Queries

Root and Derived Queries

Query the root entity to read every instantiable branch. Even when the discriminator property is not part of the fetcher, Jimmer reads it internally and returns an object of the actual entity type.

Java

ClientTable client = ClientTable.$;

List<Client> clients = sqlClient
    .createQuery(client)
    .select(client.fetch(ClientFetcher.$.name()))
    .execute();

Kotlin

val clients = sqlClient.createQuery(Client::class) {
    select(table.fetchBy {
        name()
    })
}.execute()

For example, an ORG row is returned as Organization, while a Person row is returned as Person. A query created directly for Organization only returns that branch and exposes its properties through the normal generated table type.

Type-specific Fetcher Branches

Use forType when a root fetcher must load properties declared by derived types:

Java

ClientFetcher fetcher = ClientFetcher.$
    .name()
    .forType(OrganizationFetcher.$.taxCode())
    .forType(PersonFetcher.$.firstName().lastName());

Kotlin

val clients = sqlClient.createQuery(Client::class) {
    select(table.fetchBy {
        name()
        forType(Organization::class) {
            taxCode()
        }
        forType(Person::class) {
            firstName()
            lastName()
        }
    })
}.execute()

Only the matching branch is loaded on each returned object. Type branches can also contain associations and work for both inheritance strategies.

Type Predicates and Downcasts

Generated root and intermediate tables provide polymorphic operations:

Operation	Meaning
instanceOf(Type)	Match Type and all of its instantiable derived types
exactType(Type)	Match only the exact type
treatAs(TypeTable)	Downcast with inner semantics; non-matching rows are removed
tryTreatAs(TypeTable)	Downcast with left/nullable semantics; non-matching rows produce null derived properties

Java

ClientTable client = ClientTable.$;
OrganizationTable organization =
    client.treatAs(OrganizationTable.class);

sqlClient
    .createQuery(client)
    .where(client.instanceOf(Organization.class))
    .select(client.id(), organization.taxCode())
    .execute();

Kotlin

sqlClient.createQuery(Client::class) {
    val organization = table.asTableEx().treatAs<Organization>()
    where(table.asTableEx().instanceOf<Organization>())
    select(table.id, organization.taxCode)
}.execute()

These operations are also available on association paths whose target belongs to an inheritance hierarchy.

Root Query Type Matching

Root queries use TypeMatchMode.POLYMORPHIC by default. Use TypeMatchMode.EXACT when an instantiable root query must return only rows whose discriminator is exactly the root type:

sqlClient
    .createQuery(ClientTable.$)
    .typeMatchMode(TypeMatchMode.EXACT)
    .select(ClientTable.$)
    .execute();

TypeMatchMode has three values:

• AUTO: exact for an instantiable type, polymorphic for an abstract type.
• EXACT: only the requested type; invalid for an abstract type.
• POLYMORPHIC: the requested type and all instantiable derived types.

Inheritance-aware mutations use the same values but default to AUTO, as described in Mutations.