{ “title”: “Replacing Atomic Table”, “language”: “en” }

Atomicity Replace

Doris supports atomic table replacement operations for two tables. This is only applicable to OLAP tables.

Applicable scenarios

  • Atomic overwrite operations
  • In certain cases, users may want to rewrite data in a table. However, the “delete and load” approach causes a data invisibility window. To solve that, Doris allows users to create a new table of the same schema using the CREATE TABLE LIKE statement, import the new data into this new table, and then atomically replace the old table with the new table. For atomic replacement at the partition level, please refer to the temporary partitiondocumentation.

Syntax

ALTER TABLE [db.]tbl1 REPLACE WITH TABLE tbl2
[PROPERTIES('swap' = 'true')];

Replace table tbl1 with table tbl2.

If swap is true, after the replacement, data in tbl1 will be replaced by that in tbl2, while data in tbl2 will be replaced by that in tbl1. In other words, the two tables will swap data.

If swap is false, after the replacement, data in tbl1 will be replaced by that in tbl2 and tbl2 will be deleted.

Implementation

In fact, table replacement is to combine the following operations into one atomic operation.

Assuming that table A is to be replaced with table B, and swap is set to true. The operations to be implemented are as follows:

  1. Rename table B to table A.
  2. Rename table A to table B.

If swap is set to false, the operations are as follows:

  1. Delete table A.
  2. Rename table B to table A.

Note

  • swap defaults to true, meaning to swap the data between two tables.
  • If swap is set to false, the table being replaced (table A) will be deleted and cannot be recovered.
  • The replacement operation can only be implemented between two OLAP tables and it does not check for table schema consistency.
  • The replacement operation does not change the existing privilege settings because privilege checks are based on table names.