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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 TableRename Table
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
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 CommentTo change the comment of a table you have to change the
Add SerDe Properties
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
Alter Table Storage Properties
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 StatementsSee Alter Either Table or Partition below for more DDL statements that alter tables. Alter PartitionAdd Partitions
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:
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.
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 PartitionsPartitions can be added to a table dynamically, using a Hive INSERT statement (or a Pig STORE statement). See these documents for details and examples:
Rename Partition
This statement lets you change the value of a partition column. Exchange Partition
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 However, users can run
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
Drop Partitions
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).
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.
(Un)Archive Partition
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 PartitionAlter Table/Partition 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/Partition Touch
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
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
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 Table/Partition Concatenate
If the table or partition contains many small RCFiles or ORC files, then the above command will merge them into larger files. In case of RCFile the merge happens at block level whereas for ORC files the merge happens at stripe level thereby avoiding the overhead of decompressing and decoding the data. Alter Column
Rules for Column NamesColumn names are case insensitive.
Change Column Name/Type/Position/Comment
This command will allow users to change a column's name, data type, comment, or position, or an arbitrary combination of them. The PARTITION clause is available in Hive 0.14.0 and later; see Upgrading Pre-Hive 0.13.0 Decimal Columns for usage. Example:
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
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. The PARTITION clause is available in Hive 0.14.0 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 Partition With Partial Partition SpecificationAs of Hive 0.14 (HIVE-8411), users are able to provide a partial partition spec for certain ALTER PARTITION statements, similar to dynamic partitioning. So rather than having to issue an ALTER PARTITION statement for each partition that needs to be changed:
You can change many existing partitions at once using a single ALTER statement using a partial partition specification
Similar to dynamic partitioning, hive.exec.dynamic.partition must be set to true to enable use of partial partition specs during ALTER PARTITION. This is supported for the following operations:
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Create/Drop/Alter View
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Create View
CREATE VIEW creates a view with the given name. An error is thrown if a table or view with the same name already exists. You can use IF NOT EXISTS to skip the error. If no column names are supplied, the names of the view's columns will be derived automatically from the defining SELECT expression. (If the SELECT contains unaliased scalar expressions such as x+y, the resulting view column names will be generated in the form _C0, _C1, etc.) When renaming columns, column comments can also optionally be supplied. (Comments are not automatically inherited from underlying columns.) A CREATE VIEW statement will fail if the view's defining SELECT expression is invalid. Note that a view is a purely logical object with no associated storage. (No support for materialized views is currently available in Hive.) When a query references a view, the view's definition is evaluated in order to produce a set of rows for further processing by the query. (This is a conceptual description; in fact, as part of query optimization, Hive may combine the view's definition with the query's, e.g. pushing filters from the query down into the view.) A view's schema is frozen at the time the view is created; subsequent changes to underlying tables (e.g. adding a column) will not be reflected in the view's schema. If an underlying table is dropped or changed in an incompatible fashion, subsequent attempts to query the invalid view will fail. Views are read-only and may not be used as the target of LOAD/INSERT/ALTER. For changing metadata, see ALTER VIEW. A view may contain ORDER BY and LIMIT clauses. If a referencing query also contains these clauses, the query-level clauses are evaluated after the view clauses (and after any other operations in the query). For example, if a view specifies LIMIT 5, and a referencing query is executed as (select * from v LIMIT 10), then at most 5 rows will be returned. Starting with Hive 0.13.0, the view's select statement can include one or more common table expressions (CTEs) as shown in the SELECT syntax. For examples of CTEs in CREATE VIEW statements, see Common Table Expression. Example of view creation:
Use SHOW CREATE TABLE to display the CREATE VIEW statement that created a view. Drop View
DROP VIEW removes metadata for the specified view. (It is illegal to use DROP TABLE on a view.) When dropping a view referenced by other views, no warning is given (the dependent views are left dangling as invalid and must be dropped or recreated by the user). In Hive 0.7.0 or later, DROP returns an error if the view doesn't exist, unless IF EXISTS is specified or the configuration variable hive.exec.drop.ignorenonexistent is set to true. Example:
Alter View Properties
As with ALTER TABLE, you can use this statement to add your own metadata to a view. Alter View As Select
Alter View As Select changes the definition of a view, which must exist. The syntax is similar to that for CREATE VIEW and the effect is the same as for CREATE OR REPLACE VIEW. Note: The view must already exist, and if the view has partitions, it could not be replaced by Alter View As Select. |
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