Check out this tip to learn more. Using ADD you can add columns at the end of existing columns. Now i am trying to copy data from hive table to another table which as parquet format defined at table creation. Previous Post How to write Group by and Order by query with column position number in Hive. The final phase of query optimization involves generating Java bytecode to run on each machine. // For datasource tables, disallow setting serde or specifying partition, "Operation not allowed: ALTER TABLE SET FILEFORMAT ", "for a specific partition is not supported ", "for tables created with the datasource API", "org.apache.spark.sql.execution.ProjectExec", "org.apache.spark.sql.catalyst.expressions.AttributeReference", "org.apache.spark.sql.execution.FileSourceScanExec", "org.apache.spark.sql.catalyst.TableIdentifier", "org.apache.spark.sql.hive.execution.HiveTableScanExec", "org.apache.spark.sql.catalyst.catalog.HiveTableRelation", "org.apache.spark.sql.catalyst.catalog.CatalogTable", "org.apache.spark.sql.catalyst.catalog.CatalogTableType", "org.apache.spark.sql.catalyst.catalog.CatalogStorageFormat", "org.apache.hadoop.hive.ql.io.avro.AvroContainerInputFormat", "org.apache.hadoop.hive.ql.io.avro.AvroContainerOutputFormat", "org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe", "org.apache.spark.sql.catalyst.expressions.ExprId", * Relation conversion from metastore relations to data source relations for better performance, * - When writing to non-partitioned Hive-serde Parquet/Orc tables, * - When scanning Hive-serde Parquet/ORC tables. So your latest data will be in HDFS and old partitions in S3 and you can query that hive table seamlessly. ALTER TABLE log_messages ADD PARTITION (year = 2019, month = 12) LOCATION 's3n://bucket_name/logs/2019/12'; 1 2 You can learn more about it here). Hive Insert into Partition Table. We will describe the API for these data sources in a later section. You can manually add new partitions to a Hive table if that table is partitioned. Apache Hive ALTER TABLE Command and Examples, Today I discovered a bug that Hive can not recognise the existing data for a newly added column to a partitioned external table. Take the following table we created for our customers: Let’s see what happens with existing data if you add new columns and then load new data into a table in Hive. Insert some data in this table. Creating Hive Table. ALTER TABLE ADD PARTITION in Hive Alter table statement is used to change the table structure or properties of an. This had to be done in HiveClientImpl.scala. There is no upper limit to the number of defined subpartitions. I will be using this table for most of the examples below. We found a docker image, but this wasn't the latest version, so we forked it and upgraded it to the latest version. Alter Table Rename Table Let us assume we have a table called employee with fields such as Id, Name, Salary, Designation, Dept, and yoj. The destination can create a managed internal table or an external table. Let us create a table to manage “Wallet expenses”, which any digital wallet channel may have to track customers’ spend behavior, having the following columns: In order to track monthly expenses, we want to create a partitioned table with columns month and spender. INSERT INTO Syntax & Examples. Download the GoDataDriven brochure for a complete overview of available training sessions and data engineering, data science, data analyst and analytics translator learning journeys. table_name. We can also drop partition from hive tables. Add partitions to the table, optionally with a custom location for each partition added. Develop Your Data Science Capabilities. 2) extend metastore API to support storing and retrieving stats for a particular table/partition. Insert some data in this table. Share. ALTER TABLE RENAME TO statement changes the table name of an existing table in the database. One possible approach mentioned in HIVE-1079 is to infer view partitions automatically based on the partitions of the underlying tables. The ALTER VIEW ADD/DROP partition syntax is identical to ALTER TABLE, except that it is illegal to specify a LOCATION clause. Before SQL Server 2012 number of partitions was limited to 1,000. Pin. I hope you will find it useful. best-practices by registering for the GoDataDriven newsletter. I am passionate about Cloud, Data Analytics, Machine Learning, and Artificial Intelligence. We were playing around and we accidentally changed the format of the partitioned table to Avro, so we had an Avro table with a Parquet partition in it...and IT WORKED!! Include the TABLESPACE clause to specify the tablespace in which the new partition will reside. To automatically detect new partition directories added through Hive or HDFS operations: In Impala 2.3 and higher, the RECOVER PARTITIONS clause scans a partitioned table to detect if any new partition directories were added outside of Impala, such as by Hive ALTER TABLE statements or by hdfs dfs or hadoop fs commands. We want the Hive Metastore to use PostgreSQL to be able to access it from Hive and Spark simultaneously. Syntax: [ database_name. ] Now, what if we want to drop some partition or add a new partition to the table? If the table is partitioned the columns gets added at the end but before the partitioned column. However, beginning with Spark 2.1, Alter Table Partitions is also supported for tables defined using the datasource API. Partitions make data querying more efficient. I like to learn and try out new things. ADD AND DROP PARTITION ADD PARTITION. INTO command will append to an existing table and not replace it from HIVE V0.8.0 and later. This is fairly easy to do for use case #1, but potentially very difficult for use cases #2 and #3. create table tb_emp (empno string, ename string, job string, managerno string, hiredate string, salary double, jiangjin double, deptno string ) row format delimited fields terminated by '\t'; We have created partitioned tables, inserted data into them. Syntax add or replace hive column. Add Partition. To automatically detect new partition directories added through Hive or HDFS operations: In Impala 2.3 and higher, the RECOVER PARTITIONS clause scans a partitioned table to detect if any new partition directories were added outside of Impala, such as by Hive ALTER TABLE statements or by hdfs dfs or hadoop fs commands. with partition with restrict. Loading Data into External Partitioned Table From HDFS. In addition, it can push operations from the logical plan into data sources that support predicate or projection pushdown. 0 Shares. We use Catalyst’s general tree transformation framework in four phases, as shown below: (1) analyzing a logical plan to resolve references, (2) logical plan optimization, (3) physical planning, and (4) code generation to compile parts of the query to Java bytecode. We can also rename existing partitions using below query. Required fields are marked * Comment. Share. Propagating and coercing types through expressions: for example, we cannot know the return type of 1 + col until we have resolved col and possibly casted its subexpressions to a compatible types. To run this image, use (note that we exposed port 5432 so we can use this for Hive): Configuring Hive to use the Hive Metastore. One option is to delete existing external table and create new table that includes new column. Hadoop. What's the difference? Overwriting Existing Partition. For dynamic partitioning: --Set following two properties for your Hive session: SET hive.exec.dynamic.partition=true; SET hive.exec.dynamic.partition.mode=nonstrict;--Create your staging table without Partition. Of course we also had to add this to the catalog's interface.scala Solution . But what about data when you have an external hive table? In the SparkSqlAstBuilder we had to create a new function to be able to interpret the grammar and add the requested step to the logical plan. For example in the above weather table the data can be partitioned on the basis of year and month and when query is fired on weather table this partition can be used as one of the column. Previous Post How to write Group by and Order by query with column position number in Hive. We can run below query to add partition to table. add or replace hive column. If a property was already set, overrides the old value with the new one. We're implemented the following steps: So Spark doesn't support changing the file format of a partition. Both internal/managed and external table supports column partition. I want to create partitions on that table but I couldn't find a way to alter existing non-partitioned table to create partitions in that table. So, how to create a management table? Since this is Hive metadata operation, your data files wont be touched. Your email address will not be published. This is supported only for tables created using the Hive format. Hive. Tweet. In that case, you can set up a job that will move old data to S3 ( It is Amazons cheap store service. Partitioning allows Hive to run queries on a specific set of data in the table based on the value of partition column used in the query. It then selects a plan using a cost model. Posted on January 16, 2015 by admin. Now naturally the question arises, how efficiently we can store this data, definitely it has to be compressed. The RECOVER PARTITIONS clause automatically recognizes any data … Command: INSERT OVERWRITE TABLE expenses PARTITION (month, spender) stored as sequence file SELECT month, spender, merchant, mode, amount FROM expenses; Commands Used on Partitions in Hive. I Cant do this with just an ALTER statement: CREATE TABLE [Log]. Specifies a table name, which may be optionally qualified with a database name. It just removes these details from table metadata. We are telling hive this partition for this table is has its data at this location. create a table based on Parquet data which is actually located at another partition of the previously created table. - create hive table with multi format partitions *** FAILED *** (4 seconds, 265 milliseconds). Hive doe not drop that data. Next, we will start learning about bucketing an equally important aspect in Hive with its unique features and use cases. Our preference goes out to having one table which can handle all data, no matter the format. Next Post Insert overwrite table values in Hive … The first step that we usually do is transform the data into a format such as Parquet that can easily be queried by Hive/Impala. Determining which attributes refer to the same value to give them a unique ID (which later allows optimization of expressions such as col = col). Hive is metastore for tables. Adds a partition to the partitioned table. REPLACE COLUMNS removes all existing columns and adds the new set of columns. The logical optimization phase applies standard rule-based optimizations to the logical plan. Other ALTER TABLE commands which operate on partitions (e.g. The syntax is as follows. Consider use case, you have a huge amount of data but you do not use old data that frequently (something like log data). We simulated this by adding the following line to our unit test: With this setting, the test passed. Hive stores tables in partitions. However, beginning with Spark 2.1, Alter Table Partitions is also supported for tables defined using the datasource API. Adding Partition To Table. New subpartitions must be of the same type (LIST, RANGE or HASH) as existing subpartitions. The ALTER TABLE… ADD SUBPARTITION command adds a subpartition to an existing partition; the partition must already be subpartitioned. At the moment, cost-based optimization is only used to select join algorithms: for relations that are known to be small, Spark SQL uses a broadcast join, using a peer-to-peer broadcast facility available in Spark. This is the default table type in Hive The tables created by default are management tables, which are ordinary tables. The destination can write to a new or existing Hive table. In Hive you can achieve this with a partitioned table, where you can set the format of each partition. Hadoop. Hive. We could read all the data...but wait, what?!!? We also figured out how to run a given unit test. Of course we can. Pin. ADD COLUMNS. table_identifier. // TODO a partition spec is allowed to have optional values. So what should this command do? Syntax ALTER TABLE table_identifier ADD COLUMNS ( col_spec [ , ... ] ) Parameters. and the definitions are based on the ones described in the Apache Hive Language manual. When storing view partition descriptors in the metastore, Hive omits the storage descriptor entirely. We thus intend to implement richer cost-based optimization in the future. Required fields are marked *. Each partition consists of one or more distinct column name/value combinations. Apache Hive organizes tables into partitions. Using ADD you can add columns at the end of existing columns. Spark unfortunately doesn't implement this. The physical planner also performs rule-based physical optimizations, such as pipelining projections or filters into one Spark map operation. The first would be to create a brand new partitioned table (you can do this by following this tip) and then simply copy the data from your existing table into the new table and do a table rename. Partitions are used to divide the table into related parts. Stay up to date on the latest insights and Download the Data & AI Training Guide 2021, Deep Dive into Spark SQL’s Catalyst Optimizer, We offer an in-depth Data Science with Spark course, org.apache.hadoop.hive.ql.io.parquet.serde.ParquetHiveSerDe, org.apache.hadoop.hive.ql.io.parquet.MapredParquetInputFormat, org.apache.hadoop.hive.ql.io.parquet.MapredParquetOutputFormat, org.apache.hadoop.hive.serde2.avro.AvroSerDe, org.apache.hadoop.hive.ql.io.avro.AvroContainerInputFormat, org.apache.hadoop.hive.ql.io.avro.AvroContainerOutputFormat, Hadoop to be able to store and access the files, Add this jar to Hive lib directory (in our case the Hive version was 2.3.1), Create a configuration directory and copy hadoop and hive base configurations, Change configurations in hive-site.xml so we actually use the Hive Metastore we just started, In a terminal set paths so we can start HiveServer2, where hadoop_version=3.0.0, hive_version=2.3.1, In another terminal set the same paths and start beeline, where hadoop_version=3.0.0, hive_version=2.3.1, Add a partition where we'll add Avro data, Insert data into last existing partition using beeline, Double check that the formats are correct. Post navigation. Today I discovered a bug that Hive can not recognise the existing data for a newly added column to a partitioned external table. We can use DML(Data Manipulation Language) queries in Hive to import or add data to the table. What if we want to add some more country partitions manually ex:- Dubai and Nepal. Create Table Syntax: CREATE TABLE [IF NOT EXISTS] [db_name. Partitioning is a way of dividing a table into related parts based on the values of particular columns like date, city, and department. Now, what if we want to drop some partition or add a new partition to the table? Looking at this code we decided to set HiveUtils.CONVERT_METASTORE_PARQUET.key to false, meaning that we won't optimize to data source relations in case we altered the partition file format. Syntax . You can add ,rename and drop a Hive Partition in an existing table. We went digging in the code again and we discovered the following method in HiveStrategies.scala. Each partition of a table is associated with a particular value(s) of partition column(s). Let us try to answer these questions in this blog post. Still we learned a lot about Apache Spark and it's internals. Metastore. This is supported for Avro backed tables as well, for Hive 0.14 and later. 3) add an ANALYZE TABLE [PARTITION] statement in Hive QL to gather stats for existing tables/partitions. This is supported only for tables created using the Hive format. And thus make the Parquet execution plan similar to the Avro execution plan? Well it should make sure that the serde properties are set properly on the partition level. Downside is that you will have to execute alter table command to redefine partitions on new table. Parameters. There are two choices as workarounds: 1. New partitions must be of the same type (LIST, RANGE or HASH) as existing partitions. What are the steps required to partition an already existing table? The following queries rename the column name and column data type using the above data: and then we could use this in HiveStrategies.scala to change the previously mentioned method: With these changes our tests also succeeded. Spark SQL uses Catalyst rules and a Catalog object that tracks the tables in all data sources to resolve these attributes. There is alternative for bulk loading of partitions into hive table. Partitioning of table. ANTLR ANother Tool for Language Recognition can generate a grammar that can be built and walked. Leave a comment . Here we are adding new information about partition to table metadata. The best explanation that we found was on the Databricks site, the article about Deep Dive into Spark SQL’s Catalyst Optimizer This will not only add support for setting the fileformat of a partition but also on a table itself. The new partition rules must reference the same column specified in the partitioning rules that define the existing partition(s). Next Post Insert overwrite table values in Hive with examples. All other phases are purely rule-based. Hive Alter Table - Learn Hive in simple and easy steps from basic to advanced concepts with clear examples including Introduction, Architecture, Installation, Data Types, Create Database, Use Database, Alter Database, Drop Database, Tables, Create Table, Alter Table, Load Data to Table, Insert Table, Drop Table, Views, Indexes, Partitioning, Show, Describe, Built-In Operators, Built-In Functions We will learn how to get distinct values as well as count of distinct values. The table is in orc format and it is managed table. Starting from SQL Server 2012 it was lifted up to 15,000 by default. In this post, I explained ALTER TABLE test_external ADD COLUMNS (col2 STRING);. In the table Int_Test we already have couple of country partitions. However if you had partitioned the existing table using “PARTITIONED BY” clause, then you will be allowed you add partition using the ALTER TABLE command. Writes to an existing table When the Hive destination writes to an existing table and partition columns are not defined in stage properties, the destination automatically uses the same partitioning as the existing table. If you do not specify a tablespace, the partition will reside in the default tablespace. Hive Partitions is a way to organizes tables into partitions by dividing tables into different parts based on partition keys. We can overwrite an existing partition with help of OVERWRITE INTO TABLE partitioned_user clause. So we need to support FILEFORMAT in case a partition is set, thus we had to add the following line to SqlBase.g4. This clause always begins with PARTITION BY, and follows the same syntax and other rules as apply to the partition_options clause for CREATE TABLE (for more detailed information, see Section 13.1.18, “CREATE TABLE Statement”), and can also be used to partition an existing table that is not already partitioned. So for now, we are punting on this approach. Create Table from Existing Table. If you also want to drop data along with partition fro external tables then you have to do it manually. If partitions are added in Hive tables that are not subpaths of the storage location, those partitions are not added to the corresponding external tables in Snowflake. Loading Data into External Partitioned Table From HDFS. Let's see if we can check out the Apache Spark code base and create a failing unit test. partition… We don't want to have two different tables: one for the historical data in Parquet format and one for the incoming data in Avro format. We decided to implement an extra check to avoid optimising the execution when a partition has a different file format than the main table. There is alternative for bulk loading of partitions into hive table. Now we have a unit test which succeeds in which we can set the file format for a partition. This is currently violated. Add partitions on existing table in Hive. Since we're working with Spark SQL, we had to modify SparkSqlParser which creates a SparkSqlAstBuilder which extends AstBuilder. Incoming data is usually in a format different than we would like for long-term storage. There are two different approaches we could use to accomplish this task. Pin. Does this mean we can have our partitions at diffrent locations? How to add partition to an existing table in Hive? We have created partitioned tables, inserted data into them. * ALTER TABLE table [PARTITION spec] SET FILEFORMAT format; // Expected format: INPUTFORMAT input_format OUTPUTFORMAT output_format, // Expected format: SEQUENCEFILE | TEXTFILE | RCFILE | ORC | PARQUET | AVRO. We decided to add a property, hasMultiFormatPartitions to the CatalogTable which reflects if we have a table with multiple different formats in it's partitions. Partition is helpful when the table has one or more Partition keys. There are 3 major milestones in this subtask: 1) extend the insert statement to gather table/partition level stats on-the-fly. Your email address will not be published. First we had to discover that Spark uses ANTLR to generate its SQL parser. Not just in different locations but also in different file systems. Sets the SERDE or SERDEPROPERTIES in Hive tables. Adding partitions to an existing table. We don't need this for our current case, but might come in handy some other time. Partitioning. You can also manually update or drop a Hive partition directly on HDFS using Hadoop commands, if you do so you need to run the MSCK command to synch up HDFS files with Hive Metastore. Having data on HDFS folder, we are going to build a Hive table which is compatible with the format of data. The RECOVER PARTITIONS clause automatically recognizes any data … For example, if the storage location associated with the Hive table (and corresponding Snowflake external table) is s3://path/ , then all partition locations in the Hive table must also be prefixed by s3://path/ . Since it is used for data warehousing, the data for production system hive tables would definitely be at least in terms of hundreds of gigs. We will see how to create a partitioned table in Hive and how to import data into the table. There can be instances … For the reason that data moving while loading data into Hive table is not expected, an external table shall be created. When working with the partition you can also specify to overwrite only when the partition exists using the IF NOT EXISTS option. Let us try to answer these questions in this blog post. 0 Shares. The users want easy access to the data with Hive or Spark. delta.``: The location of an existing Delta table. But we're still not done, because we also need a definition for the new commands. create a table based on Avro data which is actually located at a partition of the previously created table. In order to create a table on a partition you need to specify the Partition scheme during creation of a table. Your email address will not be published. In this blog, we will learn how to filter rows from spark dataframe using Where and Filter functions. Partition keys are basic elements for determining how the data is stored in the table. Hive first introduced INSERT INTO starting version 0.8 which is used to append the data/records/rows into a table or partition. Scala’s pattern matching and quasiquotes) in a novel way to build an extensible query optimizer. You can find this docker image on GitHub (source code is at link). ALTER TABLE ADD PARTITION in Hive Alter table statement is used to change the table structure or properties of an existing table in Hive. You can't add a partition to a non-partitioned table (aka a table that did not specify partitions via PARTITIONED BY during its creation). To have performant queries we need the historical data to be in Parquet format. Since our users also use Spark, this was something we had to fix. Leave a Reply Cancel reply. First we need to create a table and change the format of a given partition. 2. Creates one or more partition columns for the table. Comment document.getElementById("comment").setAttribute( "id", "a3eec05f6cd7f62f96200dd6b8f21b3d" );document.getElementById("d9ff7d4539").setAttribute( "id", "comment" ); Save my name, email, and website in this browser for the next time I comment. The columns can be partitioned on an existing table or while creating a new Hive table. TOUCH/ARCHIVE) are not supported. ALTER Partitions. 1. INSERT OVERWRITE is used to replace any existing data in the table or partition and insert with the new rows. Later now, we need to add a partition on STUDENT_JOINING_DATE column. The syntax is as below. Connect to spark and make sure we access the Hive Metastore we set up: So it doesn't work. The final test can be found at: MultiFormatTableSuite.scala Tweet. Post navigation. Hive provides multiple ways to add data to the tables.