What does MSCK repair table do?

Use the MSCK REPAIR TABLE command to update the metadata in the catalog after you add Hive compatible partitions. The MSCK REPAIR TABLE command scans a file system such as Amazon S3 for Hive compatible partitions that were added to the file system after the table was created.

When should I run MSCK repair?

Yes, you need to run msck repair table daily once you have loaded a new partition in HDFS location.

Why do we do MSCK repair?

The MSCK REPAIR TABLE command was designed to manually add partitions that are added to or removed from the file system, such as HDFS or S3, but are not present in the metastore. This task assumes you created a partitioned external table named emp_part that stores partitions outside the warehouse.

What is MSCK?

Similar to how fsck stands for filesystem consistency check, msck is Hive's metastore consistency check.

What does alter table recover partitions do?

ALTER TABLE RECOVER PARTITIONS is the command that is widely used in Hive to refresh partitions as new partitions are directly added to the file system by other users. Qubole has added path validation to the ALTER TABLE RECOVER PARTITIONS command. The command only recovers valid paths.

MSCK Repair for recovering the Hive Partitions | Spark with Hive | Spark Interview Questions

What does MSCK repair do in Hive?

MSCK REPAIR TABLE recovers all the partitions in the directory of a table and updates the Hive metastore. When creating a table using PARTITIONED BY clause, partitions are generated and registered in the Hive metastore.

How do I refresh metadata in Hive?

How do you refresh a Hive table?

You can refresh the table after the job is complete. After the job finishes, run the following command in Hive: > refresh tablename; This will refresh the data in the table, updating the new data.

How do I recover my Hive partition?

When the partitions directories still exist in the HDFS, simply run this command: MSCK REPAIR TABLE table_name; It adds the partitions definitions to the metastore based on what exists in the table directory.

What is analyze table compute statistics in Hive?

analyze command is basically used for gathering statistics for a table, columns and partitions. For existing tables and/or partitions, the user can issue the ANALYZE command to gather statistics and write them into Hive MetaStore not just to display data of the table.

How do you refresh Athena table?

AWS gives us a few ways to refresh the Athena table partitions. We can use the user interface, run the MSCK REPAIR TABLE statement using Hive, or use a Glue Crawler. This article will show you how to create a new crawler and use it to refresh an Athena table. If the crawler already exists, we can reuse it.

How do I drop a 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.

How can I see partitions in Hive?

You can see Hive MetaStore tables,Partitions information in table of "PARTITIONS". You could use "TBLS" join "Partition" to query special table partitions.

How do you make a bucket in Hive?

How do I add a partition to a table?

To add the partitioned index of a new data partition to a specific table space location separate from the table space location of the data partition, the partition level INDEX IN clause is added as an option on the ALTER TABLE ADD PARTITION statement.

What is purge in Hive?

Hive will remove all of its data and metadata from the hive meta-store. The hive DROP TABLE statement comes with a PURGE option. In case if the PURGE option is mentioned the data will be completely lost and cannot be recovered later but if not mentioned then data will move to . Trash/current directory.

What is Cascade in Hive?

The CASCADE|RESTRICT clause is available in Hive 1.1. 0. ALTER TABLE ADD|REPLACE COLUMNS with CASCADE command changes the columns of a table's metadata, and cascades the same change to all the partition metadata. RESTRICT is the default, limiting column changes only to table metadata.

Can we update Hive external table?

To support ACID, Hive tables should be created with TRANSACTIONAL table property. Transaction tables can be created, update, and read from only the ACID Transaction Manager session. External tables cannot be created to support ACID since the changes on external tables are beyond Hive control.

What does refresh table in SQL do?

The REFRESH TABLE statement can be used to remove a table space from the logical page list and reset recover-pending status. This can only be done by using REFRESH TABLE to repopulate a materialized query table where the materialized query table is the only table in the table space.

What is Impala refresh?

REFRESH is used to avoid inconsistencies between Impala and external metadata sources, namely Hive Metastore (HMS) and NameNodes. The REFRESH statement is only required if you load data from outside of Impala. Updated metadata, as a result of running REFRESH , is broadcast to all Impala coordinators.

What is difference between Hive and Impala?

Apache Hive might not be ideal for interactive computing whereas Impala is meant for interactive computing. Hive is batch based Hadoop MapReduce whereas Impala is more like MPP database. Hive supports complex types but Impala does not. Apache Hive is fault-tolerant whereas Impala does not support fault tolerance.

How do I update Hive Metastore?

How do I sync a partition in Hive?

What happens when a managed table is dropped?

If a managed table or partition is dropped, the data and metadata associated with that table or partition are deleted. If the PURGE option is not specified, the data is moved to a trash folder for a defined duration.