[GitHub] [arrow] emkornfield commented on a change in pull request #10106: ARROW-5640: [Go] Implement Arrow Map Array

[GitBox <gi...@apache.org>]

emkornfield commented on a change in pull request #10106:
URL: https://github.com/apache/arrow/pull/10106#discussion_r619876807



##########
File path: go/arrow/array/map.go
##########
@@ -0,0 +1,232 @@
+// 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.
+
+package array // import "github.com/apache/arrow/go/arrow/array"
+
+import (
+	"github.com/apache/arrow/go/arrow"
+	"github.com/apache/arrow/go/arrow/memory"
+)
+
+// Map represents an immutable sequence of Key/Value structs. It is a
+// logical type that is implemented as a List<Struct: key, value>.
+type Map struct {
+	*List
+	keys, items Interface
+}
+
+// NewMapData returns a new Map array value, from data
+func NewMapData(data *Data) *Map {
+	a := &Map{List: &List{}}
+	a.refCount = 1
+	a.setData(data)
+	return a
+}
+
+// KeysSorted checks the datatype that was used to construct this array and
+// returns the KeysSorted boolean value used to denote if the key array is
+// sorted for each list element.
+func (a *Map) KeysSorted() bool { return a.DataType().(*arrow.MapType).KeysSorted }
+
+func (a *Map) validateData(data *Data) {
+	if len(data.childData) != 1 || data.childData[0] == nil {
+		panic("arrow/array: expected one child array for map array")
+	}
+
+	if data.childData[0].dtype.ID() != arrow.STRUCT {
+		panic("arrow/array: map array child should be struct type")
+	}
+
+	if data.childData[0].NullN() != 0 {
+		panic("arrow/array: map array child array should ahve no nulls")
+	}
+
+	if len(data.childData[0].childData) != 2 {
+		panic("arrow/array: map array child array should have two fields")
+	}
+
+	if data.childData[0].childData[0].NullN() != 0 {
+		panic("arrow/array: map array keys array should have no nulls")
+	}
+}
+
+func (a *Map) setData(data *Data) {
+	a.validateData(data)
+
+	a.List.setData(data)
+	a.keys = MakeFromData(data.childData[0].childData[0])
+	a.items = MakeFromData(data.childData[0].childData[1])
+}
+
+// Keys returns the full Array of Key values, equivalent to grabbing
+// the key field of the child struct.
+func (a *Map) Keys() Interface { return a.keys }
+
+// Items returns the full Array of Item values, equivalent to grabbing
+// the Value field (the second field) of the child struct.
+func (a *Map) Items() Interface { return a.items }
+
+func (a *Map) Retain() {
+	a.List.Retain()
+	a.keys.Retain()
+	a.items.Retain()
+}
+
+func (a *Map) Release() {
+	a.List.Release()
+	a.keys.Release()
+	a.items.Release()
+}
+
+func arrayEqualMap(left, right *Map) bool {
+	// since Map is implemented using a list, we can just use arrayEqualList
+	return arrayEqualList(left.List, right.List)

Review comment:
       it isn't.  To my knowledge the keySorted doesn't have strong semantics other than to indicate the keys follow some logical ordering.




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