WriteBatch operations (put, delete) fail when using set_default_column_family but work with explicit column_family argument

[DisplayL]

Description:

There appears to be a bug in how WriteBatch handles the default column family set via set_default_column_family.

Expected Behavior:

Calling write_batch.set_default_column_family(cf_handle) should allow subsequent calls to write_batch.put(key, value) and write_batch.delete(key) (or write_batch[key] = value and del write_batch[key]) to operate on the specified column family cf_handle.

Actual Behavior:

Operations that explicitly pass the column family handle work correctly:

write_batch.put(key, value, cf_handle) -> Works
write_batch.delete(key, cf_handle) -> Works

However, operations relying on the default column family set previously do not work as expected:

write_batch.set_default_column_family(cf_handle) write_batch.put(key, value) -> Fails (operation seems to have no effect, data not written to the intended CF)
write_batch.set_default_column_family(cf_handle) write_batch.delete(key) -> Fails (operation seems to have no effect, data not deleted from the intended CF)

[Congyuwang]

Fixed by #181