How to Update or Drop a Hive Partition?
- Update Hive Partition You can use the Hive ALTER TABLE command to change the HDFS directory location of a specific partition. ...
- Rename Hive Partition You can also use ALTER TABLE with PARTITION RENAME to rename the Hive partition. ...
- Drop or Delete Hive Partition Hive drop or delete partition is performed using ALTER TABLE tablename DROP command. ...
- Conclusion ...
- Reference ...
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Can we drop partition?
ALTER TABLE DROP PARTITION allows you to drop a partition and its data. If you would like to drop the partition but keep its data in the table, the Oracle partition must be merged into one of the adjacent partitions. Note: Far and away, the "drop partition" syntax is the fastest way to remove large volumes of data.
Can we drop a partition in Oracle?
You can remove multiple partitions or subpartitions from a range or list partitioned table with the DROP PARTITION and DROP SUBPARTITION clauses of the SQL ALTER TABLE statement. For example, the following SQL statement drops multiple partitions from the range-partitioned table sales .
How do I drop multiple partitions at a time in Hive?
Drop multiple partitions With the below alter script, we provide the exact partitions we would like to delete. hive> ALTER TABLE sales drop if exists partition (year = 2020, quarter = 1), partition (year = 2020, quarter = 2);
How do I drop a column from a partitioned table in Hive?
The only way to drop column is using replace command. Lets say, I have a table TEST with id, name and case column. We want to drop id column of table TEST. So provide all those columns which you want to be the part of table in replace columns clause.
How do I delete a partition in Oracle?
It is easy to delete data from a specific partition: this statement clears down all the data for February 2012:delete from t23 partition (feb2012);alter table t23 truncate partition feb2012;alter table t23 drop partition feb2012;
What happens when you drop a partition?
DROP PARTITION command deletes a partition and any data stored on that partition.
Does drop table delete partition?
When you drop a range-, hash-, or list-partitioned table, then the database drops all the table partitions. If you drop a composite-partitioned table, then all the partitions and subpartitions are also dropped.
How do I drop multiple tables in Hive?
But there are multipe ways to do it, for example :With a shell script : hive -e "show tables 'temp_*'" | xargs -I '{}' hive -e 'drop table {}'Or by putting your tables in a specific database and dropping the whole database. Create table temp.table_name; Drop database temp cascade;
What are the 2 types of partitioning in Hive?
Usually when loading files (big files) into Hive tables static partitions are preferred. Static Partition saves your time in loading data compared to dynamic partition. You “statically” add a partition in the table and move the file into the partition of the table. We can alter the partition in the static partition.
Can we drop a column in Hive?
Hive allows us to delete one or more columns by replacing them with the new columns. Thus, we cannot drop the column directly.
How do I drop a partition in SQL?
For example, to drop the first partition, issue the following statements: DELETE FROM sales partition (dec98); ALTER TABLE sales DROP PARTITION dec98; This method is most appropriate for small tables, or for large tables when the partition being dropped contains a small percentage of the total data in the table.
How can I see partitions in Hive table?
This command lists all the partitions for a table. The general syntax for showing partitions is as follows: SHOW PARTITIONS [db_name.] table_name [PARTITION(partition_spec)];
Does drop table delete partition?
When you drop a range-, hash-, or list-partitioned table, then the database drops all the table partitions. If you drop a composite-partitioned table, then all the partitions and subpartitions are also dropped.
Does drop partition delete data?
Data itself are stored in files in the partition location(folder). If you drop partition of external table, the location remain untouched, but unmounted as partition (metadata about this partition is deleted).
Does drop partition release space?
the ALTER TABLE DROP PARTITION always returns the space back to the tablespace for reuse by other segments.
How do I drop a partition in SQL Server?
Drop a partition function from the current database. Syntax DROP PARTITION FUNCTION pf_name [;] Key pf_name The partition function to drop. This command requires that the partition function is not currently being used by any partition schemes.
Why use Apache Hive partitions?
Just like relational databases, Apache Hive partitions are used to improve the performance of the HiveQL queries. In Hive, partitions are dividing and storing relevant data into HDFS sub directory.
How to change HDFS directory?
You can use Hive ALTER TABLE command to change the HDFS directory location or add new directory. Alter command will change the partition directory.
Why do we partition data in relational databases?
In general, partitions in relational databases are used to increase the performance of the SQL queries. The partition is the concept of storing relevant data in the same place. For example, let us say you want to query the data monthly bases, then you can partition your data on month.
What does drop partition do?
This command will remove the data and metadata for this partition. The drop partition will actually move data to the .Trash/Current directory if Trash is configured, unless PURGE is specified, but the metadata is completely lost.
What is partition column in hive?
Partition columns are extra column visible in your Hive table. You can also exclude those partition columns if you don’t want to show them on your reports. In the subsequent sections, we will check how to update or drop partition that are already present in Hive tables.
Can you partition employee data on YoJ?
Now, if you partition the above employee data on year of join (yoj), it will divide employee data into multiple sub directories.
How to delete partitions in hive?
Hive drop or delete partition is performed using ALTER TABLE tablename DROP command. Dropping a partition from a table removes the data from HDFS and from Hive Metastore.
What is a hive partition?
Hive partition breaks the table into multiple tables (on HDFS multiple subdirectories) based on the partition key. Partition key could be one or multiple columns. For each distinct value of the partition key, a subdirectory will be created on HDFS.
What is hive alt table?
Hive ALTER TABLE command is used to update or drop a partition from a Hive Metastore and HDFS location (managed table). 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.
How to change HDFS directory location?
You can use the Hive ALTER TABLE command to change the HDFS directory location of a specific partition. The below example update the state=NC partition location from the default Hive store to a custom location /data/state=NC.
When you manually modify the partitions directly on HDFS, do you need to run MSCK REPAIR TABLE?
When you manually modify the partitions directly on HDFS, you need to run MSCK REPAIR TABLE to update the Hive Metastore. Not doing so will result in inconsistent results.
Can you rename partitions on HDFS?
Alternatively, you can also rename the partition directory on the HDFS. let’s rename partition state=’NY’ back to it’s original state=’AL’
Does Hadoop move data to trash?
Note: Data moving to .Trash directory happens only for Internal/Managed table. For the external table, DROP partition just removes the partition from Hive Metastore and the partition is still present on HDFS. You need to run explicitly hadoop fs -rm commnad to remove the partition from HDFS.
Requirement
Suppose we are having a hive partition table. This table is partitioned by the year of joining. Our requirement is to drop multiple partitions in hive.
Solution
If you already have a partitioned table, then skip this step else read this post for creating a table and loading data into it.
Wrapping Up
In this post, we have seen how we can add multiple partitions as well as drop multiple partitions from the hive table. We can drop multiple specific partitions as well as any range kind of partition.
How does hive work?
Hive organizes tables into partitions. It is a way of dividing a table into related parts based on the values of partitioned columns such as date, city, and department. Using partition, it is easy to query a portion of the data.
Why are tables subdivided into buckets?
Tables or partitions are sub-divided into buckets, to provide extra structure to the data that may be used for more efficient querying. Bucketing works based on the value of hash function of some column of a table.
Update a Hive partition
Let’s say you had an issue with the way the data was loaded into a partition and now you have found a way to fix the data and fixed it. The corrected date is under hdfs://user/svc_account/fixed_date/2020/2. Here is the alter command to update the partition of the table sales.
Drop multiple partitions
With the below alter script, we provide the exact partitions we would like to delete.
Requirement
Components Involved
Sample Data
- Let’s say we are having given sample data: Here, 1 record belongs to 1 partition as we will store data partitioned by the year of joining. In actual, there will be many records for each partition.
Solution
- Step 1: Create Table & Load data
If you already have a partitioned table, then skip this step else read thispost for creating a table and loading data into it. - Step 2: Drop Multiple Partitions
If you see sample data, we are having 10 partitions of the year from 2005 to 2014. Let’s check the partitions in the table: In case, you want to add multiple partitions in the table, then mention all the partitions in the query like given below: Here, all the given partitions will get added to the table i…
Wrapping Up
- In this post, we have seen how we can add multiple partitions as well as drop multiple partitions from the hive table. We can drop multiple specific partitions as well as any range kind of partition. Sharing is caring!