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spanner: Add snippets for ReadContext (googleapis#3662)
spanner: Add snippets for ReadContext
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...xamples/src/main/java/com/google/cloud/examples/spanner/snippets/ReadContextSnippets.java
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| /* | ||
| * Copyright 2018 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. | ||
| */ | ||
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| /* | ||
| * EDITING INSTRUCTIONS | ||
| * This file is referenced in spanner/ReadContext's javadoc. Any change | ||
| * to this file should be reflected in spanner/ReadContext's javadoc. | ||
| */ | ||
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| package com.google.cloud.examples.spanner.snippets; | ||
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| import com.google.cloud.spanner.DatabaseClient; | ||
| import com.google.cloud.spanner.Key; | ||
| import com.google.cloud.spanner.KeySet; | ||
| import com.google.cloud.spanner.ReadContext; | ||
| import com.google.cloud.spanner.ResultSet; | ||
| import com.google.cloud.spanner.Statement; | ||
| import com.google.cloud.spanner.Struct; | ||
| import com.google.spanner.v1.ResultSetStats; | ||
| import java.util.Arrays; | ||
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| /** | ||
| * This class contains snippets for {@link com.google.cloud.spanner.ReadContext} interface. | ||
| */ | ||
| public class ReadContextSnippets { | ||
| private final DatabaseClient dbClient; | ||
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| public ReadContextSnippets(DatabaseClient dbClient) { | ||
| this.dbClient = dbClient; | ||
| } | ||
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| ResultSet read() { | ||
| // [START read_context_read] | ||
| ReadContext readContext = dbClient.singleUse(); | ||
| ResultSet resultSet = | ||
| readContext.read( | ||
| "Albums", | ||
| // KeySet.all() can be used to read all rows in a table. KeySet exposes other | ||
| // methods to read only a subset of the table. | ||
| KeySet.all(), | ||
| Arrays.asList("SingerId", "AlbumId", "AlbumTitle")); | ||
| // [END read_context_read] | ||
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| return resultSet; | ||
| } | ||
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| ResultSet readUsingIndex() { | ||
| // [START read_context_read_index] | ||
| ReadContext readContext = dbClient.singleUse(); | ||
| ResultSet resultSet = | ||
| readContext.readUsingIndex( | ||
| "Albums", | ||
| "AlbumsByAlbumTitle", | ||
| KeySet.all(), | ||
| Arrays.asList("AlbumId", "AlbumTitle")); | ||
| // [END read_context_read_index] | ||
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| return resultSet; | ||
| } | ||
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| Struct readRow() { | ||
| // [START read_context_read_row] | ||
| ReadContext readContext = dbClient.singleUse(); | ||
| Struct row = | ||
| readContext.readRow("Albums", Key.of(2, 1), Arrays.asList("MarketingBudget")); | ||
| // [END read_context_read_row] | ||
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| return row; | ||
| } | ||
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| Struct readRowUsingIndex() { | ||
| // [START read_context_read_index] | ||
| ReadContext readContext = dbClient.singleUse(); | ||
| Struct row = | ||
| readContext.readRowUsingIndex("Albums", "AlbumsByAlbumId", Key.of(1, "Green"), | ||
| Arrays.asList("AlbumId", "AlbumTitle")); | ||
| // [END read_context_read_index] | ||
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| return row; | ||
| } | ||
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| ResultSet executeQuery() { | ||
| // [START read_context_execute_query] | ||
| // Rows without an explicit value for MarketingBudget will have a MarketingBudget equal to | ||
| // null. | ||
| ReadContext readContext = dbClient.singleUse(); | ||
| ResultSet resultSet = | ||
| readContext.executeQuery( | ||
| Statement.of( | ||
| "SELECT SingerId, AlbumId, MarketingBudget, LastUpdateTime FROM Albums")); | ||
| // [END read_context_execute_query] | ||
| return resultSet; | ||
| } | ||
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| ResultSetStats analyzeQuery() { | ||
| // [START read_context_analyze_query] | ||
| ReadContext rc = dbClient.singleUse(); | ||
| ResultSet resultSet = | ||
| rc.analyzeQuery( | ||
| Statement.of("SELECT SingerId, AlbumId, MarketingBudget FROM Albums"), | ||
| ReadContext.QueryAnalyzeMode.PROFILE); | ||
| while (resultSet.next()) { | ||
| // Discard the results. We're only processing because getStats() below requires it. | ||
| resultSet.getCurrentRowAsStruct(); | ||
| } | ||
| ResultSetStats stats = resultSet.getStats(); | ||
| // [END read_context_analyze_query] | ||
| return stats; | ||
| } | ||
| } | ||
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