Hive installation guide says that Hive can be applied to RDBMS, my question is, sounds like Hive can exist without Hadoop, right? It's an independent HQL engineer that could work with any data source?
You can run Hive in local mode to use it without Hadoop for debugging purposes. See below url
https://cwiki.apache.org/confluence/display/Hive/GettingStarted#GettingStarted-Hive,Map-ReduceandLocal-Mode
Hive provided JDBC driver to query hive like JDBC, however if you are planning to run Hive queries on production system, you need Hadoop infrastructure to be available. Hive queries eventually converts into map-reduce jobs and HDFS is used as data storage for Hive tables.
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Is Hive and Impala integration possible?
After data processing in hive i want to store result data in impala for better read, is it possible?
If yes can you please share one example.
Both hive and impala, do not store any data. The data is stored in the HDFS location and hive an impala both are used just to visualize/transform the data present in the HDFS.
So yes, you can process the data using hive and then read it using impala, considering both of them have been setup properly. But since impala needs to be refreshed, you need to run the invalidate metadata and refresh commands
Impala uses the HIVE metastore to read the data. Once you have a table created in hive, it is possible to read the same and query the same using Impala. All you need is to refresh the table or trigger INVALIDATE METADATA in impala to read the data.
Hope this helps :)
Hive and impala are two different query engines. Each query engine is unique in terms of its architecture as well as performance. We can use hive metastore to get metadata and running query using impala. The common usecase is to connect impala/hive from tableau. If we are visualizing hive from tableau, we can get the latest data without any work around. If we keep on loading the data continuously, metadata will be updated as well. Impala does not aware of those changes. So we should run metadata invalidate query by connecting impalad to refresh its state and sync with the latest info available in metastore. So that user will get the same results as hive when the run the same query from tableau using impala engine.
There is no configuration parameter available now to run this invalidation query periodically. This blog reads well to execute meta data invalidation query through oozie scheduler periodically to handle such problems, Or simply we can set up a cronjob from the server itself.
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What is the difference between hbase and hive? (Hadoop)
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In my project, we are using Hadoop 2, Spark, Scala. Scala is the programming language and Spark is using here for analysing. we are using Hive and HBase both. I can access all details like file etc. of HDFS using Hive.
But my confusions are -
When I can able to performed all jobs using Hive, Then why HBase is required to store the data. Is it not an overhead?
What are the functionality of HIVE and HBase?
If we only used Hive, Then what should be the problem?
Can anyone please let me know.
When I can able to performed all jobs using Hive, Then why HBASE is required to store the data. Is it not a overhead?
What are the functionality of Hive and Hbase
HBase is No Sql database which stores the data in key value pair. Hive has integration with Hbase.Hbase HIve Integration
Advantage :- Hive queries over HBase. Think joins and a easy way to do aggregates and simple operations on your Hbase data.
Hbase gives you a scalable storage infrastructure that keeps data online. StumbleUpon uses Hbase for their live website. Hive is not a real-time query engine, so its data store could not be used for similar purposes. Hive over HBase gives you the benefit of both worlds.
If we only used Hive, Then what should be the problem?
If we will use Hive There is no problem . But in project there so many scenarios we have to consider .
Performance
Storage
Stability of used technology
Compatibility (Hive ware house is easily accessible for most of the Tools in Hadoop)
When I can able to performed all jobs using Hive, Then why HBase is
required to store the data. Is it not an overhead?
I can't say it's overhead or not. But HBase responds to requests in real-time as its database when it comes to Hive it runs jobs on MapReduce/Spark/Tez engines.
What are the functionality of Hive and HBase?
Hive:
It's a SQL-like language that gets translated into MapReduce/Spark/Tez jobs. it only runs batch processes on Hadoop. for more check this how Hive queries run on MapReduce engine
HBase:
It's key/value store database which runs on top of HDFS/S3(on AWS). It does real-time operations for requests.
If we only used Hive, Then what should be the problem?
As discussed If the query needs to process in real-time then HBase is the choice over Hive.
I have used Sqoop to ingest data from Oracle to Hadoop and it worked well. It took only 4 mins to bring 86 million records from Oracle to Hive table without using partitions on Sqoop. Can anyone give some details about Oracle Hadoop connectors, Will it perform better than Sqoop?
Most of connectors would have the performance close to same as you'll have have a set of MapReduce jobs on the very end of your workflow and this would play the main role in your overall performance.
Oracle provides a set of different connectors for accessing the Hive and you could check a nice overview about standard solutions but I doubt that on the very end you will expect significant performance differences other then you see in Sqoop:
https://docs.oracle.com/cd/E37231_01/doc.20/e36961/start.htm#BDCUG119
Sqoop is a generic tool for working with the relational databases from Hadoop realm, and it is not limited by Oracle only. Besides it has an integration with other Hadoop solutions like Oozie for making complicated workflows, which makes it a good candidate over other types of connectors.
Personally myself I prefer Sqoop for Hadoop-driven import-export operations and connector approach for querying the data in Hadoop.
Sqoop will leverage a standard JDBC connection. Oracles connector will work with a fastloader/fastexport class integrated into the sqoop connection. It should be faster that Sqoop.
I am looking into using Hive on our Hadoop cluster to then use Presto to do some analytics on the data stored in Hadoop but I am still confused about some things:
Files are stored in Hadoop (some kind of file manager)
Hive needs tables to store data from Hadoop (data manager)
Do both Hadoop and Hive store their data separate or does Hive just use the files from Hadoop? (in terms of hard disk space and so on?)
-> So does Hive import data from Hadoop in tables and leave Hadoop alone or how must I see this?
Can Presto be used without Hive and just on Hadoop directly?
Thanks in advance for answering my questions :)
First things first: files are stored in Hadoop Distributed File System (HDFS). Is that what you call Data manager?
Actually Hive can use both - "regular" files in HDFS or tables which are once again "regular" files with additional metadata stored in special datastore (it is called warehouse).
Concerning Presto - it has a built-in support for Hive metastore, but you can also write your own connector plugin for any data source.
Please read more info about Hive connector configuration here and about connector plugins here.
I am a newbie to Hadoop / Hive and I have just started reading the docs. There are lots of blogs on installing Hadoop in cluster mode. Also, I know that Hive runs on top of Hadoop.
My question is: Hadoop is installed on all the cluster nodes. Should I also install Hive on all the cluster nodes or only on the master node?
No, it is not something you install on worker nodes. Hive is a Hadoop client. Just run Hive according to the instructions you see at the Hive site.
From Cloudera's Hive installation Guide:
Install Hive on your client machine(s) from which you submit jobs; you do not need to install it on the nodes in your Hadoop cluster.
Hive is basically used for processing structured and semi-structured data in Hadoop. We can also perform Analysis of large datasets which is present in HDFS and also in Amazon S3 filesystem using Hive. In order to query data hive also provides query language known as HiveQL which is similar to SQL. Using Hive one can easily run Ad-hoc queries for the data analysis. Using Hive we don’t need to write complex Map-Reduce jobs, we just need to submit SQL queries. Hive converts these SQL queries into MapReduce jobs.
Finally Hive SQL will get converted to MapReduce jobs and we don't have to submit MapReduce job from all node in a Hadoop cluster, in the same way we don't need Hive to be installed in all node of Hadoop cluster