substrait-extensions 0.87.0

# Substrait Dialect Schema Definition
# This schema defines the structure for Substrait dialect files, which specify how
# functions and types are supported in different execution environments.

$id: http://substrait.io/schemas/dialect
$schema: https://json-schema.org/draft/2020-12/schema
title: Dialect
additionalProperties: false
type: object

properties:
  name:
    type: string
    description: Optional name of the dialect (e.g., "MySQL", "PostgreSQL", "Spark").
  metadata:
    type: object
    description: Arbitrary data created by the dialect author.
  dependencies:
    type: object
    description: >
      A map of extension files depended on by this dialect.
      Keys are aliases for extensions, which are used within the dialect.
      Values are URNs.
    additionalProperties:
      type: string
    minProperties: 1

  supported_types:
    type: array
    uniqueItems: true
    description: >
      Types that are supported by this dialect. If not present or empty, all
      standard types are supported.
    items:
      oneOf:
        - enum:
          - BOOL
          - I8
          - I16
          - I32
          - I64
          - FP32
          - FP64
          - BINARY
          - FIXED_BINARY
          - STRING
          - VARCHAR
          - FIXED_CHAR
          - PRECISION_TIME
          - PRECISION_TIMESTAMP
          - PRECISION_TIMESTAMP_TZ
          - DATE
          - TIME
          - INTERVAL_COMPOUND
          - INTERVAL_DAY
          - INTERVAL_YEAR
          - UUID
          - DECIMAL
          - STRUCT
          - LIST
          - MAP
        - $ref: "#/definitions/type_bool"
        - $ref: "#/definitions/type_i8"
        - $ref: "#/definitions/type_i16"
        - $ref: "#/definitions/type_i32"
        - $ref: "#/definitions/type_i64"
        - $ref: "#/definitions/type_fp32"
        - $ref: "#/definitions/type_fp64"
        - $ref: "#/definitions/type_binary"
        - $ref: "#/definitions/type_fixed_binary"
        - $ref: "#/definitions/type_string"
        - $ref: "#/definitions/type_varchar"
        - $ref: "#/definitions/type_fixed_char"
        - $ref: "#/definitions/type_precision_time"
        - $ref: "#/definitions/type_precision_timestamp"
        - $ref: "#/definitions/type_precision_timestamp_tz"
        - $ref: "#/definitions/type_date"
        - $ref: "#/definitions/type_time"
        - $ref: "#/definitions/type_interval_compound"
        - $ref: "#/definitions/type_interval_day"
        - $ref: "#/definitions/type_interval_year"
        - $ref: "#/definitions/type_uuid"
        - $ref: "#/definitions/type_decimal"
        - $ref: "#/definitions/type_struct"
        - $ref: "#/definitions/type_list"
        - $ref: "#/definitions/type_map"
        - $ref: "#/definitions/type_user_defined"

  supported_relations:
    type: array
    uniqueItems: true
    description: >
      Relations that are supported by this dialect.  If not present or empty,
      all relations are supported.
    items:
      oneOf:
        - enum:
          - READ
          - FILTER
          - FETCH
          - AGGREGATE
          - SORT
          - JOIN
          - PROJECT
          - SET
          - CROSS
          - REFERENCE
          - WRITE
          - DDL
          - UPDATE
          - HASH_JOIN
          - MERGE_JOIN
          - NESTED_LOOP_JOIN
          - CONSISTENT_PARTITION_WINDOW
          - EXCHANGE
          - EXPAND
        - $ref: "#/definitions/read_relation"
        - $ref: "#/definitions/filter_relation"
        - $ref: "#/definitions/fetch_relation"
        - $ref: "#/definitions/aggregate_relation"
        - $ref: "#/definitions/sort_relation"
        - $ref: "#/definitions/join_relation"
        - $ref: "#/definitions/project_relation"
        - $ref: "#/definitions/set_relation"
        - $ref: "#/definitions/extension_single_relation"
        - $ref: "#/definitions/extension_multi_relation"
        - $ref: "#/definitions/extension_leaf_relation"
        - $ref: "#/definitions/cross_relation"
        - $ref: "#/definitions/reference_relation"
        - $ref: "#/definitions/write_relation"
        - $ref: "#/definitions/ddl_relation"
        - $ref: "#/definitions/update_relation"
        - $ref: "#/definitions/hash_join_relation"
        - $ref: "#/definitions/merge_join_relation"
        - $ref: "#/definitions/nested_loop_join_relation"
        - $ref: "#/definitions/consistent_partition_window_relation"
        - $ref: "#/definitions/exchange_relation"
        - $ref: "#/definitions/expand_relation"

  supported_expressions:
    type: array
    uniqueItems: true
    description: >
      Expressions that are supported by this dialect.  If not present or empty,
      all expressions are supported.
    items:
      oneOf:
        - enum:
          - LITERAL
          - SELECTION
          - SCALAR_FUNCTION
          - WINDOW_FUNCTION
          - IF_THEN
          - SWITCH
          - SINGULAR_OR_LIST
          - MULTI_OR_LIST
          - CAST
          - SUBQUERY
          - NESTED
          - DYNAMIC_PARAMETER
          - EXECUTION_CONTEXT_VARIABLE
        - $ref: "#/definitions/literal_expression"
        - $ref: "#/definitions/selection_expression"
        - $ref: "#/definitions/scalar_function_expression"
        - $ref: "#/definitions/window_function_expression"
        - $ref: "#/definitions/if_then_expression"
        - $ref: "#/definitions/switch_expression"
        - $ref: "#/definitions/singular_or_list_expression"
        - $ref: "#/definitions/multi_or_list_expression"
        - $ref: "#/definitions/cast_expression"
        - $ref: "#/definitions/subquery_expression"
        - $ref: "#/definitions/nested_expression"
        - $ref: "#/definitions/dynamic_parameter_expression"
        - $ref: "#/definitions/execution_context_variable"

  supported_scalar_functions:
    type: array
    description: Regular functions that operate on scalar values.
    items:
      $ref: "#/definitions/dialect_function"
  supported_aggregate_functions:
    type: array
    description: Functions that aggregate multiple rows into a single result.
    items:
      $ref: "#/definitions/dialect_function"
  supported_window_functions:
    type: array
    description: Functions that operate over a window of rows.
    items:
      $ref: "#/definitions/dialect_function"

  supported_execution_behavior:
    type: object
    additionalProperties: false
    properties:
      supported_variable_evaluation_mode:
        type: array
        uniqueItems: true
        items:
          oneOf:
            - enum:
              - PER_PLAN
              - PER_RECORD
        description: >
          Supported execution context variable evaluation modes:
          * PER_PLAN: Variables are evaluated once per Substrait plan
            execution. All records in a single plan execution will see the
            same values for execution context variables like `current_date`
            and `current_timestamp`.
          * PER_RECORD: Variables are evaluated once per record during
            execution. Each record may see different values for execution
            context variables if the execution context changes between records.

definitions:
  # Definitions used for functions
  dialect_function:
    type: object
    additionalProperties: false
    required: [source, name, supported_impls]
    properties:
      source:
        type: string
        description: Dependency (alias) in which the function is declared.
      name:
        type: string
        description: >
          The name of the function as declared in the extension it is defined in.
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        type: object
        description: system specific metadata for the function
        $ref: "#/definitions/system_function_metadata"
      required_options:
        type: object
        description: >
          Function-specific options that must be supported by the dialect.  These
          are the exact list of options that must be used.  If no options are
          listed here, no options must be present.
      supported_impls:
        type: array
        description: >
          List of one or more implementations supported by this function. Use
          argument signatures to identify the implementations.
        minItems: 1
        items:
          type: string
      variadic:
        type: object
        description: >
          If present, indicates the function accepts a variable number of arguments.
          Specifies the minimum and/or maximum number of arguments allowed.
        properties:
          min:
            type: integer
            description: "Minimum number of arguments required"
            minimum: 1
          max:
            type: integer
            description: "Maximum number of arguments allowed"
            minimum: 1
        additionalProperties: false
  system_function_metadata:
    type: object
    additionalProperties: false
    description: >
      System specific metadata for use in mapping Substrait to and from
      Common metadata fields are defined for use across dialects.
      Individual dialects may include additional metadata to serve their purposes.
    properties:
      name:
        type: string
        description: >
          The name for this function in the system modelled by the dialect.
          For example, "+" might be the system name for "add".
      notation:
        type: string
        enum:
          - INFIX
          - POSTFIX
          - PREFIX
          - FUNCTION
        default: FUNCTION
        description: >
          The notation used to invoke this function in the system modelled by
          the dialect. For example, a function with system_name "+" could be
          invoked as follow:
          * INFIX:    "a + b"
          * POSTFIX:  "a b +",
          * PREFIX:   "+ a b"
          * FUNCTION: "func(a, b)"

  # Definitions used for types
  type_base:
    type: object
    description: Dialect properties shared by all types
    properties:
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        type: object
        description: system specific metadata for the type
        $ref: "#/definitions/system_type_metadata"
  system_type_metadata:
    type: object
    additionalProperties: false
    description: >
      System specific metadata for use in mapping Substrait to and from the system representation.
      Common metadata fields are defined for use across dialects.
      Individual dialects may include additional metadata to serve their purposes.
    properties:
      name:
        type: string
        description: >
          The name for this type in the system modelled by the dialect.
      supported_as_column:
        type: boolean
        description: >
          Whether this type can be used as a column in a table.  Types listed
          here are always supported as literals.
  type_bool:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: BOOL
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_i8:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: I8
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_i16:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: I16
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_i32:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: I32
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_i64:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: I64
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_fp32:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: FP32
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_fp64:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: FP64
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_binary:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: BINARY
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_fixed_binary:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: FIXED_BINARY
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_string:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: STRING
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_varchar:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: VARCHAR
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_fixed_char:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: FIXED_CHAR
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_precision_time:
    type: object
    additionalProperties: false
    required: [type, max_precision]
    properties:
      type:
        const: PRECISION_TIME
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
      max_precision:
        description: >-
          The maximum subsecond precision for the PRECISION_TIME data type
          supported by this dialect.

          Since the maximum precision in Substrait for PRECISION_TIME is 12
          the value must be in range: 0 <= max_precision <= 12.
        type: integer
        minimum: 0
        maximum: 12
  type_precision_timestamp:
    type: object
    additionalProperties: false
    required: [type, max_precision]
    properties:
      type:
        const: PRECISION_TIMESTAMP
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
      max_precision:
        description: >-
          The maximum subsecond precision for the PRECISION_TIMESTAMP data type
          supported by this dialect.

          Since the maximum precision in Substrait for PRECISION_TIMESTAMP is
          12 the value must be in range: 0 <= max_precision <= 12.
        type: integer
        minimum: 0
        maximum: 12
  type_precision_timestamp_tz:
    type: object
    additionalProperties: false
    required: [type, max_precision]
    properties:
      type:
        const: PRECISION_TIMESTAMP_TZ
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
      max_precision:
        description: >-
          The maximum subsecond precision for the PRECISION_TIMESTAMP_TZ data
          type supported by this dialect.

          Since the maximum precision in Substrait for PRECISION_TIMESTAMP_TZ is
          12 the value must be in range: 0 <= max_precision <= 12.
        type: integer
        minimum: 0
        maximum: 12
  type_date:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: DATE
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_time:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: TIME
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_interval_compound:
    type: object
    additionalProperties: false
    required: [type, max_precision]
    properties:
      type:
        const: INTERVAL_COMPOUND
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
      max_precision:
        description: >-
          The maximum subsecond precision for the INTERVAL_COMPOUND data type
          supported by this dialect.

          Since the maximum precision in Substrait for INTERVAL_COMPOUND is 12
          the value must be in range: 0 <= max_precision <= 12.
        type: integer
        minimum: 0
        maximum: 12
  type_interval_day:
    type: object
    additionalProperties: false
    required: [type, max_precision]
    properties:
      type:
        const: INTERVAL_DAY
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
      max_precision:
        description: >-
          The maximum subsecond precision for the INTERVAL_DAY data type
          supported by this dialect.


          Since the maximum precision in Substrait for INTERVAL_DAY is 9
          the value must be in range: 0 <= max_precision <= 9.
        type: integer
        minimum: 0
        maximum: 9
  type_interval_year:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: INTERVAL_YEAR
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_uuid:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: UUID
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_decimal:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: DECIMAL
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_struct:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: STRUCT
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_list:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: LIST
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_map:
    type: object
    additionalProperties: false
    required: [type]
    properties:
      type:
        const: MAP
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"
  type_user_defined:
    type: object
    additionalProperties: false
    required: [type, source, name]
    properties:
      type:
        const: USER_DEFINED
      source:
        type: string
        description: "Dependency (alias) where this type is declared"
      name:
        type: string
        description: >
          The name of the type as declared in the extension it is defined in.
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      system_metadata:
        $ref: "#/definitions/system_type_metadata"

  # Definitions used for relations
  join_types:
    type: array
    uniqueItems: true
    description: The list of possible join types used by join relations.
    items:
      enum:
        - INNER
        - OUTER
        - LEFT
        - RIGHT
        - LEFT_SEMI
        - RIGHT_SEMI
        - LEFT_ANTI
        - RIGHT_ANTI
        - LEFT_SINGLE
        - RIGHT_SINGLE
        - LEFT_MARK
        - RIGHT_MARK
  read_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: READ
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      read_types:
        type: array
        uniqueItems: true
        description: The list of possible read types used by the read relation.
        items:
          enum:
            - VIRTUAL_TABLE
            - LOCAL_FILES
            - NAMED_TABLE
            - EXTENSION_TABLE
            - ICEBERG_TABLE
    required: [relation]
  filter_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: FILTER
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [relation]
  fetch_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: FETCH
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [relation]
  aggregate_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: AGGREGATE
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [relation]
  sort_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: SORT
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [relation]
  join_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: JOIN
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      join_types:
        $ref: "#/definitions/join_types"
    required: [relation]
  project_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: PROJECT
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [relation]
  set_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: SET
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      operations:
        type: array
        uniqueItems: true
        description: The list of valid set operations used by a set relation.
        items:
          enum:
            - MINUS_PRIMARY
            - MINUS_PRIMARY_ALL
            - MINUS_MULTISET
            - INTERSECTION_PRIMARY
            - INTERSECTION_MULTISET
            - INTERSECTION_MULTISET_ALL
            - UNION_DISTINCT
            - UNION_ALL
    required: [relation]
  extension_single_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: EXTENSION_SINGLE
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      message_types:
        type: array
        uniqueItems: true
        description: >
          The list of supported message types.  Use the URI (e.g.
          type.googleapis.com/google.profile.Person) that is related to the
          detail field.
        items:
          type: string
    required: [relation]
  extension_multi_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: EXTENSION_MULTI
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      message_types:
        type: array
        uniqueItems: true
        description: >
          The list of supported message types.  Use the URI (e.g.
          type.googleapis.com/google.profile.Person) that is related to the
          detail field.
        items:
          type: string
    required: [relation]
  extension_leaf_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: EXTENSION_LEAF
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      message_types:
        type: array
        uniqueItems: true
        description: >
          The list of supported message types.  Use the URI (e.g.
          type.googleapis.com/google.profile.Person) that is related to the
          detail field.
        items:
          type: string
    required: [relation]
  cross_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: CROSS
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [relation]
  reference_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: REFERENCE
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [relation]
  write_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: WRITE
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      write_types:
        type: array
        uniqueItems: true
        description: The list of valid write types a write relation can perform.
        items:
          enum:
            - NAMED_TABLE
            - EXTENSION_TABLE
    required: [relation]
  ddl_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: DDL
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      write_types:
        type: array
        uniqueItems: true
        description: The list of valid types a ddl relation can operate on.
        items:
          enum:
            - NAMED_OBJECT
            - EXTENSION_OBJECT
    required: [relation]
  update_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: UPDATE
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [relation]
  hash_join_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: HASH_JOIN
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      join_types:
        $ref: "#/definitions/join_types"
    required: [relation]
  merge_join_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: MERGE_JOIN
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      join_types:
        $ref: "#/definitions/join_types"
    required: [relation]
  nested_loop_join_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: NESTED_LOOP_JOIN
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      join_types:
        $ref: "#/definitions/join_types"
    required: [relation]
  consistent_partition_window_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: CONSISTENT_PARTITION_WINDOW
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [relation]
  exchange_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: EXCHANGE
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      kinds:
        type: array
        uniqueItems: true
        description: The list of valid exchanges an exchange relation can perform.
        items:
          enum:
            - SCATTER_BY_FIELDS
            - SINGLE_TARGET
            - MULTI_TARGET
            - ROUND_ROBIN
            - BROADCAST
    required: [relation]
  expand_relation:
    type: object
    additionalProperties: false
    properties:
      relation:
        const: EXPAND
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      field_types:
        type: array
        uniqueItems: true
        description: The valid methods that control how an expand relation behaves.
        items:
          enum:
            - SWITCHING_FIELD
            - CONSTANT_FIELD
    required: [relation]

  # Definitions used for expressions
  literal_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: LITERAL
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      # Type restriction not needed as types are restricted explicitly by supported_types.
    required: [expression]
  selection_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: SELECTION
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [expression]
  scalar_function_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: SCALAR_FUNCTION
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [expression]
  window_function_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: WINDOW_FUNCTION
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [expression]
  if_then_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: IF_THEN
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [expression]
  switch_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: SWITCH
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [expression]
  singular_or_list_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: SINGULAR_OR_LIST
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [expression]
  multi_or_list_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: MULTI_OR_LIST
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [expression]
  # embedded_function_expression not included due to insufficient proto support.
  cast_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: CAST
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      failure_options:
        type: array
        uniqueItems: true
        description: The permissible failure options for cast operations.
        items:
          enum:
            - RETURN_NULL
            - THROW_EXCEPTION
    required: [expression]
  subquery_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: SUBQUERY
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      subquery_types:
        type: array
        description: The possible subquery types for a subquery relation.
        items:
          enum:
            - SCALAR
            - IN_PREDICATE
            - SET_PREDICATE
            - SET_COMPARISON
    required: [expression]
  nested_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: NESTED
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
      nested_types:
        type: array
        description: The valid nested types.
        items:
          enum:
            - STRUCT
            - LIST
            - MAP
    required: [expression]
  dynamic_parameter_expression:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: DYNAMIC_PARAMETER
      metadata:
        type: object
        description: Arbitrary data created by the dialect author.
    required: [expression]
  execution_context_variable:
    type: object
    additionalProperties: false
    properties:
      expression:
        const: EXECUTION_CONTEXT_VARIABLE
      variable_types:
        type: array
        description: The possible execution context variable types.
        items:
          oneOf:
            - enum:
              - CURRENT_TIMESTAMP
              - CURRENT_TIMEZONE
              - CURRENT_DATE
    required: [expression]