cassandra

Cassandra cqlsh命令大全

由 北城以北 提交于 2020-01-23 01:01:11
一：CQL 简介 CQL是Cassandra Query Language的缩写，目前作为Cassandra默认并且主要的交互接口。CQL和SQL语法很相似，主要的区别是cql不支持join和子查询,相对来说没有sql那么强大。 二：Shell 命令 // 登录shell D:\Java\apache-cassandra-3.11.0\bin>cqlsh D:\Java\apache-cassandra-3.11.0\bin>cqlsh --help D:\Java\apache-cassandra-3.11.0\bin>cqlsh --version // 使用用户名和密码登录，默认用户名和密码都是cassandra D:\Java\apache-cassandra-3.11.0\bin>cqlsh -u 'cassandra' -p 'cassandra' // 启动时执行cql（可用于导入数据，或者执行文件中的cql） D:\Java\apache-cassandra-3.11.0\bin>cqlsh --file="D:\users.cql" // 帮助命令 cqlsh> help // 捕获命令，所有的select查询的结果都将保存在output文件中 cqlsh> capture 'D:\Java\apache-cassandra-3.11.0\data\output'

Serialize a Python dict into a Cassandra 1.2 column

由 穿精又带淫゛_ 提交于 2020-01-22 20:37:28
问题 The problem I'm trying to save a serialized object (using cPickle) into a Cassandra 1.2 column, I'm using the python cql library. I've already tried defining the column as text (utf8 string) and blob, in both cases I'm receiving the same error: The object is a Python dict: obj = {'id':'sometextid', 'time_created':05/12/2013, #<---- datetime 'some other string property': 'some other value' } The error is this: raise cql.ProgrammingError("Bad Request: %s" % ire.why) cql.apivalues

Cassandra replication system - how it works

由 我是研究僧i 提交于 2020-01-22 16:18:28
问题 Does Cassandra replicate only on write procedure (with chosen consistency level)? Is there any auto-replicate option for absent nodes, if I want symmetric data in every node? If I plug in a new node to the cluster, there is no auto replication. How can I sync data from other nodes with the new one? If I want replication like multimaster (2 nodes) with slave backup (1 node) known from MySQL, what is the proper way to set up and manage that on Cassandra (3 nodes)? How about two nodes? 回答1:

Does Cassandra support sharding?

由 ℡╲_俬逩灬. 提交于 2020-01-22 13:20:23
问题 Does Apache Cassandra support sharding? Apologize that this question must seem trivial, but I cannot seem to find the answer. I have read that Cassandra was partially modeled after GAE's Big Table which shards on a massive scale. But most of the documentation I'm currently finding on Cassandra seems to imply that Cassandra does not partition data horizontally across multiple machines, but rather supports many many duplicate machines. This would imply that Cassandra is a good fit high

Does Cassandra support sharding?

由 亡梦爱人 提交于 2020-01-22 13:20:00
问题 Does Apache Cassandra support sharding? Apologize that this question must seem trivial, but I cannot seem to find the answer. I have read that Cassandra was partially modeled after GAE's Big Table which shards on a massive scale. But most of the documentation I'm currently finding on Cassandra seems to imply that Cassandra does not partition data horizontally across multiple machines, but rather supports many many duplicate machines. This would imply that Cassandra is a good fit high

Does Cassandra support sharding?

由 ﹥＞﹥吖頭↗ 提交于 2020-01-22 13:19:48
问题 Does Apache Cassandra support sharding? Apologize that this question must seem trivial, but I cannot seem to find the answer. I have read that Cassandra was partially modeled after GAE's Big Table which shards on a massive scale. But most of the documentation I'm currently finding on Cassandra seems to imply that Cassandra does not partition data horizontally across multiple machines, but rather supports many many duplicate machines. This would imply that Cassandra is a good fit high

Cassandra denormalization datamodel

由 喜你入骨 提交于 2020-01-22 09:29:33
问题 I read that in nosql (cassandra for instance) data is often stored denormalized. For instance see this SO answer or this website. An example is if you have a column family of employees and departments and you want to execute a query: select * from Emps where Birthdate = '25/04/1975' Then you have to make a column family birthday_Emps and store the ID of each employee as a column. So then you can query the birthday_Emps family for the key '25/04/1975' and instantly get all the ID's of the

How to compute summary statistic on Cassandra table with Spark DataFrame?

由 强颜欢笑 提交于 2020-01-22 03:58:12
问题 I'm trying to get the min, max mean of some Cassandra/SPARK data but I need to do it with JAVA. import org.apache.spark.sql.DataFrame; import static org.apache.spark.sql.functions.*; DataFrame df = sqlContext.read() .format("org.apache.spark.sql.cassandra") .option("table", "someTable") .option("keyspace", "someKeyspace") .load(); df.groupBy(col("keyColumn")) .agg(min("valueColumn"), max("valueColumn"), avg("valueColumn")) .show(); EDITED to show working version: Make sure to put " around the

Not quite clear about a Cassandra's anti-pattern

由 落爺英雄遲暮 提交于 2020-01-21 07:52:45
问题 Suppose,there is a table with the following structure: create table cities ( root text, name text, primary key(root,name) ) with clustering order by (name asc); -- for getting them sorted insert into cities(root,name) values('.','Moscow'); insert into cities(root,name) values('.','Tokio'); insert into cities(root,name) values('.','London'); select * from cities where root='.'; -- get'em sorted asc When specifying the replication factor of 3 for the keyspace and using RandomPartitioner,there

Why nosql with cassandra instead of mysql?

由 时光毁灭记忆、已成空白 提交于 2020-01-21 02:59:05
问题 I work on large database (hundreds of GB) and Mysql now gives me more or less satisfaction. I hesitate to cassandra on launch. What I want to know everything before, so this kind of DBMS NoSQL is supposed to be faster than MySQL? Several points: The change in the number of column on a row In Mysql, they must all be defined in advance. The columns set in the structure of the table. NoSQL in, they can be varied. There is real difference performance on a fixed structure ? and why ? Do not make
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