Hive | 易学教程

Clear All Existing Entries In DynamoDB Table In AWS Data Pipeline

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问题 My goal is to take daily snapshots of an RDS table and put it in a DynamoDB table. The table should only contain data from a single day. For this have a Data Pipeline set up to query a RDS table and publish the results into S3 in CSV format. Then a HiveActivity imports this CSV into a DynamoDB table by creating external tables for the file and an existing DynamoDB table. This works great, but older entries from the previous day still exist in the DynamoDB table. I want to do this within Data

Calculating multiple averages across different parts of the table?

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问题 I have the following transactions table: customer_id purchase_date product category department quantity store_id 1 2020-10-01 Kit Kat Candy Food 2 store_A 1 2020-10-01 Snickers Candy Food 1 store_A 1 2020-10-01 Snickers Candy Food 1 store_A 2 2020-10-01 Snickers Candy Food 2 store_A 2 2020-10-01 Baguette Bread Food 5 store_A 2 2020-10-01 iPhone Cell phones Electronics 2 store_A 3 2020-10-01 Sony PS5 Games Electronics 1 store_A I would like to calculate the average number of products purchased

Hive快捷查询：不启用Mapreduce job启用Fetch task三种方式介绍

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如果查询表的某一列，Hive中默认会启用MapReduce job来完成这个任务，如下： hive>select id,name from m limit 10;--执行时hive会启用MapReduce job 我们都知道，启用MapReduce Job是会消耗系统开销的。对于这个问题，从Hive0.10.0版本开始，对于简单的不需要聚合的类似 SELECT <col> from <table> LIMIT n语句，不需要起MapReduce job，直接通过Fetch task获取数据，可以通过下面几种方法实现：方法一： hive>set hive.fetch.task.conversion=more;--开启fetch任务，就不启用MapReduce job； hive>select id,name from m limit 10; 方法二： hive>bin/hive --hiveconf hive.fetch.task.conversion=more 方法三：上面的两种方法都可以开启了Fetch任务，但是都是临时起作用的；如果你想一直启用这个功能，可以在${HIVE_HOME}/conf/hive-site.xml里面加入以下配置： <property> <name>hive.fetch.task.conversion</name> <value>more<

epoch with milliseconds to timestamp with milliseconds conversion in Hive

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问题 How can I convert unix epoch with milliseconds to timestamp with milliseconds In Hive? Neither cast() nor from_unixtime() function is working to get the timestamp with milliseconds. I tried .SSS but the function just increases the year and doesn't take it as a part of millisecond. scala> spark.sql("select from_unixtime(1598632101000, 'yyyy-MM-dd hh:mm:ss.SSS')").show(false) +-----------------------------------------------------+ |from_unixtime(1598632101000, yyyy-MM-dd hh:mm:ss.SSS)| +-------

Why Hive can not support non-equi join?

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问题 I found that the Hive does not support non-equi join.Is it just because it is difficult to convert non-equi join to Map reduce? 回答1: Yes, the problem is in current map-reduce implementation. How common equi-join is implemented in MapReduce? Input records are being copied in chunks to the mappers, mappers produce output as key-value pairs, which are collected and distributed between reducers using some function in such way that each reducer will process the whole key, in other words, mapper

Why Hive can not support non-equi join?

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How to provide arguments to IN Clause in HIve

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问题 Is there any way to read arguments in HIVEquery which can substitute to an IN Clause. I have the below query with me. Select count (*) from table where id in ('1','2','3','4','5'). Is there any way to supply the arguments to IN Clause from a text file ? 回答1: Use in_file: Put all ids into file, one id in a row. Select count (*) from table where in_file(id, '/tmp/myfilename'); --local file Also you can pass the list of values as a single parameter to the IN: https://stackoverflow.com/a/56963448

Optimizing query with multiple sums?

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问题 I have table products : +----------+-----------+----------+---------+ |family_id |shopper_id |product_id|quantity | +----------+-----------+----------+---------+ |A |1 |Kit Kat |10 | |A |1 |Kit Kat |5 | |A |1 |Snickers |9 | |A |2 |Kit Kat |7 | |B |3 |Kit Kat |2 | +----------+---------- +----------+---------+ For each product, I want to calculate 2 totals: total quantity per shopper total quantity per family. Sum of total quantities for all shoppers in the same family. The final table should

Is it possible to compress json in hive external table?

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问题 I want to know how to compress json data in hive external table. How can it be done? I have created external table like this: CREATE EXTERNAL TABLE tweets ( id BIGINT,created_at STRING,source STRING,favorited BOOLEAN )ROW FORMAT SERDE "com.cloudera.hive.serde.JSONSerDe" LOCATION "/user/cloudera/tweets"; and I had set the compression properties set mapred.output.compress=true; set hive.exec.compress.output=true; set mapred.output.compression.codec=org.apache.hadoop.io.compress.GzipCodec; set

[Hive]I got “ArrayIndexOutOfBoundsException” while I query the hive database

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问题 I always get "ArrayIndexOutOfBoundsException" while I query the hive base(both hive-0.11.0 and hive-0.12.0), but sometimes not. Here is the error java.lang.RuntimeException: Hive Runtime Error while closing operators: java.lang.ArrayIndexOutOfBoundsException: 0 at org.apache.hadoop.hive.ql.exec.mr.ExecReducer.close(ExecReducer.java:313) at org.apache.hadoop.io.IOUtils.cleanup(IOUtils.java:232) at org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:539) at org.apache.hadoop