schema.go

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

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

// TODO(mcgreevy): add a function to generate a schema from a struct.

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}
}

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"
	IntegerFieldType   FieldType = "INTEGER"
	FloatFieldType     FieldType = "FLOAT"
	BooleanFieldType   FieldType = "BOOLEAN"
	TimestampFieldType FieldType = "TIMESTAMP"
	RecordFieldType    FieldType = "RECORD"
)