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Two Tables of Atomic Swap (Swap)
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Last updated: 2024-06-27 11:08:50
Two Tables of Atomic Swap (Swap)
Last updated: 2024-06-27 11:08:50
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From version 0.14, Doris supports atomic replacement operations between two tables. This operation is only suitable for OLAP tables. For partition-level replacement operations, refer to Temporary Partition.

Syntax Description

ALTER TABLE [db.]tbl1 REPLACE WITH TABLE tbl2
[PROPERTIES('swap' = 'true')];
Replace table tbl1 with table tbl2.
If the swap parameter is true, after replacement, the data in the tbl1 table is the original data in the tbl2 table. The data in the tbl2 table is the original data in the tbl1 table. The data of the two tables is swapped.
If the swap parameter is false, after replacement, the data in the tbl1 table is the original data in the tbl2 table. The tbl2 table is deleted.

Principles

The table replacement feature, in fact, is to aggregate the following operations into one atomic operation. Assuming table A is to be replaced with table B, and swap is true, the operations are as follows:
1. Rename table B to table A.
2. Rename table A to table B.
If swap is false, the operations are as follows:
1. Delete table A.
2. Rename table B to table A.

Notes

1. The swap parameter defaults to true. Replacing a table is equivalent to swapping the data of the two tables.
2. If the swap parameter is false, the replaced table (Table A) will be deleted and cannot be recovered.
3. The replacement operation can only occur between two OLAP tables, and it does not check whether the table structures of the two tables are the same.
4. The replacement operation does not change the original permission settings. Because permission checks are table name-based.

Best Practice

1. Atomic overwrite operation. In some cases, users may want to overwrite the data of a table. However, if deleting first and then importing is adopted, there will be a period of time when the data cannot be viewed. At this time, users can first use the CREATE TABLE LIKE statement to create a new table with the same structure, import the new data into the new table, and then replace the old table atomically through the replace operation to achieve the goal. For atomic overwrite operations at the partition level, refer to Temporary Partition.
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