擷取交易的修訂統計資料

為協助您進一步瞭解、改善及診斷交易問題，Spanner 可讓您存取交易提交統計資料。目前，您可以擷取交易的變異總數。

使用提交統計資料的時機

在下列情況下，瞭解交易的變異數計數可能會很有幫助。

針對往返程進行最佳化

為改善應用程式效能，您可以在每個交易中盡可能執行更多工作，藉此減少資料庫往返次數。在這種情況下，您希望盡可能增加每筆交易的變異數量，同時維持在系統限制內。

如要判斷每筆交易可提交多少列，且不超過限制，請先在交易中提交一列。這可讓您瞭解每個資料列的變異數計數基準。接著，將系統限制除以基準值，即可取得每筆交易的資料列數。如要進一步瞭解如何計算突變事件，請參閱這份附註。

請注意，針對往返程進行最佳化不一定有益，尤其是如果這會導致更多鎖定競爭的情況。您可以使用鎖定統計資料，排解資料庫中的鎖定衝突問題。

監控交易，避免達到系統限制

隨著應用程式用量增加，交易中的突變數量也可能隨之增加。為避免觸及系統限制而導致交易最終失敗，您可以主動監控變異數計數提交統計資料。如果您發現同一個交易的這個值有增加的趨勢，可能就該按照前面章節所述，重新最佳化交易了。

如何存取提交統計資料

根據預設，系統不會傳回提交統計資料。相反地，您需要在每個 CommitRequest 上將 return_commit_stats 標記設為 true。如果提交作業超過交易可用的變異上限，提交作業就會失敗，並傳回 INVALID_ARGUMENT 錯誤。

以下範例說明如何使用 Spanner 用戶端程式庫傳回提交統計資料。

擷取修訂統計資料

以下範例說明如何使用 Spanner 用戶端程式庫取得提交統計資料。

C++

下列程式碼會在 CommitOptions 上呼叫 set_return_stats()，並傳回 6 的突變數，因為我們會插入或更新 2 列和每列 3 欄。

void GetCommitStatistics(google::cloud::spanner::Client client) {
  namespace spanner = ::google::cloud::spanner;

  auto commit = client.Commit(
      spanner::Mutations{
          spanner::UpdateMutationBuilder(
              "Albums", {"SingerId", "AlbumId", "MarketingBudget"})
              .EmplaceRow(1, 1, 200000)
              .EmplaceRow(2, 2, 400000)
              .Build()},
      google::cloud::Options{}.set<spanner::CommitReturnStatsOption>(true));

  if (!commit) throw std::move(commit).status();
  if (commit->commit_stats) {
    std::cout << "Updated data with " << commit->commit_stats->mutation_count
              << " mutations.\n";
  }
  std::cout << "Update was successful [spanner_get_commit_stats]\n";
}

C#

在 C# 中，系統不會直接透過 API 傳回提交統計資料。而是由預設記錄器以「資訊」記錄層級記錄。

以下程式碼會將 SpannerConnectionStringBuilder 的 LogCommitStats 屬性設為 true，為所有交易啟用提交統計資料記錄功能。程式碼也會實作範例記錄器，保留對上次看到的提交回應的參照。接著，系統會從這個回應中擷取 MutationCount 並顯示。

using Google.Cloud.Spanner.Data;
using Google.Cloud.Spanner.V1;
using Google.Cloud.Spanner.V1.Internal.Logging;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading.Tasks;

public class LogCommitStatsAsyncSample
{
    public async Task<long> LogCommitStatsAsync(string projectId, string instanceId, string databaseId)
    {
        // Commit statistics are logged at level Info by the default logger.
        // This sample uses a custom logger to access the commit statistics.
        // See https://googleapis.github.io/google-cloud-dotnet/docs/Google.Cloud.Spanner.Data/logging.html
        // for more information on how to use loggers.
        var logger = new CommitStatsSampleLogger();
        var options = new SessionPoolOptions();
        var poolManager = SessionPoolManager.Create(options, logger);
        var connectionStringBuilder = new SpannerConnectionStringBuilder
        {
            ConnectionString = $"Data Source=projects/{projectId}/instances/{instanceId}/databases/{databaseId}",
            // Set LogCommitStats to true to enable logging commit statistics for all transactions on the connection.
            // LogCommitStats can also be enabled/disabled for individual Spanner transactions.
            LogCommitStats = true,
            SessionPoolManager = poolManager,
        };

        using var connection = new SpannerConnection(connectionStringBuilder);
        await connection.OpenAsync();

        using var cmd = connection.CreateDmlCommand("INSERT Singers (SingerId, FirstName, LastName) VALUES (110, 'Virginia', 'Watson')");
        var rowCount = await cmd.ExecuteNonQueryAsync();
        var mutationCount = logger._lastCommitResponse.CommitStats.MutationCount;

        Console.WriteLine($"{rowCount} row(s) inserted...");
        Console.WriteLine($"{mutationCount} mutation(s) in transaction...");

        return mutationCount;
    }

    /// <summary>
    /// Sample logger that keeps a reference to the last seen commit response.
    /// Use the default logger if you only want to log the commit stats.
    /// </summary>
    public class CommitStatsSampleLogger : Logger
    {
        internal CommitResponse _lastCommitResponse;

        /// <summary>
        /// This method is called when a transaction that requested commit stats is committed.
        /// </summary>
        public override void LogCommitStats(CommitRequest request, CommitResponse response)
        {
            _lastCommitResponse = response;
            base.LogCommitStats(request, response);
        }

        protected override void LogImpl(LogLevel level, string message, Exception exception) =>
            WriteLine(exception == null ? $"{level}: {message}" : $"{level}: {message}, Exception: {exception}");

        protected override void LogPerformanceEntries(IEnumerable<string> entries)
        {
            string separator = Environment.NewLine + "  ";
            WriteLine($"Performance:{separator}{string.Join(separator, entries)}");
        }

        private void WriteLine(string line) => Trace.TraceInformation(line);
    }
}

Go

以下程式碼會設定 ReturnCommitStats 標記，並在交易成功提交時列印出突變數量。

import (
	"context"
	"fmt"
	"io"

	"cloud.google.com/go/spanner"
)

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

	resp, err := client.ReadWriteTransactionWithOptions(ctx, func(ctx context.Context, txn *spanner.ReadWriteTransaction) error {
		stmt := spanner.Statement{
			SQL: `INSERT Singers (SingerId, FirstName, LastName)
					VALUES (110, 'Virginia', 'Watson')`,
		}
		rowCount, err := txn.Update(ctx, stmt)
		if err != nil {
			return err
		}
		fmt.Fprintf(w, "%d record(s) inserted.\n", rowCount)
		return nil
	}, spanner.TransactionOptions{CommitOptions: spanner.CommitOptions{ReturnCommitStats: true}})
	if err != nil {
		return fmt.Errorf("commitStats.ReadWriteTransactionWithOptions: %w", err)
	}
	fmt.Fprintf(w, "%d mutations in transaction\n", resp.CommitStats.MutationCount)
	return nil
}

Java

import com.google.cloud.spanner.CommitResponse;
import com.google.cloud.spanner.DatabaseClient;
import com.google.cloud.spanner.DatabaseId;
import com.google.cloud.spanner.Mutation;
import com.google.cloud.spanner.Options;
import com.google.cloud.spanner.Spanner;
import com.google.cloud.spanner.SpannerOptions;
import java.util.Arrays;

public class GetCommitStatsSample {

  static void getCommitStats() {
    // TODO(developer): Replace these variables before running the sample.
    final String projectId = "my-project";
    final String instanceId = "my-instance";
    final String databaseId = "my-database";

    try (Spanner spanner =
        SpannerOptions.newBuilder().setProjectId(projectId).build().getService()) {
      final DatabaseClient databaseClient = spanner
          .getDatabaseClient(DatabaseId.of(projectId, instanceId, databaseId));
      getCommitStats(databaseClient);
    }
  }

  static void getCommitStats(DatabaseClient databaseClient) {
    final CommitResponse commitResponse = databaseClient.writeWithOptions(Arrays.asList(
        Mutation.newInsertOrUpdateBuilder("Albums")
            .set("SingerId")
            .to("1")
            .set("AlbumId")
            .to("1")
            .set("MarketingBudget")
            .to("200000")
            .build(),
        Mutation.newInsertOrUpdateBuilder("Albums")
            .set("SingerId")
            .to("2")
            .set("AlbumId")
            .to("2")
            .set("MarketingBudget")
            .to("400000")
            .build()
    ), Options.commitStats());

    System.out.println(
        "Updated data with " + commitResponse.getCommitStats().getMutationCount() + " mutations.");
  }
}

Node.js

以下程式碼會設定 returnCommitStats 旗標，並傳回 6 個突變數，因為我們會在每個資料列中插入或更新 2 列和 3 欄。

// 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);

// Instantiate Spanner table objects.
const albumsTable = database.table('Albums');

// Updates rows in the Venues table.
try {
  const [response] = await albumsTable.upsert(
    [
      {SingerId: '1', AlbumId: '1', MarketingBudget: '200000'},
      {SingerId: '2', AlbumId: '2', MarketingBudget: '400000'},
    ],
    {returnCommitStats: true},
  );
  console.log(
    `Updated data with ${response.commitStats.mutationCount} mutations.`,
  );
} catch (err) {
  console.error('ERROR:', err);
} finally {
  // Close the database when finished.
  database.close();
}

PHP

use Google\Cloud\Spanner\SpannerClient;
use Google\Cloud\Spanner\Transaction;

/**
 * Creates a database and tables for sample data.
 * Example:
 * ```
 * create_database($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function get_commit_stats(string $instanceId, string $databaseId): void
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $commitStats = $database->runTransaction(function (Transaction $t) {
        $t->updateBatch('Albums', [
            [
                'SingerId' => 1,
                'AlbumId' => 1,
                'MarketingBudget' => 200000,
            ],
            [
                'SingerId' => 2,
                'AlbumId' => 2,
                'MarketingBudget' => 400000,
            ]
        ]);
        $t->commit(['returnCommitStats' => true]);
        return $t->getCommitStats();
    });

    print('Updated data with ' . $commitStats['mutationCount'] . ' mutations.' . PHP_EOL);
}

Python

Python 用戶端程式庫不會直接透過 API 傳回提交統計資料，而是使用 stdout 記錄這些資料，層級為 Info。

以下程式碼會設定 database.log_commit_stats = True，為所有交易啟用提交統計資料記錄功能。程式碼也會實作範例記錄器，以便保留最近看到的修訂回應參照。接著，系統會從這個回應中擷取 mutation_count，並顯示該值。

def log_commit_stats(instance_id, database_id):
    """Inserts sample data using DML and displays the commit statistics."""

    # By default, commit statistics are logged via stdout at level Info.
    # This sample uses a custom logger to access the commit statistics.
    class CommitStatsSampleLogger(logging.Logger):
        def __init__(self):
            self.last_commit_stats = None
            super().__init__("commit_stats_sample")

        def info(self, msg, *args, **kwargs):
            if kwargs["extra"] and "commit_stats" in kwargs["extra"]:
                self.last_commit_stats = kwargs["extra"]["commit_stats"]
            super().info(msg)

    spanner_client = spanner.Client()
    instance = spanner_client.instance(instance_id)
    database = instance.database(database_id, logger=CommitStatsSampleLogger())
    database.log_commit_stats = True

    def insert_singers(transaction):
        row_ct = transaction.execute_update(
            "INSERT Singers (SingerId, FirstName, LastName) "
            " VALUES (110, 'Virginia', 'Watson')"
        )

        print("{} record(s) inserted.".format(row_ct))

    database.run_in_transaction(insert_singers)
    commit_stats = database.logger.last_commit_stats
    print("{} mutation(s) in transaction.".format(commit_stats.mutation_count))

Ruby

以下程式碼會設定 return_commit_stats 旗標，並傳回 6 個突變數，因為我們會在每個資料列中插入或更新 2 列和 3 欄。

# 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

records = [
  { SingerId: 1, AlbumId: 1, MarketingBudget: 200_000 },
  { SingerId: 2, AlbumId: 2, MarketingBudget: 400_000 }
]
commit_options = { return_commit_stats: true }
resp = client.upsert "Albums", records, commit_options: commit_options
puts "Updated data with #{resp.stats.mutation_count} mutations."

後續步驟

• CommitStats REST 參考資料。
• CommitStats gRPC 參考資料。