groovy sql eachRow和rows方法 [英] groovy sql eachRow and rows method

问题描述

我对grails和groovy很陌生。
任何人都可以请向我解释这两个groovy sql方法之间的区别

  sql.eachRow 
 sql .rows 
  

另外，哪种效率更高？

我正在研究从数据库中检索数据的应用程序（结果集非常大），并将其写入CSV文件或返回JSON格式。

I想知道上面提到的两种方法中的哪一种用来使该过程更快更有效。

任何人都可以向我解释这两个groovy
sql方法之间的
差异sql.eachRow sql.rows

很难确切地说出你指的是哪2种方法，因为每种方法都有大量的重载版本。然而，在任何情况下， eachRow 都不会返回任何内容。

  void eachRow（String sql，Closure闭包）
  

而 rows 返回行列表

 列行（String sql）
   eachRow ，闭包就作为第二个参数处理每一行，例如
  sql.eachRow（select * from PERSON where lastname ='murphy'）{row  - > 
 println$ row.firstname
} 
  
如果您使用 rows 这些行被返回，因此应该由调用者处理，例如
  rows（select * from PERSON where lastname ='murphy'）。each {row  - > 
 println$ row.firstname
} 
  
 
 
 
 
 
另外，哪种效率更高？ 
 
这个问题几乎无法回答。即使我自己实现了这些方法，也无法知道哪个方法会更好地执行 ，因为我不知道 
 
 
 
 
您使用的是什么硬件
 
 
您定位的是哪个JVM 
 
 
您使用的是什么版本的Groovy 
 > 
 
您将传递哪些参数
 
 
此方法是您应用程序性能的瓶颈
 
 
 
 
 
或影响方法性能的任何其他因素，这些因素无法单独由源代码确定。您可以通过衡量每种方法的效果来获得有效答案的唯一方法。
 
 
 
尽管我上面已经说过，但如果这两者之间的表现差异有任何意义，我会感到惊讶，所以如果我是你，我会选择哪一个你觉得更方便。如果您稍后发现此方法是性能瓶颈，请尝试使用另一个瓶颈（但我敢打赌，您一美元一分钱就不会有任何区别）。
 
I am new to grails and groovy.
Can anyone please explain to me the difference between these two groovy sql methods
sql.eachRow
sql.rows
Also, which is more efficient?

I am working on an application that retrieves data from the database(the resultset is very huge) and writes it to CSV file or returns a JSON format.

I was wondering which of the two methods mentioned above to use to have the process done faster and efficient.
解决方案

  
Can anyone please explain to me the
  difference between these two groovy
  sql methods sql.eachRow sql.rows
It's difficult to tell exactly which 2 methods you're referring 2 because there are a large number of overloaded versions of each method. However, in all cases, eachRow returns nothing
void eachRow(String sql, Closure closure)
whereas rows returns a list of rows
List rows(String sql) 
So if you use eachRow, the closure passed in as the second parameter should handle each row, e.g.
sql.eachRow("select * from PERSON where lastname = 'murphy'") { row ->
    println "$row.firstname"
}
whereas if you use rows the rows are returned, and therefore should be handled by the caller, e.g.
rows("select * from PERSON where lastname = 'murphy'").each {row ->
    println "$row.firstname"        
}



  
Also, which is more efficient?
This question is almost unanswerable. Even if I had implemented these methods myself there's no way of knowing which one will perform better for you because I don't know


what hardware you're using
what JVM you're targeting
what version of Groovy you're using
what parameters you'll be passing
whether this method is a bottleneck for your application's performance


or any of the other factors that influence a method's performance that cannot be determined from the source code alone. The only way you can get a useful answer to the question of which method is more efficient for you is by measuring the performance of each.

Despite everything I've said above, I would be amazed if the performance difference between these two was in any way significant, so if I were you, I would choose whichever one you find more convenient. If you find later on that this method is a performance bottleneck, try using the other one instead (but I'll bet you a dollar to a dime it makes no difference).

                        
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