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Snowflake ID
Snowflake IDs, or snowflakes, are a form of unique identifier used in distributed computing. The format was created by Twitter and is used for the IDs of tweets. The format has been adopted by other companies, including Discord and Instagram. The Mastodon social network uses a modified version. Format Snowflakes are 64 bits in binary. (Only 63 are used to fit in a signed integer.) The first 41 bits are a timestamp, representing milliseconds since the chosen epoch. The next 10 bits represent a machine ID, preventing clashes. Twelve more bits represent a per-machine sequence number, to allow creation of multiple snowflakes in the same millisecond. The final number is generally serialized in decimal. Snowflakes are sortable by time, because they are based on the time they were created. Additionally, the time a snowflake was created can be calculated from the snowflake. This can be used to get snowflakes (and their associated objects) that were created before or after a particula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epoch (computing)
In computing, an epoch is a date and time from which a computer measures system time. Most computer systems determine time as a number representing the seconds removed from particular arbitrary date and time. For instance, Unix and POSIX measure time as the number of seconds that have passed since Thursday 1 January 1970 00:00:00 UT, a point in time known as the Unix epoch. Windows NT systems, up to and including Windows 11 and Windows Server 2022, measure time as the number of 100-nanosecond intervals that have passed since 1 January 1601 00:00:00 UTC, making that point in time the epoch for those systems. Computing epochs are nearly always specified as midnight Universal Time on some particular date. Variation in detail Software timekeeping systems vary widely in the precision of time measurement (granularity); some systems may use time units as large as a day, while others may use nanoseconds. For example, for an epoch date of midnight UTC (00:00) on 1 January 1900, and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Universally Unique Identifier
A universally unique identifier (UUID) is a 128-bit label used for information in computer systems. The term globally unique identifier (GUID) is also used. When generated according to the standard methods, UUIDs are, for practical purposes, unique. Their uniqueness does not depend on a central registration authority or coordination between the parties generating them, unlike most other numbering schemes. While the probability that a UUID will be duplicated is not zero, it is generally considered close enough to zero to be negligible. Thus, anyone can create a UUID and use it to identify something with near certainty that the identifier does not duplicate one that has already been, or will be, created to identify something else. Information labeled with UUIDs by independent parties can therefore be later combined into a single database or transmitted on the same channel, with a negligible probability of duplication. Adoption of UUIDs is widespread, with many computing platfor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UNIX Epoch
Current Unix time () Unix time is a date and time representation widely used in computing. It measures time by the number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970, the beginning of the Unix epoch, less adjustments made due to leap seconds. Unix time originated as the system time of Unix operating systems. It has come to be widely used in other computer operating systems, file systems, programming languages, and databases. Definition Two layers of encoding make up Unix time. The first layer encodes a point in time as a scalar real number which represents the number of seconds that have passed since 00:00:00UTC on Thursday, 1 January 1970. The second layer encodes that number as a sequence of bits or decimal digits. Unix time differs from both Coordinated Universal Time (UTC) and International Atomic Time (TAI) in its handling of leap seconds. UTC includes leap seconds that adjust for the discrepancy between precise time, as measured by atomic cl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shard (database Architecture)
A database shard, or simply a shard, is a horizontal partition of data in a database or search engine. Each shard is held on a separate database server instance, to spread load. Some data within a database remains present in all shards, but some appear only in a single shard. Each shard (or server) acts as the ''single'' source for this subset of data. Database architecture Horizontal partitioning is a database design principle whereby '' rows'' of a database table are held separately, rather than being split into columns (which is what normalization and vertical partitioning do, to differing extents). Each partition forms part of a shard, which may in turn be located on a separate database server or physical location. There are numerous advantages to the horizontal partitioning approach. Since the tables are divided and distributed into multiple servers, the total number of rows in each table in each database is reduced. This reduces index size, which generally improves ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unix Time
Current Unix time () Unix time is a date and time representation widely used in computing. It measures time by the number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970, the beginning of the Unix epoch, less adjustments made due to leap seconds. Unix time originated as the system time of Unix operating systems. It has come to be widely used in other computer operating systems, file systems, programming languages, and databases. Definition Two layers of encoding make up Unix time. The first layer encodes a point in time as a scalar real number which represents the number of seconds that have passed since 00:00:00UTC on Thursday, 1 January 1970. The second layer encodes that number as a sequence of bits or decimal digits. Unix time differs from both Coordinated Universal Time (UTC) and International Atomic Time (TAI) in its handling of leap seconds. UTC includes leap seconds that adjust for the discrepancy between precise time, as measured by atomi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sorting
Sorting refers to ordering data in an increasing or decreasing manner according to some linear relationship among the data items. # ordering: arranging items in a sequence ordered by some criterion; # categorizing: grouping items with similar properties. Ordering items is the combination of categorizing them based on equivalent order, and ordering the categories themselves. Sorting information or data In , arranging in an ordered sequence is called "sorting". Sorting is a common operation in many applications, and efficient algorithms to perform it have been developed. The most common uses of sorted sequences are: * making lookup or search efficient; * making merging of sequences efficient. * enable processing of data in a defined order. The opposite of sorting, rearranging a sequence of items in a random or meaningless order, is called shuffling. For sorting, either a weak order, "should not come after", can be specified, or a strict weak order, "should come before" (spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GitHub
GitHub, Inc. () is an Internet hosting service for software development and version control using Git. It provides the distributed version control of Git plus access control, bug tracking, software feature requests, task management, continuous integration, and wikis for every project. Headquartered in California, it has been a subsidiary of Microsoft since 2018. It is commonly used to host open source software development projects. As of June 2022, GitHub reported having over 83 million developers and more than 200 million repositories, including at least 28 million public repositories. It is the largest source code host . History GitHub.com Development of the GitHub.com platform began on October 19, 2007. The site was launched in April 2008 by Tom Preston-Werner, Chris Wanstrath, P. J. Hyett and Scott Chacon after it had been made available for a few months prior as a beta release. GitHub has an annual keynote called GitHub Universe. Organizat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timestamp
A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolute notion of time, however. They can have any epoch, can be relative to any arbitrary time, such as the power-on time of a system, or to some arbitrary time in the past. The term "timestamp" derives from rubber stamps used in offices to stamp the current date, and sometimes time, in ink on paper documents, to record when the document was received. Common examples of this type of timestamp are a postmark on a letter or the "in" and "out" times on a time card. In modern times usage of the term has expanded to refer to digital date and time information attached to digital data. For example, computer files contain timestamps that tell when the file was last modified, and digital cameras add timestamps to the pictures they take, recordin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unique Identifier
A unique identifier (UID) is an identifier that is guaranteed to be unique among all identifiers used for those objects and for a specific purpose. The concept was formalized early in the development of computer science and information systems. In general, it was associated with an atomic data type. In relational databases, certain attributes of an entity that serve as unique identifiers are called primary keys. In mathematics, set theory uses the concept of '' element indices'' as unique identifiers. Classification There are some main types of unique identifiers, each corresponding to a different generation strategy: # serial numbers, assigned incrementally or sequentially, by a central authority or accepted reference. # random numbers, selected from a number space much larger than the maximum (or expected) number of objects to be identified. Although not really unique, some identifiers of this type may be appropriate for identifying objects in many practical applic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Two's Complement
Two's complement is a mathematical operation to reversibly convert a positive binary number into a negative binary number with equivalent (but negative) value, using the binary digit with the greatest place value (the leftmost bit in big- endian numbers, rightmost bit in little-endian numbers) to indicate whether the binary number is positive or negative (the sign). It is used in computer science as the most common method of representing signed (positive, negative, and zero) integers on computers, and more generally, fixed point binary values. When the most significant bit is a one, the number is signed as negative. . Two's complement is executed by 1) inverting (i.e. flipping) all bits, then 2) adding a place value of 1 to the inverted number. For example, say the number −6 is of interest. +6 in binary is 0110 (the leftmost most significant bit is needed for the sign; positive 6 is not 110 because it would be interpreted as -2). Step one is to flip all bits, yielding 1001. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mastodon (software)
Mastodon is free and open-source software for running self-hosted social networking services. It has microblogging features similar to Twitter, which are offered by a large number of independently run nodes, known as instances, each with its own code of conduct, terms of service, privacy policy, privacy options, and content moderation policies. Each user is a member of a specific Mastodon instance (also called a server), which can interoperate as a federated social network, allowing users on different instances to interact with each other. This is intended to give users the flexibility to select a node whose policies they prefer, but keep access to a larger social network. Mastodon is also part of the Fediverse ensemble of server platforms, which use shared protocols allowing users to also interact with users on other compatible platforms, such as PeerTube and Friendica. Mastodon is crowdfunded and does not contain ads. Mastodon was created by Eugen Rochko and announced ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
