Change the way types for prepared statement parameters are calculated

[sidorares]

Currently types are inferred based on what is in the input (Date -> mysql date, js number -> mysql double, everything else - string ). This used to work ok until mysql server version 8.0.22

Calling execute('SELECT * from foo limit ?' , 1) results in Incorrect arguments to mysqld_stmt_execute` error. The type of the parameter server expects ( LONGINT ) is incompatible to what is actually sent ( DOUBLE ).

The fix is to use parameters column definitions returned from the previous prepare() call and use types from there instead of inferring type from the provided input

[sidorares]

ref #1239

[sidorares]

@vlasky when you have time can you try this brach to see if it fixes Incorrect arguments to mysqld_stmt_execute error for you?

It's a potentially backwards incompatible change in some scenarios, I'm thinking to release it as a major version bump. Maybe alpha release initially

[kimf]

Hello @sidorares For what it's worth, I had the exact same issue as mentioned in #1239 and tried this branch with great success.

[mlucic]

Any updates on this?

[sidorares]

@mlucic unfortunately no progress here (but its quite high in my priority)

The way I want to implement this currently is different from this PR though.

The plan is:

1. Introduce a "typed parameter" helpers which would hold the value you pass together with type information. Not sure about the exact api, but it might look like this:

const mediumintparam = mysql.TypedParameter.MEDIUMINT(123);
const floatparam =  mysql.TypedParameter.FLOAT(123);

conn.execute('select ?+? as sum', [mediumintparam, floatparam]);

when used via type helper the type sent with COM_EXECUTE is always what you specify

2. when untyped js value is passed we have 2 options: infer from current value ( string / date / number / null / non-null object ) or use response from COM_PREPARE. The problem "type hint from the server" is that its not always accurate ( for example, there are scenarios when the server has no way of telling parameter type - select ?+? as sum ). I'll need to think when this hint might be useful and when not ( any feedback is appreciated! ), ideally we need a matrix where there is js type on one axis, COM_EXECUTE type hint on another axis mapped to what the driver will actually use for type

step 1) can be done now and would help solving current edge cases with a bit of manually added typings ( as in mysql types metadata in users code, not typescript )

after that we can add step 2 to make default map work with no surprises most of the time. Mysql is quite capable of casting back to a correct value on a server side, in earlier versions of this driver all .execute() parameters were converted to a string ( sometimes its even more efficient, "1" takes 2 bytes over the wire where double precision number is 8 )

example table:

Mysql type hint \ JS type	string	number	bigint	Date
LONGLONG	VAR_STRING	VAR_STRING	VAR_STRING	DATETIME
VAR_STRING	VAR_STRING	DOUBLE	VAR_STRING	DATETIME

I'm starting to think simple "always send (parameter.toString()) as VAR_STRING" unless the type is explicitly specified by user" might be actually the best behaviour