[GitHub] [arrow] jorgecarleitao commented on a change in pull request #10934: [RFC] Arrow Compute Serialized Intermediate Representation draft for discussion

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jorgecarleitao commented on a change in pull request #10934:
URL: https://github.com/apache/arrow/pull/10934#discussion_r698818377



##########
File path: format/experimental/computeir/Expression.fbs
##########
@@ -0,0 +1,351 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+include "../../Schema.fbs";
+include "Literal.fbs";
+include "InlineBuffer.fbs";
+
+namespace org.apache.arrow.computeir.flatbuf;
+
+/// Access a value for a given map key
+table MapKey {
+  key: string (required);
+}
+
+/// Struct field access
+table StructField {
+  /// The position of the field in the struct schema
+  position: uint32;
+}
+
+/// Zero-based array index
+table ArraySubscript {
+  position: uint32;
+}
+
+/// Zero-based range of elements in an array
+table ArraySlice {
+  /// The start of an array slice, inclusive
+  start_inclusive: uint32;
+  /// The end of an array slice, exclusive
+  end_exclusive: uint32;
+}
+
+/// Field name in a relation
+table FieldName {
+  position: uint32;
+}
+
+/// A union of possible dereference operations
+union Deref {
+  /// Access a value for a given map key
+  MapKey,
+  /// Access the value at a struct field
+  StructField,
+  /// Access the element at a given index in an array
+  ArraySubscript,
+  /// Access a range of elements in an array
+  ArraySlice,
+  /// Access a field of a relation
+  FieldName,
+}
+
+/// Access the data of a field
+table FieldRef {
+  /// A sequence of field names to allow referencing potentially nested fields
+  ref: Deref (required);
+  /// For Expressions which might reference fields in multiple Relations,
+  /// this index may be provided to indicate which Relation's fields
+  /// `path` points into. For example in the case of a join,
+  /// 0 refers to the left relation and 1 to the right relation.
+  relation_index: int;
+}
+
+/// A canonical (probably SQL equivalent) function
+//
+// TODO: variadics
+enum CanonicalFunctionId : uint32 {
+  // logical
+  And,
+  Not,
+  Or,
+
+  // arithmetic
+  Add,
+  Subtract,
+  Multiply,
+  Divide,
+  Power,
+  AbsoluteValue,
+  Negate,
+  Sign,
+
+  // date/time/timestamp operations
+  DateSub,
+  DateAdd,
+  DateDiff,
+  TimeAdd,
+  TimeSub,
+  TimeDiff,
+  TimestampAdd,
+  TimestampSub,
+  TimestampDiff,
+
+  // comparison
+  Equals,
+  NotEquals,
+  Greater,
+  GreaterEqual,
+  Less,
+  LessEqual,
+}
+
+table CanonicalFunction {
+  id: CanonicalFunctionId;
+}
+
+table NonCanonicalFunction {
+  name_space: string;
+  name: string (required);
+}
+
+union FunctionImpl {
+  CanonicalFunction,
+  NonCanonicalFunction,
+}
+
+/// A function call expression
+table Call {
+  /// The kind of function call this is.
+  kind: FunctionImpl (required);
+
+  /// The arguments passed to `function_name`.
+  arguments: [Expression] (required);
+
+  /// Parameters for `function_name`; content/format may be unique to each
+  /// value of `function_name`.
+  metadata: InlineBuffer;
+}
+
+/// A single WHEN x THEN y fragment.
+table CaseFragment {
+  when: Expression (required);
+  then: Expression (required);
+}
+
+/// Case statement-style expression.
+table Case {
+  cases: [CaseFragment] (required);
+  /// The default value if no cases match. This is typically NULL in SQL
+  //implementations.
+  ///
+  /// Defaulting to NULL is a frontend choice, so producers must specify NULL
+  /// if that's their desired behavior.
+  default: Expression (required);
+
+  /// Parameters for `function_name`; content/format may be unique to each
+  /// value of `function_name`.
+  metadata: InlineBuffer;
+}
+
+table Cast {
+  /// The expression to cast
+  expression: Expression (required);
+
+  /// The type to cast `argument` to.
+  type: org.apache.arrow.flatbuf.Field (required);
+
+  /// Parameters for `function_name`; content/format may be unique to each
+  /// value of `function_name`.
+  metadata: InlineBuffer;
+}
+
+table Extract {
+  /// Expression from which to extract components.
+  expression: Expression (required);
+
+  /// Field to extract from `expression`.
+  field: string (required);
+
+  /// Parameters for `function_name`; content/format may be unique to each
+  /// value of `function_name`.
+  metadata: InlineBuffer;
+}
+
+/// Whether lesser values should precede greater or vice versa,
+/// also whether nulls should preced or follow values.
+enum Ordering : uint8 {
+  ASCENDING_THEN_NULLS,
+  DESCENDING_THEN_NULLS,
+  NULLS_THEN_ASCENDING,
+  NULLS_THEN_DESCENDING

Review comment:
       Why not follow the IEEE754 recommendation?
   
   * Iceberg uses it: https://github.com/apache/iceberg/blob/master/site/docs/spec.md#sorting
   * Java uses it
   * Rust lang follows it in practice (see e.g. https://github.com/rust-lang/rust/issues/5585 and [ord-float](https://crates.io/crates/float-ord))




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