If tables are bucketed by a particular column and these tables are being used in joins then we can enable bucketed map join to improve the performance. ANALYZE statements must be transparent and not affect the performance of DML statements. To view column stats : Our forums are a great place to make new friends, discuss your favourite Hive games and suggest your ideas and improvements! Source: https://www.cloudera.com/documentation/enterprise/5-9-x/topics/impala_compute_stats.html, Your email address will not be published. Hive is Hadoopâs SQL interface over HDFS which gives a ⦠More specifically, INSERT OVERWRITE will automatically create new column stats. Trigger ANALYZE statements for DML and DDL statements that create tables or insert data on any query engine. HiveQLâs analyze command will be extended to trigger statistics computation on one or more column in a Hive table/partition. stats. < name > hive.compute.query.using.stats < / name > < value > true < / value > < description > When set to true Hive will answer a few queries like count (1) purely using stats stored in metastore. Statistics on the data of a table. We can enable the Tez engine with below property from hive shell. parameters - The ObjectInspector for the parameters: In PARTIAL1 and COMPLETE mode, the parameters are original data; In PARTIAL2 and FINAL mode, the parameters are just partial aggregations (in that case, the array will always have a single element). we can improve the performance of hive queries at least by 100% to 300 % by running on Tez execution engine. “Compute Stats” is one of these optimization techniques. The information is stored in the metastore database and used by Impala to help optimize queries. You can collect the statistics on the table by using Hive ANALAYZE command. partition.stats = true; analyze table yourTable compute statistics for columns; ORC files. 2. In this patch, the column stats will also be collected automatically. 4. This would help in preparing the efficient query plan before executing a query on a large table. hive.stats.fetch.column.stats. The Hive Community. The Top Bees. The necessary changes to HiveQL are as below, analyze table t [partition p] compute statistics for [columns c,...]; Please note that table and column aliases are not supported in the analyze statement. Parameters. As a newbie to Hive, I assume I am doing something wrong. Cloudera Impala provides an interface for executing SQL queries on data(Big Data) stored in HDFS or HBase in a fast and interactive way. Visual Explain without Statistics As you may recall, the following query will summarize total hours and miles driven by driver. Hive uses column statistics, which are stored in metastore, to optimize queries. COMPUTE STATS will prepare the stats of entire table whereas COMPUTE INCREMENTAL STATS will work only on few of the partitions rather than the whole table. Recent Suggestions. Since Hive doesn't push down the filter predicate, you're pulling all of the data back to the client and then applying the filter. The same command could be used to compute statistics for one or more column of a Hive table or partition. It supports datetime, decimal, list, map. To speed up COMPUTE STATS consider the following options which can be combined. We are running Hive 1.2.1.2.5. Apache Hive is a data warehouse software project built on top of Apache Hadoop for providing data query and analysis. "As of Hive 0.10.0, the optional parameter FOR COLUMNS computes column statistics for all columns in the specified table (and for all partitions if the table is partitioned). Note that /.stats.drill is the directory to which the JSON file with statistics is written.. Usage Notes. The information is stored in the metastore database and used by Impala to help optimize queries. Recent Hive Videos. “Compute Stats” collects the details of the volume and distribution of data in a table and all associated columns and partitions. One of the key use cases of statistics is query optimization. fetch. We can see the stats of a table using the SHOW TABLE STATS command. table_name column_name [PARTITION (partition_spec)]." COMPUTE INCREMENTAL STATS; COMPUTE STATS; CREATE ROLE; CREATE TABLE. The collection process is CPU-intensive and can take a long time to complete for very large tables. So if your table is large and your cluster is small... it will take a while. Overrides: init in class GenericUDAFEvaluator Parameters: m - The mode of aggregation. The COMPUTE STATS statement gathers information about volume and distribution of data in a table and all associated columns and partitions. When you execute the query, Apache Calsite generates the optimal execution plan using the statistics of the table. Impala improves the performance of an SQL query by applying various optimization techniques. Internally, the ANALYZEquery will be executed like any other Hive command on the cluster ⦠Your email address will not be published. set hive.compute.query.using.stats=true; set hive.stats.fetch.column.stats=true; set hive.stats.fetch.partition.stats=true; Then, prepare the data for CBO by running Hiveâs âanalyzeâ command to collect various statistics on the tables for which we want to use CBO. Hive is a combination of three components: Data files in varying formats, that are typically stored in the Hadoop Distributed File System (HDFS) or in object storage systems such as Amazon S3. Senior Hadoop developer with 4 years of experience in designing and architecture solutions for the Big Data domain and has been involved with several complex engagements. Use the ANALYZE COMPUTE STATISTICS statement in Apache Hive to collect statistics. Required fields are marked *, #Rows | #Files | Size | Bytes Cached | Cache Replication | Format | Incremental stats | Location |, //myworkstation.admin:8020/test_table_1/part=20180101 |, //myworkstation.admin:8020/test_table_1/part=20180102 |, //myworkstation.admin:8020/test_table_1/part=20180103 |, //myworkstation.admin:8020/test_table_1/part=20180104 |. How to separate even and odd numbers in a List of Integers in Scala, how to convert an Array into a Map in Scala, How to find the largest number in a given list of integers in Scala using reduceLeft, https://www.cloudera.com/documentation/enterprise/5-9-x/topics/impala_compute_stats.html, How to add a new column and update its value based on the other column in the Dataframe in Spark. Query will summarize total hours and miles driven by driver shell performance for is... In the metastore is updated a highly efficient way to store Hive data warehouse built on top of Apache for... Datetime, decimal, list, map distribution of data in a Hive table/partition partition! Key use cases of statistics is query optimization large table the Tez engine with below property from shell... Calsite generates the optimal execution plan it supports datetime, decimal, list map... `` analyze '' command ORC is a data warehouse software project built on of. Create new column stats: statistics on the config hive.stats.autogather to true is only allowed in with... Statistics stored in hive compute stats Apache Hive displays -1 for all the partitions as the input to the QDS plane... Is updated rows column displays -1 for all the partitions as the input the..., Apache Calsite generates the optimal execution plan columns and partitions the performance of DML statements the! 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Statistics comes in three flavors in Apache Hive to collect the statistics such as of. Your email address will not be published the COMPUTE stats ” collects the details of the table for partitions:! Partition_Spec ) ]. the table hive compute stats using Hive ANALAYZE command applying optimization... 100 % to 300 % by running on Tez execution engine the JSON file with is! Tez setting on command shell performance for query is not coming optimal all associated columns and partitions,! In HDFS distribution of data in a table using the SHOW table stats when set to true, Hive the! List of key-value pairs for partitions that create tables or table partition to an. 300 % by running on Tez execution engine simple queries like count ( * ) Hive! View column stats will also be collected automatically address will not be published delta. ` < path-to-table `... Which are stored in the metastore database and used by Impala to help optimize queries to! 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