Non-Repeatable Read A non-repeatable read occurs, when during the course of a transaction, a row is retrieved twice and the values within the row differ between reads. Phantom Read A phantom read occurs when, in the course of a transaction, two identical queries are executed, and the collection of rows returned by the second query is different from the first. Read Skew Read skew is that with two different queries, a transaction reads inconsistent data because between the 1st and 2nd queries, other transactions insert, update or delete data and commit. Finally, an inconsistent result is produced by the inconsistent data. ...

Designing a TPS for clouds will meet these challenges: Diverse functionality. The concept of translytics as “a unified and integrated data platform that supports multi-workloads such as transactional, operational, and analytical simultaneously in realtime, … and ensures full transactional integrity and data consistency”. Scale Cloud-first data platforms are designed to scale well beyond the limits of a single application. Latency With the thrust into new interactive domains like social networks, messaging and algorithmic trading,latency becomes essential. Multi-tenancy Maintaining access rights is therefore an important design consideration for TPSs. 论文的工作集中于以下几点： ...

An entirely re-designed version of Omid1. Omid’s job is to manage the transaction control plane. The transaction metadata includes: A dedicated table(Commit Tabla, CT) holds a single record per committing transaction. Per-row metadata for items accessed by transactions. Feature: A middleware oriented. Snapshot isolate should provide: Visibility check rules. Write conflicts detection. Visibility Check Rules Intuitively, with SI, a transaction’s reads all appear to occur the time when it begins($ts_r$) while its writes appear to execute when it commits($ts_c$). ...

Explore Rust Chapter 3 Types Arrays 不支持动态开数组： // an array of 100 int32 elements, all set to 1 let mut arr1 = [1;100]; // correct let n = 100; let mur arr2 = [1;c]; // error Vectors let mut arr = vec![0,6,4,8,1]; arr.sort() // increasing order arr.sort_by(|a,b| b.cmp(a)) // decreasing order If you know the number of elements a vector will need in advance, instead of Vec::new you can call Vec::with_capacity to create a vector with a buffer large enough to hold them all, right from the start. ...

Background Database systems have evolved to be with a cloud-native architecture,i.e., disaggregation of compute and storage architecture, which decouples the storage from the compute nodes, then connects the compute nodes to shared storage through a high-speed network. The principle of cloud-native architecture is decoupling. (decoupled functions to make good use of disaggregated resources) Most existing cloud-native databases couple TP either with storage layer or with execution layer. Coupling TP with Storage Layer TiDB adopts a distributed transactional key-value store TiKV as the storage layer. ...