pgtype: Encoding []int64 works, but []Int64Valuer does not

[dpifke]

I have a query like ...WHERE status = ANY(?) where I want to select rows matching a slice of a custom type that implements Int64Valuer. (The status column in the database is a Postgres BIGINT.)

...WHERE status = ? with my type works, but the ANY(?) query fails with:

unable to encode []job.Status{job.StatusQueued, job.StatusContingent, job.StatusDispatched} into text format for unknown type (OID 0): cannot find encode plan

I can reproduce this as follows:

 m := pgtype.NewMap()                                                                                                                                                                                                   
 if plan := m.PlanEncode(0, pgtype.TextFormatCode, make([]int64, 0)); plan == nil {
   panic("plan for []int64 is nil") // OK
 }
 if plan := m.PlanEncode(0, pgtype.TextFormatCode, make([]pgtype.Int64Valuer, 0)); plan == nil {
   panic("plan for []Int64Valuer is nil") // panics
 }
 // Status implements pgtype.Int64Valuer
 if plan := m.PlanEncode(0, pgtype.TextFormatCode, make([]Status, 0)); plan == nil {
   panic("plan for []Status is nil") // panics
 }

I think I can fix this via some magic in Map.TryWrapPlanEncodeFuncs, but it isn't immediately obvious how. Suggestions?

[dpifke]

Ah, it looks like the magic I need is Map.RegisterDefaultPgType. The following worked:

 m := pgtype.NewMap()
 m.RegisterDefaultPgType(make([]Status, 0), "_int8")                                                                                                                                                                      
 if plan := m.PlanEncode(0, pgtype.TextFormatCode, make([]Status, 0)); plan == nil {
    panic("plan for []Status is nil") // OK
 }

As a documentation note, the value of the name argument to RegisterDefaultPgType was not at all clear. It says "PostgreSQL type name" but neither "BIGINT", nor "BIGINT[]", nor "_BIGINT" worked. I eventually figured it out by looking at the source.