Deserialize complex query api responses

[appflowpersiste]

I am trying to deserialize query responses for tables with multiple level of repeated nesting datatypes.

IT is getting complex as need to do this by traversing each nodes as now the API response are not flow but comes in complex structures as "f" and "v". Is there an inbuild class and methods defined in com.google.cloud:google-cloud-bigquery jar to help with the deserialization and if so then what are the class names and method names if someone can suggest.

[ms4446]

In BigQuery, when dealing with complex data structures that include nested and repeated fields, the com.google.cloud:google-cloud-bigquery Java client library simplifies the process of querying and retrieving results. The library provides a set of classes and methods that abstract the lower-level details of handling JSON responses and parsing complex data types.

Key Classes and Their Usage:

• BigQuery: This is the main class for interacting with the BigQuery service. It provides methods to execute queries and retrieve results.

• QueryJobConfiguration: This class is used to configure and execute BigQuery SQL queries.

• TableResult: This class represents the result of a BigQuery query. It provides an iterable over the rows of the result set.

• FieldValueList: Represents a row in the result set. Each FieldValueList contains multiple FieldValue objects, each corresponding to a column in the result.

• FieldValue: Represents the value of a field in a BigQuery row. It can handle different types of data, including nested and repeated fields.

Example of Handling Nested and Repeated Fields:

import com.google.cloud.bigquery.BigQuery;
import com.google.cloud.bigquery.BigQueryOptions;
import com.google.cloud.bigquery.FieldValueList;
import com.google.cloud.bigquery.QueryJobConfiguration;
import com.google.cloud.bigquery.TableResult;

public

class

BigQueryNestedExample {

    public

static

void

main(String[] args)

throws InterruptedException {
        BigQuery bigquery = BigQueryOptions.getDefaultInstance().getService();
        String query = "YOUR_QUERY_HERE"; // Replace with your query
        QueryJobConfiguration queryConfig = QueryJobConfiguration.newBuilder(query).build();
        TableResult result = bigquery.query(queryConfig);

        for (FieldValueList row : result.iterateAll()) {
            // Accessing a nested field
            FieldValue nestedFieldValue = row.get("nestedFieldName");
            if (nestedFieldValue.getAttribute() == FieldValue.Attribute.RECORD) {
                FieldValueList nestedFields = nestedFieldValue.getRecordValue();
                // Process nested fields...
            }

            // Accessing a repeated field
            FieldValue repeatedFieldValue = row.get("repeatedFieldName");
            if (repeatedFieldValue.getAttribute() == FieldValue.Attribute.REPEATED) {
                for (FieldValue value : repeatedFieldValue.getRepeatedValue()) {
                    // Process each value in the repeated field
                }
            }
        }
    }
}

[appflowpersiste]

Hi,

Thanks for the suggestion, can you please help me with couple of queries.

1. Which version of googleBigQuery jar needs to be used.

2, Is there a specific parameter we need to send in the request body while doing the API call to get a response which can be deserialized and to be able to use the above code.

[ms4446]

1. The latest version of the Google Cloud BigQuery Java client library, as of the provided update, is 2.34.2. However, it's important to always check the Maven Repository or the official GitHub repository to find the most recent and stable version. The version numbers are frequently updated to include new features and bug fixes

2. When using the Google Cloud BigQuery Java client library, you don't need to manually set specific parameters in the request body to handle the response deserialization. The library abstracts these details and provides a high-level API to interact with BigQuery.

When you execute a query using the BigQuery service object, the library internally handles the communication with the BigQuery API, including any necessary request formatting. The results are returned in a format that can be easily iterated and accessed using the classes like TableResult, FieldValueList, and FieldValue, as shown in the example code.

Here's a basic outline of the steps:

• Create a BigQuery instance.
• Create a QueryJobConfiguration with your SQL query.
• Execute the query and get a TableResult.
• Iterate over the TableResult to access individual rows and fields.

The library takes care of parsing the JSON response from BigQuery and mapping it to these Java objects. This means you can focus on writing the logic for processing your query results without worrying about the underlying JSON structure or making HTTP requests directly.

Remember to include the necessary dependencies in your project's build file (like pom.xml for Maven or build.gradle for Gradle). For example, in a Maven project, you would add:

<dependency>
<groupId>com.google.cloud</groupId>
<artifactId>google-cloud-bigquery</artifactId>
<version>VERSION</version> <!-- Replace with the desired version -->
</dependency>