why unspecified here?

cause we are not sure if the customer has inserted the UUID value in the column of type UUID/String. Hence, we are returning type as unspecified implicitly, but while making gRPC call we are making sure that if the type is unspecified we don't pass param type with the gaxOptions, this way are letting backend to figure out the type

@sakthivelmanii uuid value can be send for String column as well. So we want to make use of "unspecified" type and let backend decide it.
Ideally we should not have removed the type mapping when backend started suplorting untyped params, but we did not remove this because of breaking changes.

But will this work for parameterized queries. I think parameterized queries does not support UNSPECIFIED type.
@alkatrivedi can you check if parameterized query is working when passing a UUID value?

The case that we are talking about here is when customer triggers a following parameterized query without an explicit param type
const query = {
sql: 'SELECT @v',
params: {
v: values,
},
};
I think this fails if value is of UUID type and param type is not mentioned because client now sends a UNSPECIFIED type to backend

My suggestion here is
Ideally, if param type is not mentioned then treat the value as string.
If customer wants to treat that value as UUID then they can explicitly specify the param type.

based on the discussion with @harshachinta and @surbhigarg92

we will return the type as unspecified, allowing the backend to determine the type of the value provided

regarding the query - 'SELECT @v'

failure in this case, where the parameter type is not inferred, is expected behavior. since the query does not target a specific table, deriving type dynamically is not a valid scenario

Flash forward one year later, when this has been merged: it breaks usage of implicitly-string parameters containing a UUID, at least with the emulator.

They are detected as UUID by this line of code, and this results in a type-less struct type being passed to the backend, which it doesn't like. For example, the parameter user contains a UUID (the same query worked fine before UUID "support" was introduced):

Error: 3 INVALID_ARGUMENT: Type code must be specified, found ; 
    When parsing field #0 of code: STRUCT
    struct_type {
      fields {
        name: \"user\"
        type {
        }
      }
    }

My suggestion here is
Ideally, if param type is not mentioned then treat the value as string.
If customer wants to treat that value as UUID then they can explicitly specify the param type.

This seemed like a much more reasonable way of introducing a new feature and preserving backward compatibility.

I'll open an issue when I have time, but I'd highly appreciate proactive effort from the team to fix this, as the issue had been identified during the review process and was ignored.

@flovouin Thanks for flagging this! I will take a look

@sakthivelmanii uuid value can be send for String column as well. So we want to make use of "unspecified" type and let backend decide it.
Ideally we should not have removed the type mapping when backend started suplorting untyped params, but we did not remove this because of breaking changes.