c# - 如何使用C#将Oracle中的400万条记录更快地插入到Elasticsearch表中？

我有以下用C#编写的代码，但据此，我需要4-5天的时间才能将数据从Oracle数据库迁移到Elasticsearch。我将批量插入100条记录。是否还有其他方法可以使400万条记录的迁移速度更快(如果可能的话，迁移时间可能少于一天)？

   public static void Selection()
        {
            for(int i = 1; i < 4000000; i += 1000)
            {
                for(int j = i; j < (i+1000); j += 100)
                {
                    OracleCommand cmd = new OracleCommand(BuildQuery(j),
                                                     oracle_connection);
                    OracleDataReader reader = cmd.ExecuteReader();
                    List<Record> list=CreateRecordList(reader);
                    insert(list);
                }
            }
        }

   private static List<Record> CreateRecordList(OracleDataReader reader)
        {
            List<Record> l = new List<Record>();
            string[] str = new string[7];
            try
            {
                while (reader.Read())
                {
                    for (int i = 0; i < 7; i++)
                    {
                        str[i] = reader[i].ToString();
                    }

                    Record r = new Record(str[0], str[1], str[2], str[3],
                                str[4], str[5], str[6]);
                    l.Add(r);
                }
            }
            catch (Exception er)
            {
                string msg = er.Message;
            }
            return l;
        }

   private static string BuildQuery(int from)
        {
            int to = from + change - 1;
            StringBuilder builder = new StringBuilder();
            builder.AppendLine(@"select * from");
            builder.AppendLine("(");
            builder.AppendLine("select FIELD_1, FIELD_2,
            FIELD_3, FIELD_4, FIELD_5, FIELD_6,
            FIELD_7, ");
            builder.Append(" row_number() over(order by FIELD_1)
             rn");
            builder.AppendLine("   from tablename");
            builder.AppendLine(")");
            builder.AppendLine(string.Format("where rn between {0} and {1}",
            from, to));
            builder.AppendLine("order by rn");
            return builder.ToString();
        }

   public static void insert(List<Record> l)
        {
            try
            {
                foreach(Record r in l)
                    client.Index<Record>(r, "index", "type");
            }
            catch (Exception er)
            {
                string msg = er.Message;
            }
        }

最佳答案

ROW_NUMBER()函数将对性能产生负面影响，而您正在运行数千次。您已经在使用OracleDataReader了-它不会一次将所有四百万行都拉到您的计算机上，它基本上一次流一次或几流。

这必须在几分钟或几小时内完成，而不是几天-我们有几个进程以类似的方式在Sybase和SQL Server之间移动数百万条记录，并且花费不到五分钟。

也许试一下:

OracleCommand cmd = new OracleCommand("SELECT ... FROM TableName", oracle_connection);
int batchSize = 500;
using (OracleDataReader reader = cmd.ExecuteReader())
{
    List<Record> l = new List<Record>(batchSize);
    string[] str = new string[7];
    int currentRow = 0;

    while (reader.Read())
    {
        for (int i = 0; i < 7; i++)
        {
            str[i] = reader[i].ToString();
        }

        l.Add(new Record(str[0], str[1], str[2], str[3], str[4], str[5], str[6]));

        // Commit every time batchSize records have been read
        if (++currentRow == batchSize)
        {
            Commit(l);
            l.Clear();
            currentRow = 0;
        }
    }

    // commit remaining records
    Commit(l);
}

这是Commit的样子:

public void Commit(IEnumerable<Record> records)
{
    // TODO: Use ES's BULK features, I don't know the exact syntax

    client.IndexMany<Record>(records, "index", "type");
    // client.Bulk(b => b.IndexMany(records))... something like this
}

关于c# - 如何使用C#将Oracle中的400万条记录更快地插入到Elasticsearch表中？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/31028381/