我对Elixir和Phoenix完全陌生,目前正在研究“ Programming Phoenix”一书。
我已经读到第7章,并且有一个名为categories
的数据库表,其中具有列name
和name
上的数据库级唯一性约束。
如果在已经存在名为“ Hello”的类别时运行以下行,则会得到预期的Ecto.ConstraintError
:
> Rumbl.Repo.insert!(%Rumbl.Multimedia.Category{name: "Hello"})
[debug] QUERY ERROR db=3.2ms queue=4.9ms idle=9982.9ms
INSERT INTO "categories" ("name","inserted_at","updated_at") VALUES ($1,$2,$3) RETURNING "id" ["Hello", ~N[2020-04-18 07:05:04], ~N[2020-04-18 07:05:04]]
** (Ecto.ConstraintError) constraint error when attempting to insert struct:
* categories_name_index (unique_constraint)
[现在,这本书告诉我,可以将选项on_conflict: :nothing
添加到对insert!
的调用中,这将防止引发错误。但是实际上发生的是我收到了postgres语法错误:
> Rumbl.Repo.insert!(%Rumbl.Multimedia.Category{name: "Hello"}, on_conflict: :nothing)
** (Postgrex.Error) ERROR 42601 (syntax_error) syntax error at or near "ON"
query: INSERT INTO "categories" ("name","inserted_at","updated_at") VALUES ($1,$2,$3) ON CONFLICT DO NOTHING RETURNING "id"
(ecto_sql) lib/ecto/adapters/sql.ex:612: Ecto.Adapters.SQL.raise_sql_call_error/1
(ecto) lib/ecto/repo/schema.ex:657: Ecto.Repo.Schema.apply/4
(ecto) lib/ecto/repo/schema.ex:263: anonymous fn/15 in Ecto.Repo.Schema.do_insert/4
(ecto) lib/ecto/repo/schema.ex:164: Ecto.Repo.Schema.insert!/4
[debug] QUERY ERROR db=0.0ms queue=0.8ms idle=9038.9ms
INSERT INTO "categories" ("name","inserted_at","updated_at") VALUES ($1,$2,$3) ON CONFLICT DO NOTHING RETURNING "id" ["Hello", ~N[2020-04-18 07:05:13], ~N[2020-04-18 07:05:13]]
版本号:
ON CONFLICT
是在9.5中添加的,因此解决方案是升级我的postgres服务器。