Usage

version: '2'
plugins:
- name: kt
  wasm:
    url: https://downloads.sqlc.dev/plugin/sqlc-gen-kotlin_1.2.0.wasm
    sha256: 22b437ecaea66417bbd3b958339d9868ba89368ce542c936c37305acf373104b
sql:
- schema: src/main/resources/authors/postgresql/schema.sql
  queries: src/main/resources/authors/postgresql/query.sql
  engine: postgresql
  codegen:
  - out: src/main/kotlin/com/example/authors/postgresql
    plugin: kt
    options:
      package: com.example.authors.postgresql

Options

Option	Description
package	Kotlin package for the generated code.
emit_exact_table_names	Keep table names as-is instead of singularizing them for data class names.
inflection_exclude_table_names	Table names to exclude from singularization.
json_serializer	Enables jsonb deserialization. jackson2 (com.fasterxml.jackson) or jackson3 (tools.jackson).
json_types	List of {column, kt_type} entries mapping a json/jsonb column to a Kotlin type.

Deserializing jsonb into Kotlin data classes

By default a jsonb column maps to String. With json_serializer enabled and a matching json_types entry, the column is deserialized into a Kotlin data class you provide. The plugin references your class by its fully-qualified name — it does not generate it.

  - out: src/main/kotlin/com/example/events
    plugin: kt
    options:
      package: com.example.events
      json_serializer: jackson3       # or jackson2
      json_types:
      - column: events.payload          # table.column or schema.table.column
        kt_type: com.example.events.dto.Payload

QueriesImpl then takes a JsonMapper in its constructor and uses it to serialize/deserialize the column:

val mapper = JsonMapper.builder().addModule(kotlinModule()).build()
val db = QueriesImpl(conn, mapper)

See examples/src/main/resources/jsontest for example usage.

IN-list queries with sqlc.slice()

sqlc.slice() lets a single parameter expand into a variable-length IN (...) list:

-- name: ListEventsByIds :many
SELECT id, name, payload, metadata FROM events
WHERE id IN (sqlc.slice('ids'))
ORDER BY id;

generates a List parameter and expands the placeholders at runtime:

fun listEventsByIds(ids: List<Long>): List<Event>

An empty list expands to IN (NULL), which matches no rows. This works on both MySQL and PostgreSQL. (On PostgreSQL you can also use the native array form, WHERE id = ANY($1::bigint[]), which likewise produces a List parameter.)

Nullable numeric and boolean columns

JDBC's primitive getters — getInt, getLong, getShort, getByte, getDouble, getFloat, getBoolean — return 0/0.0/false for a SQL NULL, so on their own they cannot distinguish "absent" from "zero". Row mappers therefore guard a nullable column with wasNull():

data class Reading (
  val countBig: Long?,
  val requiredBig: Long
)

// generated read
Reading(
    results.getLong(1).takeUnless { results.wasNull() },  // nullable -> guarded
    results.getLong(2)                                    // NOT NULL -> plain read
)

A genuine 0 still reads as 0; only SQL NULL becomes null. NOT NULL columns are read directly, and getters that already return a reference type (getString, getBigDecimal, getObject) need no guard because they report NULL as null.

See examples/src/main/resources/nulltest for example usage.