Support LowCardinality(Decimal) data types

Why it matters

This feature enables users to efficiently store and query decimal values with low cardinality by combining the benefits of LowCardinality optimization and precise decimal representation. It reduces memory usage and improves query performance for columns with many repeated decimal values.

How to use it

Users can declare a column with the LowCardinality(Decimal) data type in table definitions, for example:
sql<br>CREATE TABLE example_table (<br> value LowCardinality(Decimal(18, 6))<br>) ENGINE = MergeTree() ORDER BY tuple();<br>
This will enable low cardinality optimization on the decimal column.