reset_counts() method and command

[simonw]

Thought: maybe there should be a .reset_counts() method too, for if the table gets out of date with the triggers.

One way that could happen is if a table is dropped and recreated - the counts in the _counts table would likely no longer match the number of rows in that table.

Originally posted by @simonw in #215 (comment)

[simonw]

This is a little tricky. We should assume that the existing values in the _counts table cannot be trusted at all when this method is called - so we should probably clear that table entirely and then re-populate it.

But that means we need to figure out which tables in the database have the counts triggers defined.

[simonw]

I think this should be accompanied by a sqlite-utils reset-counts command.

[simonw]

To detect tables, look at the names of the triggers - {table}{counts_table}_insert and {table}{counts_table}_delete.

[simonw]

A table.has_count_triggers property.