MapReduce执行计划及优化

Stella981
• 阅读 654

WordCount:

select rank, count(*) cnt from city group by rank;

MapReduce执行计划及优化

Map与Reduce 都是一个JVM进程，可以理解为都是一个独立的应用程序

MapReduce 框架的作用就是自动帮你把map端的输出，经过shuffle后变为reduce端的输入

方法：

public void map(Text value,Context context);

public void reduce(Text key, Iterable values, Context context)

Shuffle:

MapReduce执行计划及优化

MapReduce执行计划及优化

MapReduce执行计划及优化

MapReduce执行计划及优化

 MapReduce执行计划及优化

MapReduce执行计划及优化

common join

MapReduce执行计划及优化

Map Join

 MapReduce执行计划及优化

MapReduce执行计划及优化

MapReduce执行计划及优化

MapReduce

word count：

### 执行计划
explain select
a.name,a.entity_id
from
tangbao.shop a
join
ods_order_org.instancedetail b
on a.entity_id=b.entity_id
where b.pt='20180501';

+--------------------------------------------------------------------------------------------------------------------+--+
| Explain |
+--------------------------------------------------------------------------------------------------------------------+--+
| STAGE DEPENDENCIES: |
| Stage-4 is a root stage |
| Stage-3 depends on stages: Stage-4 |
| Stage-0 depends on stages: Stage-3 |
| |
| STAGE PLANS: |
| Stage: Stage-4 |
| Map Reduce Local Work |
| Alias -> Map Local Tables: |
| a |
| Fetch Operator |
| limit: -1 |
| Alias -> Map Local Operator Tree: |
| a |
| TableScan |
| alias: a |
| filterExpr: entity_id is not null (type: boolean) |
| Statistics: Num rows: 1000 Data size: 235780 Basic stats: COMPLETE Column stats: NONE |
| Filter Operator |
| predicate: entity_id is not null (type: boolean) |
| Statistics: Num rows: 500 Data size: 117890 Basic stats: COMPLETE Column stats: NONE |
| HashTable Sink Operator |
| keys: |
| 0 entity_id (type: string) |
| 1 entity_id (type: string) |
| |
| Stage: Stage-3 |
| Map Reduce |
| Map Operator Tree: |
| TableScan |
| alias: b |
| filterExpr: (entity_id is not null and (pt = '20180501')) (type: boolean) |
| Statistics: Num rows: 164539402 Data size: 16453940224 Basic stats: COMPLETE Column stats: NONE |
| Filter Operator |
| predicate: entity_id is not null (type: boolean) |
| Statistics: Num rows: 82269701 Data size: 8226970112 Basic stats: COMPLETE Column stats: NONE |
| Map Join Operator |
| condition map: |
| Inner Join 0 to 1 |
| keys: |
| 0 entity_id (type: string) |
| 1 entity_id (type: string) |
| outputColumnNames: _col9, _col38 |
| Statistics: Num rows: 90496673 Data size: 9049667319 Basic stats: COMPLETE Column stats: NONE |
| Select Operator |
| expressions: _col9 (type: string), _col38 (type: string) |
| outputColumnNames: _col0, _col1 |
| Statistics: Num rows: 90496673 Data size: 9049667319 Basic stats: COMPLETE Column stats: NONE |
| File Output Operator |
| compressed: false |
| Statistics: Num rows: 90496673 Data size: 9049667319 Basic stats: COMPLETE Column stats: NONE |
| table: |
| input format: org.apache.hadoop.mapred.TextInputFormat |
| output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat |
| serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe |
| Local Work: |
| Map Reduce Local Work |
| |
| Stage: Stage-0 |
| Fetch Operator |
| limit: -1 |
| Processor Tree: |
| ListSink |
| |
+--------------------------------------------------------------------------------------------------------------------+--+

explain select
a.name,a.entity_id
from
tangbao.shop a
left join
ods_order_org.instancedetail b
on a.entity_id=b.entity_id
where b.pt='20180501';

+--------------------------------------------------------------------------------------------------------------------+--+
| Explain |
+--------------------------------------------------------------------------------------------------------------------+--+
| STAGE DEPENDENCIES: |
| Stage-4 is a root stage , consists of Stage-1 |
| Stage-1 |
| Stage-0 depends on stages: Stage-1 |
| |
| STAGE PLANS: |
| Stage: Stage-4 |
| Conditional Operator |
| |
| Stage: Stage-1 |
| Map Reduce |
| Map Operator Tree: |
| TableScan |
| alias: a |
| Statistics: Num rows: 1000 Data size: 235780 Basic stats: COMPLETE Column stats: NONE |
| Reduce Output Operator |
| key expressions: entity_id (type: string) |
| sort order: + |
| Map-reduce partition columns: entity_id (type: string) |
| Statistics: Num rows: 1000 Data size: 235780 Basic stats: COMPLETE Column stats: NONE |
| value expressions: name (type: string) |
| TableScan |
| alias: b |
| Statistics: Num rows: 4821977155 Data size: 284496652145 Basic stats: PARTIAL Column stats: PARTIAL |
| Reduce Output Operator |
| key expressions: entity_id (type: string) |
| sort order: + |
| Map-reduce partition columns: entity_id (type: string) |
| Statistics: Num rows: 4821977155 Data size: 284496652145 Basic stats: PARTIAL Column stats: PARTIAL |
| value expressions: pt (type: string) |
| Reduce Operator Tree: |
| Join Operator |
| condition map: |
| Left Outer Join0 to 1 |
| keys: |
| 0 entity_id (type: string) |
| 1 entity_id (type: string) |
| outputColumnNames: _col9, _col38, _col117 |
| Statistics: Num rows: 5304174985 Data size: 312946324142 Basic stats: COMPLETE Column stats: NONE |
| Filter Operator |
| predicate: (_col117 = '20180501') (type: boolean) |
| Statistics: Num rows: 2652087492 Data size: 156473162041 Basic stats: COMPLETE Column stats: NONE |
| Select Operator |
| expressions: _col9 (type: string), _col38 (type: string) |
| outputColumnNames: _col0, _col1 |
| Statistics: Num rows: 2652087492 Data size: 156473162041 Basic stats: COMPLETE Column stats: NONE |
| File Output Operator |
| compressed: false |
| Statistics: Num rows: 2652087492 Data size: 156473162041 Basic stats: COMPLETE Column stats: NONE |
| table: |
| input format: org.apache.hadoop.mapred.TextInputFormat |
| output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat |
| serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe |
| |
| Stage: Stage-0 |
| Fetch Operator |
| limit: -1 |
| Processor Tree: |
| ListSink |
| |
+--------------------------------------------------------------------------------------------------------------------+--+

explain select
avg(fee),max(fee)
from
olap_pc_history_report.tmp_tp_p_join
group by
entity_id,curr_date,kindpay_id;

+-------------------------------------------------------------------------------------------------------------------------------+--+
| Explain |
+-------------------------------------------------------------------------------------------------------------------------------+--+
| STAGE DEPENDENCIES: |
| Stage-1 is a root stage |
| Stage-0 depends on stages: Stage-1 |
| |
| STAGE PLANS: |
| Stage: Stage-1 |
| Map Reduce |
| Map Operator Tree: |
| TableScan |
| alias: tmp_tp_p_join |
| Statistics: Num rows: 155435158 Data size: 40145589195 Basic stats: COMPLETE Column stats: NONE |
| Select Operator |
| expressions: entity_id (type: string), curr_date (type: string), kindpay_id (type: string), fee (type: double) |
| outputColumnNames: entity_id, curr_date, kindpay_id, fee |
| Statistics: Num rows: 155435158 Data size: 40145589195 Basic stats: COMPLETE Column stats: NONE |
| Group By Operator |
| aggregations: avg(fee), max(fee) |
| keys: entity_id (type: string), curr_date (type: string), kindpay_id (type: string) |
| mode: hash |
| outputColumnNames: _col0, _col1, _col2, _col3, _col4 |
| Statistics: Num rows: 155435158 Data size: 40145589195 Basic stats: COMPLETE Column stats: NONE |
| Reduce Output Operator |
| key expressions: _col0 (type: string), _col1 (type: string), _col2 (type: string) |
| sort order: +++ |
| Map-reduce partition columns: _col0 (type: string), _col1 (type: string), _col2 (type: string) |
| Statistics: Num rows: 155435158 Data size: 40145589195 Basic stats: COMPLETE Column stats: NONE |
| value expressions: _col3 (type: structcount:bigint,sum:double,input:double), _col4 (type: double) |
| Reduce Operator Tree: |
| Group By Operator |
| aggregations: avg(VALUE._col0), max(VALUE._col1) |
| keys: KEY._col0 (type: string), KEY._col1 (type: string), KEY._col2 (type: string) |
| mode: mergepartial |
| outputColumnNames: _col0, _col1, _col2, _col3, _col4 |
| Statistics: Num rows: 77717579 Data size: 20072794597 Basic stats: COMPLETE Column stats: NONE |
| Select Operator |
| expressions: _col3 (type: double), _col4 (type: double) |
| outputColumnNames: _col0, _col1 |
| Statistics: Num rows: 77717579 Data size: 20072794597 Basic stats: COMPLETE Column stats: NONE |
| File Output Operator |
| compressed: false |
| Statistics: Num rows: 77717579 Data size: 20072794597 Basic stats: COMPLETE Column stats: NONE |
| table: |
| input format: org.apache.hadoop.mapred.TextInputFormat |
| output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat |
| serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe |
| |
| Stage: Stage-0 |
| Fetch Operator |
| limit: -1 |
| Processor Tree: |
| ListSink |
| |
+-------------------------------------------------------------------------------------------------------------------------------+--+

set hive.map.aggr=false;

set hive.groupby.skewindata=true;

explain select
avg(fee),max(fee)
from
olap_pc_history_report.tmp_tp_p_join
group by
entity_id,curr_date,kindpay_id;

+-------------------------------------------------------------------------------------------------------------------------------+--+
| Explain |
+-------------------------------------------------------------------------------------------------------------------------------+--+
| STAGE DEPENDENCIES: |
| Stage-1 is a root stage |
| Stage-2 depends on stages: Stage-1 |
| Stage-0 depends on stages: Stage-2 |
| |
| STAGE PLANS: |
| Stage: Stage-1 |
| Map Reduce |
| Map Operator Tree: |
| TableScan |
| alias: tmp_tp_p_join |
| Statistics: Num rows: 155435158 Data size: 40145589195 Basic stats: COMPLETE Column stats: NONE |
| Select Operator |
| expressions: curr_date (type: string), entity_id (type: string), fee (type: double), kindpay_id (type: string) |
| outputColumnNames: curr_date, entity_id, fee, kindpay_id |
| Statistics: Num rows: 155435158 Data size: 40145589195 Basic stats: COMPLETE Column stats: NONE |
| Reduce Output Operator |
| key expressions: entity_id (type: string), curr_date (type: string), kindpay_id (type: string) |
| sort order: +++ |
| Map-reduce partition columns: rand() (type: double) |
| Statistics: Num rows: 155435158 Data size: 40145589195 Basic stats: COMPLETE Column stats: NONE |
| value expressions: fee (type: double) |
| Reduce Operator Tree: |
| Group By Operator |
| aggregations: avg(VALUE._col0), max(VALUE._col0) |
| keys: KEY._col0 (type: string), KEY._col1 (type: string), KEY._col2 (type: string) |
| mode: partial1 |
| outputColumnNames: _col0, _col1, _col2, _col3, _col4 |
| Statistics: Num rows: 155435158 Data size: 40145589195 Basic stats: COMPLETE Column stats: NONE |
| File Output Operator |
| compressed: true |
| table: |
| input format: org.apache.hadoop.mapred.SequenceFileInputFormat |
| output format: org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat |
| serde: org.apache.hadoop.hive.serde2.lazybinary.LazyBinarySerDe |
| |
| Stage: Stage-2 |
| Map Reduce |
| Map Operator Tree: |
| TableScan |
| Reduce Output Operator |
| key expressions: _col0 (type: string), _col1 (type: string), _col2 (type: string) |
| sort order: +++ |
| Map-reduce partition columns: _col0 (type: string), _col1 (type: string), _col2 (type: string) |
| Statistics: Num rows: 155435158 Data size: 40145589195 Basic stats: COMPLETE Column stats: NONE |
| value expressions: _col3 (type: structcount:bigint,sum:double,input:double), _col4 (type: double) |
| Reduce Operator Tree: |
| Group By Operator |
| aggregations: avg(VALUE._col0), max(VALUE._col1) |
| keys: KEY._col0 (type: string), KEY._col1 (type: string), KEY._col2 (type: string) |
| mode: final |
| outputColumnNames: _col0, _col1, _col2, _col3, _col4 |
| Statistics: Num rows: 77717579 Data size: 20072794597 Basic stats: COMPLETE Column stats: NONE |
| Select Operator |
| expressions: _col3 (type: double), _col4 (type: double) |
| outputColumnNames: _col0, _col1 |
| Statistics: Num rows: 77717579 Data size: 20072794597 Basic stats: COMPLETE Column stats: NONE |
| File Output Operator |
| compressed: false |
| Statistics: Num rows: 77717579 Data size: 20072794597 Basic stats: COMPLETE Column stats: NONE |
| table: |
| input format: org.apache.hadoop.mapred.TextInputFormat |
| output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat |
| serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe |
| |
| Stage: Stage-0 |
| Fetch Operator |
| limit: -1 |
| Processor Tree: |
| ListSink |
| |
+-------------------------------------------------------------------------------------------------------------------------------+--+

set hive.optimize.skewjoin=true;

explain select
a.name,a.entity_id
from
ods_shop_org.shop a
join
ods_order_org.instancedetail b
on a.entity_id=b.entity_id
where b.pt='20180501';

+------------------------------------------------------------------------------------------------------------------+--+
| Explain |
+------------------------------------------------------------------------------------------------------------------+--+
| STAGE DEPENDENCIES: |
| Stage-7 is a root stage , consists of Stage-1 |
| Stage-1 |
| Stage-4 depends on stages: Stage-1 , consists of Stage-8 |
| Stage-8 |
| Stage-3 depends on stages: Stage-8 |
| Stage-0 depends on stages: Stage-3 |
| |
| STAGE PLANS: |
| Stage: Stage-7 |
| Conditional Operator |
| |
| Stage: Stage-1 |
| Map Reduce |
| Map Operator Tree: |
| TableScan |
| alias: a |
| filterExpr: entity_id is not null (type: boolean) |
| Statistics: Num rows: 443697 Data size: 88739406 Basic stats: COMPLETE Column stats: NONE |
| Filter Operator |
| predicate: entity_id is not null (type: boolean) |
| Statistics: Num rows: 221849 Data size: 44369803 Basic stats: COMPLETE Column stats: NONE |
| Reduce Output Operator |
| key expressions: entity_id (type: string) |
| sort order: + |
| Map-reduce partition columns: entity_id (type: string) |
| Statistics: Num rows: 221849 Data size: 44369803 Basic stats: COMPLETE Column stats: NONE |
| value expressions: name (type: string) |
| TableScan |
| alias: b |
| filterExpr: (entity_id is not null and (pt = '20180501')) (type: boolean) |
| Statistics: Num rows: 164539402 Data size: 16453940224 Basic stats: COMPLETE Column stats: NONE |
| Filter Operator |
| predicate: entity_id is not null (type: boolean) |
| Statistics: Num rows: 82269701 Data size: 8226970112 Basic stats: COMPLETE Column stats: NONE |
| Reduce Output Operator |
| key expressions: entity_id (type: string) |
| sort order: + |
| Map-reduce partition columns: entity_id (type: string) |
| Statistics: Num rows: 82269701 Data size: 8226970112 Basic stats: COMPLETE Column stats: NONE |
| Reduce Operator Tree: |
| Join Operator |
| condition map: |
| Inner Join 0 to 1 |
| handleSkewJoin: true |
| keys: |
| 0 entity_id (type: string) |
| 1 entity_id (type: string) |
| outputColumnNames: _col9, _col38 |
| Statistics: Num rows: 90496673 Data size: 9049667319 Basic stats: COMPLETE Column stats: NONE |
| Select Operator |
| expressions: _col9 (type: string), _col38 (type: string) |
| outputColumnNames: _col0, _col1 |
| Statistics: Num rows: 90496673 Data size: 9049667319 Basic stats: COMPLETE Column stats: NONE |
| File Output Operator |
| compressed: false |
| Statistics: Num rows: 90496673 Data size: 9049667319 Basic stats: COMPLETE Column stats: NONE |
| table: |
| input format: org.apache.hadoop.mapred.TextInputFormat |
| output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat |
| serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe |
| |
| Stage: Stage-4 |
| Conditional Operator |
| |
| Stage: Stage-8 |
| Map Reduce Local Work |
| Alias -> Map Local Tables: |
| 1 |
| Fetch Operator |
| limit: -1 |
| Alias -> Map Local Operator Tree: |
| 1 |
| TableScan |
| HashTable Sink Operator |
| keys: |
| 0 reducesinkkey0 (type: string) |
| 1 reducesinkkey0 (type: string) |
| |
| Stage: Stage-3 |
| Map Reduce |
| Map Operator Tree: |
| TableScan |
| Map Join Operator |
| condition map: |
| Inner Join 0 to 1 |
| keys: |
| 0 reducesinkkey0 (type: string) |
| 1 reducesinkkey0 (type: string) |
| outputColumnNames: _col9, _col38 |
| Select Operator |
| expressions: _col9 (type: string), _col38 (type: string) |
| outputColumnNames: _col0, _col1 |
| Statistics: Num rows: 90496673 Data size: 9049667319 Basic stats: COMPLETE Column stats: NONE |
| File Output Operator |
| compressed: false |
| Statistics: Num rows: 90496673 Data size: 9049667319 Basic stats: COMPLETE Column stats: NONE |
| table: |
| input format: org.apache.hadoop.mapred.TextInputFormat |
| output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat |
+------------------------------------------------------------------------------------------------------------------+--+
| Explain |
+------------------------------------------------------------------------------------------------------------------+--+
| serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe |
| Local Work: |
| Map Reduce Local Work |
| |
| Stage: Stage-0 |
| Fetch Operator |
| limit: -1 |
| Processor Tree: |
| ListSink |
| |
+------------------------------------------------------------------------------------------------------------------+--+

explain select
a.name,a.entity_id
from
ods_order_org.instancedetail a
left semi join
tangbao.shop b
on a.entity_id=b.entity_id
where a.pt='20180501';

+--------------------------------------------------------------------------------------------------------------------+--+
| Explain |
+--------------------------------------------------------------------------------------------------------------------+--+
| STAGE DEPENDENCIES: |
| Stage-4 is a root stage |
| Stage-3 depends on stages: Stage-4 |
| Stage-0 depends on stages: Stage-3 |
| |
| STAGE PLANS: |
| Stage: Stage-4 |
| Map Reduce Local Work |
| Alias -> Map Local Tables: |
| b |
| Fetch Operator |
| limit: -1 |
| Alias -> Map Local Operator Tree: |
| b |
| TableScan |
| alias: b |
| filterExpr: entity_id is not null (type: boolean) |
| Statistics: Num rows: 1000 Data size: 235780 Basic stats: COMPLETE Column stats: NONE |
| Filter Operator |
| predicate: entity_id is not null (type: boolean) |
| Statistics: Num rows: 500 Data size: 117890 Basic stats: COMPLETE Column stats: NONE |
| Select Operator |
| expressions: entity_id (type: string) |
| outputColumnNames: entity_id |
| Statistics: Num rows: 500 Data size: 117890 Basic stats: COMPLETE Column stats: NONE |
| Group By Operator |
| keys: entity_id (type: string) |
| mode: hash |
| outputColumnNames: _col0 |
| Statistics: Num rows: 500 Data size: 117890 Basic stats: COMPLETE Column stats: NONE |
| HashTable Sink Operator |
| keys: |
| 0 entity_id (type: string) |
| 1 _col0 (type: string) |
| |
| Stage: Stage-3 |
| Map Reduce |
| Map Operator Tree: |
| TableScan |
| alias: a |
| filterExpr: (entity_id is not null and (pt = '20180501')) (type: boolean) |
| Statistics: Num rows: 82269701 Data size: 16453940224 Basic stats: COMPLETE Column stats: NONE |
| Filter Operator |
| predicate: entity_id is not null (type: boolean) |
| Statistics: Num rows: 41134851 Data size: 8226970212 Basic stats: COMPLETE Column stats: NONE |
| Map Join Operator |
| condition map: |
| Left Semi Join 0 to 1 |
| keys: |
| 0 entity_id (type: string) |
| 1 _col0 (type: string) |
| outputColumnNames: _col9, _col29 |
| Statistics: Num rows: 45248337 Data size: 9049667429 Basic stats: COMPLETE Column stats: NONE |
| Select Operator |
| expressions: _col9 (type: string), _col29 (type: string) |
| outputColumnNames: _col0, _col1 |
| Statistics: Num rows: 45248337 Data size: 9049667429 Basic stats: COMPLETE Column stats: NONE |
| File Output Operator |
| compressed: false |
| Statistics: Num rows: 45248337 Data size: 9049667429 Basic stats: COMPLETE Column stats: NONE |
| table: |
| input format: org.apache.hadoop.mapred.TextInputFormat |
| output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat |
| serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe |
| Local Work: |
| Map Reduce Local Work |
| |
| Stage: Stage-0 |
| Fetch Operator |
| limit: -1 |
| Processor Tree: |
| ListSink |
| |
+--------------------------------------------------------------------------------------------------------------------+--+

stringhivestagenummapreducehadoopkeys前端前端
点赞
收藏
评论区
推荐文章
blmius blmius
•
3年前
MySQL:[Err] 1292 - Incorrect datetime value: ‘0000-00-00 00:00:00‘ for column ‘CREATE_TIME‘ at row 1
文章目录问题用navicat导入数据时，报错：原因这是因为当前的MySQL不支持datetime为0的情况。解决修改sql\mode:sql\mode:SQLMode定义了MySQL应支持的SQL语法、数据校验等，这样可以更容易地在不同的环境中使用MySQL。全局s
4133
0
0
Easter79 Easter79
•
3年前
swap空间的增减方法
（1）增大swap空间去激活swap交换区：swapoff v /dev/vg00/lvswap扩展交换lv：lvextend L 10G /dev/vg00/lvswap重新生成swap交换区：mkswap /dev/vg00/lvswap激活新生成的交换区：swapon v /dev/vg00/lvswap
1268
0
0
helloworld_34035044 helloworld_34035044
•
2年前
皕杰报表之UUID
​在我们用皕杰报表工具设计填报报表时，如何在新增行里自动增加id呢？能新增整数排序id吗？目前可以在新增行里自动增加id，但只能用uuid函数增加UUID编码，不能新增整数排序id。uuid函数说明：获取一个UUID，可以在填报表中用来创建数据ID语法：uuid()或uuid(sep)参数说明：sep布尔值，生成的uuid中是否包含分隔符''，缺省为
1149
0
0
待兔 待兔
•
4个月前
手写Java HashMap源码
HashMap的使用教程HashMap的使用教程HashMap的使用教程HashMap的使用教程HashMap的使用教程22
1072
0
0
Jacquelyn38 Jacquelyn38
•
3年前
2020年前端实用代码段，为你的工作保驾护航
有空的时候，自己总结了几个代码段，在开发中也经常使用，谢谢。1、使用解构获取json数据let jsonData  id: 1,status: "OK",data: 'a', 'b';let  id, status, data: number   jsonData;console.log(id, status, number )
2389
0
0
Wesley13 Wesley13
•
3年前
Java获得今日零时零分零秒的时间（Date型）
publicDatezeroTime()throwsParseException{    DatetimenewDate();    SimpleDateFormatsimpnewSimpleDateFormat("yyyyMMdd00:00:00");    SimpleDateFormatsimp2newS
1259
0
0
Wesley13 Wesley13
•
3年前
mysql设置时区
mysql设置时区mysql\_query("SETtime\_zone'8:00'")ordie('时区设置失败，请联系管理员！');中国在东8区所以加8方法二：selectcount(user\_id)asdevice,CONVERT\_TZ(FROM\_UNIXTIME(reg\_time),'08:00','0
1319
0
0
Wesley13 Wesley13
•
3年前
00：Java简单了解
浅谈Java之概述Java是SUN(StanfordUniversityNetwork)，斯坦福大学网络公司)1995年推出的一门高级编程语言。Java是一种面向Internet的编程语言。随着Java技术在web方面的不断成熟，已经成为Web应用程序的首选开发语言。Java是简单易学，完全面向对象，安全可靠，与平台无关的编程语言。
1257
0
0
Stella981 Stella981
•
3年前
Django中Admin中的一些参数配置
设置在列表中显示的字段，id为django模型默认的主键list_display('id','name','sex','profession','email','qq','phone','status','create_time')设置在列表可编辑字段list_editable
1175
0
0
Wesley13 Wesley13
•
3年前
MySQL部分从库上面因为大量的临时表tmp_table造成慢查询
背景描述Time:20190124T00:08:14.70572408:00User@Host:@Id:Schema:sentrymetaLast_errno:0Killed:0Query_time:0.315758Lock_
1523
0
0
Python进阶者 Python进阶者
•
10个月前
Excel中这日期老是出来00：00：00，怎么用Pandas把这个去除
大家好，我是皮皮。一、前言前几天在Python白银交流群【上海新年人】问了一个Pandas数据筛选的问题。问题如下：这日期老是出来00：00：00，怎么把这个去除。二、实现过程后来【论草莓如何成为冻干莓】给了一个思路和代码如下：pd.toexcel之前把这
510
0
0
Stella981
Stella981
Lv1
接天莲叶无穷碧，映日荷花别样红。
文章
1.7w
粉丝
42
获赞
28
热门文章
OpenVPN下载、安装、配置及使用详解
GitHub神器，一个可以白嫖全网无损音乐的神器
OpenWrt 路由器过滤广告的N种方法
Python—执行系统命令的四种方法（os.system、os.popen、commands、subprocess）
SS端加密以及obfs混淆