03-optional/

03-optional

What Optional() does to each type, and how an optional field differs from an optional filter.

• Optional() on every type that supports it, one field each
• Bool cannot be optional — use Default(false) instead
• An optional field becomes optional in proto and a nullable column in SQL
• filter.Eq("is_featured").Optional() — a required field used as an optional filter
• A string uuid primary key: Immutable(), DefaultFunc() and PROTO().ReadOnly()
• Server generated fields drop out of create and update requests
• Create().Upsert("slug").Ignore() — a taken slug keeps the stored row instead of failing

Entity

sqlite/ent/schema/article.go is one Article, grouped into four blocks.

The key. field.String("id") with DefaultFunc(logic.NewUUID). It is Immutable() and PROTO().ReadOnly(), so the server mints it and clients never send it. Look at CreateArticleRequest in the generated schema.proto — the field is not there.

The column is TEXT PRIMARY KEY on sqlite and postgresql, and VARCHAR(36) PRIMARY KEY on mysql. The uuid is generated in Go, not by the database.

Optional fields. One per type, so you can compare them side by side:

A required field gets NOT NULL and a required validation rule. An optional one gets neither.

Bool. is_featured is Default(false). Bool has no Optional(). A missing proto bool arrives as false, so there is no way to tell "not sent" from "sent as false". A default says what happens instead.

Optional field vs optional filter

Two different things:

• field.String("subtitle").Optional() — the value may be missing.
• filter.Eq("is_featured").Optional() — the filter may be missing.

is_featured is required on the entity, but the last query in Queries() uses it as an optional filter. Send it and the rows are narrowed. Leave it out and the filter is skipped. The same query does this with Range and Search too.

Re-posting the same slug

query.Create().Upsert("slug").Ignore() puts ON CONFLICT (slug) DO NOTHING on the insert. A slug that is already taken leaves the stored article alone, and since no row comes back the caller gets sql.ErrNoRows. That is the signal nothing was inserted, not a failure to log.

slug can be the conflict target because it is Unique(). A target that is not the primary key, a Unique() field or the fields of a Unique() index is rejected when you generate, not when the query runs.

Run

cd sqlite
make run     # serves on :8080