See Related Information for details about reading and Yourself and point Impala database, tables, or partitions at them, and manually removeįolders when no longer needed. Prior to Impala 2.6, you had to create folders In Impala 2.6 and higher, Impala DDL statements such as CREATE DATABASE, CREATE TABLE, DROPĭATABASE CASCADE, DROP TABLE, and ALTER TABLE PARTITION can create or removeįolders as needed in the Amazon S3 system. The ADD PARTITION or DROP PARTITION clauses. Removing the associated folders when you issue ALTER TABLE statements with In Impala 2.6 and higher, Impala automatically handles creating or LOCATION attribute of a table or partition to make Impala query data from TABLE statements that affect large numbers of partitions. Minimize bottlenecks due to communication with the metastore database, or causing otherĭDL operations on the same table to wait, test the effects of performing ALTER Single-partition ALTER TABLE statements in quick succession. The performance and scalability of this technique is similar to issuing a sequence of In no changes) even if no partitions match the conditions. LOAD DATA and INSERT statements also only apply to oneĪ DDL statement that applies to multiple partitions is considered successful (resulting Still only apply to one partition at a time: the SET LOCATION andĪDD PARTITION clauses. INCREMENTAL STATS statement, and with the PARTITION clause of This syntax with the PARTITION clause in the COMPUTE The SET FILEFORMAT, SET TBLPROPERTIES, SET The extended syntax involving comparison operators and multiple partitions applies to Of an ETL pipeline that periodically consolidates and rewrites the underlying data filesĪlter table fast_growing_data partition (year = 2016, month in (10,11,12)) set fileformat parquet This technique can also be used to change the file format of groups of partitions, as part Separated by commas, and the operation only applies to the partitions that match all theĬonditions (similar to using an AND clause):Īlter table historical_data drop partition (year < 1995, last_name like 'A%') In Impala 2.8 and higher, the expression for the partition clause with aĭROP or SET operation can include comparison operatorsįor example, you might drop a group of partitions corresponding to a particular date rangeĪlter table historical_data drop partition (year < 1995) Īlter table historical_data drop partition (year = 1996 and month between 1 and 6) įor tables with multiple partition keys columns, you can specify multiple conditions The exception is renaming a table for an external table, the underlying data (managed by Impala) as for external tables (with data files located in arbitrary Most of the ALTER TABLE operations work the same for internal tables PARTITION ( partition_spec) clause, you must includeĪll the partitioning columns in the specification. Whenever you specify partitions in an ALTER TABLE statement, through the Into the table using LOAD DATA or updating the table's Must prepare any Parquet data files containing complex types outside Impala, and bring them Remember thatĬhanging the file format for a table does not convert the data files within the table you Or you can use ALTER TABLE SET FILEFORMAT toĬhange the format of an existing table to Parquet so that Impala can query it. Use Impala to update metadata for a staging table in a non-Parquet file format where theĭata is populated by Hive. Work for complex type columns in Parquet tables, the complex type support in theĪLTER TABLE statement applies to all file formats. For example, you can use anĬlause to modify the table layout for complex type columns. Metadata for tables containing complex types ( ARRAY, In Impala 2.3 and higher, the ALTER TABLE statement can change the Syntax: ALTER TABLE old_table_name RENAME TO new_table_nameĪLTER TABLE name ADD COLUMNS ( col_spec)ĪLTER TABLE name REPLACE COLUMNS ( col_spec)ĪLTER TABLE name ADD COLUMN col_specĪLTER TABLE name DROP column_nameĪLTER TABLE name CHANGE column_name col_spec ALTER TABLE name SET OWNER USER user_nameĪLTER TABLE name SET OWNER ROLE role_name - Kudu tables only.ĪLTER TABLE name ALTER column_name The data files to include extra fields, or converting them to a different file format. Typically need to perform corresponding physical filesystem operations, such as rewriting Moved to different paths.) When you do an ALTER TABLE operation, you RENAME TO clause is the one exception it can cause HDFS files to be Operations do not actually rewrite, move, and so on the actual data files. Metastore database that Impala shares with Hive. In Impala, this is primarily a logical operation that updates the table metadata in the The ALTER TABLE statement changes the structure or properties of an
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