Reduce
Reduce( reducer, initial, arrayOrSet )Reduce( reducer, initial, arrayOrSet )Reduce( reducer, initial, arrayOrSet )Reduce( reducer, initial, arrayOrSet )reduce( reducer, initial, arrayOrSet )Not available in this language yet.Reduce( reducer, initial, arrayOrSet )Not available in this language yet.Description
The Reduce function applies a reducer
Lambda function serially to each member
of arrayOrSet (which is an Array,
Page, or Set) to
produce a single value (any scalar, array, object, etc.).
When the reducer function is called, it is provided with an
accumulator that represents the current state of the result, and the
current item from arrayOrSet. The value that the reducer returns
becomes the accumulator for the next iteration. Subsequent invocations
of reducer can see the results of earlier invocations.
When Reduce starts, the accumulator is set to the initial value.
When Reduce completes its processing, the current value
of the accumulator is returned.
Parameters
| Argument | Type | Definition and Requirements |
|---|---|---|
|
The function to apply to each item in The function must have the signature
The return value from the |
|
|
Any |
The |
|
The items to be reduced. |
Examples
The following query demonstrates the simplest reducer, which counts the
items in arrayOrSet. It does this by adding 1 to the accumulator
for each item:
Value result = await client.Query(
Reduce(
Lambda(Arr("acc", "value"), Add(Var("acc"), 1)),
0,
Arr(1, 2, 3, 4, 5)
)
);result, err := client.Query(
f.Reduce(
f.Lambda(
f.Arr{"acc", "value"},
f.Add(f.Var("acc"), 1),
),
0,
f.Arr{1, 2, 3, 4, 5}))System.out.println(
client.query(
Reduce(
Lambda(
Arr(Value("acc"), Value("val")),
Add(Var("acc"), Value(1))
),
Value(0),
Arr(Value(1), Value(2), Value(3), Value(4), Value(5))
)
).get());client.query(
q.Reduce(
q.Lambda((acc, value) => q.Add(acc, 1)),
0,
[ 1, 2, 3, 4, 5 ],
)
)
.then((ret) => console.log(ret))print(client.query(
q.reduce(
q.lambda_(["acc", "value"], q.add(q.var("acc"), 1)),
0,
[ 1, 2, 3, 4, 5 ],
)
))Not available in this language yet.println(Await.result(
client.query(
Reduce(
Lambda(Arr("acc", "val"), Add(Var("acc"), 1)),
0,
Arr(1, 2, 3, 4, 5)
)
),
5.seconds
))Not available in this language yet.555555The following query demonstrates how to sum the values in arrayOrSet.
It does this by adding the value of each item to the accumulator:
Value result = await client.Query(
Reduce(
Lambda(Arr("acc", "value"), Add(Var("acc"), Var("value"))),
0,
Arr(1, 2, 3, 4, 5)
)
);result, err := client.Query(
f.Reduce(
f.Lambda(
f.Arr{"acc", "value"},
f.Add(f.Var("acc"), f.Var("value")),
),
0,
f.Arr{1, 2, 3, 4, 5}))System.out.println(
client.query(
Reduce(
Lambda(
Arr(Value("acc"), Value("value")),
Add(Var("acc"), Var("value"))
),
Value(0),
Arr(Value(1), Value(2), Value(3), Value(4), Value(5))
)
).get());client.query(
q.Reduce(
q.Lambda((acc, value) => q.Add(acc, value)),
0,
[ 1, 2, 3, 4, 5 ]
)
)
.then((ret) => console.log(ret))print(client.query(
q.reduce(
q.lambda_(["acc", "value"], q.add(q.var("acc"), q.var("value"))),
0,
[ 1, 2, 3, 4, 5 ],
)
))Not available in this language yet.println(Await.result(
client.query(
Reduce(
Lambda(Arr("acc", "value"), Add(Var("acc"), Var("value"))),
0,
Arr(1, 2, 3, 4, 5)
)
),
5.seconds
))Not available in this language yet.151515151515The following query demonstrates how to count, sum, and compute the minimum and maximum values, plus the average. This time, our accumulator is an object with multiple keys, and our Lambda function now performs all of those calculations:
Value result = await client.Query(
Reduce(
Lambda(
Arr("acc", "value"),
Let(
"count", Add(Select("count", Var("acc")), 1),
"total", Add(Select("total", Var("acc")), Var("value")),
"min", Select("min", Var("acc")),
"max", Select("max", Var("acc"))
).In(
Obj(
"count", Var("count"),
"total", Var("total"),
"min", If(
LTE(Var("value"), Var("min")),
Var("value"),
Var("min")
),
"max", If(
GTE(Var("value"), Var("max")),
Var("value"),
Var("max")
),
"avg", Divide(Var("total"), Var("count"))
)
)
),
Obj(
"count", 0,
"total", 0,
"min", 999999,
"max", -999999,
"avg", 0
),
Arr(1, 2, 3, 4, 5)
)
);result, err := client.Query(
f.Reduce(
f.Lambda(
f.Arr{"acc", "value"},
f.Let().Bind(
"count", f.Add(f.Select("count", f.Var("acc")), 1)).Bind(
"total", f.Add(f.Select("total", f.Var("acc")), f.Var("value"))).Bind(
"min", f.Select("min", f.Var("acc"))).Bind(
"max", f.Select("max", f.Var("acc"))).In(
f.Obj{
"count": f.Var("count"),
"total": f.Var("total"),
"min": f.If(
f.LTE(f.Var("value"), f.Var("min")),
f.Var("value"),
f.Var("min")),
"max": f.If(
f.GTE(f.Var("value"), f.Var("max")),
f.Var("value"),
f.Var("max")),
"avg": f.Divide(f.Var("total"), f.Var("count")),
})),
f.Obj{
"count": 0,
"total": 0,
"min": 99999,
"max": -99999,
"avg": 0,
},
f.Arr{1, 2, 3, 4, 5}))System.out.println(
client.query(
Reduce(
Lambda(
Arr(Value("acc"), Value("value")),
Let(
"count", Add(Select(Path("count"), Var("acc")), Value(1))
"total", Add(Select(Path("total"), Var("acc")), Var("value"))
"min", Select(Path("min"), Var("acc"))
"max", Select(Path("max"), Var("acc"))
).in(
Obj(
"count", Var("count"),
"total", Var("total"),
"min", If(LTE(Var("value"), Var("min")), Var("value"), Var("min")),
"max", If(GTE(Var("value"), Var("max")), Var("value"), Var("max")),
"avg", Divide(Var("total"), Var("count"))
)
)
),
Obj(
"count", Value(0),
"total", Value(0),
"min", Value(999999),
"max", Value(-999999),
"avg", Value(0),
),
Arr( Value(1), Value(2), Value(3), Value(4), Value(5) )
)
).get());client.query(
q.Reduce(
q.Lambda((acc, value) => q.Let(
{
count: q.Add(q.Select('count', acc), 1),
total: q.Add(q.Select('total', acc), value),
min: q.Select('min', acc),
max: q.Select('max', acc),
},
{
count: q.Var('count'),
total: q.Var('total'),
min: q.If(q.LTE(value, q.Var('min')), value, q.Var('min')),
max: q.If(q.GTE(value, q.Var('max')), value, q.Var('max')),
avg: q.Divide(q.Var('total'), q.Var('count')),
}
)),
{
count: 0,
total: 0,
min: 999999,
max: -999999,
avg: 0,
},
[ 1, 2, 3, 4, 5 ]
)
)
.then((ret) => console.log(ret))print(client.query(
q.reduce(
q.lambda_(["acc", "value"], q.let(
{
"count": q.add(q.select("count", q.var("acc")), 1),
"total": q.add(q.select("total", q.var("acc")), q.var("value")),
"min": q.select("min", q.var("acc")),
"max": q.select("max", q.var("acc")),
},
{
"count": q.var("count"),
"total": q.var("total"),
"min": q.if_(
q.lte(q.var("value"), q.var("min")),
q.var("value"),
q.var("min")
),
"max": q.if_(
q.gte(q.var("value"), q.var("max")),
q.var("value"),
q.var("max")
),
"avg": q.divide(q.var("total"), q.var("count")),
}
)),
{
"count": 0,
"total": 0,
"min": 999999,
"max": -999999,
"avg": 0,
},
[ 1, 2, 3, 4, 5 ]
)
))Not available in this language yet.println(Await.result(
client.query(
Reduce(
Lambda {
(acc, value) => Let {
val count = Add(Select("count", acc), 1)
val total = Add(Select("total", acc), value)
val min = Select("min", acc)
val max = Select("max", acc)
Obj(
"count" -> count,
"total" -> total,
"min" -> If(LTE(value, min), value, min),
"max" -> If(GTE(value, max), value, max),
"avg" -> Divide(total, count)
)
}
},
Obj(
"count" -> 0,
"total" -> 0,
"min" -> 999999,
"max" -> -999999,
"avg" -> 0,
),
Arr( 1, 2, 3, 4, 5 )
)
),
5.seconds
))Not available in this language yet.{
"object": {
"count": 5,
"total": 15,
"min": 1,
"max": 5,
"avg": 3
}
}map[avg:3 count:5 max:5 min:1 total:15]{count: 5, avg: 3, min: 1, total: 15, max: 5}{ count: 5, total: 15, min: 1, max: 5, avg: 3 }{'count': 5, 'total': 15, 'min': 1, 'max': 5, 'avg': 3}{count: 5, avg: 3, min: 1, total: 15, max: 5}Was this article helpful?
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