• Summary of basic operation methods of hash type in Ruby


    1. Create hash:Just like creating arrays, we can create a hash instance through the hash class: ? 1 2 h1 = Hash.new             #The default value is nil h2 = Hash.new(“This is my first hash instance”) #The default value is “this is my first hash instance”: Both of the above examples create an empty hash instance. […]

  • Summary of basic operation methods of hash structure in Ruby


    About hashLet’s first understand the basic idea of hash:Set the number of objects to be stored as num, then we use len memory units to store them (len > = Num); Take the keyword of each object ki as the argument, use a function H (KI) to reflect the memory address of Ki, that is, […]

  • [PHP data structure] hash table search


    Does the search of the last article have a sense of meaning? Because we are really exposed to the optimization of time complexity. It is definitely a qualitative leap from O (n) of linear search to o (logn) of half search. However, what is the core requirement of our half search? That is, the original […]

  • The use of Yii redis hash


      The hash of redis allows users to store multiple key value pairs in a redis key. Here are some common commands and their use in Yii. HMGET HMGET:HMGET key-name key [key …]Gets the value of one or more keys from the hash. HMSET HMSET:HMSET key-name key name [key name …]Set values for one or […]

  • Hash join: a new feature of MySQL 8.0


    MySQL development team officially released MySQL 8.0.18 GA on October 14, 2019, bringing some new features and enhanced functions. One of the most striking is that the multi table join query supports hash join. Let’s first look at the official description: MySQL implements hash join for inner join query. For example, starting from MySQL 8.0.18, […]

  • MySQL 8.0.18 hash join test (recommended)


    Hash Join Hash join does not require any index to execute and is more efficient than the current block nested loop algorithm in most cases. The following is an example code to introduce MySQL 8.0.18 hash join test. The specific contents are as follows: CREATE TABLE COLUMNS_hj as select * from information_schema.`COLUMNS`; INSERT INTO COLUMNS […]

  • MySQL 8.0.18 hash join does not support left / right join connection


    In MySQL 8.0.18, a new function of hash join has been added, which is applicable to the fields that have not been indexed to do equivalent Association query. In previous versions, if the joined fields were not indexed, the query speed would be very slow, and the optimizer would use BNL (block nesting) algorithm. Hash […]

  • Analysis of two simple sorting methods in Java HashMap


    This article mainly introduces the Java HashMap two simple sorting method analysis, the article through the example code introduction is very detailed, to everybody’s study or the work has the certain reference study value, the need friend may refer to The storage of HashMap is not sequential, but implemented according to the hashcode of key […]

  • Blockstack-9: blockstack architecture


    Original link: https://medium.com/coinmonks/blockstack-a-decentralized-naming-and-storage-system-using-blockchain-445ff60190f7 Part I: blockstack’s 4-tier architecture Blockstack’s 4-tier architecture: first floor:Blockchains like bitcoin store an authoritative global consensus on the state of the system. Layer 2 – Virtual Chain:A blockchain independent layer that accepts input from the blockchain and can create any type of state machine. For example, a DNS state machine can […]

  • Learn from blockchain-1-transaction|block|pow by building blockchain


    Original link: https://medium.com/@vanflymen/learn –blockchains-by-building-one-117428612f46 Transaction Block proof of work You’re here because, like me, you’re excited about the rise of cryptocurrencies. You want to know how blockchains work – the basic technology behind them. But understanding blockchain is not easy – at least not for me. I had a hard time browsing dense videos, learning […]

  • Combined mining specification


    Combined mining Aux assist Note: this standard is used by namecoin, but the new merge mining data may propose a new BiP to replace it, using something based on p2pool merge mining. content term Supporting workload proof block Merkle branch Combined mining coinbase Artificial Hawthorn example note term Auxiliary Proof-of-Work (POW) a.k.“AuxPOW”。 This is how […]

  • Explain the command use of MD5 code and SHA1 code of the check file in Linux


    md5sumUsage: md5sum [options]… [file]Display or check the MD5 (128-bit) check sum.If there is no file option or “-” at the file, it is read from standard input. – B, — binary read in binary mode– C, — check read the check value of MD5 from the file and check it– t, — text read in […]