query many

[greg-rychlewski]

Closes #143

Introduces new functions query_many, prepare_many, prepare_execute_many and execute_many that allow the user to obtain results for queries that return multiple results, like text queries with multiple statements or stored procedures.

The main idea is:

• Introduce 2 new structs: MyXQL.Queries and MyXQL.TextQueries
• Keep a result state in addition to the decoder state while receiving the packets.
  • The result state will keep track of whether this is a single or multiple result and if multiple, store the results already obtained.
  • This lets us decide whether or not to keep going when MySQL says there are more results. And if we are retrieving multiple results to keep the partial results stored somewhere.
  • Keeping this separate from the decoder state means we don't have to copy the partial results through all of the decoder functions. Or to pass the information to determine whether it's a single or multi result query

[greg-rychlewski]

sorry I just saw some minor typos in a couple of the tests and forgot to change the error message when raising for multiple results.

[wojtekmach]

👍

[wojtekmach]

excellent coverage!

[wojtekmach]

Thank you!

[greg-rychlewski]

Would you guys want to add Ecto.Adapters.SQL.query_many/query_many! to ecto_sql? Even though this is the only adapter implementing the function, there might be a benefit if most people are using Ecto vs this driver directly.

I can submit a PR if you think it's a good idea. And I guess return something like {:error, :not_supported} if the adapter is not exporting the appropriate function?

[josevalim]

We could add query_many. It should just raise not supported for the other adapters.