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What’s MaxDOP MaxDOP(max degree of parallelism) is an option to limit the number of processors to use in parallel plan execution. For a single query you asked to sql server, it may use multiple worker threads to process it (each query in fact contains many operations internally). The MaxDOP limit the concurrency in that case. What’s the proper value? By default, it’s 0, which means no limit, and sql server may use all the processors it has to process a query. MaxDOP = 1 When setting it as 1, you alwase process the query sequentially. You suppress the parallel plan generation. Why? While thi

yield is a contextual keywords. When it shows in a statement, it means the method or get accessor in which it appears is an iterator. Thus it provides a simple way to define an iterator, rather than a class that implements IEnumerable or IEnumerator. When you use the yield contextual keyword in a statement, you indicate that the method, operator, or get accessor in which it appears is an iterator. Using yield to define an iterator removes the need for an explicit extra class (the class that holds the state for an enumeration, see IEnumerator for an example) when you implement the IEnumerable

FluentValidation Knowledge * The RuleFor method create a validation rule. To specify a validation rule for a particular property, call the RuleFor method, passing a lambda expression that indicates the property that you wish to validate. * Rules are run syncronously By default, all rules in FluentValidation are separate and cannot influence one another. This is intentional and necessary for asynchronous validation to work. * Must, NotNull…. are built-in validators. WithMessage is a method on a validator. When defines condition for validator(s). * Append multiple validators on a same

.net, asp.net, c# c# is like java language specification; .net is like jdk/javase/javaee asp.net: is like springboot 1. default, as, is 2. sln: solution ——> csproj: c sharp project ——> files .sln vs .csproj Key concepts ref: c# concepts * solution: a complete application, similar to maven project. It contains several c# project like frontend, backend, library to compose a complete application. * project: similar to maven module. It can be a web project, a library, a windows program, etc. * assembly: similar to maven jar. A c# project is corresponding to an assembly. An assembly can b

why REST? The World Wide Web is arguably the world’s largest distributed application. Understanding the key architectural principles underlying the Web can help explain its technical success and may lead to improvements in other distributed applications, particularly those that are amenable to the same or similar methods of interaction. REST contributes both the rationale behind the modern Web’s software architecture and a significant lesson in how software engineering principles can be systematically applied in the design and evaluation of a real software system. —- Fielding’s REST dissertati

great free learning website with quiz great online editor & debugger Python学习资料/文章/指南整理 Zen of Python By typing import this, you can see the zen of python. Some need more explanation: Explicit is better than implicit: It is best to spell out exactly what your code is doing. This is why adding a numeric string to an integer requires explicit conversion, rather than having it happen behind the scenes, as it does in other languages. Flat is better than nested: Heavily nested structures (lists of lists, of lists, and on and on…) should be avoided. Errors should never pass silently: In general,

k8s is a platform to manage containerized workloads and services. Concepts kubernetes Objects 1. Kubernetes abstract a desired state of cluster as objects. 2. an object configuration includes: 1. spec: describe the desired state 1. apiVersion: the api version of kubernetes 2. metadata: the name & namespace 3. spec: the desired state definition. 2. status: describe the actual state of the object 3. cluster state (understanding kubernetes objects): 1. what containerized applications are running and where they’re running 2. how many reso

Huawei Obs is an object storage service on cloud. Concepts Object 1. The real complete file or byte stream to save 2. object name is the unique id in a bucket 1. it’s used as part of url path. The naming restrictions are fit to url path naming restrictions. 3. Access(based on version in fact) 1. Object ACL: 1. general control to object: read object, read/write object ACL, only users in the same account 2. Object policy 1. fine-grained control to object: fine-grained actions(put,delete…) on object, all users 4. multi-versions 1.

What’s beam beam is a open-source, unified model for defining both batched & streaming data-parallel processing pipelines. * open-source (apache v2 license) * to define data-parallel processing pipelines * an unified model to define pipelines. The real processing is run by the underlying runner (eg. spark, apache apex, etc.). all available runners * can process both batched (bounded datasets) & streaming (unbounded datasets) datasets Use it See the wordcount examples, wordcount src Now we define a simple pipeline and run it. Transform, Count are all built-in atom operations to define t

chmod, chown understanding linux file permissions File permissions are defined by permission group and permission type 1. permission group * owner(u) * group(g) * all other users(a) 2. permission type * read (r - 4) * write(w - 2) * execute(x - 1) permission presentation The permission in the command line is displayed as _rwxrwxrwx 1 owner:group * the first character (underscore _ here) is the special permission flag that can vary. * the following three groups of rwx represent permission of owner, group and all other users respectively. If the ow