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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 (
"fmt"
"reflect"
"golang.org/x/net/context"
"google.golang.org/api/iterator"
)
// A pageFetcher returns a page of rows, starting from the row specified by token.
type pageFetcher interface {
fetch(ctx context.Context, s service, token string) (*readDataResult, error)
setPaging(*pagingConf)
}
func newRowIterator(ctx context.Context, s service, pf pageFetcher) *RowIterator {
it := &RowIterator{
ctx: ctx,
service: s,
pf: pf,
}
it.pageInfo, it.nextFunc = iterator.NewPageInfo(
it.fetch,
func() int { return len(it.rows) },
func() interface{} { r := it.rows; it.rows = nil; return r })
return it
}
// A RowIterator provides access to the result of a BigQuery lookup.
type RowIterator struct {
ctx context.Context
service service
pf pageFetcher
pageInfo *iterator.PageInfo
nextFunc func() error
// StartIndex can be set before the first call to Next. If PageInfo().Token
// is also set, StartIndex is ignored.
StartIndex uint64
rows [][]Value
schema Schema // populated on first call to fetch
structLoader structLoader // used to populate a pointer to a struct
}
// Next loads the next row into dst. Its return value is iterator.Done if there
// are no more results. Once Next returns iterator.Done, all subsequent calls
// will return iterator.Done.
//
// dst may implement ValueLoader, or may be a *[]Value, *map[string]Value, or struct pointer.
//
// If dst is a *[]Value, it will be set to to new []Value whose i'th element
// will be populated with the i'th column of the row.
//
// If dst is a *map[string]Value, a new map will be created if dst is nil. Then
// for each schema column name, the map key of that name will be set to the column's
// value.
//
// If dst is pointer to a struct, each column in the schema will be matched
// with an exported field of the struct that has the same name, ignoring case.
// Unmatched schema columns and struct fields will be ignored.
//
// Each BigQuery column type corresponds to one or more Go types; a matching struct
// field must be of the correct type. The correspondences are:
//
// 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
//
// A repeated field corresponds to a slice or array of the element type.
// A RECORD type (nested schema) corresponds to a nested struct or struct pointer.
// All calls to Next on the same iterator must use the same struct type.
//
// It is an error to attempt to read a BigQuery NULL value into a struct field.
// If your table contains NULLs, use a *[]Value or *map[string]Value.
func (it *RowIterator) Next(dst interface{}) error {
var vl ValueLoader
switch dst := dst.(type) {
case ValueLoader:
vl = dst
case *[]Value:
vl = (*valueList)(dst)
case *map[string]Value:
vl = (*valueMap)(dst)
default:
if !isStructPtr(dst) {
return fmt.Errorf("bigquery: cannot convert %T to ValueLoader (need pointer to []Value, map[string]Value, or struct)", dst)
}
}
if err := it.nextFunc(); err != nil {
return err
}
row := it.rows[0]
it.rows = it.rows[1:]
if vl == nil {
// This can only happen if dst is a pointer to a struct. We couldn't
// set vl above because we need the schema.
if err := it.structLoader.set(dst, it.schema); err != nil {
return err
}
vl = &it.structLoader
}
return vl.Load(row, it.schema)
}
func isStructPtr(x interface{}) bool {
t := reflect.TypeOf(x)
return t.Kind() == reflect.Ptr && t.Elem().Kind() == reflect.Struct
}
// PageInfo supports pagination. See the google.golang.org/api/iterator package for details.
func (it *RowIterator) PageInfo() *iterator.PageInfo { return it.pageInfo }
func (it *RowIterator) fetch(pageSize int, pageToken string) (string, error) {
pc := &pagingConf{}
if pageSize > 0 {
pc.recordsPerRequest = int64(pageSize)
pc.setRecordsPerRequest = true
}
if pageToken == "" {
pc.startIndex = it.StartIndex
}
it.pf.setPaging(pc)
res, err := it.pf.fetch(it.ctx, it.service, pageToken)
if err != nil {
return "", err
}
it.rows = append(it.rows, res.rows...)
it.schema = res.schema
return res.pageToken, nil
}
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