演示如何使用默认流将复杂数据附加到表中。
代码示例
Go
试用此示例之前，请按照 BigQuery 快速入门：使用客户端库中的 Go 设置说明进行操作。 如需了解详情，请参阅 BigQuery Go API 参考文档。
如需向 BigQuery 进行身份验证，请设置应用默认凭据。 如需了解详情，请参阅为客户端库设置身份验证。
import (
"context"
"fmt"
"io"
"math/rand"
"time"
"cloud.google.com/go/bigquery/storage/managedwriter"
"cloud.google.com/go/bigquery/storage/managedwriter/adapt"
"github.com/GoogleCloudPlatform/golang-samples/bigquery/snippets/managedwriter/exampleproto"
"google.golang.org/protobuf/proto"
)
// generateExampleMessages generates a slice of serialized protobuf messages using a statically defined
// and compiled protocol buffer file, and returns the binary serialized representation.
func generateExampleDefaultMessages(numMessages int) ([][]byte, error) {
msgs := make([][]byte, numMessages)
for i := 0; i < numMessages; i++ {
// instantiate a new random source.
random := rand.New(
rand.NewSource(time.Now().UnixNano()),
)
// Our example data embeds an array of structs, so we'll construct that first.
sl := make([]*exampleproto.SampleStruct, 5)
for i := 0; i < int(random.Int63n(5)+1); i++ {
sl[i] = &exampleproto.SampleStruct{
SubIntCol: proto.Int64(random.Int63()),
}
}
m := &exampleproto.SampleData{
BoolCol: proto.Bool(true),
BytesCol: []byte("some bytes"),
Float64Col: proto.Float64(3.14),
Int64Col: proto.Int64(123),
StringCol: proto.String("example string value"),
// These types require special encoding/formatting to transmit.
// DATE values are number of days since the Unix epoch.
DateCol: proto.Int32(int32(time.Now().UnixNano() / 86400000000000)),
// DATETIME uses the literal format.
DatetimeCol: proto.String("2022-01-01 12:13:14.000000"),
// GEOGRAPHY uses Well-Known-Text (WKT) format.
GeographyCol: proto.String("POINT(-122.350220 47.649154)"),
// NUMERIC and BIGNUMERIC can be passed as string, or more efficiently
// using a packed byte representation.
NumericCol: proto.String("99999999999999999999999999999.999999999"),
BignumericCol: proto.String("578960446186580977117854925043439539266.34992332820282019728792003956564819967"),
// TIME also uses literal format.
TimeCol: proto.String("12:13:14.000000"),
// TIMESTAMP uses microseconds since Unix epoch.
TimestampCol: proto.Int64(time.Now().UnixNano() / 1000),
// Int64List is an array of INT64 types.
Int64List: []int64{2, 4, 6, 8},
// This is a required field in the schema, and thus must be present.
RowNum: proto.Int64(23),
// StructCol is a single nested message.
StructCol: &exampleproto.SampleStruct{
SubIntCol: proto.Int64(random.Int63()),
},
// StructList is a repeated array of a nested message.
StructList: sl,
}
b, err := proto.Marshal(m)
if err != nil {
return nil, fmt.Errorf("error generating message %d: %w", i, err)
}
msgs[i] = b
}
return msgs, nil
}
// appendToDefaultStream demonstrates using the managedwriter package to write some example data
// to a default stream.
func appendToDefaultStream(w io.Writer, projectID, datasetID, tableID string) error {
// projectID := "myproject"
// datasetID := "mydataset"
// tableID := "mytable"
ctx := context.Background()
// Instantiate a managedwriter client to handle interactions with the service.
client, err := managedwriter.NewClient(ctx, projectID,
managedwriter.WithMultiplexing(), // Enables connection sharing.
)
if err != nil {
return fmt.Errorf("managedwriter.NewClient: %w", err)
}
// Close the client when we exit the function.
defer client.Close()
// We need to communicate the descriptor of the protocol buffer message we're using, which
// is analagous to the "schema" for the message. Both SampleData and SampleStruct are
// two distinct messages in the compiled proto file, so we'll use adapt.NormalizeDescriptor
// to unify them into a single self-contained descriptor representation.
var m *exampleproto.SampleData
descriptorProto, err := adapt.NormalizeDescriptor(m.ProtoReflect().Descriptor())
if err != nil {
return fmt.Errorf("NormalizeDescriptor: %w", err)
}
// Build the formatted reference to the destination table.
tableReference := managedwriter.TableParentFromParts(projectID, datasetID, tableID)
// Instantiate a ManagedStream, which manages low level details like connection state and provides
// additional features like a future-like callback for appends, etc. Default streams are provided by
// the system, so there's no need to create them.
managedStream, err := client.NewManagedStream(ctx,
managedwriter.WithType(managedwriter.DefaultStream),
managedwriter.WithDestinationTable(tableReference),
managedwriter.WithSchemaDescriptor(descriptorProto),
)
if err != nil {
return fmt.Errorf("NewManagedStream: %w", err)
}
// Automatically close the writer when we're done.
defer managedStream.Close()
// First, we'll append a single row.
rows, err := generateExampleDefaultMessages(1)
if err != nil {
return fmt.Errorf("generateExampleMessages: %w", err)
}
// We can append data asyncronously, so we'll check our appends at the end.
var results []*managedwriter.AppendResult
result, err := managedStream.AppendRows(ctx, rows)
if err != nil {
return fmt.Errorf("AppendRows first call error: %w", err)
}
results = append(results, result)
// This time, we'll append three more rows in a single request.
rows, err = generateExampleMessages(3)
if err != nil {
return fmt.Errorf("generateExampleMessages: %w", err)
}
result, err = managedStream.AppendRows(ctx, rows)
if err != nil {
return fmt.Errorf("AppendRows second call error: %w", err)
}
results = append(results, result)
// Finally, we'll append two more rows.
rows, err = generateExampleMessages(2)
if err != nil {
return fmt.Errorf("generateExampleMessages: %w", err)
}
result, err = managedStream.AppendRows(ctx, rows)
if err != nil {
return fmt.Errorf("AppendRows third call error: %w", err)
}
results = append(results, result)
// We've been collecting references to our status callbacks to allow us to append in a faster
// asynchronous fashion. Normally you could do this in another goroutine or similar, but for
// this example we'll now iterate through those results and verify they were all successful.
for k, v := range results {
// GetResult blocks until we receive a response from the API.
recvOffset, err := v.GetResult(ctx)
if err != nil {
return fmt.Errorf("append %d returned error: %w", k, err)
}
fmt.Fprintf(w, "Successfully appended data at offset %d.\n", recvOffset)
}
// This stream is a default stream, which means it doesn't require any form of finalization
// or commit. The rows were automatically committed to the table.
return nil
}
后续步骤
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