mysql Summary and accumulation of database performance tuning.Understand MySQL Deadlock handling methods in performance testing and tuning, You don't understand ? More articles about In addition, If disabled InnoDB Deadlock detection, The parameters need to be adjusted in time innodb_lock_wait_timeout Value, To meet the actual needs. In other words, When confirming that the deadlock detection function affects the performance of the system and disabling deadlock detection will not have a negative impact, You can try closing innodb_deadlock_detect Options. Here, If deadlock detection is disabled, Instead, it depends on parameters innodb_lock_wait_timeout It may be more efficient to release transactions that occupy lock resources for a long time. įor highly concurrent systems, When a large number of threads wait for the same lock, Deadlock detection may cause performance degradation. ĭeadlock timeout (innodb_lock_wait_timeout): This parameter can be used to handle undetectable deadlocks, Or avoid waiting for a long time for a long transaction. After opening InnoDB When locking, it will detect whether it will cause deadlock after locking, If you lock it, Just roll back the transaction with the lowest cost. The default value for this parameter is ON, That is, open deadlock detection. ĭeadlock detection (innodb_deadlock_detect): stay MySQL 8.0 in, Added a new dynamic variable innodb_deadlock_detect, Used to control InnoDB Whether to perform deadlock detection. MySQL The database passed deadlock detection (innodb_deadlock_detect) And deadlock timeout (innodb_lock_wait_timeout) These two parameters are used for deadlock resolution. In order to make the transaction form a clear lock operation queue and avoid deadlock. (3) Modify multiple tables in the same transaction, Or different rows in a table, Perform operations in the same order each time. (2) A lower isolation level is recommended, Such as READ COMMITTED. Especially don't let the relevant MySQL Session suspends uncommitted transactions for a long time. (1) Try to keep things short, Commit the transaction immediately after making a series of associated update operations, To reduce the possibility of deadlock. We need to pay attention to the following points in the use of transactions : When a deadlock occurs, It is usually due to lengthy transactions in the program of the project, Or because the isolation level is not set properly. OR use the CASE Statement in your WHERE Clause: Select et.Emp,Ĭast(et.SHOW STATUS LIKE '%lock%' Deadlock avoidance WHERE (et.Chrg_Date BETWEEN er.Rate_Start AND er.Rate_Exp) THEN Convert(varchar(10), getdate(), 101) Select et.Emp,Ĭast(et.Chrg_Date as DATEtime) as 'Chrg_Date', I am sure there are other ways to do this but this way will replace the null Rate_Exp date with the current date. You didn't specify the DBMS type the answer below is for sql-server. I've gone around in circles using the Between operator in a sub query to isolate the correct rate based on the charge date, but have not had any luck. The query (returns dupes caused by multiple rate entries(obviously)): Select Emp_Time.Emp,Ĭast(Emp_Time.Chrg_Date as DATE) as 'Chrg_Date',Įmp_Time.Chrg_Hrs * Emp_Rate.Rate as 'Cost'ĭesired output: Emp Chrg_Date Chrg_Code Chrg_Hrs Rate Cost Table examples (null values in the rate table indicate current rate): CREATE TABLE Emp_Rate My question is similar to the one asked here: Retro-active effective date changes with overlapping dates but I'm not dealing with retro-activity or overlapping date ranges. I'm trying to generate a costing query that outputs employee time card information and calculates cost based on an effective employee costing rate.
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