datafusion_functions_aggregate_common::aggregate::groups_accumulator::accumulate

Function accumulate

Source 
pub fn accumulate<T, F>(
    group_indices: &[usize],
    values: &PrimitiveArray<T>,
    opt_filter: Option<&BooleanArray>,
    value_fn: F,
)
where
    T: ArrowPrimitiveType + Send,
    F: FnMut(usize, T::Native) + Send,
Expand description

Invokes value_fn(group_index, value) for each non null, non filtered value of value,

§Arguments:

  • group_indices: To which groups do the rows in values belong, (aka group_index)
  • values: the input arguments to the accumulator
  • opt_filter: if present, only rows for which is Some(true) are included
  • value_fn: function invoked for (group_index, value) where value is non null

§Example

 ┌─────────┐   ┌─────────┐   ┌ ─ ─ ─ ─ ┐
 │ ┌─────┐ │   │ ┌─────┐ │     ┌─────┐
 │ │  2  │ │   │ │ 200 │ │   │ │  t  │ │
 │ ├─────┤ │   │ ├─────┤ │     ├─────┤
 │ │  2  │ │   │ │ 100 │ │   │ │  f  │ │
 │ ├─────┤ │   │ ├─────┤ │     ├─────┤
 │ │  0  │ │   │ │ 200 │ │   │ │  t  │ │
 │ ├─────┤ │   │ ├─────┤ │     ├─────┤
 │ │  1  │ │   │ │ 200 │ │   │ │NULL │ │
 │ ├─────┤ │   │ ├─────┤ │     ├─────┤
 │ │  0  │ │   │ │ 300 │ │   │ │  t  │ │
 │ └─────┘ │   │ └─────┘ │     └─────┘
 └─────────┘   └─────────┘   └ ─ ─ ─ ─ ┘

group_indices   values        opt_filter

In the example above, value_fn is invoked for each (group_index, value) pair where opt_filter[i] is true and values is non null

value_fn(2, 200)
value_fn(0, 200)
value_fn(0, 300)