Function rank_str 

pub fn rank_str<T: Integer>(
    arr: StringAVT<'_, T>,
) -> Result<IntegerArray<i32>, KernelError>

Computes standard SQL ROW_NUMBER() ranking for string data with lexicographic ordering.

Assigns sequential rank values based on lexicographic string comparison, implementing ROW_NUMBER() semantics for textual data. Essential for alphabetical ranking and string-based analytical operations.

Parameters

• arr - String array view containing textual values for ranking

Returns

Returns Result<IntegerArray<i32>, KernelError> containing:

• Success: Rank values from 1 to n for valid string elements
• Error: KernelError if capacity validation fails
• Zero values for null string elements
• Null mask indicating positions with valid ranks

String Ranking Semantics

• Lexicographic order: Uses standard string comparison (dictionary order)
• Case sensitivity: Comparisons are case-sensitive (“A” < “a”)
• Unicode support: Proper handling of UTF-8 encoded string data
• ROW_NUMBER() behaviour: Tied strings receive different ranks by position

Error Conditions

• Capacity errors: Returns KernelError if mask capacity validation fails
• Memory allocation: May fail with insufficient memory for large datasets

Use Cases

• Alphabetical ranking: Creating alphabetically ordered rankings
• Text analysis: Establishing lexicographic ordinality in textual data
• Database operations: SQL ROW_NUMBER() implementation for string columns
• Sorting applications: Providing ranking information for string sorting

Examples

use minarrow::StringArray;
use simd_kernels::kernels::window::rank_str;

let arr = StringArray::<u32>::from_slice(&["zebra", "apple", "banana"]);
let result = rank_str((&arr, 0, arr.len())).unwrap();
// Output: [3, 1, 2] - lexicographic ranking