Read rows with a prefix

Create a query with a prefix.

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Code sample

C++

To learn how to install and use the client library for Bigtable, see Bigtable client libraries.

To authenticate to Bigtable, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

namespace cbt = ::google::cloud::bigtable;
using ::google::cloud::StatusOr;
[](cbt::Table table) {
  // Read and print the rows.
  for (StatusOr<cbt::Row>& row : table.ReadRows(
           cbt::RowRange::Prefix("phone"), cbt::Filter::PassAllFilter())) {
    if (!row) throw std::move(row).status();
    PrintRow(*row);
  }
}

C#

To learn how to install and use the client library for Bigtable, see Bigtable client libraries.

To authenticate to Bigtable, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

/// <summary>
/// /// Reads rows starting with a prefix from an existing table.
///</summary>
/// <param name="projectId">Your Google Cloud Project ID.</param>
/// <param name="instanceId">Your Google Cloud Bigtable Instance ID.</param>
/// <param name="tableId">Your Google Cloud Bigtable table ID.</param>
public async Task<string> ReadPrefix(string projectId = "YOUR-PROJECT-ID", string instanceId = "YOUR-INSTANCE-ID", string tableId = "YOUR-TABLE-ID")
{
    BigtableClient bigtableClient = BigtableClient.Create();
    TableName tableName = new TableName(projectId, instanceId, tableId);

    string prefix = "phone";
    char prefixEndChar = prefix[prefix.Length - 1];
    prefixEndChar++;
    string end = prefix.Substring(0, prefix.Length - 1) + prefixEndChar;
    RowSet rowSet = RowSet.FromRowRanges(RowRange.Closed(prefix, end));
    ReadRowsStream readRowsStream = bigtableClient.ReadRows(tableName, rowSet);

    string result = "";
    await foreach (var row in readRowsStream)
    {
        result += PrintRow(row);
    }

    return result;
}

Go

To learn how to install and use the client library for Bigtable, see Bigtable client libraries.

To authenticate to Bigtable, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

func readPrefix(w io.Writer, projectID, instanceID string, tableName string) error {
	// projectID := "my-project-id"
	// instanceID := "my-instance-id"
	// tableName := "mobile-time-series"

	ctx := context.Background()
	client, err := bigtable.NewClient(ctx, projectID, instanceID)
	if err != nil {
		return fmt.Errorf("bigtable.NewClient: %w", err)
	}
	defer client.Close()

	tbl := client.Open(tableName)
	err = tbl.ReadRows(ctx, bigtable.PrefixRange("phone#"),
		func(row bigtable.Row) bool {
			printRow(w, row)
			return true
		},
	)
	if err != nil {
		return fmt.Errorf("tbl.ReadRows: %w", err)
	}

	return nil
}

Java

To learn how to install and use the client library for Bigtable, see Bigtable client libraries.

To authenticate to Bigtable, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

public static void readPrefix() {
  // TODO(developer): Replace these variables before running the sample.
  String projectId = "my-project-id";
  String instanceId = "my-instance-id";
  String tableId = "mobile-time-series";
  readPrefix(projectId, instanceId, tableId);
}

public static void readPrefix(String projectId, String instanceId, String tableId) {
  // Initialize client that will be used to send requests. This client only needs to be created
  // once, and can be reused for multiple requests. After completing all of your requests, call
  // the "close" method on the client to safely clean up any remaining background resources.
  try (BigtableDataClient dataClient = BigtableDataClient.create(projectId, instanceId)) {
    Query query = Query.create(TableId.of(tableId)).prefix("phone");
    ServerStream<Row> rows = dataClient.readRows(query);
    for (Row row : rows) {
      printRow(row);
    }
  } catch (IOException e) {
    System.out.println(
        "Unable to initialize service client, as a network error occurred: \n" + e.toString());
  }
}

Node.js

To learn how to install and use the client library for Bigtable, see Bigtable client libraries.

To authenticate to Bigtable, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

const prefix = 'phone#';

await table
  .createReadStream({
    prefix,
  })
  .on('error', err => {
    // Handle the error.
    console.log(err);
  })
  .on('data', row => printRow(row.id, row.data))
  .on('end', () => {
    // All rows retrieved.
  });

PHP

To learn how to install and use the client library for Bigtable, see Bigtable client libraries.

To authenticate to Bigtable, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

use Google\Cloud\Bigtable\BigtableClient;

/**
 * Read using a row key prefix
 *
 * @param string $projectId The Google Cloud project ID
 * @param string $instanceId The ID of the Bigtable instance
 * @param string $tableId The ID of the table to read from
 */
function read_prefix(
    string $projectId,
    string $instanceId,
    string $tableId
): void {
    // Connect to an existing table with an existing instance.
    $dataClient = new BigtableClient([
        'projectId' => $projectId,
    ]);
    $table = $dataClient->table($instanceId, $tableId);

    $prefix = 'phone#';
    $end = $prefix;
    // Increment the last character of the prefix so the filter matches everything in between
    $end[-1] = chr(
        ord($end[-1]) + 1
    );

    $rows = $table->readRows([
        'rowRanges' => [
            [
                'startKeyClosed' => $prefix,
                'endKeyClosed' => $end,
            ]
        ]
    ]);

    foreach ($rows as $key => $row) {
        print_row($key, $row);
    }
}

Python

To learn how to install and use the client library for Bigtable, see Bigtable client libraries.

To authenticate to Bigtable, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

def read_prefix(project_id, instance_id, table_id):
    from google.cloud import bigtable
    from google.cloud.bigtable.row_set import RowSet

    client = bigtable.Client(project=project_id, admin=True)
    instance = client.instance(instance_id)
    table = instance.table(table_id)
    prefix = "phone#"
    end_key = prefix[:-1] + chr(ord(prefix[-1]) + 1)

    row_set = RowSet()
    row_set.add_row_range_from_keys(prefix.encode("utf-8"), end_key.encode("utf-8"))

    rows = table.read_rows(row_set=row_set)
    for row in rows:
        print_row(row)

Ruby

To learn how to install and use the client library for Bigtable, see Bigtable client libraries.

To authenticate to Bigtable, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

# instance_id = "my-instance"
# table_id    = "my-table"
bigtable = Google::Cloud::Bigtable.new
table = bigtable.table instance_id, table_id

prefix = "phone#"
end_key = prefix[0...-1] + prefix[-1].next
range = table.new_row_range.between prefix, end_key
table.read_rows(ranges: range).each do |row|
  print_row row
end

What's next

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