While prescanning a large database, minetestmapper may keep the database
locked for too long, causing minetest to complain, and even bail out
sometimes. Minetest will print warnings like:
SQLite3 database has been locked for <duration>
The new option --sqlite3-limit-prescan-query-size limits the number
of records queried from the database in a single query, thus limiting
the duration of the lock.
If minetest kept the database locked for 1 second or more, *and* if
the database was modified in that time, minetestmapper will issue a warning,
and suggest using --sqlite3-limit-prescan-query-size.
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