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Can select Block insert?
Answering your question – yes, you can block any insert during read and this is called “Pessimistic Concurrency”.
How do I lock a record in MySQL?
A record lock is a lock on an index record. For example, SELECT c1 FROM t WHERE c1 = 10 FOR UPDATE; prevents any other transaction from inserting, updating, or deleting rows where the value of t. c1 is 10 . Record locks always lock index records, even if a table is defined with no indexes.
Is MySQL insert thread safe?
The client library is thread-safe per connection. Unless you are using the asynchronous C API functions mentioned previously, multiple threads cannot send a query to the MySQL server at the same time on the same connection.
Are SQL databases thread safe?
The use of DDL SQL statements might not be threadsafe. Data manipulation language (DML) statements are threadsafe. Using the server mode for SQL is the preferred method for accessing databases with multithreaded applications.
How to improve insert into select in MySQL?
You can change READ-UNCOMMITTED to READ-COMMITTED which is a better isolation level. Everyone using Innodb tables probably got use to the fact Innodb tables perform non locking reads, meaning unless you use some modifiers such as LOCK IN SHARE MODE or FOR UPDATE, SELECT statements will not lock any rows while running.
When do two SELECT queries block each other?
A SELECT query will place a temporary shared lock when it reads a block of values from the table, and remove it when it done reading. For the time the lock exists, you will not be able to do anything with the data in the locked area. Two SELECT queries will never block each other (unless they are SELECT FOR UPDATE)
How to improve insert into source table in MySQL?
In MySQL before 5.1 replication is statement based which means statements replied on the master should cause the same effect as on the slave. If Innodb would not locking rows in source table other transaction could modify the row and commit before transaction which is running INSERT .. SELECT statement.
What happens when Select is locked in MySQL?
SELECT had chance to access it it will also be modified in the same order on the slave. If transaction tries to modify the row after it was accessed and so locked by INSERT … SELECT, transaction will have to wait until statement is completed to make sure it will be executed on the slave in proper order.