impala

「分布式技术专题」三种常见的数据库查询引擎执行模型

由 元气小坏坏 提交于 2021-02-18 20:46:44
注： 本文涉及到的相关资料图片摘自 CARNEGIE MELLON DATABASE GROUP 发表的 CMU SCS 15-721 (Spring 2019) :: Query Execution & Processing （点击可查看） 1. 迭代模型/火山模型（Iterator Model） 又称 Volcano Model 或者 Pipeline Model 。 该计算模型将关系代数中每一种操作抽象为一个 Operator，将整个 SQL 构建成一个 Operator 树，查询树自顶向下的调用next()接口，数据则自底向上的被拉取处理。 火山模型的这种处理方式也称为拉取执行模型（Pull Based）。 大多数关系型数据库都是使用迭代模型的，如 SQLite、MongoDB、Impala、DB2、SQLServer、Greenplum、PostgreSQL、Oracle、MySQL 等。 火山模型的优点在于：简单，每个 Operator 可以单独实现逻辑。 火山模型的缺点：查询树调用 next() 接口次数太多，并且一次只取一条数据，CPU 执行效率低；而 Joins, Subqueries, Order By 等操作经常会阻塞。 2. 物化模型（Materialization Model） 物化模型的处理方式是：每个 operator 一次处理所有的输入

Installing cloudera impala without cloudera manager

由 倾然丶 夕夏残阳落幕 提交于 2021-02-18 06:59:59
问题 Kindly provide the link for installing the imapala in ubuntu without cloudera manager. Couldn't able to install with official link. Unable to locate package impala using these queries : sudo apt-get install impala # Binaries for daemons sudo apt-get install impala-server # Service start/stop script sudo apt-get install impala-state-store # Service start/stop script 回答1: First you need to get the list of packages and store it in /etc/apt/sources.list.d/ , then update the packages, then you

Hive/Impala performance with string partition key vs Integer partition key

由 梦想的初衷 提交于 2021-02-07 19:54:36
问题 Are numeric columns recommended for partition keys? Will there be any performance difference when we do a select query on numeric column partitions vs string column partitions? 回答1: No, there is no such recommendation. Consider this: The thing is that partition representation in Hive is a folder with a name like 'key=value' or it can be just 'value' but anyway it is string folder name. So it is being stored as string and is being cast during read/write. Partition key value is not packed

Hive/Impala performance with string partition key vs Integer partition key

由 梦想的初衷 提交于 2021-02-07 19:53:16
问题 Are numeric columns recommended for partition keys? Will there be any performance difference when we do a select query on numeric column partitions vs string column partitions? 回答1: No, there is no such recommendation. Consider this: The thing is that partition representation in Hive is a folder with a name like 'key=value' or it can be just 'value' but anyway it is string folder name. So it is being stored as string and is being cast during read/write. Partition key value is not packed

Impala: Show tables like query

由 南楼画角 提交于 2021-02-07 14:45:47
问题 I am working with Impala and fetching the list of tables from the database with some pattern like below. Assume i have a Database bank , and tables under this database are like below. cust_profile cust_quarter1_transaction cust_quarter2_transaction product_cust_xyz .... .... etc Now i am filtering like show tables in bank like '*cust*' It is returning the expected results like, which are the tables has a word cust in its name. Now my requirement is i want all the tables which will have cust

Query parameters with Impala ODBC driver

由 …衆ロ難τιáo~ 提交于 2021-01-28 03:37:26
问题 I'm using the Impala ODBC driver provided by Cloudera. I can't seem to use query parameters correctly. For instance: OdbcCommand command = DbConnection.CreateCommand(); command.CommandText = "INSERT INTO TABLE test VALUES(?, ?)"; command.Parameters.Add("key", OdbcType.VarChar).Value = "csharp"; command.Parameters.Add("val", OdbcType.VarChar).Value = "test"; command.ExecuteNonQuery(); throws the following exception. {"ERROR [HY000] [Cloudera][ImpalaODBC] (110) Error while executing a query in

Select first row of group with criteria

由 自闭症网瘾萝莉.ら 提交于 2021-01-27 22:07:16
问题 I have a table in this format: FieldA FieldB FieldC 1111 ABC X 1111 DEF Y 1111 GHI X 2222 JKL Y 2222 MNO X 3333 PQR U 3333 STT U I want to select one FieldB per FieldA with preference to X in FieldC (if there no X, pick another one). I've tried using the RANK function with PARTITION BY but I find it too inconsistent and I have now reached a wall. My output would look like this: FieldA FieldB FieldC 1111 ABC X 2222 MNO X 3333 PQR U Query: Select rank() over (partition by Field3 order by Field1

AWS Lambda Error: Unable to import module 'function_name': No module named 'module._module'

由 蓝咒 提交于 2021-01-27 19:24:07
问题 Please see the screenshots in particular after reading. I am deploying a python script on AWS Lambda which uses the package impyla which has a dependency on the package bitarray . from impala.dbapi import connect My python file is called authorize_ingress.py which has a function called handle_authorize_ingress(event, context) which are properly configured. See the screenshots below: My function's file: The handler in lambda specified: The handler in code itself: and my zip file has everything

Select first row of group with criteria

由 与世无争的帅哥 提交于 2021-01-27 19:11:07
问题 I have a table in this format: FieldA FieldB FieldC 1111 ABC X 1111 DEF Y 1111 GHI X 2222 JKL Y 2222 MNO X 3333 PQR U 3333 STT U I want to select one FieldB per FieldA with preference to X in FieldC (if there no X, pick another one). I've tried using the RANK function with PARTITION BY but I find it too inconsistent and I have now reached a wall. My output would look like this: FieldA FieldB FieldC 1111 ABC X 2222 MNO X 3333 PQR U Query: Select rank() over (partition by Field3 order by Field1

Getting detailed Impyla error message

由 不羁的心 提交于 2021-01-27 18:33:40
问题 When I execute a SQL statement in Impala using Python/Impyla, I am just getting an exception with a generic error message like ""Operation is in ERROR_STATE". How do I get more detailed information about the error that occurred? 回答1: The cursor object has a _last_operation field that can be used to get more detailed information. E.g. try: cur.execute(sql) except Exception, e: op = cur._last_operation abort(400,"ERROR: %s"%op.get_log()) Output might be: Complete (0 out of 0) Error while
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