Function split_constant_prefix

datafusion/pruning/src/pruning_predicate.rs:1940–1954

Returns unescaped constant prefix of a LIKE pattern (possibly empty) and the remaining pattern (possibly empty)

(pattern: &str)

/// Returns unescaped constant prefix of a LIKE pattern (possibly empty) and the remaining pattern (possibly empty)
fn split_constant_prefix(pattern: &str) -> (String, &str) {
    let mut prefix = String::with_capacity(pattern.len());
    let mut iter = pattern.char_indices();
    while let Some((idx, c)) = iter.next() {
        match c {
            '%' | '_' => return (prefix, &pattern[idx..]),
            '\\' => match iter.next() {
                Some((_, escaped)) => prefix.push(escaped),
                None => prefix.push('\\'),
            },
            _ => prefix.push(c),
        }
    }
    (prefix, "")
}

/// Increment a UTF8 string by one, returning `None` if it can't be incremented.
/// This makes it so that the returned string will always compare greater than the input string