lwt | 易学教程

How the LWT- Light Weight Transaction is working when we use IF NOT EXIST?

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问题 The question is that, When we use INSERT INTO USERS (login, email, name, login_count) values ('jbellis', 'jbellis@datastax.com', 'Jonathan Ellis', 1) IF NOT EXISTS in IF NOT EXIST exactly which columns are compared together? primary key(partition-key + clustering-key)? or just partition-key? 回答1: Here is a diagram of the 4 phases of LWT: http://www.slideshare.net/doanduyhai/cassandra-introduction-nantesjug/89 The original blog post is here: http://www.datastax.com/dev/blog/lightweight

Cassandra LWT reads

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问题 It's my understanding that LWT inserts are always done with SERIAL consistency level. If true, does that mean that reading a row inserted as LWT, can be safely read with a consistency level of ANY? In other words, I assume an LWT insert is fully consistent, making any subsequent read also fully consistent, regardless of consistency level? 回答1: Your assumption is incorrect due to two reasons. SERIAL only implies QUORUM consistency level for writes There is a possibility that a single LWT will

Ocaml Lwt - some implementations of multiplayer game

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问题 I'm going on to writing a simple implementation of tic-tac-toe server (via telnet). The task - players connect to server and after they send START the server looks for a partner who typed START too, and game begins. A piece of code: let handle_income () = let con = Lwt_unix.accept sock in con >>= fun (cli, addr) -> let player = Lwt.return {state = Sleeping; descriptor = Lwt.return cli} in send_to_client player "Welcome to the server. To start game type in START and press Enter"; player;; let

Ocaml Lwt - some implementations of multiplayer game

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I'm going on to writing a simple implementation of tic-tac-toe server (via telnet). The task - players connect to server and after they send START the server looks for a partner who typed START too, and game begins. A piece of code: let handle_income () = let con = Lwt_unix.accept sock in con >>= fun (cli, addr) -> let player = Lwt.return {state = Sleeping; descriptor = Lwt.return cli} in send_to_client player "Welcome to the server. To start game type in START and press Enter"; player;; let rec make_ready player = player >>= fun {state; descriptor} -> send_to_client player "Waiting for start