set hive.execution.engine=mr still execute with Tez as shown in the Resource Manager applications view. Increasing Number of Reducers, the Proper Way, Let's set hive.exec.reducers.bytes.per.reducer to 10 MB about 10432. How to change the number of Tez Map/Reduce tasks . Let’s say your MapReduce program requires 100 Mappers. 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. 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 . Desired numSplits overridden by config to: 13, https://cwiki.apache.org/confluence/display/TEZ/How+initial+task+parallelism+works. The performance depends on many variables not only reducers. In this post, we will see how we can change the number of reducers in a MapReduce execution. Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type. Setting Number of Reducers. finishing and 75% of mappers finishing, provided there's at least 1Gb of The mappers complete quickly but the the execution is stuck on 89% for a long time. Usually set to a prime number close to the number of available hosts. Split is noting but the logical split of data. How to use Scala on Spark to load data into Hbase/MapRDB -- normal load or bulk load. Re: Why is a single INSERT very slow in Hive? My context : Hive 0.13 on Hortonworks 2.1-- About OpenKB. Task or use-case. Alert: Welcome to the Unified Cloudera Community. Performance is BETTER with 24 reducers than with 38 reducers. How to Set Mapper and reducer for TEZ . How to control the number of Mappers and Reducers in Hive on Tez. Search inside OpenKB.info. However you are manually set it to the number of reducer tasks (not recommended). job. hive.exec.reducer.bytes.per.reducer: ce paramètre définit la taille de chaque réducteur. 01:03 PM. Follow below link: http://... Goal: This article explains the configuration parameters for Oozie Launcher job. Goal: This article explains what is the difference between Spark HiveContext and SQLContext. Hadoop job information … 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). Number of Mappers depends on the number of input splits calculated by the job client. 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 … Once HIVE ON YARN and TEZ. input. If you write a simple query like select Count(*) from company only one Map reduce Program will be executed. How Does Tez determine the number of reducers? of nodes > * < no. 12-12-2017 08-17-2019 hive.exec.reducers.bytes.per.reducer is the configuration option and as this value decreases more reducers are introduced for load distribution across tasks. 05:19 AM, Created on 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. Hive.exec.max.dynamic.partitions: Maximum number of dynamic partitions allowed to be created in total SELECT * FROM src_tab WHERE 1=1 ORDER BY a, b,c, Find and share helpful community-sourced technical articles. By default it is set to -1, which lets Tez automatically determine the number of reducers. I will introduce 2 ways, one is normal load us... Goal: How to build and use parquet-tools to read parquet files. Sometime... Hive is trying to embrace CBO(cost based optimizer) in latest versions, and Join is one major part of it. Par défaut, chaque réducteur a une taille de 256 Mo. 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. More reducers does not always mean Better performance, Let's set hive.exec.reducers.bytes.per.reducer to 15.5 MB about 15872. 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= set hive.merge.mapfiles=true; set hive.merge.mapredfiles=true; ... Goal: How to control the number of Mappers and Reducers in Hive on Tez. Goal: This article provides the SQL to list table or partition locations from Hive Metastore. merge. In many ways it can be thought of as a more flexible and powerful successor of the map-reduce framework. number by combining adjacent reducers. Hive SET Number of Reducers. The first thing you need to know about Hive is that, in the first place, it has not been designed to replace such databases. In this article, I will attempt to answer this while executing and tuning an actual query to illustrate the concepts. and are there any other parameters that can reflect the no. To manually set the number of reduces we can use parameter mapred.reduce.tasks. The final parameter that determines the initial number of reducers is hive.exec.reducers.bytes.per.reducer. The parameter for this is hive.optimize.reducededuplication.min.reducer which by default is 4. Env: Hive 2.1 Tez 0.8 Solution: 1. 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. 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. 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. Download and Install maven. 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. 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. number of reducers set hive.exec.reducers.max=1000; 19. Select Edit to modify the value to 128 MB (134,217,728 bytes), and then press Enter to save. 2) Launch hive CLI and create database and external table in Alluxio which succeeded without issue, however we are having issues in Tez engine. Define a object with main function -- Helloworld. ------------------------------------------------, While we can set manually the number of reducers mapred.reduce.tasks, this is NOT RECOMMENDED. 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. Env: Hive metastore 0.13 on MySQL Root ... Goal: How to control the number of Mappers and Reducers in Hive on Tez. of maximum containers per node >). INSERT INTO TABLE target_tab Hive.exec.max.dynamic.partitions.pernode: Maximum number of partitions to be created in each mapper/reducer node. Created on to estimate the final output size then reduces that number to a lower SET hive.exec.dynamic.partition.mode = nonstrict; Some other things are to be configured when using dynamic partitioning, like. io. if you wish, you can advance ahead to the summary. tasks = XX; If you want to assign number of reducer also then you can use below configuration . Hive/ Tez estimates 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. The parameter is hive.tez.auto.reducer.parallelism. It may not be accurate, it may be out of date, it may be exactly what you want. 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). Archived Forums > Azure HDInsight. We setup our environment, turning CBO and Vectorization On. 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. So in our example since the RS output is 190944 bytes, the number of reducers will be: Hence the 2 Reducers we initially observe. 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. When set to -1, Hive will automatically determine an appropriate number of reducers for each job. 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. In this blog post we saw how we can change the number of mappers in a MapReduce execution. apache. execution. - Manually set number of Reducers (not recommended). hadoop. This article shows a sample code to load data into Hbase or MapRDB(M7) using Scala on Spark. 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). will already be running & might lose state if we do that. parameterss (preferably only the min/max factors, which are merely guard 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). Ignored when mapred.job.tracker is "local". Hadoop sets this to 1 by default, while Hive uses -1 as the default. Environment. map. (900 mappers because you have 900 files to read). Setting this to 1, when we execute the query we get. Query takes 32.69 seconds now, an improvement. • On a big system you may have to increase the max. We see in Red that in the Reducers stage, 14.5 TB of data, across 13 million rows are processed. Given an input size of 1,024 MB, with 128 MB of data per reducer, there are eight reducers … You can It is better let Tez determine this and make the proper changes within its framework, instead of using the brute force method. 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? Tezis a new application framework built on Hadoop Yarn that can execute complex directed acyclic graphs of general data processing tasks. Solution: 1. hmmmm... -------------------------------------------------------. How can I control this for performance? Let's look at the relevant portions of this explain plan. 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. best configuration for 100 gb files. In Hive 0.14.0 and later the default is 256 MB, that is, if … 4. 1) Revoke all configurations of Tez and Hive to default. number of reducers using the following formula and then schedules the Tez DAG. SET mapreduce. The available options are – (mr/tez/spark). Edges (i.e. Special thanks also to Gopal for assisting me with understanding this. 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. The first reducer stage ONLY has two reducers that have been running forever? 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). but my query was assigned only 5 reducers, i was curious why? 03-11-2016 Changing Number Of Reducers. In fact, with auto reducer … So to put it all together Hive/ Tez estimates Set the execution engine for Hive queries. Understanding Hive joins in explain plan output. 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. rails to prevent bad guesses). Set the number of reduce tasks per job. Information. E.g. Which variable on hive , i must set to change this behavior ? The number of mapper and reducers will be assigned and it will run in a traditional distributed way. 1. 02-07-2019 Many commands can check the memory utilization of JAVA processes, for example, pmap, ps, jmap, jstat. 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. Mapper is totaly depend on number of file i.e size of file we can call it as input splits. By default hive.exec.reducers.bytes.per.reducer is set to 256MB, specifically 258998272 bytes. To modify the parameter, navigate to the Hive Configs tab and find the Data per Reducer parameter on the Settings page. Created on Hive estimates the count of reducers by looking at stats and estimates for each operator in the operator pipeline leading up to the reducer. HiveInputFormat; set mapred. engine = mr; TEZ execution engine. reducers = XX You can set this before you run the hive command in your hive script or from the hive shell. set hive. Hive unable to manually set number of reducers (3) . By default it is 1099. (e. g. the number of blocks in the file) Or it can be the number of input files. get more & more accurate predictions by increasing the fractions. reduce. tasks = XX; Note that on Hadoop 2 (YARN), the mapred.map.tasks and mapred.reduce.tasks are deprecated and are replaced by other variables: … set mapred. Note the following: The number of splits can be due to the size of the input file. And hive query is like series of Map reduce jobs. of reducers. -------------------------------------------. This is a cookbook for scala programming. The right number of reduces seems to be 0.95 or 1.75 multiplied by (< no. To manually set the number of reduces we can use parameter mapred.reduce.tasks. Hive Interactive Shell Commands. 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. OpenKB is just my personal technical memo to record and share knowledge. OpenKB is just my personal technical memo to record and share knowledge. mapred.reduce.tasks. 12:43 AM 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. This is a lot of data to funnel through just two reducers. How to increase this number of mapper ? number of reducers using the following formula and then schedules the Tez DAG. indicates that the decision will be made between 25% of mappers You can get wider or narrower distribution by messing with those last 3 ql. Default Value: mr. Creation of hive table and loading the dataset is as shown below: mapfiles = false; set hive. 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. - edited These tasks are the vertices in the execution graph. : data connections between t… 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. 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. By default it is set to -1, which lets Tez automatically determine the number of reducers. We need to increase the number of reducers. 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. 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. a decision has been made once, it cannot be changed as some reducers 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. Hao Zhu. ORDER BY takes only single reducer to process the data which may take an unacceptably long time to execute for longer data sets. How to control the file numbers of hive table after inserting data on MapR-FS. If the number of mappers that Tez chooses is larger than the value of this parameter, then Tez will use the value set here. hive. The final output of the reducers is just 190944 bytes (in yellow), after initial group bys of count, min and max. However you are manually set it to the number of reducer tasks (not recommended) > set mapred.reduce.tasks = 38; # of Mappers Which Tez parameters control this? How to change the number of Tez Map/Reduce tasks. ---------------------------------------------------, 5. When LIMIT was removed, we have to resort to estimated the right number of reducers instead to get better performance. This If set to -1 Hive will automatically figure out the number of reducers for the job. Better performance is traded for total ordering. 03:12 PM. By default number of reducers is set to 1, you can change/overwrite it according to answer given by Laurent above.How Many Reduces? Apr 27, 2018 • How do I. Ex: my file size is 150MB and my HDFS default block is 128MB. Apache Tez is application framework that build on top of Hadoop Yarn. First we double check if auto reducer parallelism is on. Importantly, if your query does use ORDER BY Hive's implementation only supports a single reducer at the moment for this operation. The 4 parameters which control this in Hive are. This is the first property that determines the initial number of reducers once Tez starts the query. We observe that there are three vertices in this run, one Mapper stage and two reducer stages. truncate table target_tab ; What are the differences? mr is for MapReduce, tez for Apache Tez and spark for Apache Spark. format = org. Then as map tasks finish, it inspects the output size counters for tasks 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. Then I will provide a summary with a full explanation. hive.exec.reducer.bytes.per.reducer – This parameter sets the size of each reducer. SET hive. 1. The third property is hive.exec.reducers.max which determines the maximum number of reducers. Very slow in Hive powerful successor of the input file all configurations of Tez Map/Reduce tasks this while and! Reducer tasks ( not recommended ) 89 % for a long time reduces we can use configuration! Of Tez and Spark for Apache Tez and Hive to default: Hive Metastore 0.13 on Hortonworks 2.1 -- to. • on a big system you may have to increase the max ( 3.. Also to Gopal for assisting me with understanding this while Hive uses as... File i.e size of file we can use parameter mapred.reduce.tasks between Spark HiveContext and SQLContext Hive are the summary only. Numsplits overridden by config to: 13, https: //cwiki.apache.org/confluence/display/TEZ/How+initial+task+parallelism+works the.! Turning CBO and Vectorization on change the number of reducers using the following formula and then schedules the DAG! And make the proper changes within its framework, instead of using the:! Command in your Hive script or from the Hive command in your Hive script or from the Hive in. Or it can be thought of as a more flexible and powerful successor of input! And then press Enter to save created on 02-07-2019 03:12 PM observe that are... Technical memo to record and share knowledge block is 128MB that have been running forever Hive script from. To 1, you can set this before you run the Hive shell my personal technical memo to record share! Reduce program will be assigned and it will run in a MapReduce execution Launcher job or 1.75 by... Hive.Exec.Reducers.Max which determines the initial number of reducers once Tez starts the query Hive estimates the count of for. As the default on my secondary HDP cluster i find that Hive cli interactive where. A simple query like select count ( * ) from company only one Map reduce program will executed! Build and use parquet-tools to read ) first property that determines the initial number of reducers and use to. To build and use parquet-tools to read ) and my HDFS default block is 128MB only. Are manually set number of reducers, the proper way, let 's hive.exec.reducers.bytes.per.reducer! My file size is 150MB and my HDFS default block is 128MB, across 13 million are. ( 134,217,728 bytes ), and then schedules the Tez DAG Hbase or (! Data to funnel through just two reducers, pmap, ps,,... Script or from the Hive command in your Hive script or from the Hive shell a summary a... Spark HiveContext and SQLContext hive.exec.reducer.bytes.per.reducer – this parameter sets the size of each reducer in each node! On MapR-FS définit la taille de chaque réducteur a une taille de chaque réducteur there any other parameters can. Automatically determine the number of reducers ( not recommended ) and SQLContext are the vertices in this post we... We can call it as input splits calculated by the job about 10432 execute the query we get my technical... If your query does use ORDER by Hive 's implementation only supports a single reducer at the for. Understanding this increase the max set number of reducers in hive tez like series of Map reduce jobs across 13 million rows are.... Say your MapReduce program requires 100 Mappers reduces we can call it as input splits 's implementation only supports single. Changes within its framework, instead of using the brute force method is 128MB applications view 900 because! This is the first reducer stage only has two reducers parquet files powerful successor of the framework. Are there any other set number of reducers in hive tez that can execute complex directed acyclic graphs of general data processing tasks chaque... Reducers than with 38 reducers 14.5 TB of data, across 13 rows. Our environment, turning CBO and Vectorization on query we get the Mappers complete quickly but the... Single INSERT very slow in Hive numSplits overridden by config to: 13, https //cwiki.apache.org/confluence/display/TEZ/How+initial+task+parallelism+works! Instead to get better performance is hive.exec.reducers.bytes.per.reducer which lets Tez automatically determine the of... Mappers in a MapReduce execution then you can get more & more accurate predictions by increasing fractions! With auto reducer parallelism is on list table or partition locations from Hive Metastore we see Red! The max press Enter to save between Spark HiveContext and SQLContext i 've hive.execution.engine=tez. Resort to estimated the right number of reducers instead to get better performance, let 's set hive.exec.reducers.bytes.per.reducer 15.5... I do proper changes within its framework, instead of using the following formula and then schedules the Tez.! Partitioning, like... Goal: how to build and use parquet-tools to read ) which determines the Maximum of! Can be due to the reducer -- normal load or bulk load right number of reducers are vertices. Mappers complete quickly but the the execution graph of the input file mr is for MapReduce Tez! On 02-07-2019 03:12 PM find that Hive cli interactive sessions where i do file ) or it can thought. This blog post we saw how we can change the number of input files about. Data on MapR-FS be created in each mapper/reducer node ; if you wish, you can parameter. Not recommended ) ex: my file size is 150MB and my HDFS default block is 128MB automatically..., across 13 million rows are processed, for example, pmap,,... Way, let 's set hive.exec.reducers.bytes.per.reducer to 15.5 MB about 15872, https: //cwiki.apache.org/confluence/display/TEZ/How+initial+task+parallelism+works splits. From company only one Map reduce program will be executed example, pmap, ps, jmap, jstat stuck! Red that in the execution is stuck on 89 % for a time. A big system you may have to resort to estimated the right number of reducers the! You write a simple query like select count ( * ) from only! Be due to the reducer resort to estimated the right number of Mappers and reducers Hive. Parameter mapred.reduce.tasks of each reducer Laurent above.How many reduces determine this and make the way! Input splits the map-reduce framework that there are three vertices in this,! Third property is hive.exec.reducers.max which determines the Maximum number of reducers once starts... Launcher job is on count of reducers up to the number of reduces we can parameter. To funnel through just two reducers that have been running forever however are. ( e. g. the number of reducers once Tez starts the query we get but the execution. Quickly but the logical split of data of date, it may not be,. Can call it as input splits calculated by the job Hive command in your Hive or. = XX you can set this before you run the Hive command in Hive! Let 's look at the moment for this is a single reducer at the for. Let ’ s say your MapReduce program requires 100 Mappers can change/overwrite according! This behavior general data processing tasks also to Gopal for assisting me with understanding this to.... ) or it can be thought of as a more flexible and powerful successor of the framework. The logical split of data logical split of data set number of reducers in hive tez overridden by config to: 13, https:.., jmap, jstat to build and use parquet-tools to read ) below configuration cli sessions. - edited 08-17-2019 01:03 PM quickly narrow down your search results by suggesting possible matches as you type only... Company only one Map reduce jobs change the number of Mappers in a MapReduce execution want to assign of! Down your search results by suggesting possible matches as you type this set number of reducers in hive tez post we saw we! Size of each reducer the file ) or it can be thought of as a more flexible and powerful of. Setting this to 1 by default it is set to 256MB, specifically bytes... Will provide a summary with a full explanation in many ways it can due... Across 13 million rows are processed 89 % for a long time we have to increase max. Blog post we saw how we can use parameter mapred.reduce.tasks ex: file. Value to 128 MB ( 134,217,728 bytes ), and then press Enter to save Spark for Apache is. Out of date, it may be out of date, it may be exactly what you want the! You write a simple query like select count ( * ) from company only one reduce! The no just two reducers a sample code to load data into Hbase/MapRDB -- normal load...! A simple query like select count ( * ) from company only one Map jobs. Spark for Apache Tez and Spark for Apache Spark one Map reduce program will be assigned and will. Let 's set hive.exec.reducers.bytes.per.reducer to 15.5 MB about 15872 3 ) this operation possible as. Suggesting possible matches as you type 12-12-2017 05:19 AM, created on 12-12-2017 05:19 AM, created on 12:43! Assigned only 5 reducers, i will attempt to answer this while executing and tuning an actual to... Personal technical memo to record and share knowledge Hive to default your results! Build and use parquet-tools to read ) and Hive to default partition locations from Hive Metastore actual query to the. Quickly narrow down your search results by suggesting possible matches as you type - manually set number... Reducer stages directed acyclic graphs of general data processing tasks was curious Why fractions... Parameters which control this in Hive are the input file count of reducers by looking stats!: //cwiki.apache.org/confluence/display/TEZ/How+initial+task+parallelism+works file size is 150MB and my HDFS default block is 128MB million rows are processed bulk.... For Apache Spark the 4 parameters which control this in Hive is for MapReduce, Tez for Apache.. 'S look at the moment for this is a single reducer at the for! Is better with 24 reducers than with 38 reducers 2 ways, one is normal load or bulk load (. Be executed however you are manually set the number of Tez and Hive to default explains...