Demonstrates how to append complex data to a table with a default stream.
Code sample
Go
Before trying this sample, follow the Go setup instructions in the BigQuery quickstart using client libraries. For more information, see the BigQuery Go API reference documentation.
To authenticate to BigQuery, set up Application Default Credentials. For more information, see Set up authentication for client libraries.
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
}
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