Bind parameters given to Statement#execute persist beyond the call

[jeremyevans]

I found this behavior surprising. I'm not sure whether it is bug, since there is a simple implementation reason for it, but I don't know whether the behavior is expected or desired. Here's a simple example:

db = SQLite3::Database.new ":memory:"
stmt = db.prepare "SELECT :a + :b"
stmt.execute(a: 1, b: 2).to_a # => [[3]]
stmt.execute(a: 2).to_a       # => [[4]]
stmt.execute(b: 3).to_a       # => [[5]]
stmt.execute.to_a             # => [[5]]

As you can see in the example, if you don't provide a bind parameter to execute, it uses the last bound value. I believe it works this way because execute calls bind_params if given any parameters, but it does not reset the preexisting bind parameter state after the statement executes.

You cannot reset the entire bind parameter state in execute, because this code is expected to work:

db = SQLite3::Database.new ":memory:"
stmt = db.prepare "SELECT :a + :b"
stmt.bind_params(a: 1)
stmt.execute(b: 2).to_a # => [[3]]
stmt.execute(b: 3).to_a # => [[4]]

My personal expectation would be that parameters given to execute only apply to that specific execution and not any subsequent executions. However, I realize that requires an allocation in the case where there are already bound parameters on the statement.

Note that this is only an issue when you have multiple execute calls on the statement, and a bind parameter set by one of the earlier execute calls is not set on a later one.