zoukankan      html  css  js  c++  java
  • DataRow indexing performance (integer vs. string)

    SOURCE:  http://www.codeproject.com/KB/database/datarow_indexing.aspx

    Article:

    Introduction

     

    Background

    When I was developing an application for Pocket PC that used quite large DataSet, I wondered where I could gain at least some bits of performance. I was filling some data to a tree view control, storing some data else, doing selects from DataTable and getting the data from columns of DataRows. As you know, you can access the DataRow's columns by using either string indexing (dataRow["NAME"] or integer indexing dataRow[3]).

    I thought I could test performance of both indexers - I just wanted to know if I could still use string indexers (they are more comfortable to work with) - or to rework the code of this app to use integer indexing. So here comes the performance tester.

    The code

    The approach to solve this problem was to create large enough database (DataTable in my case), then in loops traverse the rows, and test the indexing itself. This is done by passing it as a parameter to a dummy function: dummy(dataRow["STR1"]));.

    The DataTable's structure is as follows:

    The columns are named by their data types, so STR1 is a string, INT1 an integer, DATE1 the DateTime etc.

    The program first generates user-entered number of rows, then n-times does integer indexing test and string indexing test. The indexing test m-times gets each row in table and calls dummy function on each column of that row.

    There is a measuring - how long does it take to do the integer indexing test and the string indexing test.

    In the end, the application writes out how much did take integer and string indexing in total, and each one in average.

    Example:

    int indexing
    total: 42171,875 ms
    each: 421,71875 ms
    
    string indexing
    total: 149312,5 ms
    each: 1493,125 ms 
    

    Conclusion

    According to the tests on my machine (Intel Core2 Duo 1,86 GHz, 1 GB RAM) the integer indexing is approximately 3.5 - 4 times faster than the string indexing (results vary according to row count and repetition count).

    Clearly, integer indexing is faster, but when we take in account that both indexers take a very short time (about 1 µs) to access a column, the difference is noticeable only when applied on large amounts of data.

    i will translate this article.while datacolumn is not contained.so add datacolumn test.

    result:

    How many rows in testing DataTable? 100000
    How many times to process all rows in one loop? 100
    How many times to repeat int/string indexing? 10
    generating data...
    ------------------------ 0 ---------------------------
    1.int indexing:   23583.912ms
    2.string indexing:   39206.376 ms
    3.DataColumn indexing:   20148.9728ms
    ------------------------ 1 ---------------------------
    1.int indexing:   22842.8464ms
    2.string indexing:   38715.6704 ms
    3.DataColumn indexing:   20599.6208ms
    ------------------------ 2 ---------------------------
    1.int indexing:   23393.6384ms
    2.string indexing:   39586.9232 ms
    3.DataColumn indexing:   21080.312ms
    ------------------------ 3 ---------------------------
    1.int indexing:   21540.9744ms
    2.string indexing:   36011.7824 ms
    3.DataColumn indexing:   19918.6416ms
    ------------------------ 4 ---------------------------
    1.int indexing:   24665.4672ms
    2.string indexing:   36642.6896 ms
    3.DataColumn indexing:   18947.2448ms
    ------------------------ 5 ---------------------------
    1.int indexing:   21110.3552ms
    2.string indexing:   38275.0368 ms
    3.DataColumn indexing:   20479.448ms
    ------------------------ 6 ---------------------------
    1.int indexing:   22332.112ms
    2.string indexing:   39476.7648 ms
    3.DataColumn indexing:   20329.232ms
    ------------------------ 7 ---------------------------
    1.int indexing:   23964.4592ms
    2.string indexing:   38885.9152 ms
    3.DataColumn indexing:   21671.1616ms
    ------------------------ 8 ---------------------------
    1.int indexing:   23163.3072ms
    2.string indexing:   39877.3408 ms
    3.DataColumn indexing:   21140.3984ms
    ------------------------ 9 ---------------------------
    1.int indexing:   22862.8752ms
    2.string indexing:   39636.9952 ms
    3.DataColumn indexing:   21230.528ms
    #####################################################
    1# INT indexing
     total: 229459.9472 ms
     each: 22945.99472 ms
    2# STRING indexing
     total: 386315.4944 ms
     each: 38631.54944 ms
    3# DataColumn indexing
     total: 205545.56 ms
     each: 20554.556 ms

  • 相关阅读:
    Android漂亮的对话框项目sweet-alert-dialog
    JAVA并发编程4_线程同步之volatile关键字
    JAVA并发编程3_线程同步之synchronized关键字
    JAVA并发编程2_线程安全&内存模型
    JAVA并发编程1_多线程的实现方式
    JAVA 反射
    第五百三十九天 how can I 坚持
    第五百三十八天 how can I 坚持
    第五百三十七天 how can I 坚持
    第五百三十六天 how can I 坚持
  • 原文地址:https://www.cnblogs.com/AloneSword/p/2237537.html
Copyright © 2011-2022 走看看