MarkLogic 10 Product DocumentationAccessPlan.prototype.groupToArrays
AccessPlan.prototype.groupToArrays( groups as namedGroupdef[], [aggregates as aggregatedef[]] ) as ModifyPlan
Summary
This method performs multiple group-by operations on a row set and produces a single row with a column for each group having an array value whose items are the rows for the group. Each item is an object with properties for the group keys and aggregates.
The aggregates for the operation are specified as the second parameter instead of in a prototype.select operation (unlike SQL).
| Parameters | |
|---|---|
| groups |
The sets of grouping keys. Each group is specified with the
op.namedGroup function, which supplies the name
for the group column in the output row. Each group must have a unique set of keys
but multiple groups can have the same key.
As a convenience, the parameter also accepts unnamed groups with the op.group, op.rollup, or op.cube functions or (for a group with a single key) a column named with a string or a column parameter function such as op.col or constructed from an expression with the op.as function. The row objects produced by the group-to-arrays operation include the key columns from each group. A group can be empty to group over all of the rows in the row set. |
| aggregates | This parameter specifies either columns to sample or aggregate functions to apply to a column for all of the rows in the group. Sampled columns can be existing columns or new columns created by an expression specified with op.as. Often a sampled column might have a constant value within the group such as a title or label closely associated with a numeric identifier used as the grouping key. |
Usage Notes
The groupToArrays operation differs from the groupBy operation as follows:
- Instead of taking a single set of grouping keys, the groupToArrays operation takes multiple sets of grouping keys.
- For each combination of the values of the grouping keys in each set, the groupToArrays operation produces an output object with properties for the group keys and the aggregates. The output object doesn't have properties for grouping keys belonging to other groups but not the current group.
- The output objects for each group are aggregated into a different array.
groupToArrays is a method of the following classes:
See Also
-
- op.namedGroup function
- op.rollup function
- op.cube function
- prototype.groupByUnion function
Example
// Calculate the total expenses separately for each category and for each location.
const op = require('/MarkLogic/optic');
op.fromView('main', 'expenses')
.groupToArrays(
[op.namedGroup('CategoryTotal', 'Category'),
op.namedGroup('LocationTotal', 'Location'),
op.namedGroup('AllTotal')
],
op.sum("TotalAmount", "Amount")
)
.result();