Query con parametro BYTES

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Esegui una query sui dati utilizzando un parametro BYTES.

Esempio di codice

C++

Per scoprire come installare e utilizzare la libreria client per Spanner, consulta la pagina relativa alle librerie client di Spanner. 

void QueryWithBytesParameter(google::cloud::spanner::Client client) {
  namespace spanner = ::google::cloud::spanner;
  spanner::Bytes example_bytes("Hello World 1");
  spanner::SqlStatement select(
      "SELECT VenueId, VenueName FROM Venues"
      " WHERE VenueInfo = @venue_info",
      {{"venue_info", spanner::Value(example_bytes)}});
  using RowType = std::tuple<std::int64_t, absl::optional<std::string>>;
  auto rows = client.ExecuteQuery(std::move(select));
  for (auto& row : spanner::StreamOf<RowType>(rows)) {
    if (!row) throw std::move(row).status();
    std::cout << "VenueId: " << std::get<0>(*row) << "\t";
    std::cout << "VenueName: " << std::get<1>(*row).value() << "\n";
  }
  std::cout << "Query completed for [spanner_query_with_bytes_parameter]\n";
}

C#

Per scoprire come installare e utilizzare la libreria client per Spanner, consulta la pagina relativa alle librerie client di Spanner. 


using Google.Cloud.Spanner.Data;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;

public class QueryWithBytesAsyncSample
{
    public class Venue
    {
        public int VenueId { get; set; }
        public string VenueName { get; set; }
    }

    public async Task<List<Venue>> QueryWithBytesAsync(string projectId, string instanceId, string databaseId)
    {
        string connectionString = $"Data Source=projects/{projectId}/instances/{instanceId}/databases/{databaseId}";
        // Initialize a Bytes array to use for querying.
        string sampleText = "Hello World 1";
        byte[] exampleBytes = Encoding.UTF8.GetBytes(sampleText);

        using var connection = new SpannerConnection(connectionString);
        var cmd = connection.CreateSelectCommand("SELECT VenueId, VenueName FROM Venues WHERE VenueInfo = @ExampleBytes");
        cmd.Parameters.Add("ExampleBytes", SpannerDbType.Bytes, exampleBytes);

        var venues = new List<Venue>();
        using var reader = await cmd.ExecuteReaderAsync();
        while (await reader.ReadAsync())
        {
            venues.Add(new Venue
            {
                VenueId = reader.GetFieldValue<int>("VenueId"),
                VenueName = reader.GetFieldValue<string>("VenueName")
            });
        }
        return venues;
    }
}

Go

Per scoprire come installare e utilizzare la libreria client per Spanner, consulta la pagina relativa alle librerie client di Spanner. 


import (
	"context"
	"fmt"
	"io"

	"cloud.google.com/go/spanner"
	"google.golang.org/api/iterator"
)

func queryWithBytes(w io.Writer, db string) error {
	ctx := context.Background()
	client, err := spanner.NewClient(ctx, db)
	if err != nil {
		return err
	}
	defer client.Close()

	var exampleBytes = []byte("Hello World 1")
	stmt := spanner.Statement{
		SQL: `SELECT VenueId, VenueName FROM Venues
            	WHERE VenueInfo = @venueInfo`,
		Params: map[string]interface{}{
			"venueInfo": exampleBytes,
		},
	}
	iter := client.Single().Query(ctx, stmt)
	defer iter.Stop()
	for {
		row, err := iter.Next()
		if err == iterator.Done {
			return nil
		}
		if err != nil {
			return err
		}
		var venueID int64
		var venueName string
		if err := row.Columns(&venueID, &venueName); err != nil {
			return err
		}
		fmt.Fprintf(w, "%d %s\n", venueID, venueName)
	}
}

Java

Per scoprire come installare e utilizzare la libreria client per Spanner, consulta la pagina relativa alle librerie client di Spanner. 

static void queryWithBytes(DatabaseClient dbClient) {
  ByteArray exampleBytes =
      ByteArray.fromBase64(BaseEncoding.base64().encode("Hello World 1".getBytes()));
  Statement statement =
      Statement.newBuilder(
              "SELECT VenueId, VenueName FROM Venues " + "WHERE VenueInfo = @venueInfo")
          .bind("venueInfo")
          .to(exampleBytes)
          .build();
  try (ResultSet resultSet = dbClient.singleUse().executeQuery(statement)) {
    while (resultSet.next()) {
      System.out.printf(
          "%d %s\n", resultSet.getLong("VenueId"), resultSet.getString("VenueName"));
    }
  }
}

Node.js

Per scoprire come installare e utilizzare la libreria client per Spanner, consulta la pagina relativa alle librerie client di Spanner. 

// Imports the Google Cloud client library.
const {Spanner} = require('@google-cloud/spanner');

/**
 * TODO(developer): Uncomment the following lines before running the sample.
 */
// const projectId = 'my-project-id';
// const instanceId = 'my-instance';
// const databaseId = 'my-database';

// Creates a client
const spanner = new Spanner({
  projectId: projectId,
});

// Gets a reference to a Cloud Spanner instance and database.
const instance = spanner.instance(instanceId);
const database = instance.database(databaseId);

const fieldType = {
  type: 'bytes',
};

const exampleBytes = new Buffer.from('Hello World 1');

const query = {
  sql: `SELECT VenueId, VenueName FROM Venues
          WHERE VenueInfo = @venueInfo`,
  params: {
    venueInfo: exampleBytes,
  },
  types: {
    venueInfo: fieldType,
  },
};

// Queries rows from the Venues table.
try {
  const [rows] = await database.run(query);

  rows.forEach(row => {
    const json = row.toJSON();
    console.log(`VenueId: ${json.VenueId}, VenueName: ${json.VenueName}`);
  });
} catch (err) {
  console.error('ERROR:', err);
} finally {
  // Close the database when finished.
  database.close();
}

PHP

Per scoprire come installare e utilizzare la libreria client per Spanner, consulta la pagina relativa alle librerie client di Spanner. 

use Google\Cloud\Spanner\SpannerClient;
use Google\Cloud\Spanner\Database;

/**
 * Queries sample data from the database using SQL with a BYTES parameter.
 * Example:
 * ```
 * query_data_with_bytes_parameter($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function query_data_with_bytes_parameter(string $instanceId, string $databaseId): void
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $exampleBytes = base64_encode('Hello World 1');

    $results = $database->execute(
        'SELECT VenueId, VenueName FROM Venues ' .
        'WHERE VenueInfo = @venueInfo',
        [
            'parameters' => [
                'venueInfo' => $exampleBytes
            ],
            'types' => [
                'venueInfo' => Database::TYPE_BYTES
            ]
        ]
    );

    foreach ($results as $row) {
        printf('VenueId: %s, VenueName: %s' . PHP_EOL,
            $row['VenueId'], $row['VenueName']);
    }
}

Python

Per scoprire come installare e utilizzare la libreria client per Spanner, consulta la pagina relativa alle librerie client di Spanner. 

# instance_id = "your-spanner-instance"
# database_id = "your-spanner-db-id"
spanner_client = spanner.Client()
instance = spanner_client.instance(instance_id)
database = instance.database(database_id)

exampleBytes = base64.b64encode("Hello World 1".encode())
param = {"venue_info": exampleBytes}
param_type = {"venue_info": param_types.BYTES}

with database.snapshot() as snapshot:
    results = snapshot.execute_sql(
        "SELECT VenueId, VenueName FROM Venues " "WHERE VenueInfo = @venue_info",
        params=param,
        param_types=param_type,
    )

    for row in results:
        print("VenueId: {}, VenueName: {}".format(*row))

Ruby

Per scoprire come installare e utilizzare la libreria client per Spanner, consulta la pagina relativa alle librerie client di Spanner. 

# project_id  = "Your Google Cloud project ID"
# instance_id = "Your Spanner instance ID"
# database_id = "Your Spanner database ID"

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new project: project_id
client  = spanner.client instance_id, database_id

example_bytes = StringIO.new "Hello World 1"
sql_query = "SELECT VenueId, VenueName FROM Venues
             WHERE VenueInfo = @venue_info"

params      = { venue_info: example_bytes }
param_types = { venue_info: :BYTES }

client.execute(sql_query, params: params, types: param_types).rows.each do |row|
  puts "#{row[:VenueId]} #{row[:VenueName]}"
end

Passaggi successivi

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