How to insert slice - postgresql

Question

I have a postgres db that I would like to generate tables for and write to using Gorp, however I get an error message when I try to insert due to the slices contained within my structs "sql: converting argument $4 type: unsupported type []core.EmbeddedStruct, a slice of struct.
My structs look as follows:
type Struct1 struct {
ID string
Name string
Location string
EmbeddedStruct []EmbeddedStruct
}
type EmbeddedStruct struct {
ID string
Name string
struct1Id string
EmbeddedStruct2 []EmbeddedStruct2
}
type EmbeddedStruct2 struct {
ID string
Name string
embeddedStructId string
}
func (repo *PgStruct1Repo) Write(t *core.Struct1) error {
trans, err := createTransaction(repo.dbMap)
defer closeTransaction(trans)
if err != nil {
return err
}
// Check to see if struct1 item already exists
exists, err := repo.exists(t.ID, trans)
if err != nil {
return err
}
if !exists {
log.Debugf("saving new struct1 with ID %s", t.ID)
err = trans.Insert(t)
if err != nil {
return err
}
return nil
}
return nil
}
Does anyone have any experience with/or know if Gorp supports inserting slices? From what I've read it seems to only support slices for SELECT statements

Answer 1

Gorp supports inserting a variadic number of slices, so if you have a slice records, you can do:
err = db.Insert(records...)
However, from your question it seems you want to save a single record that has a slice struct field.
https://github.com/go-gorp/gorp
gorp doesn't know anything about the relationships between your structs (at least not yet).
So, you have to handle the relationship yourself. The way I personally would solve this issue is to have Gorp ignore the slice on the parent:
type Struct1 struct {
ID string
Name string
Location string
EmbeddedStruct []EmbeddedStruct `db:"-"`
}
And then use the PostInsert hook to save the EmbeddedStruct (side note, this is a poor name as it is not actually an embedded struct)
func (s *Struct1) PostInsert(sql gorp.SqlExecutor) error {
for i := range s.EmbeddedStruct {
s.EmbeddedStruct[i].struct1Id = s.ID
}
return sql.Insert(s.EmbeddedStruct...)
}
And then repeat the process on EmbeddedStruct2.
Take care to setup the relationships properly on the DB side to ensure referential integrity (e.g. ON DELETE CASCADE / RESTRICT), and it would probably be a good idea to wrap the whole thing in a transaction.