vendor/cloud.google.com/go/bigquery/schema.go - airflow-on-k8s-operator - Git at Google

 // Copyright 2015 Google LLC
 //
 // Licensed 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 bigquery

 import (
 	"encoding/json"
 	"errors"
 	"fmt"
 	"reflect"
 	"sync"

 	bq "google.golang.org/api/bigquery/v2"
 )

 // Schema describes the fields in a table or query result.
 type Schema []*FieldSchema

 // FieldSchema describes a single field.
 type FieldSchema struct {
 	// The field name.
 	// Must contain only letters (a-z, A-Z), numbers (0-9), or underscores (_),
 	// and must start with a letter or underscore.
 	// The maximum length is 128 characters.
 	Name string

 	// A description of the field. The maximum length is 16,384 characters.
 	Description string

 	// Whether the field may contain multiple values.
 	Repeated bool
 	// Whether the field is required.  Ignored if Repeated is true.
 	Required bool

 	// The field data type.  If Type is Record, then this field contains a nested schema,
 	// which is described by Schema.
 	Type FieldType
 	// Describes the nested schema if Type is set to Record.
 	Schema Schema
 }

 func (fs *FieldSchema) toBQ() *bq.TableFieldSchema {
 	tfs := &bq.TableFieldSchema{
 		Description: fs.Description,
 		Name:        fs.Name,
 		Type:        string(fs.Type),
 	}

 	if fs.Repeated {
 		tfs.Mode = "REPEATED"
 	} else if fs.Required {
 		tfs.Mode = "REQUIRED"
 	} // else leave as default, which is interpreted as NULLABLE.

 	for _, f := range fs.Schema {
 		tfs.Fields = append(tfs.Fields, f.toBQ())
 	}

 	return tfs
 }

 func (s Schema) toBQ() *bq.TableSchema {
 	var fields []*bq.TableFieldSchema
 	for _, f := range s {
 		fields = append(fields, f.toBQ())
 	}
 	return &bq.TableSchema{Fields: fields}
 }

 func bqToFieldSchema(tfs *bq.TableFieldSchema) *FieldSchema {
 	fs := &FieldSchema{
 		Description: tfs.Description,
 		Name:        tfs.Name,
 		Repeated:    tfs.Mode == "REPEATED",
 		Required:    tfs.Mode == "REQUIRED",
 		Type:        FieldType(tfs.Type),
 	}

 	for _, f := range tfs.Fields {
 		fs.Schema = append(fs.Schema, bqToFieldSchema(f))
 	}
 	return fs
 }

 func bqToSchema(ts *bq.TableSchema) Schema {
 	if ts == nil {
 		return nil
 	}
 	var s Schema
 	for _, f := range ts.Fields {
 		s = append(s, bqToFieldSchema(f))
 	}
 	return s
 }

 // FieldType is the type of field.
 type FieldType string

 const (
 	// StringFieldType is a string field type.
 	StringFieldType FieldType = "STRING"
 	// BytesFieldType is a bytes field type.
 	BytesFieldType FieldType = "BYTES"
 	// IntegerFieldType is a integer field type.
 	IntegerFieldType FieldType = "INTEGER"
 	// FloatFieldType is a float field type.
 	FloatFieldType FieldType = "FLOAT"
 	// BooleanFieldType is a boolean field type.
 	BooleanFieldType FieldType = "BOOLEAN"
 	// TimestampFieldType is a timestamp field type.
 	TimestampFieldType FieldType = "TIMESTAMP"
 	// RecordFieldType is a record field type. It is typically used to create columns with repeated or nested data.
 	RecordFieldType FieldType = "RECORD"
 	// DateFieldType is a date field type.
 	DateFieldType FieldType = "DATE"
 	// TimeFieldType is a time field type.
 	TimeFieldType FieldType = "TIME"
 	// DateTimeFieldType is a datetime field type.
 	DateTimeFieldType FieldType = "DATETIME"
 	// NumericFieldType is a numeric field type. Numeric types include integer types, floating point types and the
 	// NUMERIC data type.
 	NumericFieldType FieldType = "NUMERIC"
 )

 var (
 	errNoStruct             = errors.New("bigquery: can only infer schema from struct or pointer to struct")
 	errUnsupportedFieldType = errors.New("bigquery: unsupported type of field in struct")
 	errInvalidFieldName     = errors.New("bigquery: invalid name of field in struct")
 	errBadNullable          = errors.New(`bigquery: use "nullable" only for []byte and struct pointers; for all other types, use a NullXXX type`)
 	errEmptyJSONSchema      = errors.New("bigquery: empty JSON schema")
 	fieldTypes              = map[FieldType]bool{
 		StringFieldType:    true,
 		BytesFieldType:     true,
 		IntegerFieldType:   true,
 		FloatFieldType:     true,
 		BooleanFieldType:   true,
 		TimestampFieldType: true,
 		RecordFieldType:    true,
 		DateFieldType:      true,
 		TimeFieldType:      true,
 		DateTimeFieldType:  true,
 		NumericFieldType:   true,
 	}
 )

 var typeOfByteSlice = reflect.TypeOf([]byte{})

 // InferSchema tries to derive a BigQuery schema from the supplied struct value.
 // Each exported struct field is mapped to a field in the schema.
 //
 // The following BigQuery types are inferred from the corresponding Go types.
 // (This is the same mapping as that used for RowIterator.Next.) Fields inferred
 // from these types are marked required (non-nullable).
 //
 //   STRING      string
 //   BOOL        bool
 //   INTEGER     int, int8, int16, int32, int64, uint8, uint16, uint32
 //   FLOAT       float32, float64
 //   BYTES       []byte
 //   TIMESTAMP   time.Time
 //   DATE        civil.Date
 //   TIME        civil.Time
 //   DATETIME    civil.DateTime
 //   NUMERIC     *big.Rat
 //
 // The big.Rat type supports numbers of arbitrary size and precision. Values
 // will be rounded to 9 digits after the decimal point before being transmitted
 // to BigQuery. See https://cloud.google.com/bigquery/docs/reference/standard-sql/data-types#numeric-type
 // for more on NUMERIC.
 //
 // A Go slice or array type is inferred to be a BigQuery repeated field of the
 // element type. The element type must be one of the above listed types.
 //
 // Nullable fields are inferred from the NullXXX types, declared in this package:
 //
 //   STRING      NullString
 //   BOOL        NullBool
 //   INTEGER     NullInt64
 //   FLOAT       NullFloat64
 //   TIMESTAMP   NullTimestamp
 //   DATE        NullDate
 //   TIME        NullTime
 //   DATETIME    NullDateTime
 //
 // For a nullable BYTES field, use the type []byte and tag the field "nullable" (see below).
 // For a nullable NUMERIC field, use the type *big.Rat and tag the field "nullable".
 //
 // A struct field that is of struct type is inferred to be a required field of type
 // RECORD with a schema inferred recursively. For backwards compatibility, a field of
 // type pointer to struct is also inferred to be required. To get a nullable RECORD
 // field, use the "nullable" tag (see below).
 //
 // InferSchema returns an error if any of the examined fields is of type uint,
 // uint64, uintptr, map, interface, complex64, complex128, func, or chan. Future
 // versions may handle these cases without error.
 //
 // Recursively defined structs are also disallowed.
 //
 // Struct fields may be tagged in a way similar to the encoding/json package.
 // A tag of the form
 //     bigquery:"name"
 // uses "name" instead of the struct field name as the BigQuery field name.
 // A tag of the form
 //     bigquery:"-"
 // omits the field from the inferred schema.
 // The "nullable" option marks the field as nullable (not required). It is only
 // needed for []byte, *big.Rat and pointer-to-struct fields, and cannot appear on other
 // fields. In this example, the Go name of the field is retained:
 //     bigquery:",nullable"
 func InferSchema(st interface{}) (Schema, error) {
 	return inferSchemaReflectCached(reflect.TypeOf(st))
 }

 var schemaCache sync.Map

 type cacheVal struct {
 	schema Schema
 	err    error
 }

 func inferSchemaReflectCached(t reflect.Type) (Schema, error) {
 	var cv cacheVal
 	v, ok := schemaCache.Load(t)
 	if ok {
 		cv = v.(cacheVal)
 	} else {
 		s, err := inferSchemaReflect(t)
 		cv = cacheVal{s, err}
 		schemaCache.Store(t, cv)
 	}
 	return cv.schema, cv.err
 }

 func inferSchemaReflect(t reflect.Type) (Schema, error) {
 	rec, err := hasRecursiveType(t, nil)
 	if err != nil {
 		return nil, err
 	}
 	if rec {
 		return nil, fmt.Errorf("bigquery: schema inference for recursive type %s", t)
 	}
 	return inferStruct(t)
 }

 func inferStruct(t reflect.Type) (Schema, error) {
 	switch t.Kind() {
 	case reflect.Ptr:
 		if t.Elem().Kind() != reflect.Struct {
 			return nil, errNoStruct
 		}
 		t = t.Elem()
 		fallthrough

 	case reflect.Struct:
 		return inferFields(t)
 	default:
 		return nil, errNoStruct
 	}
 }

 // inferFieldSchema infers the FieldSchema for a Go type
 func inferFieldSchema(rt reflect.Type, nullable bool) (*FieldSchema, error) {
 	// Only []byte and struct pointers can be tagged nullable.
 	if nullable && !(rt == typeOfByteSlice || rt.Kind() == reflect.Ptr && rt.Elem().Kind() == reflect.Struct) {
 		return nil, errBadNullable
 	}
 	switch rt {
 	case typeOfByteSlice:
 		return &FieldSchema{Required: !nullable, Type: BytesFieldType}, nil
 	case typeOfGoTime:
 		return &FieldSchema{Required: true, Type: TimestampFieldType}, nil
 	case typeOfDate:
 		return &FieldSchema{Required: true, Type: DateFieldType}, nil
 	case typeOfTime:
 		return &FieldSchema{Required: true, Type: TimeFieldType}, nil
 	case typeOfDateTime:
 		return &FieldSchema{Required: true, Type: DateTimeFieldType}, nil
 	case typeOfRat:
 		return &FieldSchema{Required: !nullable, Type: NumericFieldType}, nil
 	}
 	if ft := nullableFieldType(rt); ft != "" {
 		return &FieldSchema{Required: false, Type: ft}, nil
 	}
 	if isSupportedIntType(rt) || isSupportedUintType(rt) {
 		return &FieldSchema{Required: true, Type: IntegerFieldType}, nil
 	}
 	switch rt.Kind() {
 	case reflect.Slice, reflect.Array:
 		et := rt.Elem()
 		if et != typeOfByteSlice && (et.Kind() == reflect.Slice || et.Kind() == reflect.Array) {
 			// Multi dimensional slices/arrays are not supported by BigQuery
 			return nil, errUnsupportedFieldType
 		}
 		if nullableFieldType(et) != "" {
 			// Repeated nullable types are not supported by BigQuery.
 			return nil, errUnsupportedFieldType
 		}
 		f, err := inferFieldSchema(et, false)
 		if err != nil {
 			return nil, err
 		}
 		f.Repeated = true
 		f.Required = false
 		return f, nil
 	case reflect.Ptr:
 		if rt.Elem().Kind() != reflect.Struct {
 			return nil, errUnsupportedFieldType
 		}
 		fallthrough
 	case reflect.Struct:
 		nested, err := inferStruct(rt)
 		if err != nil {
 			return nil, err
 		}
 		return &FieldSchema{Required: !nullable, Type: RecordFieldType, Schema: nested}, nil
 	case reflect.String:
 		return &FieldSchema{Required: !nullable, Type: StringFieldType}, nil
 	case reflect.Bool:
 		return &FieldSchema{Required: !nullable, Type: BooleanFieldType}, nil
 	case reflect.Float32, reflect.Float64:
 		return &FieldSchema{Required: !nullable, Type: FloatFieldType}, nil
 	default:
 		return nil, errUnsupportedFieldType
 	}
 }

 // inferFields extracts all exported field types from struct type.
 func inferFields(rt reflect.Type) (Schema, error) {
 	var s Schema
 	fields, err := fieldCache.Fields(rt)
 	if err != nil {
 		return nil, err
 	}
 	for _, field := range fields {
 		var nullable bool
 		for _, opt := range field.ParsedTag.([]string) {
 			if opt == nullableTagOption {
 				nullable = true
 				break
 			}
 		}
 		f, err := inferFieldSchema(field.Type, nullable)
 		if err != nil {
 			return nil, err
 		}
 		f.Name = field.Name
 		s = append(s, f)
 	}
 	return s, nil
 }

 // isSupportedIntType reports whether t is an int type that can be properly
 // represented by the BigQuery INTEGER/INT64 type.
 func isSupportedIntType(t reflect.Type) bool {
 	switch t.Kind() {
 	case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int:
 		return true
 	default:
 		return false
 	}
 }

 // isSupportedIntType reports whether t is a uint type that can be properly
 // represented by the BigQuery INTEGER/INT64 type.
 func isSupportedUintType(t reflect.Type) bool {
 	switch t.Kind() {
 	case reflect.Uint8, reflect.Uint16, reflect.Uint32:
 		return true
 	default:
 		return false
 	}
 }

 // typeList is a linked list of reflect.Types.
 type typeList struct {
 	t    reflect.Type
 	next *typeList
 }

 func (l *typeList) has(t reflect.Type) bool {
 	for l != nil {
 		if l.t == t {
 			return true
 		}
 		l = l.next
 	}
 	return false
 }

 // hasRecursiveType reports whether t or any type inside t refers to itself, directly or indirectly,
 // via exported fields. (Schema inference ignores unexported fields.)
 func hasRecursiveType(t reflect.Type, seen *typeList) (bool, error) {
 	for t.Kind() == reflect.Ptr || t.Kind() == reflect.Slice || t.Kind() == reflect.Array {
 		t = t.Elem()
 	}
 	if t.Kind() != reflect.Struct {
 		return false, nil
 	}
 	if seen.has(t) {
 		return true, nil
 	}
 	fields, err := fieldCache.Fields(t)
 	if err != nil {
 		return false, err
 	}
 	seen = &typeList{t, seen}
 	// Because seen is a linked list, additions to it from one field's
 	// recursive call will not affect the value for subsequent fields' calls.
 	for _, field := range fields {
 		ok, err := hasRecursiveType(field.Type, seen)
 		if err != nil {
 			return false, err
 		}
 		if ok {
 			return true, nil
 		}
 	}
 	return false, nil
 }

 // bigQuerySchemaJSONField is an individual field in a JSON BigQuery table schema definition
 // (as generated by https://github.com/GoogleCloudPlatform/protoc-gen-bq-schema).
 type bigQueryJSONField struct {
 	Description string              `json:"description"`
 	Fields      []bigQueryJSONField `json:"fields"`
 	Mode        string              `json:"mode"`
 	Name        string              `json:"name"`
 	Type        string              `json:"type"`
 }

 // convertSchemaFromJSON generates a Schema:
 func convertSchemaFromJSON(fs []bigQueryJSONField) (Schema, error) {
 	convertedSchema := Schema{}
 	for _, f := range fs {
 		convertedFieldSchema := &FieldSchema{
 			Description: f.Description,
 			Name:        f.Name,
 			Required:    f.Mode == "REQUIRED",
 			Repeated:    f.Mode == "REPEATED",
 		}
 		if len(f.Fields) > 0 {
 			convertedNestedFieldSchema, err := convertSchemaFromJSON(f.Fields)
 			if err != nil {
 				return nil, err
 			}
 			convertedFieldSchema.Schema = convertedNestedFieldSchema
 		}

 		// Check that the field-type (string) maps to a known FieldType:
 		if _, ok := fieldTypes[FieldType(f.Type)]; !ok {
 			return nil, fmt.Errorf("unknown field type (%v)", f.Type)
 		}
 		convertedFieldSchema.Type = FieldType(f.Type)

 		convertedSchema = append(convertedSchema, convertedFieldSchema)
 	}
 	return convertedSchema, nil
 }

 // SchemaFromJSON takes a JSON BigQuery table schema definition
 // (as generated by https://github.com/GoogleCloudPlatform/protoc-gen-bq-schema)
 // and returns a fully-populated Schema.
 func SchemaFromJSON(schemaJSON []byte) (Schema, error) {

 	var bigQuerySchema []bigQueryJSONField

 	// Make sure we actually have some content:
 	if len(schemaJSON) == 0 {
 		return nil, errEmptyJSONSchema
 	}

 	if err := json.Unmarshal(schemaJSON, &bigQuerySchema); err != nil {
 		return nil, err
 	}

 	return convertSchemaFromJSON(bigQuerySchema)
 }
	// Copyright 2015 Google LLC
	//
	// Licensed 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 bigquery

	import (
	"encoding/json"
	"errors"
	"fmt"
	"reflect"
	"sync"

	bq "google.golang.org/api/bigquery/v2"
	)

	// Schema describes the fields in a table or query result.
	type Schema []*FieldSchema

	// FieldSchema describes a single field.
	type FieldSchema struct {
	// The field name.
	// Must contain only letters (a-z, A-Z), numbers (0-9), or underscores (_),
	// and must start with a letter or underscore.
	// The maximum length is 128 characters.
	Name string

	// A description of the field. The maximum length is 16,384 characters.
	Description string

	// Whether the field may contain multiple values.
	Repeated bool
	// Whether the field is required. Ignored if Repeated is true.
	Required bool

	// The field data type. If Type is Record, then this field contains a nested schema,
	// which is described by Schema.
	Type FieldType
	// Describes the nested schema if Type is set to Record.
	Schema Schema
	}

	func (fs FieldSchema) toBQ() bq.TableFieldSchema {
	tfs := &bq.TableFieldSchema{
	Description: fs.Description,
	Name: fs.Name,
	Type: string(fs.Type),
	}

	if fs.Repeated {
	tfs.Mode = "REPEATED"
	} else if fs.Required {
	tfs.Mode = "REQUIRED"
	} // else leave as default, which is interpreted as NULLABLE.

	for _, f := range fs.Schema {
	tfs.Fields = append(tfs.Fields, f.toBQ())
	}

	return tfs
	}

	func (s Schema) toBQ() *bq.TableSchema {
	var fields []*bq.TableFieldSchema
	for _, f := range s {
	fields = append(fields, f.toBQ())
	}
	return &bq.TableSchema{Fields: fields}
	}

	func bqToFieldSchema(tfs bq.TableFieldSchema) FieldSchema {
	fs := &FieldSchema{
	Description: tfs.Description,
	Name: tfs.Name,
	Repeated: tfs.Mode == "REPEATED",
	Required: tfs.Mode == "REQUIRED",
	Type: FieldType(tfs.Type),
	}

	for _, f := range tfs.Fields {
	fs.Schema = append(fs.Schema, bqToFieldSchema(f))
	}
	return fs
	}

	func bqToSchema(ts *bq.TableSchema) Schema {
	if ts == nil {
	return nil
	}
	var s Schema
	for _, f := range ts.Fields {
	s = append(s, bqToFieldSchema(f))
	}
	return s
	}

	// FieldType is the type of field.
	type FieldType string

	const (
	// StringFieldType is a string field type.
	StringFieldType FieldType = "STRING"
	// BytesFieldType is a bytes field type.
	BytesFieldType FieldType = "BYTES"
	// IntegerFieldType is a integer field type.
	IntegerFieldType FieldType = "INTEGER"
	// FloatFieldType is a float field type.
	FloatFieldType FieldType = "FLOAT"
	// BooleanFieldType is a boolean field type.
	BooleanFieldType FieldType = "BOOLEAN"
	// TimestampFieldType is a timestamp field type.
	TimestampFieldType FieldType = "TIMESTAMP"
	// RecordFieldType is a record field type. It is typically used to create columns with repeated or nested data.
	RecordFieldType FieldType = "RECORD"
	// DateFieldType is a date field type.
	DateFieldType FieldType = "DATE"
	// TimeFieldType is a time field type.
	TimeFieldType FieldType = "TIME"
	// DateTimeFieldType is a datetime field type.
	DateTimeFieldType FieldType = "DATETIME"
	// NumericFieldType is a numeric field type. Numeric types include integer types, floating point types and the
	// NUMERIC data type.
	NumericFieldType FieldType = "NUMERIC"
	)

	var (
	errNoStruct = errors.New("bigquery: can only infer schema from struct or pointer to struct")
	errUnsupportedFieldType = errors.New("bigquery: unsupported type of field in struct")
	errInvalidFieldName = errors.New("bigquery: invalid name of field in struct")
	errBadNullable = errors.New(`bigquery: use "nullable" only for []byte and struct pointers; for all other types, use a NullXXX type`)
	errEmptyJSONSchema = errors.New("bigquery: empty JSON schema")
	fieldTypes = map[FieldType]bool{
	StringFieldType: true,
	BytesFieldType: true,
	IntegerFieldType: true,
	FloatFieldType: true,
	BooleanFieldType: true,
	TimestampFieldType: true,
	RecordFieldType: true,
	DateFieldType: true,
	TimeFieldType: true,
	DateTimeFieldType: true,
	NumericFieldType: true,
	}
	)

	var typeOfByteSlice = reflect.TypeOf([]byte{})

	// InferSchema tries to derive a BigQuery schema from the supplied struct value.
	// Each exported struct field is mapped to a field in the schema.
	//
	// The following BigQuery types are inferred from the corresponding Go types.
	// (This is the same mapping as that used for RowIterator.Next.) Fields inferred
	// from these types are marked required (non-nullable).
	//
	// STRING string
	// BOOL bool
	// INTEGER int, int8, int16, int32, int64, uint8, uint16, uint32
	// FLOAT float32, float64
	// BYTES []byte
	// TIMESTAMP time.Time
	// DATE civil.Date
	// TIME civil.Time
	// DATETIME civil.DateTime
	// NUMERIC *big.Rat
	//
	// The big.Rat type supports numbers of arbitrary size and precision. Values
	// will be rounded to 9 digits after the decimal point before being transmitted
	// to BigQuery. See https://cloud.google.com/bigquery/docs/reference/standard-sql/data-types#numeric-type
	// for more on NUMERIC.
	//
	// A Go slice or array type is inferred to be a BigQuery repeated field of the
	// element type. The element type must be one of the above listed types.
	//
	// Nullable fields are inferred from the NullXXX types, declared in this package:
	//
	// STRING NullString
	// BOOL NullBool
	// INTEGER NullInt64
	// FLOAT NullFloat64
	// TIMESTAMP NullTimestamp
	// DATE NullDate
	// TIME NullTime
	// DATETIME NullDateTime
	//
	// For a nullable BYTES field, use the type []byte and tag the field "nullable" (see below).
	// For a nullable NUMERIC field, use the type *big.Rat and tag the field "nullable".
	//
	// A struct field that is of struct type is inferred to be a required field of type
	// RECORD with a schema inferred recursively. For backwards compatibility, a field of
	// type pointer to struct is also inferred to be required. To get a nullable RECORD
	// field, use the "nullable" tag (see below).
	//
	// InferSchema returns an error if any of the examined fields is of type uint,
	// uint64, uintptr, map, interface, complex64, complex128, func, or chan. Future
	// versions may handle these cases without error.
	//
	// Recursively defined structs are also disallowed.
	//
	// Struct fields may be tagged in a way similar to the encoding/json package.
	// A tag of the form
	// bigquery:"name"
	// uses "name" instead of the struct field name as the BigQuery field name.
	// A tag of the form
	// bigquery:"-"
	// omits the field from the inferred schema.
	// The "nullable" option marks the field as nullable (not required). It is only
	// needed for []byte, *big.Rat and pointer-to-struct fields, and cannot appear on other
	// fields. In this example, the Go name of the field is retained:
	// bigquery:",nullable"
	func InferSchema(st interface{}) (Schema, error) {
	return inferSchemaReflectCached(reflect.TypeOf(st))
	}

	var schemaCache sync.Map

	type cacheVal struct {
	schema Schema
	err error
	}

	func inferSchemaReflectCached(t reflect.Type) (Schema, error) {
	var cv cacheVal
	v, ok := schemaCache.Load(t)
	if ok {
	cv = v.(cacheVal)
	} else {
	s, err := inferSchemaReflect(t)
	cv = cacheVal{s, err}
	schemaCache.Store(t, cv)
	}
	return cv.schema, cv.err
	}

	func inferSchemaReflect(t reflect.Type) (Schema, error) {
	rec, err := hasRecursiveType(t, nil)
	if err != nil {
	return nil, err
	}
	if rec {
	return nil, fmt.Errorf("bigquery: schema inference for recursive type %s", t)
	}
	return inferStruct(t)
	}

	func inferStruct(t reflect.Type) (Schema, error) {
	switch t.Kind() {
	case reflect.Ptr:
	if t.Elem().Kind() != reflect.Struct {
	return nil, errNoStruct
	}
	t = t.Elem()
	fallthrough

	case reflect.Struct:
	return inferFields(t)
	default:
	return nil, errNoStruct
	}
	}

	// inferFieldSchema infers the FieldSchema for a Go type
	func inferFieldSchema(rt reflect.Type, nullable bool) (*FieldSchema, error) {
	// Only []byte and struct pointers can be tagged nullable.
	if nullable && !(rt == typeOfByteSlice \|\| rt.Kind() == reflect.Ptr && rt.Elem().Kind() == reflect.Struct) {
	return nil, errBadNullable
	}
	switch rt {
	case typeOfByteSlice:
	return &FieldSchema{Required: !nullable, Type: BytesFieldType}, nil
	case typeOfGoTime:
	return &FieldSchema{Required: true, Type: TimestampFieldType}, nil
	case typeOfDate:
	return &FieldSchema{Required: true, Type: DateFieldType}, nil
	case typeOfTime:
	return &FieldSchema{Required: true, Type: TimeFieldType}, nil
	case typeOfDateTime:
	return &FieldSchema{Required: true, Type: DateTimeFieldType}, nil
	case typeOfRat:
	return &FieldSchema{Required: !nullable, Type: NumericFieldType}, nil
	}
	if ft := nullableFieldType(rt); ft != "" {
	return &FieldSchema{Required: false, Type: ft}, nil
	}
	if isSupportedIntType(rt) \|\| isSupportedUintType(rt) {
	return &FieldSchema{Required: true, Type: IntegerFieldType}, nil
	}
	switch rt.Kind() {
	case reflect.Slice, reflect.Array:
	et := rt.Elem()
	if et != typeOfByteSlice && (et.Kind() == reflect.Slice \|\| et.Kind() == reflect.Array) {
	// Multi dimensional slices/arrays are not supported by BigQuery
	return nil, errUnsupportedFieldType
	}
	if nullableFieldType(et) != "" {
	// Repeated nullable types are not supported by BigQuery.
	return nil, errUnsupportedFieldType
	}
	f, err := inferFieldSchema(et, false)
	if err != nil {
	return nil, err
	}
	f.Repeated = true
	f.Required = false
	return f, nil
	case reflect.Ptr:
	if rt.Elem().Kind() != reflect.Struct {
	return nil, errUnsupportedFieldType
	}
	fallthrough
	case reflect.Struct:
	nested, err := inferStruct(rt)
	if err != nil {
	return nil, err
	}
	return &FieldSchema{Required: !nullable, Type: RecordFieldType, Schema: nested}, nil
	case reflect.String:
	return &FieldSchema{Required: !nullable, Type: StringFieldType}, nil
	case reflect.Bool:
	return &FieldSchema{Required: !nullable, Type: BooleanFieldType}, nil
	case reflect.Float32, reflect.Float64:
	return &FieldSchema{Required: !nullable, Type: FloatFieldType}, nil
	default:
	return nil, errUnsupportedFieldType
	}
	}

	// inferFields extracts all exported field types from struct type.
	func inferFields(rt reflect.Type) (Schema, error) {
	var s Schema
	fields, err := fieldCache.Fields(rt)
	if err != nil {
	return nil, err
	}
	for _, field := range fields {
	var nullable bool
	for _, opt := range field.ParsedTag.([]string) {
	if opt == nullableTagOption {
	nullable = true
	break
	}
	}
	f, err := inferFieldSchema(field.Type, nullable)
	if err != nil {
	return nil, err
	}
	f.Name = field.Name
	s = append(s, f)
	}
	return s, nil
	}

	// isSupportedIntType reports whether t is an int type that can be properly
	// represented by the BigQuery INTEGER/INT64 type.
	func isSupportedIntType(t reflect.Type) bool {
	switch t.Kind() {
	case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int:
	return true
	default:
	return false
	}
	}

	// isSupportedIntType reports whether t is a uint type that can be properly
	// represented by the BigQuery INTEGER/INT64 type.
	func isSupportedUintType(t reflect.Type) bool {
	switch t.Kind() {
	case reflect.Uint8, reflect.Uint16, reflect.Uint32:
	return true
	default:
	return false
	}
	}

	// typeList is a linked list of reflect.Types.
	type typeList struct {
	t reflect.Type
	next *typeList
	}

	func (l *typeList) has(t reflect.Type) bool {
	for l != nil {
	if l.t == t {
	return true
	}
	l = l.next
	}
	return false
	}

	// hasRecursiveType reports whether t or any type inside t refers to itself, directly or indirectly,
	// via exported fields. (Schema inference ignores unexported fields.)
	func hasRecursiveType(t reflect.Type, seen *typeList) (bool, error) {
	for t.Kind() == reflect.Ptr \|\| t.Kind() == reflect.Slice \|\| t.Kind() == reflect.Array {
	t = t.Elem()
	}
	if t.Kind() != reflect.Struct {
	return false, nil
	}
	if seen.has(t) {
	return true, nil
	}
	fields, err := fieldCache.Fields(t)
	if err != nil {
	return false, err
	}
	seen = &typeList{t, seen}
	// Because seen is a linked list, additions to it from one field's
	// recursive call will not affect the value for subsequent fields' calls.
	for _, field := range fields {
	ok, err := hasRecursiveType(field.Type, seen)
	if err != nil {
	return false, err
	}
	if ok {
	return true, nil
	}
	}
	return false, nil
	}

	// bigQuerySchemaJSONField is an individual field in a JSON BigQuery table schema definition
	// (as generated by https://github.com/GoogleCloudPlatform/protoc-gen-bq-schema).
	type bigQueryJSONField struct {
	Description string `json:"description"`
	Fields []bigQueryJSONField `json:"fields"`
	Mode string `json:"mode"`
	Name string `json:"name"`
	Type string `json:"type"`
	}

	// convertSchemaFromJSON generates a Schema:
	func convertSchemaFromJSON(fs []bigQueryJSONField) (Schema, error) {
	convertedSchema := Schema{}
	for _, f := range fs {
	convertedFieldSchema := &FieldSchema{
	Description: f.Description,
	Name: f.Name,
	Required: f.Mode == "REQUIRED",
	Repeated: f.Mode == "REPEATED",
	}
	if len(f.Fields) > 0 {
	convertedNestedFieldSchema, err := convertSchemaFromJSON(f.Fields)
	if err != nil {
	return nil, err
	}
	convertedFieldSchema.Schema = convertedNestedFieldSchema
	}

	// Check that the field-type (string) maps to a known FieldType:
	if _, ok := fieldTypes[FieldType(f.Type)]; !ok {
	return nil, fmt.Errorf("unknown field type (%v)", f.Type)
	}
	convertedFieldSchema.Type = FieldType(f.Type)

	convertedSchema = append(convertedSchema, convertedFieldSchema)
	}
	return convertedSchema, nil
	}

	// SchemaFromJSON takes a JSON BigQuery table schema definition
	// (as generated by https://github.com/GoogleCloudPlatform/protoc-gen-bq-schema)
	// and returns a fully-populated Schema.
	func SchemaFromJSON(schemaJSON []byte) (Schema, error) {

	var bigQuerySchema []bigQueryJSONField

	// Make sure we actually have some content:
	if len(schemaJSON) == 0 {
	return nil, errEmptyJSONSchema
	}

	if err := json.Unmarshal(schemaJSON, &bigQuerySchema); err != nil {
	return nil, err
	}

	return convertSchemaFromJSON(bigQuerySchema)
	}