Changelog category (leave one):

• New Feature

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Support Dynamic type in most functions by executing them on internal types inside Dynamic.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

Most of the functions now support arguments with type Dynamic. In this case the function is executed separately on each internal data type stored inside Dynamic column.
When the result type of the function depends on the arguments types, the result of such function executed with Dynamic arguments will be Dynamic. When the result type of the function doesn't depend on the arguments types - the result will be Nullable(T) where T the usual result type of this function.

Examples:

CREATE TABLE test (d Dynamic) ENGINE=Memory;
INSERT INTO test VALUES (NULL), (1::Int8), (2::Int16), (3::Int32), (4::Int64);

SELECT d, dynamicType(d) FROM test;

┌─d────┬─dynamicType(d)─┐
│ ᴺᵁᴸᴸ │ None           │
│ 1    │ Int8           │
│ 2    │ Int16          │
│ 3    │ Int32          │
│ 4    │ Int64          │
└──────┴────────────────┘

SELECT d, d + 1 AS res, toTypeName(res), dynamicType(res) FROM test;

┌─d────┬─res──┬─toTypeName(res)─┬─dynamicType(res)─┐
│ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │ Dynamic         │ None             │
│ 1    │ 2    │ Dynamic         │ Int16            │
│ 2    │ 3    │ Dynamic         │ Int32            │
│ 3    │ 4    │ Dynamic         │ Int64            │
│ 4    │ 5    │ Dynamic         │ Int64            │
└──────┴──────┴─────────────────┴──────────────────┘

SELECT d, d < 3 AS res, toTypeName(res) FROM test;

┌─d────┬──res─┬─toTypeName(res)─┐
│ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │ Nullable(UInt8) │
│ 1    │    1 │ Nullable(UInt8) │
│ 2    │    1 │ Nullable(UInt8) │
│ 3    │    0 │ Nullable(UInt8) │
│ 4    │    0 │ Nullable(UInt8) │
└──────┴──────┴─────────────────┘

TRUNCATE TABLE test;
INSERT INTO test VALUES (NULL), ('str_1'), ('str_2');
SELECT d, dynamicType(d) FROM test;

┌─d─────┬─dynamicType(d)─┐
│ ᴺᵁᴸᴸ  │ None           │
│ str_1 │ String         │
│ str_2 │ String         │
└───────┴────────────────┘

SELECT d, upper(d) AS res, toTypeName(res) FROM test;

┌─d─────┬─res───┬─toTypeName(res)──┐
│ ᴺᵁᴸᴸ  │ ᴺᵁᴸᴸ  │ Nullable(String) │
│ str_1 │ STR_1 │ Nullable(String) │
│ str_2 │ STR_2 │ Nullable(String) │
└───────┴───────┴──────────────────┘

SELECT d, extract(d, '([0-3])') AS res, toTypeName(res) FROM test;

┌─d─────┬─res──┬─toTypeName(res)──┐
│ ᴺᵁᴸᴸ  │ ᴺᵁᴸᴸ │ Nullable(String) │
│ str_1 │ 1    │ Nullable(String) │
│ str_2 │ 2    │ Nullable(String) │
└───────┴──────┴──────────────────┘

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