joellubi commented on code in PR #43679: URL: https://github.com/apache/arrow/pull/43679#discussion_r1725516137
########## go/arrow/extensions/json.go: ########## @@ -0,0 +1,139 @@ +// 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 extensions + +import ( + "fmt" + "reflect" + "slices" + + "github.com/apache/arrow/go/v18/arrow" + "github.com/apache/arrow/go/v18/arrow/array" + "github.com/apache/arrow/go/v18/internal/json" + "github.com/apache/arrow/go/v18/parquet/schema" +) + +var jsonSupportedStorageTypes = []arrow.DataType{ + arrow.BinaryTypes.String, + arrow.BinaryTypes.LargeString, + arrow.BinaryTypes.StringView, +} + +// JSONType represents a UTF-8 encoded JSON string as specified in RFC8259. +type JSONType struct { + arrow.ExtensionBase +} + +// ParquetLogicalType implements pqarrow.ExtensionCustomParquetType. +func (b *JSONType) ParquetLogicalType() schema.LogicalType { + return schema.JSONLogicalType{} +} + +// NewJSONType creates a new JSONType with the specified storage type. +// storageType must be one of String, LargeString, StringView. +func NewJSONType(storageType arrow.DataType) (*JSONType, error) { + if !slices.Contains(jsonSupportedStorageTypes, storageType) { + return nil, fmt.Errorf("unsupported storage type for JSON extension type: %s", storageType) + } + return &JSONType{ExtensionBase: arrow.ExtensionBase{Storage: storageType}}, nil +} + +func (b *JSONType) ArrayType() reflect.Type { return reflect.TypeOf(JSONArray{}) } + +func (b *JSONType) Deserialize(storageType arrow.DataType, data string) (arrow.ExtensionType, error) { + if !(data == "" || data == "{}") { + return nil, fmt.Errorf("serialized metadata for JSON extension type must be '' or '{}', found: %s", data) + } + return NewJSONType(storageType) +} + +func (b *JSONType) ExtensionEquals(other arrow.ExtensionType) bool { + return b.ExtensionName() == other.ExtensionName() && arrow.TypeEqual(b.Storage, other.StorageType()) +} + +func (b *JSONType) ExtensionName() string { return "arrow.json" } + +func (b *JSONType) Serialize() string { return "" } + +func (b *JSONType) String() string { + return fmt.Sprintf("extension<%s[storage_type=%s]>", b.ExtensionName(), b.Storage) +} + +// JSONArray is logically an array of UTF-8 encoded JSON strings. +// Its values are unmarshaled to native Go values. +type JSONArray struct { + array.ExtensionArrayBase +} + +func (a *JSONArray) String() string { + b, err := a.MarshalJSON() + if err != nil { + panic(fmt.Sprintf("failed marshal JSONArray: %s", err)) + } + + return string(b) +} + +func (a *JSONArray) Value(i int) any { + val := a.value(i) + + var res any + if err := json.Unmarshal(val, &res); err != nil { + panic(err) + } + + return res +} + +func (a *JSONArray) ValueStr(i int) string { + return string(a.value(i)) +} + +func (a *JSONArray) value(i int) []byte { + val := a.ValueJSON(i) + b, err := val.MarshalJSON() Review Comment: The methods unfortunately obscure what actually happening, but since we're operating on `json.RawMessage` (an alias for `[]byte`) which assumes the wrapped data is already valid JSON, these calls are fairly minimal. So `valueJSON` performs a null check against the validity bitmap and then a type conversion (`string` -> `[]byte`) on the array element if not null. The implementation of `MarshalJSON` for the `json.RawMessage` type actually just returns the RawMessage bytes themselves, since it's assumed to already be valid JSON. The only additional logic it provides is to return `[]byte("null")` if the value is `nil`, so this is just to reuse trivial logic from the standard library rather than write it ourselves. So in the typical case, this is a type conversion to `[]byte` and then the slice is passed back unchanged. No mutation of the encoded value itself. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
