匯總函式

匯總

所有匯總函式都可以在 aggregate(...) 階段中做為頂層運算式使用。

名稱 說明
COUNT 傳回文件數量。
COUNT_IF 傳回運算式評估結果為 TRUE 的文件數
COUNT_DISTINCT 傳回不重複的非 NULL 值數量
SUM 傳回所有 NUMERIC 值的總和
AVERAGE 傳回所有 NUMERIC 值的平均值
MINIMUM 傳回非 NULL 的最小值
MAXIMUM 傳回非 NULL 的最大值
FIRST 傳回第一個文件的 expression 值。
LAST 傳回最後一個文件的 expression 值。
ARRAY_AGG 傳回所有輸入值的陣列。
ARRAY_AGG_DISTINCT 傳回所有不重複的輸入值所組成的陣列。

COUNT

語法：

count() -> INT64
count(expression: ANY) -> INT64

說明：

傳回先前階段的文件計數，其中 expression 評估為任何非 NULL 值。如未提供 expression，則會傳回前一階段的文件總數。

Web

// Total number of books in the collection
const countOfAll = await execute(db.pipeline()
  .collection("books")
  .aggregate(countAll().as("count"))
);

// Number of books with nonnull `ratings` field
const countField = await execute(db.pipeline()
  .collection("books")
  .aggregate(field("ratings").count().as("count"))
);
test.firestore.js
Swift
// Total number of books in the collection
let countAll = try await db.pipeline()
  .collection("books")
  .aggregate([CountAll().as("count")])
  .execute()

// Number of books with nonnull `ratings` field
let countField = try await db.pipeline()
  .collection("books")
  .aggregate([Field("ratings").count().as("count")])
  .execute()
PipelineSnippets.swift

Kotlin

// Total number of books in the collection
val countAll = db.pipeline()
    .collection("books")
    .aggregate(AggregateFunction.countAll().alias("count"))
    .execute()

// Number of books with nonnull `ratings` field
val countField = db.pipeline()
    .collection("books")
    .aggregate(AggregateFunction.count("ratings").alias("count"))
    .execute()
DocSnippets.kt

Java

// Total number of books in the collection
Task<Pipeline.Snapshot> countAll = db.pipeline()
    .collection("books")
    .aggregate(AggregateFunction.countAll().alias("count"))
    .execute();

// Number of books with nonnull `ratings` field
Task<Pipeline.Snapshot> countField = db.pipeline()
    .collection("books")
    .aggregate(AggregateFunction.count("ratings").alias("count"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Count

# Total number of books in the collection
count_all = (
    client.pipeline().collection("books").aggregate(Count().as_("count")).execute()
)

# Number of books with nonnull `ratings` field
count_field = (
    client.pipeline()
    .collection("books")
    .aggregate(Count("ratings").as_("count"))
    .execute()
)
firestore_pipelines.py

COUNT_IF

語法：

count_if(expression: BOOLEAN) -> INT64

說明：

傳回先前階段中，expression 評估為 TRUE 的文件數量。

Web

const result = await execute(db.pipeline()
  .collection("books")
  .aggregate(
    field("rating").greaterThan(4).countIf().as("filteredCount")
  )
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .aggregate([
    AggregateFunction("count_if", [Field("rating").greaterThan(4)]).as("filteredCount")
  ])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .aggregate(
        AggregateFunction.countIf(field("rating").greaterThan(4)).alias("filteredCount")
    )
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .aggregate(
        AggregateFunction.countIf(field("rating").greaterThan(4)).alias("filteredCount")
    )
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .aggregate(Field.of("rating").greater_than(4).count_if().as_("filteredCount"))
    .execute()
)
firestore_pipelines.py

COUNT_DISTINCT

語法：

count_distinct(expression: ANY) -> INT64

說明：

傳回 expression 的不重複非 NULL、非 ABSENT 值數量。

Web

const result = await execute(db.pipeline()
  .collection("books")
  .aggregate(field("author").countDistinct().as("unique_authors"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .aggregate([AggregateFunction("count_distinct", [Field("author")]).as("unique_authors")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .aggregate(AggregateFunction.countDistinct("author").alias("unique_authors"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .aggregate(AggregateFunction.countDistinct("author").alias("unique_authors"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .aggregate(Field.of("author").count_distinct().as_("unique_authors"))
    .execute()
)
firestore_pipelines.py

SUM

語法：

sum(expression: ANY) -> NUMBER

說明：

傳回所有數值的總和，並忽略非數值。如果任何值為 NaN，則傳回 NaN。

輸出內容的型別會與最寬的輸入型別相同，但下列情況除外：

  • 如果 INTEGER 無法表示為 INTEGER，系統會將其轉換為 DOUBLE。

Web

const result = await execute(db.pipeline()
  .collection("cities")
  .aggregate(field("population").sum().as("totalPopulation"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("cities")
  .aggregate([Field("population").sum().as("totalPopulation")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("cities")
    .aggregate(AggregateFunction.sum("population").alias("totalPopulation"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("cities")
    .aggregate(AggregateFunction.sum("population").alias("totalPopulation"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("cities")
    .aggregate(Field.of("population").sum().as_("totalPopulation"))
    .execute()
)
firestore_pipelines.py

AVERAGE

語法：

average(expression: ANY) -> FLOAT64

說明：

傳回所有數值的平均值，並忽略非數值。 如果任何值為 NaN，則評估結果為 NaN；如果沒有任何數值匯總，則評估結果為 NULL。

輸出內容的型別會與輸入型別相同，但下列情況除外：

  • 如果 INTEGER 無法表示為 INTEGER，系統會將其轉換為 DOUBLE。

Web

const result = await execute(db.pipeline()
  .collection("cities")
  .aggregate(field("population").average().as("averagePopulation"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("cities")
  .aggregate([Field("population").average().as("averagePopulation")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("cities")
    .aggregate(AggregateFunction.average("population").alias("averagePopulation"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("cities")
    .aggregate(AggregateFunction.average("population").alias("averagePopulation"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("cities")
    .aggregate(Field.of("population").average().as_("averagePopulation"))
    .execute()
)
firestore_pipelines.py

最低

語法：

minimum(expression: ANY) -> ANY

說明：

針對每個文件評估 expression 時，傳回非 NULL 和非缺少的最小值。

如果沒有非 NULL、非缺少的任何值，則會傳回 NULL。包括未考慮任何文件的情況。

如果有多個最小值，系統可以傳回其中一個值。值類型排序方式遵循文件排序方式。

Web

const result = await execute(db.pipeline()
  .collection("books")
  .aggregate(field("price").minimum().as("minimumPrice"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .aggregate([Field("price").minimum().as("minimumPrice")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .aggregate(AggregateFunction.minimum("price").alias("minimumPrice"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .aggregate(AggregateFunction.minimum("price").alias("minimumPrice"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .aggregate(Field.of("price").minimum().as_("minimumPrice"))
    .execute()
)
firestore_pipelines.py

MAXIMUM

語法：

maximum(expression: ANY) -> ANY

說明：

針對每個文件評估 expression 時，傳回 expression 的最大非 NULL 值 (非缺席值)。

如果沒有非 NULL、非缺少的任何值，則會傳回 NULL。包括未考慮任何文件的情況。

如果有多個最大等值，則可以傳回其中任何一個值。值類型排序方式遵循文件排序方式。

Web

const result = await execute(db.pipeline()
  .collection("books")
  .aggregate(field("price").maximum().as("maximumPrice"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .aggregate([Field("price").maximum().as("maximumPrice")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .aggregate(AggregateFunction.maximum("price").alias("maximumPrice"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .aggregate(AggregateFunction.maximum("price").alias("maximumPrice"))
    .execute();
DocSnippets.java
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

result = (
    client.pipeline()
    .collection("books")
    .aggregate(Field.of("price").maximum().as_("maximumPrice"))
    .execute()
)
firestore_pipelines.py

FIRST

語法：

first(expression: ANY) -> ANY

說明：

傳回第一個傳回的文件中 expression 的值。

LAST

語法：

last(expression: ANY) -> ANY

說明：

傳回最後一個回傳文件的 expression 值。

ARRAY_AGG

語法：

array_agg(expression: ANY) -> ARRAY<ANY>

說明：

針對每份文件評估時，傳回包含所有 expression 值的陣列。

如果運算式解析為缺席值，則會轉換為 NULL。

輸出陣列中的元素順序不穩定，不應依賴。

ARRAY_AGG_DISTINCT

語法：

array_agg_distinct(expression: ANY) -> ARRAY<ANY>

說明：

針對每份文件評估時，傳回包含所有不重複 expression 值的陣列。

如果運算式解析為缺席值，則會轉換為 NULL。

輸出陣列中的元素順序不穩定，不應依賴。