']
SQL:

assistant: SELECT "Surface" FROM "Table" WHERE "Date" = 'May 10, 2009';