For the GRPBY operator, the following input
arguments are shown:
- Group by requirement
- The columns on which groups are to be formed.
- Group by columns
- A flag that is true if there are any columns on which groups are to be
formed.
If no GROUP BY columns are specified, the GRPBY operator will still be used
if there are aggregation functions in the SELECT list, indicating that the
entire table is treated as a single group when that aggregation is
done.
- One fetch
- A flag that is true if only one row is needed as input to the aggregation,
because the column function is either MIN(C) or MAX(C) and the input is
ordered correctly on column C.
- Number of comparison columns
- The number of columns needed to determine group breaks.
- Aggregation mode
- The group by operation may be divided into multiple steps. The
aggregation mode describes the level of aggregation performed at each
step:
- Complete - Aggregation is done in a single pass.
- Partial - Aggregations are done on chunks of input rows.
- Intermediate - Partial aggregation results are processed to
generate consolidated partial results.
- Final - Partial aggregation results are processed and any final
calculations performed to generate the aggregation result.
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