Sorry, there is a mistake in the question. An explanation has been made in the answer the scenario is that there is a script task, that starts multiple processes these processes operate on multiple tables at the same time (only insert, for these t...
under the premise that the created_at column is indexed. the data volume of the table is tens of millions of levels. explain shows that the number of rows scanned is 2 million select count (*) from users where created_at < 2018-08-28 0000lv 00l...
I recently did a raffle everyone can only draw once I want to insert a record for each lucky draw request, and then read the first record for comparison to determine whether he is drawing the lottery for the first time, delete the useless record if n...
Note that our current isolation level is read uncommitted, that is, the lowest isolation level. Dirty reading occurs at this level, and A transaction modifies a row of data, but in the case of uncommitted, this row of data is read by a behavior other th...
What is the automatic locking strategy for InnoDB and Myisam in RT,MySQL, respectively? When do we need to explicitly add read-write locks? ...
what is the locking mechanism of mysql transaction serialization isolation level Open transactions in both An and B clients, if 1 if A transaction deletes a record (), B transaction cannot read deleted and uncommitted transactions in A transaction not...
as shown in the question, is there only data or indexes on the hard disk and in a data page in innodb_pool_buffer? is it impossible for a data page to have both data and indexes? ...
such as the title. see that MySQL generates a tree for the primary key, and the leaf node holds the row data corresponding to the primary key. The secondary index leaf node holds the value of the primary key. excuse me: does the leaf node of th...
I use only one primary key on the innodb, table and a clustered index (the default is a clustered index). In my query statement, the where condition is this primary key, but the query column is arbitrary. I found that the extra of the execution plan is ...
scenario: two pages are independent of each other, and the JavaScript code in them executes independently of each other. The js of these two pages share a common variable shareArray array in localStorage Action 1, page A stores a piece of data in sha...
for example, is calling their encapsulated method the same as before? Encapsulate the method, and then write their encapsulated method in the method? what would a natively written method look like? ...
there is a file that compiles errors when using Object.keys (item), dynamic updates: Error in Cannot find module @babel runtime core-js object keys Error: Cannot find module @babel runtime core-js object keys but I have already installed runti...
I wrote the login acquisition user information in app.js. After success, I assigned the content to the onLoad of globalData.xxxxx,Page and then assigned the globalData.xxxxx to data.xxxxx. I found that the assignment was not so bad. Many materials say...
use the tab page of element ui to switch the sidebar. The code is as follows: : : I think it should be a grammar problem, but I don t know what s wrong with it. Can I have a look at it? ...