1) Compared with mongo, it still has a complete Chinese document, as a code farmer in China. . Reading English documents is still a headache.
2) It should be said that the support of the open source community is still relatively fast. On that day, someone will answer questions in the group, and then the students from the original factory will teach the engineers in our district the configuration and docking procedures at the beginning. . Still very awesome.
3) Generally speaking, you can't get used to using and migrating transformations, but now it is said that SQL supports more and you haven't tried it. It sounds powerful, but their native operation statements are easy to understand.
How to treat yandex open source clickhouse as a column document database? Yandex opened a data analysis database named ClickHouse on June 5, 20 16, which is a great event for conservative Russians. What is even more surprising is that the running score of this columnar storage database exceeds that of many popular commercial MPP database software, such as Vertica. If you haven't heard of Vertica, you must have heard of michael stonebraker, winner of 20 14 Turing Award, inventor of PostgreSQL and Ingres(Sybase Sybase and SQL Server inherited from Ingres), and founder of Paradigm4 and SciDB. Michael stonebraker founded Vertica in 2005, which was later acquired by HP. HP Vertica became a high-performance representative of MPP columnar storage commercial database, and Facebook purchased Vertica data for user behavior analysis.
To put it simply, as an analytical database, ClickHouse has three characteristics: first, it runs fast, second, it has many functions, and third, it has a literary mode.
1. Fast running speed: ClickHouse runs five times faster than Vertica;
The performance of ClickHouse exceeds that of most column storage databases on the market, and it is 100- 1000 times faster than the traditional data ClickHouse, so ClickHouse still has great advantages:
100 megabyte data set:
ClickHouse is about 5 times faster than Vertica, 279 times faster than Hive and 80 1 times faster than my SQL.
10 billion data set:
ClickHouse is about five times faster than Vertica, and MySQL and Hive have been unable to complete the task.
2. Multifunctional: ClickHouse supports statistical analysis of various scenarios.
-Support SQL-like queries,
-Support a variety of library functions (such as IP conversion, URL analysis, precomputation /HyperLoglog, etc.). )
-Supports arrays and nested data structures.
-Support remote database replication deployment
3. Literary fan: At present, ClickHouse has many restrictions, and it was born for the petty bourgeoisie.
-Currently only Ubuntu systems are supported.
-No design and architecture documents are provided, the design is mysterious, only open source C++ source code.
-Ignore the Hadoop ecosystem and go your own way
How to treat Alibaba's announcement of opening the open source AliSQL database is actually a bit similar. Google opens Android for free use.
It is not difficult for others to imitate some technologies, and patents are not long-term effective.
Google may feel that it is better to make it public immediately, and we can quickly occupy the market by working together.
How to treat hackers invading database intranet? The mole cooperated with the hackers outside. If there is a mole, it will be easy.
How to treat TokuDB, a database developed in the United States? Tested TokuMX, the performance is really good, but the stability is worrying. After mongodb 3.0, wiredtiger engine was introduced, which narrowed the gap with tokumx.
I have studied the index data structure used by TokuMX and TokuDB, and the design is very clever. Although the depth of the tree has doubled, the insertion time has indeed been greatly reduced.
Finally, it was not adopted.
How do you think that free and open source CRM can hardly meet the actual business needs of enterprises? We can consider a CRM that supports users' personalized customization. Baihui's CRM is good Can be customized in the shortest time according to the needs of users, so that users can see the effect. Pay after satisfaction, no worries. The customization tool is simple and the customization speed is fast. Users can operate by themselves to adapt to future business changes. In addition, online leasing based on SAAS mode can save the cost of hardware purchase, installation and debugging, and later upgrade for enterprises. Regular after-sales visits can also solve many problems in use.
What do you think of React Native? React Native: Bringing Modern Web Technology to Mobile, published by Tom Ohino, a member of Facebook's open source React Native React Native project, describes the design concept of React Native in detail. Ono believes that although the development cost of native is higher, native is still necessary at this stage, because the user experience of the Web can't surpass native:
The native control of 1 Native experience is better;
2.Native has better gesture recognition;
3.Native has a more suitable threading model. Although Web Worker can solve some problems, such as image decoding and text rendering, it still can't be multithreaded, which affects the fluency of web pages.
What Ono didn't mention is that Native can achieve richer and more delicate animation effects. In the final analysis, Native has a better human-computer interaction experience at this stage. The author thinks that these examples are convincing and the direct reason for the emergence of React Native.
Figure 3- Ono shares React Native(Keynote) in F8.
Learn once and write everywhere.
"Learn once and write everywhere" is also an article from Ono. Because the user experience on different platforms is different, React Native doesn't force a single native code to support multiple platforms, so it doesn't mention "write once, run anywhere" (Java) and puts forward "learn once, write anywhere".
Figure 4- "Learn once and write everywhere"
This picture is a schematic diagram drawn by the author according to his own understanding. From bottom to top, it is:
1.React: Write code on different platforms based on React, "Learn once and write everywhere".
2. Virtual DOM: Compared with DOM (Document Object Model) in browser environment, virtual DOM is a lightweight expression of DOM in memory (lightweight representation of documents), which can generate UIs under different platforms through different rendering engines, and JS communicates with each other through bridge communication mechanism React Native. Bang's blog).
3.Web/iOS/Android: has implemented the Web and iOS platforms, and the Android platform is expected to be implemented in 20 15 10 (blog | React).
React mentioned in many places above is an open source Web development framework of Facebook 20 13. When I read its release, I found this passage:
Figure 5- Excerpt from the release of React (20 13)
1. The highlighted text shows that the prototype of React Native was already under development on 20 13, and now it has accumulated.
2. Another popular project recently is Flipboard/React-Canvas Github (see @rank). The rendering layer uses Web Canvas to improve the fluency of interaction, which is similar to the first attempt in the above picture.
React itself is also a huge topic. See Facebook /Reactwiki github for details.
The author thinks that "write once and run everywhere" is necessary to improve efficiency, and it does not conflict with "write once and write everywhere". We are transforming the existing component library and HybridAPI internally to adapt (supplement) the components of React Native, so as to write a code that can run on iOS and Web and be open source when it is mature.
Continuous update ...
Second, planning.
The following figure shows the business and technical transformation of React Native:
Figure 6- Business and Technology Transformation Figure 6- Business and Technology Transformation
Bottom-up:
1.React node: React supports server-side rendering, which is usually used for server-side rendering of the first screen; The typical scene is a multi-page list, and the first screen server renders the page-turning client rendering, so as to avoid requesting the page twice the first time.
2. Reflect the local basic environment:
2. 1. Framework integration: Although React Native has released the integration with existing App documents, there are still many details when integrating into existing complex apps. For example, it took two days for the iOS students in the group to integrate into the Tmall iPad client.
2.2.Neorking transformation: mainly re-establish the session, which is usually stored in the header cookie. The network IO fetch and XMLHttpRequest provided by React Native do not support rewriting cookies. Therefore, either the extension of fetch is realized under the condition of ensuring security, or the network IO (existing session mechanism) is handled by native, and then JS calls through HybridAPI, and temporarily chooses the latter.
2.3. Cache/packaging scheme: As long as resources are loaded from the server, this topic cannot be avoided, and so is React Native. Cache is used to solve the loading performance of resources when they are accessed twice, and packaging is used to solve the loading performance of resources when they are accessed for the first time.
3.MUI is a component library, which will be reformed with the idea of supplementing the native components of React.
4.HybridAPI is a set of mixed APIs of Ali, which has been shared in many public places (such as sensor @ 中中中中). React Native has established its own communication mechanism, which seems to be more efficient (unverified) and the transformation cost is not great.
5. The fastest business will be launched in mid-April, and the transformation of the whole system will be promoted through the first few business transformations. If the effect is as expected, a larger business transformation will be initiated.
More detailed planning and progress, as well as performance, stability and scalability data will be released later.
Third, risk.
1. Although three Facebook apps (group, advertising manager and F8) use React Native, with the large-scale application of React Native, it is still unknown whether the policy of the Appstore has changed, so we can only take a step forward.
* Update:
20 15.7.28 AppStore audit policy adjustment: allow dynamic loading of code running in JavascriptCore. The following figure shows the previous audit policies and compares the highlighted changes.
Does qt support domestic databases? Applications need to manipulate databases in many cases. QT supports a variety of databases, but in many cases it is necessary to install DLL drivers. This is a little troublesome. I thought that the result of using MYSQL was that the driver was difficult to install, and then I used SQLITE. If the requirements for the database are not very high, Sqlite should be able to meet the requirements.
How to treat the development of database technology to big data technology is inevitable? With the accumulation of data, there are more and more data to record the operating conditions of the objects, so big data of various industries are gradually formed. Of course, some big databases are available, and some big data are rubbish.
Please adopt!