how to check stats on hive table

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Hive table row count. This document describes changes to a) HiveQL, b) metastore schema, and c) metastore Thrift API to support column level statistics in Hive. This is also the design document. Hive Performance Tuning: Below are the list of practices that we can follow to optimize Hive Queries. These statistics are stored in the data dictionary and can be used by the optimizer to choose the most efficient execution plan for SQL statements accessing analyzed objects. Use case: One table has huge skew values on the joining column. This can vastly improve query times on the table because it collects the row count, file count, and file size (bytes) that make up the data in the table and gives that to the query planner before execution. The main difference between an internal table and an external table is simply this: An internal table is also called a managed table, meaning it’s “managed” by Hive. Get row count from all tables in hive, The HQL command is explain select * from table_name; but when not optimized not shows rows in the TableScan. on final output, intermediate data), we achieve the performance improvement in Hive Queries. 3. 1 month ago. See Column Statistics in Hive for details. 2. 826 Words ... You can check the @arcange post by clicking on HiveSQL is free again - Thank you for your support! Please note that this goes beyond HIVE-3421 - this patch adds the stats specified on both this wiki and the JIRA page. Create Table Statement. About Us; ... Loading data to table default.hivetest2 Table default.hivetest2 stats: [numFiles=1, totalSize=62] OK Time taken: 1.059 seconds ... You can check more about us here. Hive has a property which can do auto-map join when enabled. There are two ways Hive table statistics are computed. There is already a JIRA for this - HIVE-1362. Use can get data distribution details as well, struct StringColumnStatsData { 1: required i64 maxColLen, 2: required double avgColLen, 3: required i64 numNulls, 4: required i64 numDVs, struct BinaryColumnStatsData { 1: required i64 maxColLen, 2: required double avgColLen, 3: required i64 numNulls }, struct Decimal {1: required binary unscaled,3: required i16 scale}, struct DecimalColumnStatsData {1: optional Decimal lowValue,2: optional Decimal highValue,3: required i64 numNulls,4: required i64 numDVs,5: optional string bitVectors}, struct Date {1: required i64 daysSinceEpoch}, struct DateColumnStatsData {1: optional Date lowValue,2: optional Date highValue,3: required i64 numNulls,4: required i64 numDVs,5: optional string bitVectors}, union ColumnStatisticsData {1: BooleanColumnStatsData booleanStats,2: LongColumnStatsData longStats,3: DoubleColumnStatsData doubleStats,4: StringColumnStatsData stringStats,5: BinaryColumnStatsData binaryStats,6: DecimalColumnStatsData decimalStats,7: DateColumnStatsData dateStats}, struct ColumnStatisticsObj { 1: required string colName, 2: required string colType, 3: required ColumnStatisticsData statsData }, struct ColumnStatisticsDesc { 1: required bool isTblLevel, 2: required string dbName, 3: required string tableName, 4: optional string partName, 5: optional i64 lastAnalyzed }, struct ColumnStatistics { 1: required ColumnStatisticsDesc statsDesc, 2: required list statsObj; }. {"serverDuration": 123, "requestCorrelationId": "78b44eed3a004727"}, https://issues.apache.org/jira/browse/HIVE-3421. struct DoubleColumnStatsData { 1: required double lowValue, 2: required double highValue, 3: required i64 numNulls, 4: required i64 numDVs. Alternatively, you could use Hive Radiator Valves on your main radiators for room-by-room temperature control of your home. table, table name to write to. To view column stats : To display these statistics, use DESCRIBE FORMATTED … Helpers are active players who wish to help others, and are passionate about engaging with the community. ALTER TABLE COLUMN_STATISTICS ADD CONSTRAINT COLUMN_STATISTICS_PK PRIMARY KEY (CS_ID); ALTER TABLE COLUMN_STATISTICS ADD CONSTRAINT COLUMN_STATISTICS_FK1 FOREIGN KEY (TBL_ID) REFERENCES TBLS (TBL_ID) INITIALLY DEFERRED ; CREATE TABLE PART_COL_STATS ( CS_ID NUMBER NOT NULL, PART_ID NUMBER NOT NULL. HiveQL’s analyze command will be extended to trigger statistics computation on one or more column in a Hive table/partition. Gravity is the second Hive game to feature "Hardcore Mode", a variation of the game designed for the real pros! Automatic Hive Table Statistics: For newly set hive.stats.fetch.column.stats=true; set hive.stats.fetch.partition.stats=true; ... you end up doing a full table scan of your data. Powered by a free Atlassian Confluence Open Source Project License granted to Apache Software Foundation. generate an optimal query plan. created tables and/or partition, utomatically computed by default. In a following version, we will add support for height balanced histograms as well as support for dynamic partitions in the analyze command for column level statistics. Thanks. Hive Hint: Hive Multizone has been designed to let you control up to six heating zones in your home. DB_NAME VARCHAR(128) NOT NULL, COLUMN_NAME VARCHAR(128) NOT NULL, COLUMN_TYPE VARCHAR(128) NOT NULL, TABLE_NAME VARCHAR(128) NOT NULL, PART_NAME VARCHAR(128) NOT NULL. HiveQL currently supports the analyze command to compute statistics on tables and partitions. 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. HiveQL currently supports the analyze commandto compute statistics on tables and partitions. Introducing: Hive Helpers. To check that table statistics are available for a table, and see the details of those statistics, use the statement SHOW TABLE STATS table_name. Above 3 options are required to run hive streaming application, for others please check here: SHOW CREATE TABLE command Synax. To increase your query performance indexing will definitely help. bil.prag 70. You can use the DBMS_STATS package or the ANALYZE statement to gather statistics about the physical storage characteristics of a table, index, or cluster. hive1 by default. 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. Also note that currently Hive doesn’t support drop column. That doesn’t mean much more than when you drop the table, both the schema/definition AND the data are dropped. View Hive Table Statistics. Number of partition if the table is partitioned. Users can quickly get the answers for some of This article explains how to rename a database in Hive manually without modifying database locations, as the command: ALTER DATABASE test_db RENAME TO test_db_new; still does not work due to HIVE-4847 is not fixed yet. 4 Min Read. User should specify the data source format hive-streaming and required options: metastore, metastore uris for which to connect to. Set the below parameter to true to enable auto map join. As a Helper, you will be the face of the Hive — players will turn to you for help and guidance, and it is your role to provide the assistance they need. This chapter explains how to create a table and how to insert data into it. Once done, you can execute the below query to get the total size of all the tables in Hive in bytes. Copy the hive-site.xml from /conf directory to /conf folder or use the trimmed version of hive-site.xml. LOW_VALUE RAW, HIGH_VALUE RAW, NUM_NULLS BIGINT, NUM_DISTINCTS BIGINT, BIT_VECTOR, BLOB,  /* introduced in HIVE-16997 in Hive 3.0.0 */, AVG_COL_LEN DOUBLE, MAX_COL_LEN BIGINT, NUM_TRUES BIGINT, NUM_FALSES BIGINT, LAST_ANALYZED BIGINT NOT NULL). Totally Random stats (Hive) 0 comments / 0 reblogs. * from passwords a, passwords2 b where a.col0=b.col1; OK STAGE DEPENDENCIES: Stage-7 is a root stage , consists of Stage-1 Stage-1 Stage-4 depends on stages: Stage-1 , consists of Stage-8 Stage-8 Stage-3 depends on … If you use the Hive-based methods of gathering statistics, see the Hive wiki for information about the … Overwrite). Please note that the document doesn’t describe the changes needed to persist histograms in the metastore yet. You can either set this from the command line or from the hive-site.xml file. Statistics such as the number of rows of a table or partition and the histograms of a particular interesting column are important in many ways. Statistics serve as the input to the cost functions of the optimizer so that it can compare different plans and choose among them. hive -e 'select count (distinct fieldid) from table1 where extracttimestamp<'2018-04-26'' > sample.out. Login into Hive Metastore DB and use the database that is used by hive. Example: hive> explain select a. ALTER TABLE COLUMN_STATISTICS ADD CONSTRAINT COLUMN_STATISTICS_FK1 FOREIGN KEY (PART_ID) REFERENCES PARTITIONS (PART_ID) INITIALLY DEFERRED; We propose to add the following Thrift structs to transport column statistics: struct BooleanColumnStatsData { 1: required i64 numTrues, 2: required i64 numFalses, 3: required i64 numNulls }. HiveQL’s analyze command will be extended to trigger statistics computation on one or more column in a Hive table/partition. Set hive.auto.convert.join to true to enable the auto map join. Using DBMS_STATS to Collect Table and Index Statistics. Is the hash table (small table's), created for the entire table or only for the selected and join key columns? When Hive Table Statistics are Computed? Sitemap, Commonly used Teradata BTEQ commands and Examples. The necessary changes to HiveQL are as below. See SHOW Statement for details. For a managed (non-external) table, data is manipulated through Hive SQL statements (LOAD DATA, INSERT, etc.) Enable Compression in Hive. tables: For existing tables and/or partitions, the user can issue the ANALYZE Search for and enable, if necessary, hive.compute.query.using.stats. Map join is highly beneficial when one table is small so that it can fit into the memory. The SHOW CREATE TABLE command Hive provided table command that can be used when you want to generate DDL for the single Hive table. Snowflake Unsupported subquery Issue and How to resolve it. The Command is similar to CREATE TABLE command, except it dumps DDL instead of creating tables. @Guilherme Braccialli If you've already analyzed the columns you can issue a describe table command to get column stats: "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). The conventions of creating a table in HIVE is quite similar to creating a table using SQL. Furthermore, we will support only static partitions, i.e., both the partition key and partition value should be specified in the analyze command. 1. When you have a hive table, you may want to check its delimiter or detailed information such as Schema. Users can quickly get the answers for some of their queries by only querying stored statistics rather than firing lon… This command shows meta data about the hive table which includes list of columns,data types and location of the table.There are three ways to describe a table in Hive. 1. CREATE TABLE TAB_COL_STATS ( CS_ID NUMBER NOT NULL, TBL_ID NUMBER NOT NULL, COLUMN_NAME VARCHAR(128) NOT NULL, COLUMN_TYPE VARCHAR(128) NOT NULL, TABLE_NAME VARCHAR(128) NOT NULL, DB_NAME VARCHAR(128) NOT NULL. such as top 10 product sold, age distribution in person table etc. Search for and enable, if necessary, hive.stats.fetch.column.stats. Users should be aware of the skew key. How to Create an Index in Amazon Redshift Table? You can view Hive table statistics using DESCRIBE command. By enabling compression at various phases (i.e. The hash table (created in map side join) spills to disk, if it does not Hardcore Mode can be enabled in the lobby via the dye in the middle slot, and comes with its own set of stats for you to compete with your … If the table is partitioned here is a quick command for you: hive> ANALYZE TABLE ops_bc_log PARTITION(day) COMPUTE STATISTICS noscan; output is. One of the key use cases of statistics is query optimization. command to gather statistics and write them into Hive MetaStore. An e… Also, can you go over https://issues.apache.org/jira/browse/HIVE-3421 and see how the two are related ? Hive cost based optimizer uses the statistics to We propose to add the following Thrift APIs to persist, retrieve and delete column statistics: bool update_table_column_statistics(1:ColumnStatistics stats_obj) throws (1:NoSuchObjectException o1, 2:InvalidObjectException o2, 3:MetaException o3, 4:InvalidInputException o4) bool update_partition_column_statistics(1:ColumnStatistics stats_obj) throws (1:NoSuchObjectException o1, 2:InvalidObjectException o2, 3:MetaException o3, 4:InvalidInputException o4), ColumnStatistics get_table_column_statistics(1:string db_name, 2:string tbl_name, 3:string col_name) throws (1:NoSuchObjectException o1, 2:MetaException o2, 3:InvalidInputException o3, 4:InvalidObjectException o4) ColumnStatistics get_partition_column_statistics(1:string db_name, 2:string tbl_name, 3:string part_name, 4:string col_name) throws (1:NoSuchObjectException o1, 2:MetaException o2, 3:InvalidInputException o3, 4:InvalidObjectException o4), bool delete_partition_column_statistics(1:string db_name, 2:string tbl_name, 3:string part_name, 4:string col_name) throws (1:NoSuchObjectException o1, 2:MetaException o2, 3:InvalidObjectException o3, 4:InvalidInputException o4) bool delete_table_column_statistics(1:string db_name, 2:string tbl_name, 3:string col_name) throws (1:NoSuchObjectException o1, 2:MetaException o2, 3:InvalidObjectException o3, 4:InvalidInputException o4). Cons: One table is read twice. Again, when you drop an internal table, Hive will delete both the schema/table definition, and it will also physically delete the data/rows(truncation) associated with that table from the Hadoop Distributed File System (HDFS). I've the patch on both JIRA and reviewboard. For general information about Hive statistics, see Statistics in Hive. The CBO engine in Hive uses statistics in the Hive Metastore to produce optimal query plans. Learn how to update delete hive tables and insert a single record in Hive table. Use ANALYZE to collect statistics for existing ... time of clicking around with no idea of what am i doing i was sure that there is an easier way to filter data from the hive data base. Column statistics are introduced in Hive 0.10.0 by HIVE-1362. Note that in V1 of the project, we will support only scalar statistics. long-running execution plans. struct LongColumnStatsData { 1: required i64 lowValue, 2: required i64 highValue, 3: required i64 numNulls, 4: required i64 numDVs. There are two types of statistics that are used for optimization: table stats (which include the uncompressed size of the table, number of rows, and number of files used to store the data) and column statistics. Partition logdata.ops_bc_log{day=20140523} stats: [numFiles=37, numRows=26095186, totalSize=654249957, rawDataSize=58080809507] Since this is an external table (EXTERNAL_TABLE), Hive will not keep any stats on the table since it is assumed that another application is changing the underlying data at will.Why keep stats if we can't trust that the data will be the same in another 5 minutes? Statistics may sometimes meet the purpose of the users' queries. There are two solutions:[crayon-5fea6338f0646722469215/]Get the delimiter of a Hive … We can see the Hive tables structures using the Describe commands. To persist column level statistics, we propose to add the following new tables. The Hive Multizone kit contains the thermostat and receiver (your Hive Hub will come with your Hive Active Heating). Hive Index – Hive Optimization Techniques, o ne of the best ways is Indexing. This is the design document. 2. Create Table is a statement used to create a table in Hive. saveAsTable ("hive_records") // After insertion, the Hive managed table has data now sql ("SELECT * FROM hive_records"). So in HDP, we have /apps/hive/warehouse as the location to store all the files. DESCRIBE EXTENDED TABLE1; For example; DESCRIBE EXTENDED test1; You should see the basic table statistics in parameter tag. Evaluate Confluence today. Is this ready for review, or is it a initial design ? analyze table t [partition p] compute statistics for [columns c,...]; Please note that table and column aliases are not supported in the analyze statement. Analyzing a table (also known as computing statistics) is a built-in Hive operation that you can execute to collect metadata on your table. Enable the ACID properties of Hive table to perform the CRUD operations. Column statistics auto gather is introduced in Hive 2.3 by HIVE-11160. The syntax and example are as follows: Syntax For information about top K statistics, see Column Level Top K Statistics. In Cloudera Manager > Clusters > … Note that delete_column_statistics is needed to remove the entries from the metastore when a table is dropped. You can collect the statistics on the table by using Hive ANALAYZE command. For the DB rename to work properly, we … db, db name to write to. Partitioning the table helps us to improve the performance of your HIVEQL queries, usually the normal hive query will take long time to process even for a single record it has to process all the records, where as if we use partition then the query performance will be fast and the selection is particularly made on those partitioned columns. Before running any CREATE TABLE or CREATE TABLE AS statements for Hive tables in Trino, you need to check that the user Trino is using to access HDFS has access to the Hive warehouse directory. Accept the default (enabled), or check to enable the hive.cbo.enable property for the HiveServer Default Group. You can check the file location by running following command in linux: [root@sandbox ~]# hdfs dfs -ls /apps/hive/warehouse We will use Indian Railways public data set for our example. Basically, for the original table use of indexing will create a separate called index table which acts as a reference. their queries by only querying stored statistics rather than firing Is there a way to check the size of the hash table created during map side join in Hive/Tez? Shreepadma, is there a jira for this ? Namit, This patch is ready for review. General information about Hive statistics, we propose to add the following tables., hive.stats.fetch.column.stats which can do auto-map join when enabled to create table is a statement used to an... Crud operations gather is introduced in Hive 2.3 by HIVE-11160, you can check @. Create an index in how to check stats on hive table Redshift table EXTENDED TABLE1 ; for example ; DESCRIBE test1... In Hive is quite similar to creating a table in Hive table are. The SHOW create table is a statement used to create table is dropped the analyze command will be to! On both JIRA and reviewboard K statistics you want to generate an optimal query plan details well...: syntax Overwrite ) room-by-room temperature control of your data initial design (! Up doing a full table scan of your data the metastore when a table in Hive Hive has property! Product sold, age distribution in person table etc. the data are dropped adds stats... I 've the patch on both JIRA and reviewboard be EXTENDED to how to check stats on hive table statistics computation on one more... Six heating zones in your home support only scalar statistics schema/definition and the page. The joining column ; set hive.stats.fetch.partition.stats=true ;... you end up doing a full table scan of home... Following new tables collect the statistics to generate DDL for the selected and join columns. Redshift table tables structures using the DESCRIBE commands one table is a statement to. Data ), we will support only scalar statistics DESCRIBE FORMATTED … we follow... Statements ( LOAD data, INSERT, etc. table 's ), for... There are two ways Hive table row count real pros end up doing a full table of! Are introduced in Hive in bytes create an index in Amazon Redshift table the syntax and example are follows! For example ; DESCRIBE EXTENDED TABLE1 ; for example ; DESCRIBE EXTENDED TABLE1 ; example! Once done, you may want to check the @ arcange post by clicking HiveSQL! The conventions of creating a table is a statement used to create table command, except it dumps DDL of! Creating tables functions of the hash table created during map side join in Hive/Tez `` Hardcore Mode,. Level statistics, we have /apps/hive/warehouse as the location to store all files. To trigger statistics computation on one or more column in a Hive table/partition the... Execute the below parameter to true to enable the ACID properties of Hive table:. Use Hive Radiator Valves on your main radiators for room-by-room temperature control of your data command or... View Hive table, data is manipulated through Hive SQL statements ( LOAD data, INSERT, etc )... Compare different plans and choose among them and use the database that is used by Hive enable auto join. To feature `` Hardcore Mode '', a variation of the key use cases of statistics is query.. To store all the files the basic table statistics: for newly created and/or. By default project License granted to Apache Software Foundation should see the basic table in... Powered by a free Atlassian Confluence Open Source project License granted to Apache Software Foundation is it initial! Is already a JIRA for this - HIVE-1362 LOAD data, INSERT, etc. free again - Thank for..., Commonly used Teradata BTEQ commands and Examples granted to Apache Software Foundation Hardcore Mode '', a of! Granted to Apache Software Foundation LOAD data, INSERT, etc. their. The following new tables from the metastore when a table in Hive in bytes '' ``... Will be EXTENDED to trigger statistics computation on one or more column in a table/partition... To create table is dropped as a reference document doesn ’ t support column... Parameter tag set hive.stats.fetch.partition.stats=true ;... you end up doing a full table scan of your home designed for HiveServer! The two are related Radiator Valves on your main radiators for room-by-room temperature of! Schema/Definition and the data are dropped statistics is query optimization of all the files HIVE-3421!, `` requestCorrelationId '': `` 78b44eed3a004727 '' }, https: //issues.apache.org/jira/browse/HIVE-3421 (! Db and use the database that is used by Hive display these statistics see! Used to create a table using SQL and reviewboard firing long-running execution plans used by.. In Hive is quite similar to create a table in Hive is quite similar to create an index in Redshift... < '2018-04-26 '' > sample.out - Thank you for your support ;... you end up doing a full scan! Performance improvement in Hive in bytes `` Hardcore Mode '', a variation of the optimizer so it... The stats specified on both this wiki and the JIRA page to update delete Hive tables INSERT... Resolve it, we will support only scalar statistics is used by Hive and key. Will create a table is a statement used to create a separate called index which! Only for the original table use of indexing will definitely help the size of all the files the from. On both this wiki and the JIRA page these statistics, see statistics in parameter tag you should the! Which can do auto-map join when enabled can view Hive table statistics using DESCRIBE command one... In the metastore yet: syntax Overwrite ) queries by only querying stored rather! Sitemap, Commonly used Teradata BTEQ commands and Examples data, INSERT, etc. and join key columns the. The location to store all the tables in Hive 2.3 by HIVE-11160 are as follows: syntax Overwrite.! Has a property which can do auto-map join when enabled the files: for created! One of the game designed for how to check stats on hive table original table use of indexing will definitely help querying! Hive Hint: Hive Multizone has been designed to let you control up to six heating in... Compute statistics on the table, both the schema/definition and the JIRA page Hive Hint: Hive Multizone been... Post by clicking on HiveSQL is free again - Thank you for your support on the joining column to its... Query optimization fit into the memory get the answers for some of their queries by only querying statistics. Introduced in Hive table statistics in Hive properties of Hive table row count created. Input to the cost functions of the users ' queries the hive.cbo.enable property for HiveServer. Or is it a initial design this patch adds the stats specified on JIRA! Level top K statistics, use DESCRIBE FORMATTED … we can see the Hive structures! About engaging with the community follows: syntax Overwrite ) you for your support tables in Hive and/or... Auto-Map join when enabled Words... you can check the size of optimizer! Schema/Definition and the JIRA page and example are as follows: syntax Overwrite ) information such as top 10 sold. Final output, intermediate data ), created for the real pros are passionate about engaging with the.. Person table etc. table created during map side join in Hive/Tez may want to generate an optimal query.. We will support only scalar statistics remove the entries from the command line or from the metastore when table... About Hive statistics, use DESCRIBE FORMATTED … we can follow to optimize Hive.! Which acts as a reference called index table which acts as a reference uses statistics. Using the DESCRIBE commands, hive.stats.fetch.column.stats the DESCRIBE commands should see the Hive and! Hiveql currently supports the analyze command will be EXTENDED to trigger statistics on! Tables and partitions or only for the original table use of indexing will a! Provided table command that can be used when you have a Hive table in! This from the hive-site.xml file can see the Hive tables structures using the DESCRIBE commands SQL (... Acid properties of Hive table improvement in Hive in bytes example ; EXTENDED! Perform the CRUD operations Hive statistics, see statistics in parameter tag control to... @ arcange post by clicking on HiveSQL is free again - Thank for. Of creating tables hive.auto.convert.join to true to enable auto map join is highly beneficial when one is...: syntax Overwrite ) DESCRIBE EXTENDED test1 ; you should see the Hive structures. The project, we propose to add the following new tables the conventions creating! ), we will support only scalar statistics as top 10 product sold, age distribution in person etc...: Hive Multizone has been designed to let you control up to six heating zones in your home get answers... Can execute the below query to get the total size of all the.... Hive metastore DB and use the database that is used by Hive the tables... You want to generate DDL for the original table use of indexing will definitely help huge skew on. A property which can do auto-map join when enabled passionate about engaging with the community for example ; DESCRIBE TABLE1. Values on the joining column the Hive tables structures using the DESCRIBE commands than firing lon… table! Both the schema/definition and the data are dropped sometimes meet the purpose of optimizer. Record in Hive is quite similar to creating a table in Hive bytes... Redshift table help others, and are passionate about engaging with the community:! The auto map join is highly beneficial when one table has huge values. Real pros ; DESCRIBE EXTENDED test1 ; you should see the basic table using. Cases of statistics is query optimization s analyze command will be EXTENDED to trigger statistics computation on one or column. Can compare different plans and choose among them details as well, such as 10!