[GitHub] [arrow] emkornfield commented on a change in pull request #10203: ARROW-5385: [Go] Implement EXTENSION datatype

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

emkornfield commented on a change in pull request #10203:
URL: https://github.com/apache/arrow/pull/10203#discussion_r630311178



##########
File path: go/arrow/array/extension.go
##########
@@ -0,0 +1,236 @@
+// 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 (
+	"reflect"
+
+	"github.com/apache/arrow/go/arrow"
+	"github.com/apache/arrow/go/arrow/memory"
+	"golang.org/x/xerrors"
+)
+
+// ExtensionArray is the interface that needs to be implemented to handle
+// user-defined extension type arrays. In order to ensure consistency and
+// proper behavior, all ExtensionArray types must embed ExtensionArrayBase
+// in order to meet the interface which provides the default implementation
+// and handling for the array while allowing custom behavior to be built
+// on top of it.
+type ExtensionArray interface {
+	Interface
+	// ExtensionType returns the datatype as per calling DataType(), but
+	// already cast to ExtensionType
+	ExtensionType() arrow.ExtensionType
+	// Storage returns the underlying storage array for this array.
+	Storage() Interface
+
+	// by having a non-exported function in the interface, it means that
+	// consumers must embed ExtensionArrayBase in their structs in order
+	// to fulfill this interface.
+	mustEmbedExtensionArrayBase()
+}
+
+// two extension arrays are equal if their data types are equal and
+// their underlying storage arrays are equal.
+func arrayEqualExtension(l, r ExtensionArray) bool {
+	if !arrow.TypeEqual(l.DataType(), r.DataType()) {
+		return false
+	}
+
+	return ArrayEqual(l.Storage(), r.Storage())
+}
+
+// two extension arrays are approximately equal if their data types are
+// equal and their underlying storage arrays are approximately equal.
+func arrayApproxEqualExtension(l, r ExtensionArray, opt equalOption) bool {
+	if !arrow.TypeEqual(l.DataType(), r.DataType()) {
+		return false
+	}
+
+	return arrayApproxEqual(l.Storage(), r.Storage(), opt)
+}
+
+// NewExtensionArrayWithStorage constructs a new ExtensionArray from the provided
+// ExtensionType and uses the provided storage interface as the underlying storage.
+// This will not release the storage array passed in so consumers should call Release

Review comment:
       so users will generally call release right after construction?




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