cai-jinlin commented on PR #59014:
URL: https://github.com/apache/doris/pull/59014#issuecomment-3649182995
`// 核心计算逻辑：比较两个等长字符串的不同字符数
static int64_t hamming_distance_impl(const char* s1, const char* s2, size_t
len) {
int64_t count = 0;
for (size_t i = 0; i < len; ++i) {
count += (s1[i] != s2[i]); // 字符不同时加1
}
return count;
}
// 向量化处理函数（Doris BE核心）
Status execute_impl(FunctionContext* context, Block& block, const
ColumnNumbers& args,
size_t result_idx, size_t rows) override {
// 获取输入列
const ColumnPtr& col_left = block.get_by_position(args[0]).column;
const ColumnPtr& col_right = block.get_by_position(args[1]).column;
// 准备结果列
auto result_col = ColumnInt64::create();
auto null_map = ColumnUInt8::create();
auto& results = result_col->get_data();
auto& nulls = null_map->get_data();
results.resize(rows);
nulls.resize_fill(rows, 0);
// 批量处理每一行
for (size_t i = 0; i < rows; ++i) {
// 检查NULL值（Doris会自动处理，这里显式检查）
if (col_left->is_null_at(i) || col_right->is_null_at(i)) {
nulls[i] = 1;
continue;
}
// 获取字符串
auto s1 = col_left->get_data_at(i);
auto s2 = col_right->get_data_at(i);
// 长度不同返回NULL
if (s1.size != s2.size) {
nulls[i] = 1;
continue;
}
// 计算汉明距离
results[i] = hamming_distance_impl(s1.data, s2.data, s1.size);
}
// 包装为可空列
block.get_by_position(result_idx).column =
ColumnNullable::create(std::move(result_col), std::move(null_map));
return Status::OK();
}`
（汉明距离定义就是等长字符串对应位置不同字符的数量）
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