MongoDB 聚合报错-Mysql Tutorial-php.cn

Home

Database

Mysql Tutorial

MongoDB 聚合报错

WBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWB

Jun 07, 2016 pm 02:58 PM

database

聚合框架它是数据聚合的一个新框架，其概念类似于数据处理的管道。每个文档通过一个由多个节点组成的管道，每个节点有自己特殊的

聚合框架它是数据聚合的一个新框架，其概念类似于数据处理的管道。每个文档通过一个由多个节点组成的管道，每个节点有自己特殊的功能（分组、过滤等），文档经过管道处理后，最后输出相应的结果。

管道基本的功能有两个：

一是对文档进行“过滤”，也就是筛选出符合条件的文档;

二是对文档进行“变换”，也就是改变文档的输出形式。

errmsg:Exceeded memory limit for $group,but didn't allow external Sort.Pass allowDiskuse:true

错误详细信息：

我这次用的表的数据量是：大约有四百万数据

我要查的是：用户接受信息最多的前五个用户

写完分析语句，严格按照语法写的；

既然出现问题，我们来一下Debug（咱们码农有力量）

如果管道没有给出预期结果，就需要进行调试，调试时，可以先只指定第一个管道操作符，如果这样得到了预期结果，那就再指定第二个管道操作符，以上面的例子说，先试着$project 操作符进行聚合，如果这个操作符结果是有效的，就在添加 $group 操作符，

如果结果还是有效的，就再添加 $sort,最后再添加 $limit 操作符，这样就可以逐步定位到造成问题的操作符了。

逐步调试发现没问题不是语法的错误

麻蛋，，原因是聚合的结果必须要限制在16M以内操作，（mongodb支持的最大影响信息的大小），否则必须放在磁盘中做缓存（allowDiskUse=True）。

最后把要统计的数据给搞出来了，喜大普奔。

更多MongoDB相关内容可以看看以下的有用链接：

MongoDB 3.0 正式版发布下载

CentOS编译安装MongoDB

CentOS 编译安装 MongoDB与mongoDB的php扩展

CentOS 6 使用 yum 安装MongoDB及服务器端配置

Ubuntu 13.04下安装MongoDB2.4.3

MongoDB入门必读(概念与实战并重)

Ubunu 14.04下MongoDB的安装指南

《MongoDB 权威指南》(MongoDB: The Definitive Guide)英文文字版[PDF]

Nagios监控MongoDB分片集群服务实战

基于CentOS 6.5操作系统搭建MongoDB服务

MongoDB 的详细介绍：请点这里
MongoDB 的下载地址：请点这里

本文永久更新链接地址：

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

How do you handle database upgrades in MySQL?Apr 30, 2025 am 12:28 AM

The steps for upgrading MySQL database include: 1. Backup the database, 2. Stop the current MySQL service, 3. Install the new version of MySQL, 4. Start the new version of MySQL service, 5. Recover the database. Compatibility issues are required during the upgrade process, and advanced tools such as PerconaToolkit can be used for testing and optimization.

What are the different backup strategies you can use for MySQL?Apr 30, 2025 am 12:28 AM

MySQL backup policies include logical backup, physical backup, incremental backup, replication-based backup, and cloud backup. 1. Logical backup uses mysqldump to export database structure and data, which is suitable for small databases and version migrations. 2. Physical backups are fast and comprehensive by copying data files, but require database consistency. 3. Incremental backup uses binary logging to record changes, which is suitable for large databases. 4. Replication-based backup reduces the impact on the production system by backing up from the server. 5. Cloud backups such as AmazonRDS provide automation solutions, but costs and control need to be considered. When selecting a policy, database size, downtime tolerance, recovery time, and recovery point goals should be considered.

What is MySQL clustering?Apr 30, 2025 am 12:28 AM

MySQLclusteringenhancesdatabaserobustnessandscalabilitybydistributingdataacrossmultiplenodes.ItusestheNDBenginefordatareplicationandfaulttolerance,ensuringhighavailability.Setupinvolvesconfiguringmanagement,data,andSQLnodes,withcarefulmonitoringandpe

How do you optimize database schema design for performance in MySQL?Apr 30, 2025 am 12:27 AM

Optimizing database schema design in MySQL can improve performance through the following steps: 1. Index optimization: Create indexes on common query columns, balancing the overhead of query and inserting updates. 2. Table structure optimization: Reduce data redundancy through normalization or anti-normalization and improve access efficiency. 3. Data type selection: Use appropriate data types, such as INT instead of VARCHAR, to reduce storage space. 4. Partitioning and sub-table: For large data volumes, use partitioning and sub-table to disperse data to improve query and maintenance efficiency.

How can you optimize MySQL performance?Apr 30, 2025 am 12:26 AM

TooptimizeMySQLperformance,followthesesteps:1)Implementproperindexingtospeedupqueries,2)UseEXPLAINtoanalyzeandoptimizequeryperformance,3)Adjustserverconfigurationsettingslikeinnodb_buffer_pool_sizeandmax_connections,4)Usepartitioningforlargetablestoi

How to use MySQL functions for data processing and calculationApr 29, 2025 pm 04:21 PM

MySQL functions can be used for data processing and calculation. 1. Basic usage includes string processing, date calculation and mathematical operations. 2. Advanced usage involves combining multiple functions to implement complex operations. 3. Performance optimization requires avoiding the use of functions in the WHERE clause and using GROUPBY and temporary tables.

An efficient way to batch insert data in MySQLApr 29, 2025 pm 04:18 PM

Efficient methods for batch inserting data in MySQL include: 1. Using INSERTINTO...VALUES syntax, 2. Using LOADDATAINFILE command, 3. Using transaction processing, 4. Adjust batch size, 5. Disable indexing, 6. Using INSERTIGNORE or INSERT...ONDUPLICATEKEYUPDATE, these methods can significantly improve database operation efficiency.

Steps to add and delete fields to MySQL tablesApr 29, 2025 pm 04:15 PM

In MySQL, add fields using ALTERTABLEtable_nameADDCOLUMNnew_columnVARCHAR(255)AFTERexisting_column, delete fields using ALTERTABLEtable_nameDROPCOLUMNcolumn_to_drop. When adding fields, you need to specify a location to optimize query performance and data structure; before deleting fields, you need to confirm that the operation is irreversible; modifying table structure using online DDL, backup data, test environment, and low-load time periods is performance optimization and best practice.

See all articles