This documentation is for an unreleased version of Apache Paimon. We recommend you use the latest stable version.

Default Value #

Paimon allows specifying default values for columns. When users write to these tables without explicitly providing values for certain columns, Paimon automatically generates default values for these columns.

Create Table #

Flink SQL does not have native support for default values, so we can only create a table without default values:

CREATE TABLE my_table (
    a BIGINT,
    b STRING,
    c INT,
    tags ARRAY<STRING>,
    properties MAP<STRING, STRING>,
    nested ROW<x INT, y STRING>
);

We support the procedure of modifying column default values in Flink. You can add default value definitions after creating the table:

-- Set simple type default values
CALL sys.alter_column_default_value('default.my_table', 'b', 'my_value');
CALL sys.alter_column_default_value('default.my_table', 'c', '5');

-- Set complex type default values
CALL sys.alter_column_default_value('default.my_table', 'tags', '[tag1, tag2, tag3]');
CALL sys.alter_column_default_value('default.my_table', 'properties', '{key1 -> value1, key2 -> value2}');
CALL sys.alter_column_default_value('default.my_table', 'nested', '{42, default_value}');

Insert Table #

For SQL commands that execute table writes, such as the INSERT, UPDATE, and MERGE commands, NULL value is parsed into the default value specified for the corresponding column.

For example:

INSERT INTO my_table (a) VALUES (1), (2);

SELECT * FROM my_table;
-- result: [[1, my_value, 5, [tag1, tag2, tag3], {key1=value1, key2=value2}, +I[42, default_value]],
--          [2, my_value, 5, [tag1, tag2, tag3], {key1=value1, key2=value2}, +I[42, default_value]]]