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Alter table statements enable you to change the structure of an existing table. You can add columns/partitions, change SerDe, add table and SerDe properties, or rename the table itself. Similarly, alter table partition statements allow you change the properties of a specific partition in the named table.

Alter Table

Rename Table

ALTER TABLE table_name RENAME TO new_table_name

This statement lets you change the name of a table to a different name.

As of version 0.6, a rename on a managed table moves its HDFS location as well. (Older Hive versions just renamed the table in the metastore without moving the HDFS location.)

Alter Table Properties

ALTER TABLE table_name SET TBLPROPERTIES table_properties

table_properties:
  : (property_name = property_value, property_name = property_value, ... )

You can use this statement to add your own metadata to the tables. Currently last_modified_user, last_modified_time properties are automatically added and managed by Hive. Users can add their own properties to this list. You can do DESCRIBE EXTENDED TABLE to get this information.

Alter Table Comment

To change the comment of a table you have to change the comment property of the TBLPROPERTIES:

ALTER TABLE table_name SET TBLPROPERTIES ('comment' = new_comment);

Add SerDe Properties

ALTER TABLE table_name SET SERDE serde_class_name [WITH SERDEPROPERTIES serde_properties]
ALTER TABLE table_name SET SERDEPROPERTIES serde_properties

serde_properties:
  : (property_name = property_value, property_name = property_value, ... )

These statements enable you to change a table's SerDe or add user-defined metadata to the table's SerDe object.

The SerDe properties are passed to the table's SerDe when it is being initialized by Hive to serialize and deserialize data. So users can store any information required for their custom SerDe here. Refer to the SerDe documentation and Hive SerDe in the Developer Guide for more information, and see Row Format, Storage Format, and SerDe above for details about setting a table's SerDe and SERDEPROPERTIES in a CREATE TABLE statement.

Example, note that both property_name and property_value must be quoted:

ALTER TABLE table_name SET SERDEPROPERTIES ('field.delim' = ',');

Alter Table Storage Properties

ALTER TABLE table_name CLUSTERED BY (col_name, col_name, ...) [SORTED BY (col_name, ...)] INTO num_buckets BUCKETS

These statements change the table's physical storage properties.

NOTE: These commands will only modify Hive's metadata, and will NOT reorganize or reformat existing data. Users should make sure the actual data layout conforms with the metadata definition.

Additional Alter Table Statements

See Alter Either Table or Partition below for more DDL statements that alter tables.

Alter Partition

Add Partitions

ALTER TABLE table_name ADD [IF NOT EXISTS] PARTITION partition_spec [LOCATION 'location1'] partition_spec [LOCATION 'location2'] ...

partition_spec:
  : (partition_col = partition_col_value, partition_col = partiton_col_value, ...)

You can use ALTER TABLE ADD PARTITION to add partitions to a table. Partition values should be quoted only if they are strings. The location must be a directory inside of which data files reside. (ADD PARTITION changes the table metadata, but does not load data. If the data does not exist in the partition's location, queries will not return any results.)

Note that it is proper syntax to have multiple partition_spec in a single ALTER TABLE, but if you do this in version 0.7, your partitioning scheme will fail. That is, every query specifying a partition will always use only the first partition. Instead, you should use the following form if you want to add many partitions in Hive 0.7:

ALTER TABLE table_name ADD PARTITION (partCol = 'value1') location 'loc1';
ALTER TABLE table_name ADD PARTITION (partCol = 'value2') location 'loc2';
...
ALTER TABLE table_name ADD PARTITION (partCol = 'valueN') location 'locN';

Specifically, the following example (which was the default example before) will FAIL silently and without error, and all queries will go only to dt='2008-08-08' partition, no matter which partition you specify.

ALTER TABLE page_view ADD PARTITION (dt='2008-08-08', country='us') location '/path/to/us/part080808'
                          PARTITION (dt='2008-08-09', country='us') location '/path/to/us/part080809';

In Hive 0.8 and later, you can add multiple partitions in a single ALTER TABLE statement as shown in the previous example.

An error is thrown if the partition_spec for the table already exists. You can use IF NOT EXISTS to skip the error.

Dynamic Partitions

Partitions can be added to a table dynamically, using a Hive INSERT statement (or a Pig STORE statement). See these documents for details and examples:

• Design Document for Dynamic Partitions
• Tutorial: Dynamic-Partition Insert
• Hive DML: Dynamic Partition Inserts
• HCatalog Dynamic Partitioning
  • Usage with Pig
  • Usage from MapReduce

Rename Partition

ALTER TABLE table_name PARTITION partition_spec RENAME TO PARTITION partition_spec;

This statement lets you change the value of a partition column.

Exchange Partition

ALTER TABLE table_name_1 EXCHANGE PARTITION (partition_spec) WITH TABLE table_name_2;

This statement lets you move the data in a partition from a table to another table that has the same schema but does not already have that partition. For details, see Exchange Partition and HIVE-4095.

Recover Partitions (MSCK REPAIR TABLE)

Hive stores a list of partitions for each table in its metastore. If, however, new partitions are directly added to HDFS (say by using hadoop fs -put command), the metastore (and hence Hive) will not be aware of these partitions unless the user runs ALTER TABLE table_name ADD PARTITION commands on each of the newly added partitions.

However, users can run

MSCK REPAIR TABLE table_name;

which will add metadata about partitions to the Hive metastore for partitions for which such metadata doesn't already exist. In other words, it will add any partitions that exist on HDFS but not in metastore to the metastore. See HIVE-874 for more details.

The equivalent command on Amazon Elastic MapReduce (EMR)'s version of Hive is

ALTER TABLE table_name RECOVER PARTITIONS;

Drop Partitions

ALTER TABLE table_name DROP [IF EXISTS] PARTITION partition_spec, PARTITION partition_spec,...

You can use ALTER TABLE DROP PARTITION to drop a partition for a table. This removes the data and metadata for this partition.

For tables that are protected by NO DROP CASCADE, you can use the predicate IGNORE PROTECTION to drop a specified partition or set of partitions (for example, when splitting a table between two Hadoop clusters).

ALTER TABLE table_name DROP [IF EXISTS] PARTITION partition_spec IGNORE PROTECTION;

The above command will drop that partition regardless of protection stats.

In Hive 0.7.0 or later, DROP returns an error if the partition doesn't exist, unless IF EXISTS is specified or the configuration variable hive.exec.drop.ignorenonexistent is set to true.

ALTER TABLE page_view DROP PARTITION (dt='2008-08-08', country='us');

(Un)Archive Partition

ALTER TABLE table_name ARCHIVE PARTITION partition_spec;
ALTER TABLE table_name UNARCHIVE PARTITION partition_spec;

Archiving is a feature to moves a partition's files into a Hadoop Archive (HAR). Note that only the file count will be reduced; HAR does not provide any compression. See LanguageManual Archiving for more information

Alter Either Table or Partition

Alter Table/Partition File Format

ALTER TABLE table_name [PARTITION partitionSpec] SET FILEFORMAT file_format

This statement changes the table's (or partition's) file format. For available file_format options, see the section above on CREATE TABLE.

Alter Table/Partition Location

ALTER TABLE table_name [PARTITION partitionSpec] SET LOCATION "new location"

Alter Table/Partition Touch

ALTER TABLE table_name TOUCH [PARTITION partitionSpec];

TOUCH reads the metadata, and writes it back. This has the effect of causing the pre/post execute hooks to fire. An example use case is if you have a hook that logs all the tables/partitions that were modified, along with an external script that alters the files on HDFS directly. Since the script modifies files outside of hive, the modification wouldn't be logged by the hook. The external script could call TOUCH to fire the hook and mark the said table or partition as modified.

Also, it may be useful later if we incorporate reliable last modified times. Then touch would update that time as well.

Note that TOUCH doesn't create a table or partition if it doesn't already exist. (See Create Table.)

Alter Table/Partition Protections

ALTER TABLE table_name [PARTITION partition_spec] ENABLE|DISABLE NO_DROP;
ALTER TABLE table_name [PARTITION partition_spec] ENABLE|DISABLE OFFLINE;

Protection on data can be set at either the table or partition level. Enabling NO_DROP prevents a table or partition from being dropped. Enabling OFFLINE prevents the data in a table or partition from being queried, but the metadata can still be accessed. Note, if any partition in a table has NO_DROP enabled, the table cannot be dropped either.

Alter Table/Partition Compact

ALTER TABLE table_name [PARTITION (partition_key = 'partition_value' [, ...])] COMPACT 'compaction_type' 

In general you do not need to request compactions when Hive transactions are being used, because the system will detect the need for them and initiate the compaction. However, if compaction is turned off for a table or you want to compact the table at a time the system would not choose to, ALTER TABLE can initiate the compaction. The statement will enqueue a request for compaction and return. To watch the progress of the compaction, use SHOW COMPACTIONS.

The compaction_type can be MAJOR or MINOR. See the Basic Design section in Hive Transactions for more information.

Alter Column

Rules for Column Names

Column names are case insensitive.

Change Column Name/Type/Position/Comment

ALTER TABLE table_name [PARTITION partition_spec] CHANGE [COLUMN] col_old_name col_new_name column_type [COMMENT col_comment] [FIRST|AFTER column_name]

This command will allow users to change a column's name, data type, comment, or position, or an arbitrary combination of them.

Example:

CREATE TABLE test_change (a int, b int, c int);

// will change column a's name to a1
ALTER TABLE test_change CHANGE a a1 INT;

// will change column a's name to a1, a's data type to string, and put it after column b. The new table's structure is: b int, a1 string, c int
ALTER TABLE test_change CHANGE a a1 STRING AFTER b;

// will change column b's name to b1, and put it as the first column. The new table's structure is: b1 int, a string, c int
ALTER TABLE test_change CHANGE b b1 INT FIRST;

NOTE: The column change command will only modify Hive's metadata, and will NOT touch data. Users should make sure the actual data layout conforms with the metadata definition.

Add/Replace Columns

ALTER TABLE table_name [PARTITION partition_spec] ADD|REPLACE COLUMNS (col_name data_type [COMMENT col_comment], ...)

ADD COLUMNS lets you add new columns to the end of the existing columns but before the partition columns. This is supported for Avro backed tables as well, for Hive 0.14 and later.

REPLACE COLUMNS removes all existing columns and adds the new set of columns. This can be done only for tables with native SerDe (DynamicSerDe, MetadataTypedColumnsetSerDe, LazySimpleSerDe and ColumnarSerDe). Refer to SerDe section of User Guide for more information. REPLACE COLUMNS can also be used to drop columns. For example:

"ALTER TABLE test_change REPLACE COLUMNS (a int, b int);" will remove column `c' from test_change's schema. Note that this does not delete underlying data, it just changes the schema.