PostgreSQL CommandType.StoredProcedure 42809: procname() is not a procedure exception

[SCVNG3R]

As it's mentioned on Npgsql documentation website, starting with Npgsql 7.0, CommandType.StoredProcedure now invokes stored procedures, and not function as before. Attempting to call a database function (such as GetBeerByType()) will result in the following exception: Npgsql.PostgresException: '42809: procname() is not a procedure

This renders Insight.Database unusable with PostgreSQL More info can be found here: Npgsql Basic Usage

Steps to reproduce

Attempt to run the HelloWorld code under Npgsql

Expected behavior

Return value from calling a database function

• Dotnet version: [netcore7]
• Npgsql: [7.0.1]
• Database: [PostgreSQL 15]
• Library version: [6.3.11]

[jonwagner]

I see that this is a transition because PG < v11 only had functions and now it supports stored procedures. NpgSQL previously mapped CommandType.StoredProcedure to functions and now is correcting the behaviour.

Their release notes mark this as a breaking change.

I believe the correct stance to take is:

• CommandType.StoredProcedure should invoke stored procedures
• If you coded your database with FUNCTIONs then you should follow the npgsql guidance of calling AppContext.SetSwitch("Npgsql.EnableStoredProcedureCompatMode", true);

As for Insight.Database, I will update the test cases to use stored procedures and ensure it works with PG11 and NPGSQL7.

[jonwagner]

sigh...this is going to be a lot harder than i expected.

• postgres and npgsql use entirely different methods for returning recordsets and output parameters between functions and procedures
• there is no CommandType.Function that allows us to distinguish between functions and procedures and get the desired functionality.

[jonwagner]

I'll try to find time to do a full pass through the PG provider but it's non-trivial.

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[Grauenwolf]

sigh...this is going to be a lot harder than i expected.

• postgres and npgsql use entirely different methods for returning recordsets and output parameters between functions and procedures
• there is no CommandType.Function that allows us to distinguish between functions and procedures and get the desired functionality.

We could add our own. Make a NpgsqlCommandType enum and add the missing value as NpgsqlCommandType.Function=100.

For the property...

public NpgsqlCommandType NpgsqlCommandType {
    { get => (CommandType)NpgsqlCommandType; }
    { set => NpgsqlCommandType = (CommandType)value; }
}

This works because enums don't have range checks.

[jonwagner]

Good news?

For v8.0, I updated the Postgres provider. Now if you use CommandType.StoredProcedure, we do a mixup on the command:

• Convert it back to CommandType.Text
• Convert to SELECT * FROM function_name (params)

And surprisingly, this works!

@Grauenwolf give it a shot after the next build.

(Note that there is no longer support for calling stored procedures, but this feels like it's better compatibility.)