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Module array

clickhouse_native_client::column

Module array 

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Array column type (Array(T)). Array column implementation

ClickHouse Documentation: https://clickhouse.com/docs/en/sql-reference/data-types/array

§Overview

Array columns store variable-length arrays of elements. All elements are stored in a single nested column (flattened), with offsets tracking where each array begins/ends.

§Important Restriction

Arrays cannot be wrapped in Nullable:

  • ❌ Nullable(Array(String)) - Error: “Nested type Array(String) cannot be inside Nullable type” (Error code 43)
  • ✅ Array(Nullable(String)) - CORRECT: Each element can be NULL

If you need to represent “no array”, use an empty array [] instead of NULL.

See: https://github.com/ClickHouse/ClickHouse/issues/1062

§Wire Format

[offsets: UInt64 * num_arrays]  // Cumulative element counts
[nested_column_data]             // All elements concatenated

Example: [[1,2], [3], [4,5,6]]

  • Offsets: [2, 3, 6] (2 elements in first array, 3 total after second, 6 total after third)
  • Nested data: [1, 2, 3, 4, 5, 6]

Structs§

ColumnArray
Column for arrays of variable length
ColumnArrayT
Typed wrapper for ColumnArray that provides type-safe access to nested column