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Coordinator DB
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Dynamic ​

Dynamic stores values of different concrete types in the same declared column. Each value retains its active type, which can be inspected or extracted by a function.

Use Dynamic when the types are not known in advance. Use Variant to restrict values to a declared alternative list.

Creating Dynamic ​

text
Dynamic
Dynamic(max_types=N)
  • N — A value from 0 through 254, defaulting to 32. This parameter is retained as type metadata; it does not limit the types admitted by CoordinatorDB.

SQL NULL is accepted without a Nullable wrapper.

Using Dynamic type in functions ​

dynamic_type(value) returns the active type name, or 'None' for NULL. dynamic_element(value, 'Type') extracts the payload when the active type matches and returns NULL otherwise.

Arithmetic uses the actual payload and retains a Dynamic result. Numeric aggregates require extraction or an explicit numeric cast. Ordering uses the active type's canonical name and then its value; distinct active numeric types are not collapsed merely because their numeric values are equal.

Examples ​

Different types in one column ​

sql
CREATE TABLE observations(id UInt32, value Dynamic);
INSERT INTO observations VALUES
    (1, CAST(7 AS UInt64)),
    (2, 'hello'),
    (3, NULL);
sql
SELECT id, dynamic_type(value)
FROM observations
ORDER BY id
FORMAT csv;
text
1,"UInt64"
2,"String"
3,"None"

Extracting a matching type ​

sql
SELECT dynamic_element(CAST('hello' AS Dynamic), 'String'),
       dynamic_element(CAST('hello' AS Dynamic), 'UInt64')
FORMAT csv;
text
"hello",\N