首先本人是在linux下完成的如上配置,windows下没有试过,在作者的文档中说,在linux下可以用setup.sh进行安装操作,本人尝试许久
pgwatch详细安装和测试
安装时一直出错,,但是网上又搜不到任何文档决定自己写一篇详细的安装文档。
1.下载pgwatch,我这里我用的版本是1.0,下载地址如下:
wget
2.解压并打开README文件,查看安装所需,这里的安装就不详细讲解
tar -zxvf pgwatch-1.0.tar.gz
vim README
------------------------------------------------------------
Requirements:
-------------
You will need a handful of components to make this work:
- Apache (webserver) # apache用作web服务器
- PHP 5 (scripting language) # php5版本
- pgsql extension for PHP (see ) # postgresql的php客户端
- PostgreSQL 9 (to store the data we collect) # postgresql支持最低版本为9
- dblink (contribution module for PostgreSQL 9) # 需要安装dblink(并非默认安装)
- For now we only support PostgreSQL >= 9.0 databases.
Older systems cannot be monitored, however, we will
add support for future database releases.
3.首先把你刚刚解压的文件夹,放在apache的目录下。(这里要注意的是要设置好文件夹的权限)
4.检测是否安装postgresql的php客户端,如果没有可以直接用yum安装:
yum installphp-pgsql.i386(我的是32位,同学们可以自己用yum search搜索下,之后重启apache)
检测是否安装脚本(php):
// Connecting, selecting database
$dbconn = pg_connect("host=192.168.30.200 port=5434 dbname=lengzijian user=postgres password=123456")
or die('Could not connect: ' . pg_last_error());
// Performing SQL query
$query = 'SELECT * FROM t_user limit 10';
$result = pg_query($query) or die('Query failed: ' . pg_last_error());
// Printing results in HTML
echo "
$col_value | \n";
// Free resultset
pg_free_result($result);
// Closing connection
pg_close($dbconn);
?>

InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB

MySQL/InnoDB supports four transaction isolation levels: ReadUncommitted, ReadCommitted, RepeatableRead and Serializable. 1.ReadUncommitted allows reading of uncommitted data, which may cause dirty reading. 2. ReadCommitted avoids dirty reading, but non-repeatable reading may occur. 3.RepeatableRead is the default level, avoiding dirty reading and non-repeatable reading, but phantom reading may occur. 4. Serializable avoids all concurrency problems but reduces concurrency. Choosing the appropriate isolation level requires balancing data consistency and performance requirements.

MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.

MySQL index cardinality has a significant impact on query performance: 1. High cardinality index can more effectively narrow the data range and improve query efficiency; 2. Low cardinality index may lead to full table scanning and reduce query performance; 3. In joint index, high cardinality sequences should be placed in front to optimize query.

The MySQL learning path includes basic knowledge, core concepts, usage examples, and optimization techniques. 1) Understand basic concepts such as tables, rows, columns, and SQL queries. 2) Learn the definition, working principles and advantages of MySQL. 3) Master basic CRUD operations and advanced usage, such as indexes and stored procedures. 4) Familiar with common error debugging and performance optimization suggestions, such as rational use of indexes and optimization queries. Through these steps, you will have a full grasp of the use and optimization of MySQL.

MySQL's real-world applications include basic database design and complex query optimization. 1) Basic usage: used to store and manage user data, such as inserting, querying, updating and deleting user information. 2) Advanced usage: Handle complex business logic, such as order and inventory management of e-commerce platforms. 3) Performance optimization: Improve performance by rationally using indexes, partition tables and query caches.


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