SQL语句优化

ORDER BY，GROUP BY和DISTINCT优化

• ORDER BY的实现与优化

  • 优化Query语句中的ORDER BY的时候，尽可能利用已有的索引来避免实际的排序计算，可以很大幅度的提升ORDER BY操作的性能。
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Redis为什么快

原因主要是以下三点：

• 纯内存操作
• 单线程操作，避免了频繁的上下文切换
• 采用了非阻塞 I/O 多路复用机制

ingress四层转发配置参考
Exposing the probe service - IBM Documentation

Due to a limitation on the Kubernetes Ingress resource to expose TCP and UDP services, the following steps can be used to create a static configuration on the Kubernetes Ingress controller to make the probe service reachable externally. This limitation does not apply to probes that use HTTP protocols to receive data.

A Cluster Administrator needs to reconfigure the nginx-ingress-controller with a “static” configuration based on Configmaps and restart the ingress controller for the changes to take effect.

权限

分配select,insert权限

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grant select,insert on sakila.* to 'z1'@'localhost' identified by '123';

重定向

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ls /opt/abc >/dev/null 2>&1  # /dev/null位桶, 2>& 须连着
ls /opt/abc &>/dev/null  # &> 须连着
echo "error: ..." 2>/var/log/err.log
ls /opt/abc >./a.log 2>&1
ls /opt/abc 1>./a.log 2>&1