Struct GroupOrderingFull

pub struct GroupOrderingFull { /* private fields */ }

Tracks grouping state when the data is ordered entirely by its group keys

When the group values are sorted, as soon as we see group n+1 we know we will never see any rows for group n again and thus they can be emitted.

For example, given SUM(amt) GROUP BY id if the input is sorted by id as soon as a new id value is seen all previous values can be emitted.

The state is tracked like this:

     ┌─────┐   ┌──────────────────┐
     │┌───┐│   │ ┌──────────────┐ │         ┏━━━━━━━━━━━━━━┓
     ││ 0 ││   │ │     123      │ │   ┌─────┃      13      ┃
     │└───┘│   │ └──────────────┘ │   │     ┗━━━━━━━━━━━━━━┛
     │ ... │   │    ...           │   │
     │┌───┐│   │ ┌──────────────┐ │   │         current
     ││12 ││   │ │     234      │ │   │
     │├───┤│   │ ├──────────────┤ │   │
     ││12 ││   │ │     234      │ │   │
     │├───┤│   │ ├──────────────┤ │   │
     ││13 ││   │ │     456      │◀┼───┘
     │└───┘│   │ └──────────────┘ │
     └─────┘   └──────────────────┘

 group indices    group_values        current tracks the most
(in group value                          recent group index
     order)

In this diagram, the current group is 13, and thus groups 0..12 can be emitted. Note that 13 can not yet be emitted as there may be more values in the next batch with the same group_id.

Implementations

impl GroupOrderingFull

pub fn new() -> Self

pub fn emit_to(&self) -> Option<EmitTo>

pub fn remove_groups(&mut self, n: usize)

remove the first n groups from the internal state, shifting all existing indexes down by n

pub fn input_done(&mut self)

Note that the input is complete so any outstanding groups are done as well

pub fn new_groups(&mut self, total_num_groups: usize)

Called when new groups are added in a batch. See documentation on super::GroupOrdering::new_groups

Trait Implementations

impl Debug for GroupOrderingFull

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for GroupOrderingFull

fn default() -> Self

Returns the “default value” for a type.