Not really happy with this solution because it might be confusing in its usage in the following scenario for example:

- run_on_master with persist on

- all the following queries are then run on master (as expected)

- run_on_slave with persist off

- next query is run on the slave (as expected)

- following queries are run either on master or slave (not sure if this is expected)
Maybe it is better to keep the run_on_master, run_on_slave,... functions only affecting the next query

And have a separate "global query hint" property management:

- new property global_query_hint with master/slave setter functions

- the query functions would use that global query hint by default unless there is a temporary one set from the run_on_master/slave functions

none