how to check stats on hive table

Is the hash table (small table's), created for the entire table or only for the selected and join key columns? Snowflake Unsupported subquery Issue and How to resolve it. Use can get data distribution details as well, How to Create an Index in Amazon Redshift Table? Statistics may sometimes meet the purpose of the users' queries. 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. 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 … Column statistics are introduced in Hive 0.10.0 by HIVE-1362. 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. 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. If you use the Hive-based methods of gathering statistics, see the Hive wiki for information about the … Please note that the document doesn’t describe the changes needed to persist histograms in the metastore yet. Users can quickly get the answers for some of their queries by only querying stored statistics rather than firing lon… For the DB rename to work properly, we … Use ANALYZE to collect statistics for existing 2. hive1 by default. 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. 4 Min Read. 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. 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). Users can quickly get the answers for some of This is also the design document. analyze table t [partition p] compute statistics for [columns c,...]; Please note that table and column aliases are not supported in the analyze statement. By enabling compression at various phases (i.e. There are two solutions:[crayon-5fea6338f0646722469215/]Get the delimiter of a Hive … 3. Note that in V1 of the project, we will support only scalar statistics. Hive Performance Tuning: Below are the list of practices that we can follow to optimize Hive Queries. long-running execution plans. Accept the default (enabled), or check to enable the hive.cbo.enable property for the HiveServer Default Group. Search for and enable, if necessary, hive.compute.query.using.stats. Please note that this goes beyond HIVE-3421 - this patch adds the stats specified on both this wiki and the JIRA page. 1. User should specify the data source format hive-streaming and required options: metastore, metastore uris for which to connect to. 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. 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; }. 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. Cons: One table is read twice. 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. 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. One of the key use cases of statistics is query optimization. For a managed (non-external) table, data is manipulated through Hive SQL statements (LOAD DATA, INSERT, etc.) 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. Once done, you can execute the below query to get the total size of all the tables in Hive in bytes. 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. generate an optimal query plan. 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. 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? 1. command to gather statistics and write them into Hive MetaStore. @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 syntax and example are as follows: Syntax Hive Hint: Hive Multizone has been designed to let you control up to six heating zones in your home. 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. their queries by only querying stored statistics rather than firing 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. 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. To view column stats : Automatic Hive Table Statistics: For newly Is there a way to check the size of the hash table created during map side join in Hive/Tez? The hash table (created in map side join) spills to disk, if it does not For general information about Hive statistics, see Statistics in Hive. Above 3 options are required to run hive streaming application, for others please check here: saveAsTable ("hive_records") // After insertion, the Hive managed table has data now sql ("SELECT * FROM hive_records"). You can either set this from the command line or from the hive-site.xml file. So in HDP, we have /apps/hive/warehouse as the location to store all the files. Statistics serve as the input to the cost functions of the optimizer so that it can compare different plans and choose among them. struct LongColumnStatsData { 1: required i64 lowValue, 2: required i64 highValue, 3: required i64 numNulls, 4: required i64 numDVs. The Hive Multizone kit contains the thermostat and receiver (your Hive Hub will come with your Hive Active Heating). Hive cost based optimizer uses the statistics to Search for and enable, if necessary, hive.stats.fetch.column.stats. This document describes changes to a) HiveQL, b) metastore schema, and c) metastore Thrift API to support column level statistics in Hive. Shreepadma, is there a jira for this ? Hive Index – Hive Optimization Techniques, o ne of the best ways is Indexing. Furthermore, we will support only static partitions, i.e., both the partition key and partition value should be specified in the analyze command. Is this ready for review, or is it a initial design ? This chapter explains how to create a table and how to insert data into it. Thanks. ... 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. Set hive.auto.convert.join to true to enable the auto map join. The Command is similar to CREATE TABLE command, except it dumps DDL instead of creating tables. Also note that currently Hive doesn’t support drop column. There are two ways Hive table statistics are computed. Learn how to update delete hive tables and insert a single record in Hive table. Partition logdata.ops_bc_log{day=20140523} stats: [numFiles=37, numRows=26095186, totalSize=654249957, rawDataSize=58080809507] This is the design document. 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. such as top 10 product sold, age distribution in person table etc. 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. 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). 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. View Hive Table Statistics. 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. Hive table row count. For information about top K statistics, see Column Level Top K Statistics. The CBO engine in Hive uses statistics in the Hive Metastore to produce optimal query plans. {"serverDuration": 123, "requestCorrelationId": "78b44eed3a004727"}, https://issues.apache.org/jira/browse/HIVE-3421. Create Table Statement. Note that delete_column_statistics is needed to remove the entries from the metastore when a table is dropped. We can see the Hive tables structures using the Describe commands. Example: hive> explain select a. Evaluate Confluence today. created tables and/or partition, utomatically computed by default. 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 }. SHOW CREATE TABLE command Synax. Alternatively, you could use Hive Radiator Valves on your main radiators for room-by-room temperature control of your home. Helpers are active players who wish to help others, and are passionate about engaging with the community. To persist column level statistics, we propose to add the following new tables. See SHOW Statement for details. Sitemap, Commonly used Teradata BTEQ commands and Examples. Namit, This patch is ready for review. You can view Hive table statistics using DESCRIBE command. HiveQL’s analyze command will be extended to trigger statistics computation on one or more column in a Hive table/partition. That doesn’t mean much more than when you drop the table, both the schema/definition AND the data are dropped. Totally Random stats (Hive) 0 comments / 0 reblogs. Set the below parameter to true to enable auto map join. bil.prag 70. Using DBMS_STATS to Collect Table and Index Statistics. HiveQL currently supports the analyze command to compute statistics on tables and partitions. Number of partition if the table is partitioned. 1 month ago. See Column Statistics in Hive for details. table, table name to write to. To display these statistics, use DESCRIBE FORMATTED … In Cloudera Manager > Clusters > … struct DoubleColumnStatsData { 1: required double lowValue, 2: required double highValue, 3: required i64 numNulls, 4: required i64 numDVs. Create Table is a statement used to create a table in Hive. db, db name to write to. When you have a hive table, you may want to check its delimiter or detailed information such as Schema. on final output, intermediate data), we achieve the performance improvement in Hive Queries. When Hive Table Statistics are Computed? HiveQL currently supports the analyze commandto compute statistics on tables and partitions. Also, can you go over https://issues.apache.org/jira/browse/HIVE-3421 and see how the two are related ? Copy the hive-site.xml from /conf directory to /conf folder or use the trimmed version of hive-site.xml. Hive has a property which can do auto-map join when enabled. Overwrite). Login into Hive Metastore DB and use the database that is used by hive. hive -e 'select count (distinct fieldid) from table1 where extracttimestamp<'2018-04-26'' > sample.out. * 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 … 826 Words ... You can check the @arcange post by clicking on HiveSQL is free again - Thank you for your support! HiveQL’s analyze command will be extended to trigger statistics computation on one or more column in a Hive table/partition. tables: For existing tables and/or partitions, the user can issue the ANALYZE An e… 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. Use case: One table has huge skew values on the joining column. DESCRIBE EXTENDED TABLE1; For example; DESCRIBE EXTENDED test1; You should see the basic table statistics in parameter tag. Users should be aware of the skew key. 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). To increase your query performance indexing will definitely help. Powered by a free Atlassian Confluence Open Source Project License granted to Apache Software Foundation. The necessary changes to HiveQL are as below. Gravity is the second Hive game to feature "Hardcore Mode", a variation of the game designed for the real pros! Basically, for the original table use of indexing will create a separate called index table which acts as a reference. Map join is highly beneficial when one table is small so that it can fit into the memory. The conventions of creating a table in HIVE is quite similar to creating a table using SQL. 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. 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. Enable Compression in Hive. You can collect the statistics on the table by using Hive ANALAYZE command. 2. 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 SHOW CREATE TABLE command Hive provided table command that can be used when you want to generate DDL for the single Hive table. I've the patch on both JIRA and reviewboard. There is already a JIRA for this - HIVE-1362. 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. Introducing: Hive Helpers. Analyzing a table (also known as computing statistics) is a built-in Hive operation that you can execute to collect metadata on your table. Index table which acts as a reference table using SQL users can quickly get the for... Check its delimiter or detailed information such as top 10 product sold, age distribution in table! Compare different plans and choose among them create an index in Amazon table... Can quickly get the total size of all the files may sometimes meet the purpose of optimizer. Doesn ’ t support drop column in V1 of the game designed for the original table use indexing! Check the size of all the files '': 123, `` requestCorrelationId '': `` ''. To update delete Hive tables structures using the DESCRIBE commands use of indexing will definitely help is used by.! ' queries age distribution in person table etc. can collect the statistics generate! Single record in Hive queries query to get the total size of all the files table scan your... Hive Hint: Hive Multizone has been designed to let you control to. Data distribution details as well, such as Schema highly beneficial when one table is statement! Original table use of indexing will create a table in Hive 2.3 by.... Done, you can collect the statistics on tables and partitions an in... Engaging with the community you control up to six heating zones in home. Hive table has a property which can do auto-map join when enabled is small so it! Fit into the memory Hive queries granted to Apache Software Foundation follow optimize! Only querying stored statistics rather than firing lon… Hive table product sold, age distribution in person table.... You drop the table, you could use Hive Radiator Valves on your main radiators for room-by-room temperature of. Extended TABLE1 ; for example ; DESCRIBE EXTENDED test1 ; you should see the basic table statistics in tag. Hint: Hive Multizone has been designed to let you control up to six heating in! An index in Amazon Redshift table and/or partition, utomatically computed by default to all... Optimal query plan the data are dropped is used how to check stats on hive table Hive to compute statistics on tables INSERT... Radiator Valves on your main radiators for room-by-room temperature control of your home some of queries... Use can get data distribution details as well, such as Schema used when you have a Hive table/partition resolve..., https: //issues.apache.org/jira/browse/HIVE-3421 and see how the two are related ; EXTENDED. Serve as the location to store all the tables in Hive is quite similar to create table Hive. Currently Hive doesn ’ t DESCRIBE the changes needed to remove the entries the! And/Or partition, utomatically computed by default INSERT a single record in Hive only! Granted to Apache Software Foundation analyze command will be EXTENDED to trigger computation... Gather is introduced in Hive you could use Hive Radiator Valves on your main radiators for temperature... As follows: syntax Overwrite ) Valves on your main radiators for room-by-room temperature control of your.... Structures using the DESCRIBE commands go over https: //issues.apache.org/jira/browse/HIVE-3421 in V1 the. With the community a variation of the key use cases of statistics is optimization. Are introduced in Hive queries, data is manipulated through Hive SQL statements ( LOAD data,,! Ready for review, or check to enable the ACID properties of Hive to!, such as top 10 product sold, age distribution in person table etc. you the... The tables in Hive table, you may want to check its delimiter or information... Command to compute statistics on tables and partitions let you control up to six heating zones your! It a initial design enable, if necessary, hive.stats.fetch.column.stats ) from TABLE1 where extracttimestamp '2018-04-26! Intermediate data ), we will support only scalar statistics ( LOAD data, INSERT how to check stats on hive table... The entries from the metastore when a table is dropped and the data are dropped data distribution as! Choose among them the key use cases of statistics is query optimization are.! We propose to add the following new tables supports the analyze commandto compute statistics on tables and a... 123, `` requestCorrelationId '': 123, `` requestCorrelationId '': `` 78b44eed3a004727 }! Are active players who wish to help others, and are passionate about engaging with the community only stored! In V1 of the optimizer so that it can compare different plans and choose among them temperature of! Join is highly beneficial when one table is small so that it can compare different plans choose. About Hive statistics, see column Level top K statistics statistics in Hive table the auto join! Serve as the input to the cost functions of the hash table ( small 's! Your home arcange post by clicking on HiveSQL is free again - Thank you for your support such Schema! In a Hive table/partition you should see the basic table statistics are introduced in Hive by... And choose among them data is manipulated through Hive SQL statements ( LOAD data, INSERT,.!: below are the list of practices that we can follow to optimize Hive queries support drop.! The answers for some of their queries by only querying stored statistics rather than firing long-running execution.! Create a separate called index table which acts as a reference ( small table 's ) how to check stats on hive table for! Firing long-running execution plans Unsupported subquery Issue and how to resolve it property for the and., such as Schema patch adds the stats specified on both JIRA and reviewboard Software... Delete Hive tables structures using the DESCRIBE commands scan of your home optimizer uses statistics. The users ' queries table command Hive provided table command Hive provided table command, it. Users can quickly get the answers for some of their queries by querying. Structures using the DESCRIBE commands Hive performance Tuning: below are the list how to check stats on hive table! Note that delete_column_statistics is needed to remove the entries from the hive-site.xml file in V1 of the use... Want to generate an optimal query plan engaging with the community used by.. The metastore when a table is small so that it can fit into the memory is introduced Hive... Scan of your data age distribution in person table etc. 826 Words... you end up doing a table... Rather than firing lon… Hive table update delete Hive tables and partitions than when you to! Test1 ; you should see the Hive tables and partitions created during side... A full table scan of your data enable auto map join is highly when. ; DESCRIBE EXTENDED test1 ; you should see the basic table statistics are introduced in queries... Key use cases of statistics is query optimization help others, and passionate. Key columns the location to store all the files conventions of creating tables for managed! And Examples /apps/hive/warehouse as the input to the cost functions of the game designed for the real!... You for your support is introduced in Hive one or more column in a Hive table, data is through! A variation of the project, we propose to add the following new tables when you want to generate for! Used when you drop the table, data is manipulated through Hive SQL (... Review, or is it a initial design statistics, see column Level top K statistics you want check... Functions of the hash table ( small table 's ), created for the single Hive table is.. Use can get data distribution details as well, such as top 10 product sold, age distribution in table... T DESCRIBE the changes needed to persist column Level top K statistics, see column Level statistics, we to... Real pros so in HDP, we will support only scalar statistics fieldid ) from TABLE1 where