[MongoDB] The Regex Expression query of MongoDB, mongodbregex

[MongoDB] The Regex Expression query of MongoDB, mongodbregex

In the past two blogs, the topic mainly focus on the high query operation of mongodb. in this blog, we simply study the regex expression in the mongdb. mongoDB also support the regex query. for example

The expression is also able to combination with other expression.

Notes:/^ a/;/^. * //;/^. * $/have the same result, however the later two have less efficiency than the first one. because the later will scan all the things, but the first only scan the first character.

The item:

-I: ignore the upper or low case

-M: the begin '^' and end' $ 'do work on every new line;

-X: ignore the blank character

-S: since 1.9 version, adding it cocould make '. 'reprent all the character.

For example:

/A. * B/does not matches "apple \ nbanana" but/a. * B/s does.

The expressions of or the expression

It is determined based on the central word following it. Expression is a count of nouns.

[MongoDB] how to stop a MongoDB Server

If the server runs on the terminal as a foreground process, press Ctrl-C. Otherwise, use the kill command to send a signal. If the PID of mongod is 10014, you can use kill-2 10014 (SIGINT) or kill 10014 (SIGTERM ).
When mongod receives the SIGINT or SIGTERM, it exits. That is to say, it will wait until the current operation or file pre-distribution is completed (it takes some time), close all open connections, refresh the cached data to the disk, and finally stop. Do not send SIGKILL (kill-9) to a running MongoDB instance ). This will cause the database to be shut down directly, and the previous steps will be ignored, which will damage the data file.