範例:C#「Hello World」應用程式

這個程式碼範例是以 C# 撰寫的「Hello World」應用程式,示範如何完成下列工作:

  • 連接 Cloud BigTable 執行個體
  • 建立新的資料表。
  • 將資料寫入資料表。
  • 讀取資料。
  • 刪除資料表。

執行範例

這個程式碼使用 .NET 適用的 Google Cloud 用戶端程式庫中的 C# Admin APIC# Data API 程式庫,與 Cloud Bigtable 進行通訊。

如要執行這個程式範例,請按照 GitHub 上的 .NET Cloud BigTable 範例操作說明進行。完成建構及執行快速入門步驟,建立可用於 Hello World 應用程式的資源。請務必編輯 HelloWorld.cs 檔案,新增您建立的資源名稱。

搭配 Cloud BigTable 使用 Cloud 用戶端程式庫

這個應用程式範例會連線至 Cloud BigTable,示範部分簡易作業。

連線至 Cloud BigTable

如要開始使用,請建立可用來連線至 Cloud BigTable 的兩個用戶端物件。C# Admin API 的 BigtableTableAdminClient 可協助您建立及刪除執行個體和資料表。C# Data API 的 BigtableClient 可協助您讀取及寫入資料表資料。

// BigtableTableAdminClient API lets us create, manage and delete tables.
BigtableTableAdminClient bigtableTableAdminClient = BigtableTableAdminClient.Create();

// BigtableClient API lets us read and write to a table.
BigtableClient bigtableClient = BigtableClient.Create();

建立資料表

呼叫管理員用戶端的 CreateTable() 方法,產生儲存「Hello World」問候語的 Table 物件。資料表有單一資料欄系列,會保留每個值的一個版本。

// Create a table with a single column family.
Console.WriteLine($"Create new table: {tableId} with column family: {columnFamily}, instance: {instanceId}");

// Check whether a table with given TableName already exists.
if (!TableExist(bigtableTableAdminClient))
{
    bigtableTableAdminClient.CreateTable(
        new InstanceName(projectId, instanceId),
        tableId,
        new Table
        {
            Granularity = Table.Types.TimestampGranularity.Millis,
            ColumnFamilies =
            {
                {
                    columnFamily, new ColumnFamily
                    {
                        GcRule = new GcRule
                        {
                            MaxNumVersions = 1
                        }
                    }
                }
            }
        });
    // Confirm that table was created successfully.
    Console.WriteLine(TableExist(bigtableTableAdminClient)
        ? $"Table {tableId} created successfully\n"
        : $"There was a problem creating a table {tableId}");
}
else
{
    Console.WriteLine($"Table: {tableId} already exists");
}

將資料列寫入資料表

使用包含三個簡單問候語的字串陣列 s_greetings[],做為寫入資料表的資料來源。首先,使用 MutateRow() 將單一資料列寫入資料表。接著,循環處理陣列其餘部分,建構每個問候語包含一個項目的 MutateRowsRequest 物件。使用 MutateRows() 提出一次寫入所有項目的要求。接著,循環處理傳回的回應,檢查每個項目的狀態碼,確認是否已成功寫入。

// Initialize Google.Cloud.Bigtable.V2.TableName object.
Google.Cloud.Bigtable.Common.V2.TableName tableName = new Google.Cloud.Bigtable.Common.V2.TableName(projectId, instanceId, tableId);

// Write some rows
/* Each row has a unique row key.

       Note: This example uses sequential numeric IDs for simplicity, but
       this can result in poor performance in a production application.
       Since rows are stored in sorted order by key, sequential keys can
       result in poor distribution of operations across nodes.

       For more information about how to design a Bigtable schema for the
       best performance, see the documentation:

       https://cloud.google.com/bigtable/docs/schema-design */

Console.WriteLine($"Write some greetings to the table {tableId}");

// Insert 1 row using MutateRow()
s_greetingIndex = 0;
try
{
    bigtableClient.MutateRow(tableName, rowKeyPrefix + s_greetingIndex, MutationBuilder());
    Console.WriteLine($"\tGreeting:   -- {s_greetings[s_greetingIndex],-18}-- written successfully");
}
catch (Exception ex)
{
    Console.WriteLine($"\tFailed to write greeting: --{s_greetings[s_greetingIndex]}");
    Console.WriteLine(ex.Message);
    throw;
}

// Insert multiple rows using MutateRows()
// Build a MutateRowsRequest (contains table name and a collection of entries).
MutateRowsRequest request = new MutateRowsRequest
{
    TableNameAsTableName = tableName
};

s_mapToOriginalGreetingIndex = new List<int>();
while (++s_greetingIndex < s_greetings.Length)
{
    s_mapToOriginalGreetingIndex.Add(s_greetingIndex);
    // Build an entry for every greeting (consists of rowkey and a collection of mutations).
    string rowKey = rowKeyPrefix + s_greetingIndex;
    request.Entries.Add(Mutations.CreateEntry(rowKey, MutationBuilder()));
}

// Make the request to write multiple rows.
MutateRowsResponse response = bigtableClient.MutateRows(request);

// Check the status code of each entry to ensure that it was written successfully.
foreach (MutateRowsResponse.Types.Entry entry in response.Entries)
{
    s_greetingIndex = s_mapToOriginalGreetingIndex[(int)entry.Index];
    if (entry.Status.Code == 0)
    {
        Console.WriteLine($"\tGreeting:   -- {s_greetings[s_greetingIndex],-18}-- written successfully");
    }
    else
    {
        Console.WriteLine($"\tFailed to write greeting: --{s_greetings[s_greetingIndex]}");
        Console.WriteLine(entry.Status.Message);
    }
}

Mutation MutationBuilder() =>
    Mutations.SetCell(columnFamily, columnName, s_greetings[s_greetingIndex], new BigtableVersion(DateTime.UtcNow));

建立篩選器

讀取已寫入的資料前,請先建立篩選器,藉此限制 Cloud BigTable 傳回的資料。即使資料表中含有每個值未經過垃圾收集處理的較舊版本,篩選器仍能指示 Cloud BigTable 僅傳回每個值的最新版本。

RowFilter filter = RowFilters.CellsPerRowLimit(1);

依資料列索引鍵讀取資料列

使用 ReadRow() 方法傳入您剛建立的篩選器,取得該資料列中每個值的一個版本。

// Read from the table.
Console.WriteLine("Read the first row");

int rowIndex = 0;

// Read a specific row. Apply a filter to return latest only cell value accross entire row.
Row rowRead = bigtableClient.ReadRow(
    tableName, rowKey: rowKeyPrefix + rowIndex, filter: filter);
Console.WriteLine(
    $"\tRow key: {rowRead.Key.ToStringUtf8()} " +
    $"  -- Value: {rowRead.Families[0].Columns[0].Cells[0].Value.ToStringUtf8(),-16} " +
    $"  -- Time Stamp: {rowRead.Families[0].Columns[0].Cells[0].TimestampMicros}");

掃描所有資料表資料列

呼叫 ReadRows() 方法傳入篩選器,取得資料表中的所有資料列。您已傳入篩選器,因此 Cloud BigTable 只會傳回每個值的一個版本。

Console.WriteLine("Read all rows using streaming");
// stream the content of the whole table. Apply a filter to return latest only cell values accross all rows.
ReadRowsStream responseRead = bigtableClient.ReadRows(tableName, filter: filter);

Task printRead = PrintReadRowsAsync();
printRead.Wait();

async Task PrintReadRowsAsync()
{
    await responseRead.ForEachAsync(row =>
    {
        Console.WriteLine($"\tRow key: {row.Key.ToStringUtf8()} " +
                          $"  -- Value: {row.Families[0].Columns[0].Cells[0].Value.ToStringUtf8(),-16} " +
                          $"  -- Time Stamp: {row.Families[0].Columns[0].Cells[0].TimestampMicros}");
    });
}

刪除資料表

使用 DeleteTable() 方法刪除資料表。

// Clean up. Delete the table.
Console.WriteLine($"Delete table: {tableId}");

bigtableTableAdminClient.DeleteTable(name: tableName);
if (!TableExist(bigtableTableAdminClient))
{
    Console.WriteLine($"Table: {tableId} deleted successfully");
}

完整的程式碼範例

以下是不含評論的完整程式碼範例。

// Copyright 2018 Google Inc.

using System;
using System.Linq;
using System.Threading.Tasks;
using System.Collections.Generic;
using Google.Cloud.Bigtable.V2;
using Google.Cloud.Bigtable.Admin.V2;
using Grpc.Core;

namespace GoogleCloudSamples.Bigtable
{
    public class HelloWorld
    {
        private const string projectId = "YOUR-PROJECT-ID";

        private const string instanceId = "YOUR-INSTANCE-ID";

        private const string tableId = "Hello-Bigtable";
        private const string columnFamily = "cf";
        private const string columnName = "greeting";
        private static readonly string[] s_greetings = { "Hello World!", "Hello Bigtable!", "Hello C#!" };
        private static List<int> s_mapToOriginalGreetingIndex;
        private const string rowKeyPrefix = "greeting";
        private static int s_greetingIndex;

        private static void DoHelloWorld()
        {
            try
            {
                BigtableTableAdminClient bigtableTableAdminClient = BigtableTableAdminClient.Create();

                BigtableClient bigtableClient = BigtableClient.Create();

                Console.WriteLine($"Create new table: {tableId} with column family: {columnFamily}, instance: {instanceId}");

                if (!TableExist(bigtableTableAdminClient))
                {
                    bigtableTableAdminClient.CreateTable(
                        new InstanceName(projectId, instanceId),
                        tableId,
                        new Table
                        {
                            Granularity = Table.Types.TimestampGranularity.Millis,
                            ColumnFamilies =
                            {
                                {
                                    columnFamily, new ColumnFamily
                                    {
                                        GcRule = new GcRule
                                        {
                                            MaxNumVersions = 1
                                        }
                                    }
                                }
                            }
                        });
                    Console.WriteLine(TableExist(bigtableTableAdminClient)
                        ? $"Table {tableId} created successfully\n"
                        : $"There was a problem creating a table {tableId}");
                }
                else
                {
                    Console.WriteLine($"Table: {tableId} already exists");
                }

                Google.Cloud.Bigtable.Common.V2.TableName tableName = new Google.Cloud.Bigtable.Common.V2.TableName(projectId, instanceId, tableId);

                       Note: This example uses sequential numeric IDs for simplicity, but
                       this can result in poor performance in a production application.
                       Since rows are stored in sorted order by key, sequential keys can
                       result in poor distribution of operations across nodes.

                       For more information about how to design a Bigtable schema for the
                       best performance, see the documentation:

                       https://cloud.google.com/bigtable/docs/schema-design */

                Console.WriteLine($"Write some greetings to the table {tableId}");

                s_greetingIndex = 0;
                try
                {
                    bigtableClient.MutateRow(tableName, rowKeyPrefix + s_greetingIndex, MutationBuilder());
                    Console.WriteLine($"\tGreeting:   -- {s_greetings[s_greetingIndex],-18}-- written successfully");
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"\tFailed to write greeting: --{s_greetings[s_greetingIndex]}");
                    Console.WriteLine(ex.Message);
                    throw;
                }

                MutateRowsRequest request = new MutateRowsRequest
                {
                    TableNameAsTableName = tableName
                };

                s_mapToOriginalGreetingIndex = new List<int>();
                while (++s_greetingIndex < s_greetings.Length)
                {
                    s_mapToOriginalGreetingIndex.Add(s_greetingIndex);
                    string rowKey = rowKeyPrefix + s_greetingIndex;
                    request.Entries.Add(Mutations.CreateEntry(rowKey, MutationBuilder()));
                }

                MutateRowsResponse response = bigtableClient.MutateRows(request);

                foreach (MutateRowsResponse.Types.Entry entry in response.Entries)
                {
                    s_greetingIndex = s_mapToOriginalGreetingIndex[(int)entry.Index];
                    if (entry.Status.Code == 0)
                    {
                        Console.WriteLine($"\tGreeting:   -- {s_greetings[s_greetingIndex],-18}-- written successfully");
                    }
                    else
                    {
                        Console.WriteLine($"\tFailed to write greeting: --{s_greetings[s_greetingIndex]}");
                        Console.WriteLine(entry.Status.Message);
                    }
                }

                Mutation MutationBuilder() =>
                    Mutations.SetCell(columnFamily, columnName, s_greetings[s_greetingIndex], new BigtableVersion(DateTime.UtcNow));

                RowFilter filter = RowFilters.CellsPerRowLimit(1);

                Console.WriteLine("Read the first row");

                int rowIndex = 0;

                Row rowRead = bigtableClient.ReadRow(
                    tableName, rowKey: rowKeyPrefix + rowIndex, filter: filter);
                Console.WriteLine(
                    $"\tRow key: {rowRead.Key.ToStringUtf8()} " +
                    $"  -- Value: {rowRead.Families[0].Columns[0].Cells[0].Value.ToStringUtf8(),-16} " +
                    $"  -- Time Stamp: {rowRead.Families[0].Columns[0].Cells[0].TimestampMicros}");

                Console.WriteLine("Read all rows using streaming");
                ReadRowsStream responseRead = bigtableClient.ReadRows(tableName, filter: filter);

                Task printRead = PrintReadRowsAsync();
                printRead.Wait();

                async Task PrintReadRowsAsync()
                {
                    await responseRead.ForEachAsync(row =>
                    {
                        Console.WriteLine($"\tRow key: {row.Key.ToStringUtf8()} " +
                                          $"  -- Value: {row.Families[0].Columns[0].Cells[0].Value.ToStringUtf8(),-16} " +
                                          $"  -- Time Stamp: {row.Families[0].Columns[0].Cells[0].TimestampMicros}");
                    });
                }

                Console.WriteLine($"Delete table: {tableId}");

                bigtableTableAdminClient.DeleteTable(name: tableName);
                if (!TableExist(bigtableTableAdminClient))
                {
                    Console.WriteLine($"Table: {tableId} deleted successfully");
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Exception while running HelloWorld: {ex.Message}");
            }
        }

        private static bool TableExist(BigtableTableAdminClient bigtableTableAdminClient)
        {
            GetTableRequest request = new GetTableRequest
            {
                TableName = new Google.Cloud.Bigtable.Common.V2.TableName(projectId, instanceId, tableId),
                View = Table.Types.View.NameOnly
            };
            try
            {
                var tables = bigtableTableAdminClient.GetTable(request);
                return true;
            }
            catch (RpcException ex)
            {
                if (ex.StatusCode == StatusCode.NotFound)
                {
                    return false;
                }

                throw;
            }
        }

        public static int Main(string[] args)
        {
            if (projectId == "YOUR-PROJECT" + "-ID")
            {
                Console.WriteLine("Edit HelloWorld.cs and replace YOUR-PROJECT-ID with your project ID.");
                return -1;
            }
            if (instanceId == "YOUR-INSTANCE" + "-ID")
            {
                Console.WriteLine("Edit HelloWorld.cs and replace YOUR-INSTANCE-ID with your instance ID.");
                return -1;
            }

            DoHelloWorld();
            return 0;
        }
    }
}
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