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CountAggregationOnKind.java
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CountAggregationOnKind.java
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/*
* Copyright 2022 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.datastore.aggregation;
// [START datastore_count_aggregation_query_on_kind]
import static com.google.cloud.datastore.aggregation.Aggregation.count;
import com.google.cloud.datastore.AggregationQuery;
import com.google.cloud.datastore.AggregationResult;
import com.google.cloud.datastore.Datastore;
import com.google.cloud.datastore.DatastoreOptions;
import com.google.cloud.datastore.Entity;
import com.google.cloud.datastore.EntityQuery;
import com.google.cloud.datastore.Key;
import com.google.cloud.datastore.Query;
import com.google.common.collect.Iterables;
public class CountAggregationOnKind {
// Instantiates a client.
private static final Datastore datastore = DatastoreOptions.getDefaultInstance().getService();
// The kind for the new entity.
private static final String kind = "Task";
// Setting up Tasks in database
private static void setUpTasks() {
Key task1Key = datastore.newKeyFactory().setKind(kind).newKey("task1");
Key task2Key = datastore.newKeyFactory().setKind(kind).newKey("task2");
Key task3Key = datastore.newKeyFactory().setKind(kind).newKey("task3");
// Save all the tasks.
datastore.put(
Entity.newBuilder(task1Key).set("done", true).build(),
Entity.newBuilder(task2Key).set("done", false).build(),
Entity.newBuilder(task3Key).set("done", true).build());
}
// Accessing aggregation result by the generated alias.
private static void usageWithGeneratedAlias() {
EntityQuery selectAllTasks = Query.newEntityQueryBuilder().setKind(kind).build();
// Creating an aggregation query to get the count of all tasks.
AggregationQuery allTasksCountQuery =
Query.newAggregationQueryBuilder().over(selectAllTasks).addAggregation(count()).build();
// Executing aggregation query.
AggregationResult aggregationResult =
Iterables.getOnlyElement(datastore.runAggregation(allTasksCountQuery));
System.out.printf(
"Total tasks (accessible from default alias) is %d",
aggregationResult.get("property_1")); // 3
}
// Accessing aggregation result by the provided custom alias.
private static void usageWithCustomAlias() {
EntityQuery selectAllTasks = Query.newEntityQueryBuilder().setKind(kind).build();
// Creating an aggregation query to get the count of all tasks.
AggregationQuery allTasksCountQuery =
Query.newAggregationQueryBuilder()
.over(selectAllTasks)
// passing 'total_count' as alias in the aggregation query.
.addAggregation(count().as("total_count"))
.build();
// Executing aggregation query.
AggregationResult aggregationResult =
Iterables.getOnlyElement(datastore.runAggregation(allTasksCountQuery));
System.out.printf("Total tasks count is %d", aggregationResult.get("total_count")); // 3
}
public static void invoke() {
setUpTasks();
usageWithGeneratedAlias();
usageWithCustomAlias();
}
}
// [END datastore_count_aggregation_query_on_kind]