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schema.go
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schema.go
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// Copyright 2015 Google Inc. All Rights Reserved.
//
// 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 (
"errors"
"fmt"
"reflect"
"cloud.google.com/go/internal/atomiccache"
bq "google.golang.org/api/bigquery/v2"
)
// Schema describes the fields in a table or query result.
type Schema []*FieldSchema
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) asTableFieldSchema() *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.asTableFieldSchema())
}
return tfs
}
func (s Schema) asTableSchema() *bq.TableSchema {
var fields []*bq.TableFieldSchema
for _, f := range s {
fields = append(fields, f.asTableFieldSchema())
}
return &bq.TableSchema{Fields: fields}
}
// customizeCreateTable allows a Schema to be used directly as an option to CreateTable.
func (s Schema) customizeCreateTable(conf *createTableConf) {
conf.schema = s.asTableSchema()
}
func convertTableFieldSchema(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, convertTableFieldSchema(f))
}
return fs
}
func convertTableSchema(ts *bq.TableSchema) Schema {
var s Schema
for _, f := range ts.Fields {
s = append(s, convertTableFieldSchema(f))
}
return s
}
type FieldType string
const (
StringFieldType FieldType = "STRING"
BytesFieldType FieldType = "BYTES"
IntegerFieldType FieldType = "INTEGER"
FloatFieldType FieldType = "FLOAT"
BooleanFieldType FieldType = "BOOLEAN"
TimestampFieldType FieldType = "TIMESTAMP"
RecordFieldType FieldType = "RECORD"
DateFieldType FieldType = "DATE"
TimeFieldType FieldType = "TIME"
DateTimeFieldType FieldType = "DATETIME"
)
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")
)
var typeOfByteSlice = reflect.TypeOf([]byte{})
// InferSchema tries to derive a BigQuery schema from the supplied struct value.
// NOTE: All fields in the returned Schema are configured to be required,
// unless the corresponding field in the supplied struct is a slice or array.
//
// It is considered an error if the struct (including nested structs) contains
// any exported fields that are pointers or one of the following types:
// uint, uint64, uintptr, map, interface, complex64, complex128, func, chan.
// In these cases, an error will be returned.
// Future versions may handle these cases without error.
//
// Recursively defined structs are also disallowed.
func InferSchema(st interface{}) (Schema, error) {
return inferSchemaReflect(reflect.TypeOf(st))
}
var schemaCache atomiccache.Cache
type cacheVal struct {
schema Schema
err error
}
func inferSchemaReflect(t reflect.Type) (Schema, error) {
cv := schemaCache.Get(t, func() interface{} {
s, err := inferStruct(t, map[reflect.Type]bool{})
return cacheVal{s, err}
}).(cacheVal)
return cv.schema, cv.err
}
func inferStruct(t reflect.Type, seen map[reflect.Type]bool) (Schema, error) {
if seen[t] {
return nil, fmt.Errorf("bigquery: schema inference for recursive type %s", t)
}
seen[t] = true
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, seen)
default:
return nil, errNoStruct
}
}
// inferFieldSchema infers the FieldSchema for a Go type
func inferFieldSchema(rt reflect.Type, seen map[reflect.Type]bool) (*FieldSchema, error) {
switch rt {
case typeOfByteSlice:
return &FieldSchema{Required: true, 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
}
if isSupportedIntType(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
}
f, err := inferFieldSchema(et, seen)
if err != nil {
return nil, err
}
f.Repeated = true
f.Required = false
return f, nil
case reflect.Struct, reflect.Ptr:
nested, err := inferStruct(rt, seen)
if err != nil {
return nil, err
}
return &FieldSchema{Required: true, Type: RecordFieldType, Schema: nested}, nil
case reflect.String:
return &FieldSchema{Required: true, Type: StringFieldType}, nil
case reflect.Bool:
return &FieldSchema{Required: true, Type: BooleanFieldType}, nil
case reflect.Float32, reflect.Float64:
return &FieldSchema{Required: true, Type: FloatFieldType}, nil
default:
return nil, errUnsupportedFieldType
}
}
// inferFields extracts all exported field types from struct type.
func inferFields(rt reflect.Type, seen map[reflect.Type]bool) (Schema, error) {
var s Schema
fields, err := fieldCache.Fields(rt)
if err != nil {
return nil, err
}
for _, field := range fields {
f, err := inferFieldSchema(field.Type, seen)
if err != nil {
return nil, err
}
f.Name = field.Name
s = append(s, f)
}
return s, nil
}
// isSupportedIntType reports whether t 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,
reflect.Uint8, reflect.Uint16, reflect.Uint32:
return true
default:
return false
}
}