Tag：Level
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Time：2021-2-27
summary introduce Black level correction is the lowest point of black. In terms of 8bit data, it refers to the video signal level without a line of bright output on a certain calibrated display device. Define the corresponding signal level when the image data is 0. reason So why do we need black level correction? […]
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Time：2021-2-24
SQL self study notes affair Basic introduction of 1.0 transaction 2.0 automatic and manual commit of transactions Four characteristics of 3.0 transaction 4.0 transaction isolation level DCL
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Time：2021-2-19
preface In short, database transaction is to ensure that a set of data operations either all succeed or all fail. In mysql, transactions are implemented in the engine layer. The native MyISAM engine does not support transactions, which is one of the important reasons why InnoDB will replace it. Isolation and isolation level When multiple […]
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Time：2021-2-16
Because the data storage of HBase uses HDFS, and HDFS does not support random reading and writing, so the data writing of HBase adopts LSM algorithm. LSM algorithm is generally divided into memory and disk to store data. In the implementation of HBase, the memory part is called memstore, which adopts jump table to maintain […]
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Time：2021-2-15
In memory column store im column storage is a new feature introduced by Oracle 12.1.0.2. Im column storage is an optional part of SGA, which stores copies of tables, table partitions or other database objects. Im column storage is included in the Oracle database in memory option. This part is operated in Oracle 12.1.0.2. 1 […]
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Time：2021-2-14
1. RDD caching mechanism cache, persist One reason spark is very fast is that RDD supports caching. After successful caching, if the dataset is used by subsequent operations, it will be directly obtained from the cache. Although the cache also has the risk of loss, due to the dependency between RDDS, if the cache data […]
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Time：2021-2-13
It is better to prepare for the rain than to dig a well in the face of thirst What is a business Database transaction refers to a series of operations executed as a single logical unit of work, either all or none. A database transaction usually contains a sequence of operations to read or write […]
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Time：2021-2-11
uselogrusand go-file-rotatelogsCut log by day, source code: Iris framework package config import ( config “IrisFramework/config/Log” rotatelogs “github.com/lestrrat/go-file-rotatelogs” “github.com/rifflock/lfshook” “github.com/sirupsen/logrus” “os” “path” “time” ) const LogPath = “./storage/logs” const FileSuffix = “.log” var Log = logrus.New() func InitLog() { Log.Out = os.Stdout var loglevel logrus.Level err := loglevel.UnmarshalText([]byte(“info”)) if err != nil { Log.Panicf (failed to […]
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Time：2021-2-7
Four isolation levels 1. Read uncommitted Transaction a can read uncommitted data in transaction BDirty reading and non repeatable reading may occur 2. Read committed Transaction a can read the committed data in transaction B (through transaction view construction)There may be non repeatable reads 3. Repeatable read The queried data will not be affected by […]
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Time：2021-2-5
Transaction isolation is mainly aimed at the transaction isolation in acidIBefore understanding these kinds of database transactions, we need to understand several important concepts: Dirty reading-Transaction 1 (read) accessed the uncommitted transaction of transaction 2 (write) Illusory reading-A transaction reads twice, and the result is different Not repeatable-A transaction reads the same record twice, and […]
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Time：2021-1-29
1. Oracle is the famous Oracle company. MySQL was developed by Swedish MySQL AB company and acquired by Sun company on January 16, 2008. In 2009, sun was acquired by Oracle. 2. Oracle is a large-scale database, while MySQL is a small and medium-sized database. The market share of Oracle is 40%, while that of […]
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Time：2021-1-27
preface When a spring boot 2.2 + project was recently started, the console output was found 17:22:05 [main] DEBUG o.s.b.f.s.DefaultListableBeanFactory – Creating shared instance of singleton bean ‘org.springframework.cloud.util.random.CachedRandomPropertySourceAutoConfiguration’ 17:22:05 [main] DEBUG o.s.b.a.l.ConditionEvaluationReportLoggingListener – ============================ CONDITIONS EVALUATION REPORT ============================ Positive matches: —————– ConfigurationPropertiesRebinderAutoConfiguration matched: – @ConditionalOnBean (types: org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor; SearchStrategy: all) found bean ‘org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor’ (OnBeanCondition) ConfigurationPropertiesRebinderAutoConfiguration#configurationPropertiesBeans matched: […]
