rules

how to emulate “insert ignore” and “on duplicate key update” (sql merge) with postgresql?

随声附和 提交于 2019-11-26 14:10:30
Some SQL servers have a feature where INSERT is skipped if it would violate a primary/unique key constraint. For instance, MySQL has INSERT IGNORE . What's the best way to emulate INSERT IGNORE and ON DUPLICATE KEY UPDATE with PostgreSQL? Magnus Hagander Try to do an UPDATE. If it doesn't modify any row that means it didn't exist, so do an insert. Obviously, you do this inside a transaction. You can of course wrap this in a function if you don't want to put the extra code on the client side. You also need a loop for the very rare race condition in that thinking. There's an example of this in

Are there any rules for OOP?

故事扮演 提交于 2019-11-26 10:14:02
问题 Recently I heard that there are 9 rules for OOP(Java). I know only four as Abstraction, Polymorphism, Inheritance and Encapsulation. Are there any more rules for OOP? 回答1: Seems like what you're looking for are the Principles of Object-Oriented Design. Summarized from Agile Software Development Principles, Patterns, and Practices. These principles are the hard-won product of decades of experience in software engineering. They are not the product of a single mind, but they represent the

How do browser cookie domains work?

蓝咒 提交于 2019-11-25 22:45:35
问题 Due to weird domain/subdomain cookie issues that I\'m getting, I\'d like to know how browsers handle cookies. If they do it in different ways, it would also be nice to know the differences. In other words - when a browser receives a cookie, that cookie MAY have a domain and a path attached to it. Or not, in which case the browser probably substitutes some defaults for them. Question 1: what are they? Later, when the browser is about to make a request, it checks its cookies and filters out the

RHEL 6.8 + Oracle 11g RAC multipath 配置

一世执手 提交于 2019-11-25 20:22:33
Oracle 11g RAC + RHEL 6.8 多路径配置如下,仅供参考。 <roidb1:+ASM1:/etc/udev/rules.d>$ls 12-dm-permissions.rules 60-pcmcia.rules 90-alsa.rules 98-kexec.rules 55-usm.rules 60-raw.rules 90-hal.rules 99-fuse.rules 60-fprint-autosuspend.rules 70-persistent-net.rules 97-bluetooth-serial.rules 由于配置文件中使用了别名,所以这里也需要使用别名 <roidb1:+ASM1:/etc/udev/rules.d>$more 12-dm-permissions.rules ENV{DM_NAME}=="data*", OWNER:="grid", GROUP:="asmadmin", MODE:="660" ENV{DM_NAME}=="vot*", OWNER:="grid", GROUP:="asmadmin", MODE:="660" <roidb1:+ASM1:/etc/udev/rules.d>$ <roidb1:+ASM1:/etc/udev/rules.d>$more /etc/multipath.conf #