ALTER TABLE¶

RENAME TABLE¶

Synopsis

ALTER TABLE <table_name> RENAME TO <new_table_name>

For example:
ALTER TABLE table1 RENAME TO table2;

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

RENAME COLUMN¶

Synopsis

ALTER TABLE <table_name> RENAME COLUMN <column_name> TO <new_column_name>

For example:
ALTER TABLE table1 RENAME COLUMN id TO id2;

This statement will allow users to change a column’s name.

ADD COLUMN¶

Synopsis

ALTER TABLE <table_name> ADD COLUMN <column_name> <data_type>

For example:
ALTER TABLE table1 ADD COLUMN id text;

This statement lets you add new columns to the end of the existing column.

SET PROPERTY¶

Synopsis

ALTER TABLE <table_name> SET PROPERTY (<key> = <value>, ...)

For example:
ALTER TABLE table1 SET PROPERTY 'timezone' = 'GMT-7'
ALTER TABLE table1 SET PROPERTY 'text.delimiter' = '&'
ALTER TABLE table1 SET PROPERTY 'compression.type'='RECORD','compression.codec'='org.apache.hadoop.io.compress.SnappyCodec'

This statement will allow users to change a table property.

DROP PARTITION¶

Synopsis

ALTER TABLE <table_name> [IF EXISTS] DROP PARTITION (<partition column> = <partition value>, ...) [PURGE]

For example:
ALTER TABLE table1 DROP PARTITION (col1 = 1 , col2 = 2)
ALTER TABLE table1 DROP PARTITION (col1 = '2015' , col2 = '01', col3 = '11' )
ALTER TABLE table1 DROP PARTITION (col1 = 'TAJO' ) PURGE

You can use ALTER TABLE DROP PARTITION to drop a partition for a table. This doesn’t remove the data for a table. But if PURGE is specified, the partition data will be removed. The metadata is completely lost in all cases. An error is thrown if the partition for the table doesn’t exist. You can use IF EXISTS to skip the error.

REPAIR PARTITION¶

Tajo stores a list of partitions for each table in its catalog. If partitions are manually added to the distributed file system, the metastore is not aware of these partitions. Running the ALTER TABLE REPAIR PARTITION statement ensures that the tables are properly populated.

Synopsis

ALTER TABLE <table_name> REPAIR PARTITION

Note

Even though an information of a partition is stored in the catalog, Tajo does not recover it when its partition directory doesn’t exist in the file system.