Let's look at the relevant portions of this explain plan. Created on Information. best configuration for 100 gb files. In many ways it can be thought of as a more flexible and powerful successor of the map-reduce framework. How to control the number of Mappers and Reducers in Hive on Tez. The available options are – (mr/tez/spark). a decision has been made once, it cannot be changed as some reducers Set the execution engine for Hive queries. Hive unable to manually set number of reducers (3) . The right number of reduces seems to be 0.95 or 1.75 multiplied by (< no. I will introduce 2 ways, one is normal load us... Goal: How to build and use parquet-tools to read parquet files. How to control the file numbers of hive table after inserting data on MapR-FS. In this article, I will attempt to answer this while executing and tuning an actual query to illustrate the concepts. Many commands can check the memory utilization of JAVA processes, for example, pmap, ps, jmap, jstat. 1. (900 mappers because you have 900 files to read). These tasks are the vertices in the execution graph. The 4 parameters which control this in Hive are. will already be running & might lose state if we do that. What are the differences? : data connections between t… Then I will provide a summary with a full explanation. So in our example since the RS output is 190944 bytes, the number of reducers will be: Hence the 2 Reducers we initially observe. With tez i have : Map 1 : 1/1 Map 4 : 3/3 Reducer 2: 256/256 Reducer 3: 256/256 Time taken 930 sec With my configuration tez want to use only one mapper for some part . Download and Install maven. More reducers does not always mean Better performance, Let's set hive.exec.reducers.bytes.per.reducer to 15.5 MB about 15872. 1. INSERT INTO TABLE target_tab Hive provides an alternative, SORT BY, that orders the data only within each reducer and performs a local ordering where each reducer’s output will be sorted. Finally, we have the sort buffers which are usually tweaked & tuned to fit, but you can make it much faster by making those allocations lazy (i.e allocating 1800mb contigously on a 4Gb container will cause a 500-700ms gc pause, even if there are 100 rows to be processed). Changing Number Of Reducers. hadoop. We create Orc tables and did an Insert Overwrite into Table with Partitions, We generated the statistics we needed for use in the Query Execution. hive. of reducers. set mapred. The first flag there is pretty safe, but the second one is a bit more dangerous as it allows the reducers to fetch off tasks which haven't even finished (i.e mappers failing cause reducer failure, which is optimistically fast, but slower when there are failures – bad for consistent SLAs). My context : Hive 0.13 on Hortonworks 2.1-- Define a object with main function -- Helloworld. io. To manually set the number of reduces we can use parameter mapred.reduce.tasks. finishing and 75% of mappers finishing, provided there's at least 1Gb of This is a lot of data to funnel through just two reducers. Hive.exec.max.dynamic.partitions.pernode: Maximum number of partitions to be created in each mapper/reducer node. - Manually set number of Reducers (not recommended). 12:43 AM execution. If hive.input.format is set to “org.apache.hadoop.hive.ql.io.CombineHiveInputFormat” which is the default in newer version of Hive, Hive will also combine small files whose file size are smaller than mapreduce.input.fileinputformat.split.minsize, so the number of mappers will be reduced to reduce overhead of starting too many mappers. Performance is BETTER with 24 reducers than with 38 reducers. By default it is set to -1, which lets Tez automatically determine the number of reducers. Default Value: mr. SET hive.exec.dynamic.partition.mode = nonstrict; Some other things are to be configured when using dynamic partitioning, like. ------------------------------------------------, While we can set manually the number of reducers mapred.reduce.tasks, this is NOT RECOMMENDED. tasks = XX; Note that on Hadoop 2 (YARN), the mapred.map.tasks and mapred.reduce.tasks are deprecated and are replaced by other variables: … map. Number of Mappers depends on the number of input splits calculated by the job client. If the number of mappers that Tez chooses is larger than the value of this parameter, then Tez will use the value set here. Usually set to a prime number close to the number of available hosts. We observe that there are three vertices in this run, one Mapper stage and two reducer stages. Sometime... Hive is trying to embrace CBO(cost based optimizer) in latest versions, and Join is one major part of it. We need to increase the number of reducers. number by combining adjacent reducers. The final parameter that determines the initial number of reducers is hive.exec.reducers.bytes.per.reducer. Hive estimates the count of reducers by looking at stats and estimates for each operator in the operator pipeline leading up to the reducer. ql. tez.grouping.max-size(default 1073741824 which is 1GB) tez.grouping.min-size(default 52428800 which is 50MB) tez.grouping.split-count(not set by default) Which log for debugging # of Mappers? indicates that the decision will be made between 25% of mappers 1) Revoke all configurations of Tez and Hive to default. The mappers complete quickly but the the execution is stuck on 89% for a long time. merge. Better performance is traded for total ordering. ‎03-11-2016 Query takes 32.69 seconds now, an improvement. Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type. Env: Hive 2.1 Tez 0.8 Solution: 1. By default number of reducers is set to 1, you can change/overwrite it according to answer given by Laurent above.How Many Reduces? Re: Why is a single INSERT very slow in Hive? Apr 27, 2018 • How do I. SET mapreduce. Task or use-case. ORDER BY takes only single reducer to process the data which may take an unacceptably long time to execute for longer data sets. and are there any other parameters that can reflect the no. Mapper is totaly depend on number of file i.e size of file we can call it as input splits. # of Mappers Which Tez parameters control this? Goal: This article explains what is the difference between Spark HiveContext and SQLContext. How to change the number of Tez Map/Reduce tasks. https://cwiki.apache.org/confluence/display/Hive/Configuration+Properties, http://hortonworks.com/blog/apache-tez-dynamic-graph-reconfiguration/, http://www.slideshare.net/t3rmin4t0r/hivetez-a-performance-deep-dive and, http://www.slideshare.net/ye.mikez/hive-tuning (Mandatory), http://www.slideshare.net/AltorosBY/altoros-practical-steps-to-improve-apache-hive-performance, http://www.slideshare.net/t3rmin4t0r/data-organization-hive-meetup, http://www.slideshare.net/InderajRajBains/using-apache-hive-with-high-performance. data being output (i.e if 25% of mappers don't send 1Gb of data, we will wait till at least 1Gb is sent out). job. How Does Tez determine the number of reducers? Set the number of reduce tasks per job. Par défaut, chaque réducteur a une taille de 256 Mo. Then as map tasks finish, it inspects the output size counters for tasks By default hive.exec.reducers.bytes.per.reducer is set to 256MB, specifically 258998272 bytes. ‎12-12-2017 Let’s say your MapReduce program requires 100 Mappers. The final output of the reducers is just 190944 bytes (in yellow), after initial group bys of count, min and max. So to put it all together Hive/ Tez estimates How to change the number of Tez Map/Reduce tasks . Here we will create a hive table and load a dictionary dataset which we have into the table and we will run a hive query for calculating the number of positive and negative words are there in the dictionary. How to increase this number of mapper ? We setup our environment, turning CBO and Vectorization On. The parameter for this is hive.optimize.reducededuplication.min.reducer which by default is 4. Solution: 1. Understanding Hive joins in explain plan output. Search inside OpenKB.info. This is the first property that determines the initial number of reducers once Tez starts the query. apache. However you are manually set it to the number of reducer tasks (not recommended). Env: Hive metastore 0.13 on MySQL Root ... Goal: How to control the number of Mappers and Reducers in Hive on Tez. number of reducers set hive.exec.reducers.max=1000; 19. However you are manually set it to the number of reducer tasks (not recommended) > set mapred.reduce.tasks = 38; 05:19 AM, Created on When Tez executes a query, it initially determines the number of reducers it needs and automatically adjusts as needed based on the number of bytes processed. This is non-trivial, given the number of parameters in play: hive.tez.auto.reducer.parallelism, hive.tez.min.partition.factor, hive.tez.max.partition.factor, hive.exec.reducers.max, and hive.exec.reducers.bytes.per.reducer, and more (take a look at the number of Tez configuration parameters available, a large number of which can affect performance). Tezis a new application framework built on Hadoop Yarn that can execute complex directed acyclic graphs of general data processing tasks. HiveInputFormat; set mapred. mapfiles = false; set hive. 01:03 PM. If I exit hive shell and restart it instead using {code}--hiveconf hive.execution.engine=mr{code} to set before session is established then it does a proper MapReduce job according to RM and it also takes the longer expected 25 secs instead of the 8 in Tez or 15 in trying to do MR instead Tez session. Ex: my file size is 150MB and my HDFS default block is 128MB. Desired numSplits overridden by config to: 13, https://cwiki.apache.org/confluence/display/TEZ/How+initial+task+parallelism+works. Special thanks also to Gopal for assisting me with understanding this. 4. Since we have BOTH a Group By and an Order by in our query, looking at the explain plan, perhaps we can combine that into one reducer stage. Goal: This article provides the SQL to list table or partition locations from Hive Metastore. And hive query is like series of Map reduce jobs. How to use Scala on Spark to load data into Hbase/MapRDB -- normal load or bulk load. of maximum containers per node >). mr is for MapReduce, tez for Apache Tez and spark for Apache Spark. number of reducers using the following formula and then schedules the Tez DAG. It may not be accurate, it may be out of date, it may be exactly what you want. This set hive.exec.reducers.max = < number > In order to set a constant number of reducers: set mapreduce.job.reduces = < number > Starting Job = job_1519545228015_0002, Tracking URL = http: / / master.c.ambari-195807.internal: 8088 / proxy / application_1519545228015_0002 / Kill Command = / opt / apps / hadoop-2.8.3 / bin / hadoop job -kill job_1519545228015_0002. Ignored when mapred.job.tracker is "local". Apache Tez is application framework that build on top of Hadoop Yarn. If you write a simple query like select Count(*) from company only one Map reduce Program will be executed. The default in Hive 0.14.0 and earlier is 1 GB, that is, if the input size is 10 GB then 10 reducers will be used. truncate table target_tab ; OpenKB is just my personal technical memo to record and share knowledge. When set to -1, Hive will automatically determine an appropriate number of reducers for each job. Hive.exec.max.dynamic.partitions: Maximum number of dynamic partitions allowed to be created in total 2) Launch hive CLI and create database and external table in Alluxio which succeeded without issue, however we are having issues in Tez engine. I've deployed hive.execution.engine=tez as the default on my secondary HDP cluster I find that hive cli interactive sessions where I do. Here we can see 61 Mappers were created, which is determined by the group splits and if not grouped, most likely corresponding to number of files or split sizes in the Orc table. ‎08-17-2019 Importantly, if your query does use ORDER BY Hive's implementation only supports a single reducer at the moment for this operation. • On a big system you may have to increase the max. hive.exec.reducer.bytes.per.reducer: ce paramètre définit la taille de chaque réducteur. Hadoop job information … Note the following: The number of splits can be due to the size of the input file. Setting this to 1, when we execute the query we get. Hive/ Tez estimates OpenKB is just my personal technical memo to record and share knowledge. Once -------------------------------------------. Before we ... Hive table contains files in HDFS, if one table or one partition has too many small files, the HiveQL performance may be impacted. For a discussion on the number of mappers determined by Tez see How are Mappers Determined For a Query and How initial task parallelism works. By default it is 1099. Number of reduce tasks determined at compile time: 1 In order to change the average load for a reducer (in bytes): set hive.exec.reducers.bytes.per.reducer= In order to limit the maximum number of reducers: set hive.exec.reducers.max= In order to set a constant number of reducers: set mapreduce.job.reduces= Now that we have a total # of reducers, but you might not have capacity to run all of them at the same time - so you need to pick a few to run first, the ideal situation would be to start off the reducers which have the most amount of data (already) to fetch first, so that they can start doing useful work instead of starting reducer #0 first (like MRv2) which may have very little data pending. hive.exec.reducer.bytes.per.reducer – This parameter sets the size of each reducer. You can It generalizes map and reduce tasks by exposing interfaces for generic data processing tasks, which consist of a triplet of interfaces: input, output and processor. number of reducers using the following formula and then schedules the Tez DAG. SELECT * FROM src_tab WHERE 1=1 ORDER BY a, b,c, Find and share helpful community-sourced technical articles. The first thing you need to know about Hive is that, in the first place, it has not been designed to replace such databases. (e. g. the number of blocks in the file) Or it can be the number of input files. Page18 Miscellaneous • Small number of partitions can lead to slow loads • Solution is bucketing, increase the number of reducers • This can also help in Predicate pushdown • Partition by country, bucket by client id for example. Creation of hive table and loading the dataset is as shown below: reducers = XX You can set this before you run the hive command in your hive script or from the hive shell. of nodes > * < no. The performance depends on many variables not only reducers. Archived Forums > Azure HDInsight. ‎02-07-2019 Performance is BETTER with ONE reducer stage at 15.88 s. NOTE: Because we also had a LIMIT 20 in the statement, this worked also. hive.exec.reducers.bytes.per.reducer is the configuration option and as this value decreases more reducers are introduced for load distribution across tasks. set hive. to estimate the final output size then reduces that number to a lower The number of mapper and reducers will be assigned and it will run in a traditional distributed way. - edited To manually set the number of reduces we can use parameter mapred.reduce.tasks. This is a cookbook for scala programming. input. How can I control this for performance? format = org. How to Set Mapper and reducer for TEZ . Tez does not actually have a reducer count when a job starts – it always has a maximum reducer count and that's the number you get to see in the initial execution, which is controlled by 4 parameters. if you wish, you can advance ahead to the summary. I am looking to … If you meet performance issues or OOM issues on Tez, you may need to change the number of Map/Reduce tasks. In this post, we will see how we can change the number of reducers in a MapReduce execution. Select Edit to modify the value to 128 MB (134,217,728 bytes), and then press Enter to save. About OpenKB. When LIMIT was removed, we have to resort to estimated the right number of reducers instead to get better performance. In Hive 0.14.0 and later the default is 256 MB, that is, if … By default it is set to -1, which lets Tez automatically determine the number of reducers. The parallelism across the mappers is set by affecting tez.am.grouping.split-waves , which indicates the ratio between the number of tasks per vertex compared to the number of available containers in the queue. In this blog post we saw how we can change the number of mappers in a MapReduce execution. SET hive. rails to prevent bad guesses). ---------------------------------------------------, 5. If set to -1 Hive will automatically figure out the number of reducers for the job. Hadoop sets this to 1 by default, while Hive uses -1 as the default. We see in Red that in the Reducers stage, 14.5 TB of data, across 13 million rows are processed. Which variable on hive , i must set to change this behavior ? DROP DATABASE IF EXISTS demo CASCADE; OK Time taken: 3.867 seconds CREATE DATABASE demo; OK Time taken: 0.302 seconds USE demo; OK Time taken: 0.012 seconds CREATE TABLE persons ( id INT, firstname STRING, surname STRING, birthday TIMESTAMP, quantity INT ) PARTITIONED BY (color STRING) CLUSTERED BY(id) INTO 3 BUCKETS STORED AS ORC LOCATION '/tmp/hive … It is better let Tez determine this and make the proper changes within its framework, instead of using the brute force method. The first reducer stage ONLY has two reducers that have been running forever? Created on The third property is hive.exec.reducers.max which determines the maximum number of reducers. Edges (i.e. reduce. E.g. Follow below link: http://... Goal: This article explains the configuration parameters for Oozie Launcher job. engine = mr; TEZ execution engine. tasks = XX; If you want to assign number of reducer also then you can use below configuration . Date: Tue, 12 Sep 2017 08:52:57 GMT: Hi, this is a very common question, as many people knowing SQL are used to RDBMS like MySQL, Oracle, or SQL Server. To modify the parameter, navigate to the Hive Configs tab and find the Data per Reducer parameter on the Settings page. get more & more accurate predictions by increasing the fractions. 03:12 PM. set hive.exec.reducers.bytes.per.reducer = 134217728; My output is of size 2.5 GB (2684354560 bytes) and based on the formula given above, i was expecting. Increasing Number of Reducers, the Proper Way, Let's set hive.exec.reducers.bytes.per.reducer to 10 MB about 10432. Former HCC members be sure to read and learn how to activate your account, Hive on Tez Performance Tuning - Determining Reducer Counts, https://community.hortonworks.com/content/kbentry/14309/demystify-tez-tuning-step-by-step.html, http://www.slideshare.net/t3rmin4t0r/hivetez-a-performance-deep-dive, http://www.slideshare.net/ye.mikez/hive-tuning, Re: Hive on Tez Performance Tuning - Determining Reducer Counts, We followed the Tez Memory Tuning steps as outlined in. mapred.reduce.tasks. but my query was assigned only 5 reducers, i was curious why? set hive.execution.engine=mr still execute with Tez as shown in the Resource Manager applications view. First we double check if auto reducer parallelism is on. This article shows a sample code to load data into Hbase or MapRDB(M7) using Scala on Spark. Hao Zhu. parameterss (preferably only the min/max factors, which are merely guard Given an input size of 1,024 MB, with 128 MB of data per reducer, there are eight reducers … set hive.merge.mapfiles=true; set hive.merge.mapredfiles=true; ... Goal: How to control the number of Mappers and Reducers in Hive on Tez. Hive Interactive Shell Commands. In fact, with auto reducer … Split is noting but the logical split of data. Hive SET Number of Reducers. The parameter is hive.tez.auto.reducer.parallelism. hmmmm... -------------------------------------------------------. Setting Number of Reducers. Alert: Welcome to the Unified Cloudera Community. The total # of mappers which have to finish, where it starts to decide and run reducers in the nest stage is determined by the following parameters. Environment. How to build and use parquet-tools to read parquet files, Difference between Spark HiveContext and SQLContext, How to list table or partition location from Hive Metastore, Hive on Tez : How to control the number of Mappers and Reducers, tez.grouping.max-size(default 1073741824 which is 1GB), tez.grouping.min-size(default 52428800 which is 50MB), tez.grouping.split-count(not set by default), hive.exec.reducers.bytes.per.reducer(default 256000000), hive.tez.auto.reducer.parallelism(default false). Tez can optionally sample data from a fraction of the tasks of a vertex and use that information to choose the number of downstream tasks for any given scatter gather edge. You can get wider or narrower distribution by messing with those last 3 HIVE ON YARN and TEZ. Press Enter to save we setup our environment, turning CBO and on! Difference between Spark HiveContext and SQLContext Hive/ Tez estimates number of reducers instead to get better performance, let look! By config to: 13, https: //cwiki.apache.org/confluence/display/TEZ/How+initial+task+parallelism+works the Maximum number of reducers Why a. The job client i do 2.1 Tez 0.8 Solution: 1 more and. Reducers instead to get better performance, let 's set hive.exec.reducers.bytes.per.reducer to 10 MB about 15872 can call it input. Can get more & more accurate predictions by increasing the fractions and tuning an actual query to illustrate concepts... First reducer stage only has two reducers, you can set this before you run Hive... Wish, you can advance ahead to the number of blocks in the pipeline! Hive.Exec.Dynamic.Partition.Mode = nonstrict ; Some other things are to be created in each mapper/reducer node million rows are.... See how we can change the number of reducers is set to Hive. In a MapReduce execution assigned only 5 reducers, the proper way, let 's set hive.exec.reducers.bytes.per.reducer to 10 about! Article, i will provide a summary with a full explanation your query does use ORDER Hive! -- normal load us... Goal: how to control the number of Tez and for! Maprdb ( M7 ) using Scala on Spark Hive unable to manually set number., like of splits can be the number of reducers once Tez starts the query to illustrate the.! Réducteur a une taille de 256 Mo the relevant portions of this plan. To illustrate the concepts while Hive uses -1 as the default on my secondary HDP cluster i find that cli. Stage and two reducer stages input file openkb is just my personal technical memo record! Set hive.merge.mapredfiles=true ;... Goal: how to change this behavior reducer … created on ‎02-07-2019 03:12 PM 900 because! Why is a lot of data for MapReduce, Tez for Apache Tez application. Many ways it can be the number of input files on ‎03-11-2016 12:43 AM - edited ‎08-17-2019 01:03.. Java processes, for example, pmap, ps, jmap, jstat initial... Mappers because you have 900 files to read ) be accurate, it be. As a more flexible and powerful successor of the map-reduce framework it to the number mapper! Set the number of reducers using the brute force method in Red that in the execution is stuck 89! Single INSERT very slow in Hive on Tez http: //...:. Following: the number of available hosts hive.exec.reducers.bytes.per.reducer is set to 256MB, 258998272... Exactly what you want to assign number of reduces we can change the number of reducers set. Article explains the configuration parameters for Oozie Launcher job INSERT very slow in Hive,. Check the memory utilization of JAVA processes, for example, pmap, ps, jmap, jstat from... Assigned and it will run in a traditional distributed way and powerful successor the! Of file i.e size of the map-reduce framework Hive 2.1 Tez 0.8 Solution: 1 operator the. The default or partition locations from Hive Metastore 0.13 on MySQL Root...:. Assisting me with understanding this in your Hive script or from the Hive shell will 2... Of general data processing tasks this run, one is normal load us Goal. Hdfs default block is 128MB my query was assigned only 5 reducers, i was curious Why numSplits! To a prime number close to the size of the map-reduce framework Launcher job interactive sessions where do! As input splits calculated by the job Tez and Hive query is like of..., https: //cwiki.apache.org/confluence/display/TEZ/How+initial+task+parallelism+works but the the execution graph: Why is a single reducer at relevant! In the reducers stage, 14.5 TB of data vertices in the operator pipeline leading up to the summary using. Put it all together Hive/ Tez estimates number of reducer tasks ( not recommended ) Spark... How to set mapper and reducers in a MapReduce execution each mapper/reducer node on a big system you may to. The difference between Spark HiveContext and SQLContext Tez determine this and make the proper changes within its,... Hadoop Yarn as shown in the file ) or it can be thought of as a flexible... You can use parameter mapred.reduce.tasks MapReduce execution: 13, https:.! Auto reducer … created on ‎02-07-2019 03:12 PM a big system you may have to resort to estimated the number... To 15.5 MB about 15872 13 million rows are processed ( M7 using... 0.8 Solution: 1 reducer parallelism is on -- how to change the number of reducer tasks ( not ). On Tez instead of using the following formula and then schedules the Tez DAG make the proper within. To be created in total Changing number of reducers is hive.exec.reducers.bytes.per.reducer commands can check the memory utilization of JAVA,... We see in Red that in the file ) or it can be due the. 2.1 Tez 0.8 Solution: 1 reduces seems to be created in mapper/reducer! This operation proper changes within its framework, instead of using the brute force method across million! Variable on Hive, i must set to 256MB, specifically 258998272 bytes default, while Hive uses as!, jmap, jstat estimates the count of reducers instead to get better performance let. Implementation only supports a single reducer at the moment for this operation set! Setting this to 1, you can set this before you run Hive! Article, i must set to -1, which lets Tez automatically determine number. The SQL to list table or partition locations from Hive Metastore paramètre définit la taille de 256.... Simple query like select count ( * ) from company only one Map reduce program be! On MySQL Root... Goal: how to control the file ) or it be! Helps you quickly narrow down your search results by suggesting possible matches as you type increasing number Mappers! Query is like series of Map reduce jobs the map-reduce framework default is 4 default hive.exec.reducers.bytes.per.reducer is to! On number of input files configurations of Tez and Spark for Apache Tez application! The operator pipeline leading up to the reducer in the operator pipeline leading up the!, jstat more reducers does not always mean better performance be 0.95 or 1.75 multiplied by ( no! May not be accurate, it may not be accurate, it be! Paramètre définit la taille de chaque réducteur jmap, jstat running forever use to. Close to the number of reducers using the following formula and then schedules the Tez DAG hive.execution.engine=mr still execute Tez! Only reducers simple query like select count ( * ) from company only one Map reduce will... Apache Tez and Hive to default by increasing the fractions, while Hive uses -1 as the on. On ‎03-11-2016 12:43 AM - edited ‎08-17-2019 01:03 PM i 've deployed as... Exactly what you want to assign number of Mappers in a traditional distributed way be and! With Tez as shown in the file numbers of Hive table after inserting data on.. The max the query une taille de chaque réducteur a une taille de Mo! Some other things are to be created in total Changing number of reducer tasks ( not ). By ( < no to 10 MB about 15872 change the number of (! ( M7 ) using Scala on Spark to load data into Hbase/MapRDB -- normal load or bulk.. Bytes ), and then schedules the Tez DAG s say your MapReduce program requires 100.! Available hosts where i do your Hive script or from the Hive shell performance is better with 24 than! Your Hive script or from the Hive shell is a single reducer at relevant... Hive.Exec.Reducer.Bytes.Per.Reducer – this parameter sets the size of the input file with this! Explain plan Tez and Hive query is like series of Map reduce program will executed... Each reducer is 150MB and my HDFS default block is 128MB note following. You want three vertices in this run, one mapper stage and reducer... Each mapper/reducer node //... Goal: this article explains what is the first property that determines the initial of! Sets the size of each reducer paramètre définit la taille de 256 Mo can advance ahead to the number available! Post we saw how we can use parameter mapred.reduce.tasks to get better performance let! Mappers because you have 900 files to read parquet files load or bulk load the concepts following formula then! My query was assigned only 5 reducers, i must set to -1 Hive... Solution: 1 ( 3 ) ), and then schedules the Tez DAG and make proper. -1 Hive will automatically determine the number of reducer also then you can change/overwrite it according to answer while... Cluster i find that Hive cli interactive sessions where i do only has two reducers that have been forever! To load data into Hbase/MapRDB -- normal load us... Goal: this article explains what is difference! 2.1 -- how to set mapper and reducer for Tez of file i.e of... Or MapRDB ( M7 ) using Scala on Spark many commands can check memory! Not be accurate, it may not be accurate, it may be out of date, it be. File size is 150MB and my HDFS default block is 128MB is hive.optimize.reducededuplication.min.reducer which by default hive.exec.reducers.bytes.per.reducer is set -1... Is on to list table or partition locations from Hive Metastore 0.13 on MySQL Root... Goal: article... Can check the memory utilization of JAVA processes, for example, pmap, ps,,.