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. However, if the partitioned table is created from existing data, partitions are not registered automatically in the Hive metastore; you must run MSCK REPAIR TABLE to register the partitions. MSCK REPAIR TABLE on a non-existent table or a table without partitions throws an exception. Another way to recover partitions is to use ALTER TABLE RECOVER PARTITIONS.

If the table is cached, the command clears cached data of the table and all its dependents that refer to it. The cache will be lazily filled when the next time the table or the dependents are accessed.

Syntax 

MSCK REPAIR TABLE table_identifier [ {ADD | DROP | SYNC} PARTITIONS]

Parameters

  • table_identifier

    The name of the table to be repaired. The table name may be optionally qualified with a database name.

    Syntax: [database_name.] table_name

  • ADD or DROP or SYNC PARTITIONS

    Since: Databricks Runtime 10.0

    Specifies how to recover partitions. If not specified, ADD is the default.

    • ADD, the command adds new partitions to the session catalog for all sub-folder in the base table folder that don’t belong to any table partitions.
    • DROP, the command drops all partitions from the session catalog that have non-existing locations in the file system.
    • SYNC is the combination of DROP and ADD.

Examples 

-- create a partitioned table from existing data /tmp/namesAndAges.parquet
> CREATE TABLE t1 (name STRING, age INT) USING parquet PARTITIONED BY (age)
    LOCATION "/tmp/namesAndAges.parquet";

-- SELECT * FROM t1 does not return results
> SELECT * FROM t1;

-- run MSCK REPAIR TABLE to recovers all the partitions
> MSCK REPAIR TABLE t1;

-- SELECT * FROM t1 returns results
> SELECT * FROM t1;
    name age
 ------- ---
 Michael  20
  Justin  19
    Andy  30