[GitHub] [arrow] westonpace commented on a change in pull request #10071: ARROW-12424: [Go][Parquet] Adding Schema Package for Go Parquet

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

westonpace commented on a change in pull request #10071:
URL: https://github.com/apache/arrow/pull/10071#discussion_r634031679



##########
File path: go/parquet/schema/reflection.go
##########
@@ -0,0 +1,827 @@
+// 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 schema
+
+import (
+	"reflect"
+	"strconv"
+	"strings"
+
+	"github.com/apache/arrow/go/parquet"
+	format "github.com/apache/arrow/go/parquet/internal/gen-go/parquet"
+	"golang.org/x/xerrors"
+)
+
+type taggedInfo struct {
+	Name string
+
+	Type      parquet.Type
+	KeyType   parquet.Type
+	ValueType parquet.Type
+
+	Length      int32
+	KeyLength   int32
+	ValueLength int32
+
+	Scale      int32
+	KeyScale   int32
+	ValueScale int32
+
+	Precision      int32
+	KeyPrecision   int32
+	ValuePrecision int32
+
+	FieldID      int32
+	KeyFieldID   int32
+	ValueFieldID int32
+
+	RepetitionType  parquet.Repetition
+	ValueRepetition parquet.Repetition
+
+	Converted      ConvertedType
+	KeyConverted   ConvertedType
+	ValueConverted ConvertedType
+
+	LogicalFields      map[string]string
+	KeyLogicalFields   map[string]string
+	ValueLogicalFields map[string]string
+
+	LogicalType      LogicalType
+	KeyLogicalType   LogicalType
+	ValueLogicalType LogicalType
+}
+
+func (t *taggedInfo) CopyForKey() (ret taggedInfo) {
+	ret = *t
+	ret.Type = t.KeyType
+	ret.Length = t.KeyLength
+	ret.Scale = t.KeyScale
+	ret.Precision = t.KeyPrecision
+	ret.FieldID = t.KeyFieldID
+	ret.RepetitionType = parquet.Repetitions.Required
+	ret.Converted = t.KeyConverted
+	ret.LogicalType = t.KeyLogicalType
+	return
+}
+
+func (t *taggedInfo) CopyForValue() (ret taggedInfo) {
+	ret = *t
+	ret.Type = t.ValueType
+	ret.Length = t.ValueLength
+	ret.Scale = t.ValueScale
+	ret.Precision = t.ValuePrecision
+	ret.FieldID = t.ValueFieldID
+	ret.RepetitionType = t.ValueRepetition
+	ret.Converted = t.ValueConverted
+	ret.LogicalType = t.ValueLogicalType
+	return
+}
+
+func (t *taggedInfo) UpdateLogicalTypes() {
+	processLogicalType := func(fields map[string]string, precision, scale int32) LogicalType {
+		t, ok := fields["type"]
+		if !ok {
+			return NoLogicalType{}
+		}
+
+		switch strings.ToLower(t) {
+		case "string":
+			return StringLogicalType{}
+		case "map":
+			return MapLogicalType{}
+		case "list":
+			return ListLogicalType{}
+		case "enum":
+			return EnumLogicalType{}
+		case "decimal":
+			if v, ok := fields["precision"]; ok {
+				precision = int32FromType(v)
+			}
+			if v, ok := fields["scale"]; ok {
+				scale = int32FromType(v)
+			}
+			return NewDecimalLogicalType(precision, scale)
+		case "date":
+			return DateLogicalType{}
+		case "time":
+			unit, ok := fields["unit"]
+			if !ok {
+				panic("must specify unit for time logical type")
+			}
+			adjustedToUtc, ok := fields["isadjustedutc"]
+			if !ok {
+				adjustedToUtc = "true"
+			}
+			return NewTimeLogicalType(boolFromStr(adjustedToUtc), timeUnitFromString(strings.ToLower(unit)))
+		case "timestamp":
+			unit, ok := fields["unit"]
+			if !ok {
+				panic("must specify unit for time logical type")
+			}
+			adjustedToUtc, ok := fields["isadjustedutc"]
+			if !ok {
+				adjustedToUtc = "true"
+			}
+			return NewTimestampLogicalType(boolFromStr(adjustedToUtc), timeUnitFromString(unit))
+		case "integer":
+			width, ok := fields["bitwidth"]
+			if !ok {
+				panic("must specify bitwidth if explicitly setting integer logical type")
+			}
+			signed, ok := fields["signed"]
+			if !ok {
+				signed = "true"
+			}
+
+			return NewIntLogicalType(int8(int32FromType(width)), boolFromStr(signed))
+		case "null":
+			return NullLogicalType{}
+		case "json":
+			return JSONLogicalType{}
+		case "bson":
+			return BSONLogicalType{}
+		case "uuid":
+			return UUIDLogicalType{}
+		default:
+			panic(xerrors.Errorf("invalid logical type specified: %s", t))
+		}
+	}
+
+	t.LogicalType = processLogicalType(t.LogicalFields, t.Precision, t.Scale)
+	t.KeyLogicalType = processLogicalType(t.KeyLogicalFields, t.KeyPrecision, t.KeyScale)
+	t.ValueLogicalType = processLogicalType(t.ValueLogicalFields, t.ValuePrecision, t.ValueScale)
+}
+
+func newTaggedInfo() taggedInfo {
+	return taggedInfo{
+		Type:               parquet.Types.Undefined,
+		KeyType:            parquet.Types.Undefined,
+		ValueType:          parquet.Types.Undefined,
+		RepetitionType:     parquet.Repetitions.Undefined,
+		ValueRepetition:    parquet.Repetitions.Undefined,
+		Converted:          ConvertedTypes.NA,
+		KeyConverted:       ConvertedTypes.NA,
+		ValueConverted:     ConvertedTypes.NA,
+		FieldID:            -1,
+		KeyFieldID:         -1,
+		ValueFieldID:       -1,
+		LogicalFields:      make(map[string]string),
+		KeyLogicalFields:   make(map[string]string),
+		ValueLogicalFields: make(map[string]string),
+		LogicalType:        NoLogicalType{},
+		KeyLogicalType:     NoLogicalType{},
+		ValueLogicalType:   NoLogicalType{},
+	}
+}
+
+var int32FromType = func(v string) int32 {
+	val, err := strconv.Atoi(v)
+	if err != nil {
+		panic(err)
+	}
+	return int32(val)
+}
+
+var boolFromStr = func(v string) bool {
+	val, err := strconv.ParseBool(v)
+	if err != nil {
+		panic(err)
+	}
+	return val
+}
+
+func infoFromTags(f reflect.StructTag) *taggedInfo {
+	typeFromStr := func(v string) parquet.Type {
+		t, err := format.TypeFromString(strings.ToUpper(v))
+		if err != nil {
+			panic(xerrors.Errorf("invalid type specified: %s", v))
+		}
+		return parquet.Type(t)
+	}
+
+	repFromStr := func(v string) parquet.Repetition {
+		r, err := format.FieldRepetitionTypeFromString(strings.ToUpper(v))
+		if err != nil {
+			panic(err)
+		}
+		return parquet.Repetition(r)
+	}
+
+	convertedFromStr := func(v string) ConvertedType {
+		c, err := format.ConvertedTypeFromString(strings.ToUpper(v))
+		if err != nil {
+			panic(err)
+		}
+		return ConvertedType(c)
+	}
+
+	if ptags, ok := f.Lookup("parquet"); ok {
+		info := newTaggedInfo()
+		for _, tag := range strings.Split(strings.Replace(ptags, "\t", "", -1), ",") {
+			tag = strings.TrimSpace(tag)
+			kv := strings.SplitN(tag, "=", 2)
+			key := strings.TrimSpace(strings.ToLower(kv[0]))
+			value := strings.TrimSpace(kv[1])
+
+			switch key {
+			case "name":
+				info.Name = value
+			case "type":
+				info.Type = typeFromStr(value)
+			case "keytype":
+				info.KeyType = typeFromStr(value)
+			case "valuetype":
+				info.ValueType = typeFromStr(value)
+			case "length":
+				info.Length = int32FromType(value)
+			case "keylength":
+				info.KeyLength = int32FromType(value)
+			case "valuelength":
+				info.ValueLength = int32FromType(value)
+			case "scale":
+				info.Scale = int32FromType(value)
+			case "keyscale":
+				info.KeyScale = int32FromType(value)
+			case "valuescale":
+				info.ValueScale = int32FromType(value)
+			case "precision":
+				info.Precision = int32FromType(value)
+			case "keyprecision":
+				info.KeyPrecision = int32FromType(value)
+			case "valueprecision":
+				info.ValuePrecision = int32FromType(value)
+			case "fieldid":
+				info.FieldID = int32FromType(value)
+			case "keyfieldid":
+				info.KeyFieldID = int32FromType(value)
+			case "valuefieldid":
+				info.ValueFieldID = int32FromType(value)
+			case "repetition":
+				info.RepetitionType = repFromStr(value)
+			case "valuerepetition":
+				info.ValueRepetition = repFromStr(value)
+			case "converted":
+				info.Converted = convertedFromStr(value)
+			case "keyconverted":
+				info.KeyConverted = convertedFromStr(value)
+			case "valueconverted":
+				info.ValueConverted = convertedFromStr(value)
+			case "logical":
+				info.LogicalFields["type"] = value
+			case "keylogical":
+				info.KeyLogicalFields["type"] = value
+			case "valuelogical":
+				info.ValueLogicalFields["type"] = value
+			default:
+				switch {
+				case strings.HasPrefix(key, "logical."):
+					info.LogicalFields[strings.TrimPrefix(key, "logical.")] = value
+				case strings.HasPrefix(key, "keylogical."):
+					info.KeyLogicalFields[strings.TrimPrefix(key, "keylogical.")] = value
+				case strings.HasPrefix(key, "valuelogical."):
+					info.ValueLogicalFields[strings.TrimPrefix(key, "valuelogical.")] = value
+				}
+			}
+		}
+		info.UpdateLogicalTypes()
+		return &info
+	}
+	return nil
+}
+
+// typeToNode recurseively converts a physical type and the tag info into parquet Nodes
+//
+// to avoid having to propagate errors up potentially high numbers of recursive calls
+// we use panics and then recover in the public function NewSchemaFromStruct so that a
+// failure very far down the stack quickly unwinds.
+func typeToNode(name string, typ reflect.Type, repType parquet.Repetition, info *taggedInfo) Node {
+	// set up our default values for everything
+	var (
+		converted             = ConvertedTypes.None
+		logical   LogicalType = NoLogicalType{}
+		fieldID               = int32(-1)
+		physical              = parquet.Types.Undefined
+		typeLen               = 0
+		precision             = 0
+		scale                 = 0
+	)
+	if info != nil { // we have struct tag info to process
+		fieldID = info.FieldID

Review comment:
       Yes.  No specific reason outside of reducing complexity/noise.  Arrow simply does not have enough information to generate anything meaningful here (the current "field order" assignment is not really informative and could be easily regenerated by a user if they truly needed it).
   
   Instead the C++ implementation will just pass through the value to/from the parquet layer.




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