Adjust to limit extraneous selects.
Adjust to limit extraneous selects.

If we know we are adding a new row, we can create a new object
and add it to the session by itself, rather than adding it to
a parent. Doing the latter causes some wasted SQL.

tiddlyweb/tiddlywebplugins.sqlalchemy,tiddlyweb/tiddlywebplugins.sqlalchemy