Work with JSON data

PostgreSQL interface note: The JSON data type is not supported in PostgreSQL-dialect databases. Use the JSONB data type for PostgreSQL-dialect databases.

This page describes how to work with JSON using Spanner.

The JSON data type is a semi-structured data type used for holding JSON (JavaScript Object Notation) data. The specifications for the JSON format are described in RFC 7159.

JSON is useful to supplement a relational schema for data that is sparse or has a loosely-defined or changing structure. However, the query optimizer relies on the relational model to efficiently filter, join, aggregate, and sort at scale. Queries over JSON will have fewer built-in optimizations and fewer affordances to inspect and tune performance.

Specifications

Spanner JSON type stores a normalized representation of the input JSON document.

JSON can be nested to a maximum of 80 levels.
Whitespace is not preserved.
Comments are not supported. Transactions or queries with comments will fail.
Members of a JSON object are sorted lexicographically.
JSON array elements have their order preserved.
If a JSON object has duplicate keys, only the first one is preserved.
Primitive types (string, boolean, number, and null) have their type and value preserved.
- String type values are preserved exactly.
- Number type values are preserved, but may have their textual representation changed as a result of the normalization process. For example, an input number of 10000 may have a normalized representation of 1e+4. Number value preservation semantics are as follows:
  - Signed integers in the range of [INT64_MIN, INT64_MAX] are preserved.
  - Unsigned integers in the range of [0, UINT64_MAX] are preserved.
  - Double values that can be roundtripped from string to double to string without precision loss are preserved. If a double value cannot round trip in this manner, the transaction or query fails.
    - For example, SELECT JSON '2.2412421353246235436' fails.
    - A functional workaround is PARSE_JSON('2.2412421353246235436', wide_number_mode=>'round'), which returns JSON '2.2412421353246237'.
Use the TO_JSON(), JSON_OBJECT(), and the JSON_ARRAY() functions to construct JSON documents in SQL. These functions implement the necessary quoting and escaping characters.

The maximum permitted size of the normalized document is 10 MB.

Nullability

JSON null values are treated as SQL non-NULL.

For example:

SELECT (JSON '{"a":null}').a IS NULL; -- Returns FALSE
SELECT (JSON '{"a":null}').b IS NULL; -- Returns TRUE

SELECT JSON_QUERY(JSON '{"a":null}', "$.a"); -- Returns a JSON 'null'
SELECT JSON_QUERY(JSON '{"a":null}', "$.b"); -- Returns a SQL NULL

Encoding

JSON documents must be encoded in UTF-8. Transactions or queries with JSON documents encoded in other formats return an error.

Create a table with JSON columns

A JSON column can be added to a table when the table is created. JSON type values can be nullable.

CREATE TABLE Venues (
  VenueId   INT64 NOT NULL,
  VenueName  STRING(1024),
  VenueAddress STRING(1024),
  VenueFeatures JSON,
  DateOpened  DATE,
) PRIMARY KEY(VenueId);

Add and remove JSON columns from existing tables

A JSON column can also be added to and dropped from existing tables.

ALTER TABLE Venues ADD COLUMN VenueDetails JSON;
ALTER TABLE Venues DROP COLUMN VenueDetails;

The following sample shows how to add a JSON column called VenueDetails to the Venues table using the Spanner client libraries.

C++

void AddJsonColumn(google::cloud::spanner_admin::DatabaseAdminClient client,
                   std::string const& project_id,
                   std::string const& instance_id,
                   std::string const& database_id) {
  google::cloud::spanner::Database database(project_id, instance_id,
                                            database_id);
  auto metadata = client
                      .UpdateDatabaseDdl(database.FullName(), {R"""(
                        ALTER TABLE Venues ADD COLUMN VenueDetails JSON)"""})
                      .get();
  if (!metadata) throw std::move(metadata).status();
  std::cout << "`Venues` table altered, new DDL:\n" << metadata->DebugString();
}

C#


using Google.Cloud.Spanner.Data;
using System;
using System.Threading.Tasks;

public class AddJsonColumnAsyncSample
{
    public async Task AddJsonColumnAsync(string projectId, string instanceId, string databaseId)
    {
        string connectionString = $"Data Source=projects/{projectId}/instances/{instanceId}/databases/{databaseId}";
        string alterStatement = "ALTER TABLE Venues ADD COLUMN VenueDetails JSON";

        using var connection = new SpannerConnection(connectionString);
        using var updateCmd = connection.CreateDdlCommand(alterStatement);
        await updateCmd.ExecuteNonQueryAsync();
        Console.WriteLine("Added the VenueDetails column.");
    }
}

Go


import (
	"context"
	"fmt"
	"io"
	"regexp"

	database "cloud.google.com/go/spanner/admin/database/apiv1"
	adminpb "cloud.google.com/go/spanner/admin/database/apiv1/databasepb"
)

// addJsonColumn creates a column in the database of type JSON
func addJsonColumn(w io.Writer, db string) error {
	// db = `projects/<project>/instances/<instance-id>/database/<database-id>`
	matches := regexp.MustCompile("^(.*)/databases/(.*)$").FindStringSubmatch(db)
	if matches == nil || len(matches) != 3 {
		return fmt.Errorf("addJsonColumn: invalid database id %s", db)
	}

	ctx := context.Background()
	adminClient, err := database.NewDatabaseAdminClient(ctx)
	if err != nil {
		return err
	}
	defer adminClient.Close()

	op, err := adminClient.UpdateDatabaseDdl(ctx, &adminpb.UpdateDatabaseDdlRequest{
		Database: db,
		Statements: []string{
			"ALTER TABLE Venues ADD COLUMN VenueDetails JSON",
		},
	})
	if err != nil {
		return err
	}
	if err := op.Wait(ctx); err != nil {
		return err
	}
	fmt.Fprintf(w, "Added VenueDetails column\n")
	return nil
}

Java


import com.google.cloud.spanner.Spanner;
import com.google.cloud.spanner.SpannerOptions;
import com.google.cloud.spanner.admin.database.v1.DatabaseAdminClient;
import com.google.common.collect.ImmutableList;
import com.google.spanner.admin.database.v1.DatabaseName;
import java.util.concurrent.ExecutionException;

class AddJsonColumnSample {

  static void addJsonColumn() throws InterruptedException, ExecutionException {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "my-project";
    String instanceId = "my-instance";
    String databaseId = "my-database";

    addJsonColumn(projectId, instanceId, databaseId);
  }

  static void addJsonColumn(String projectId, String instanceId, String databaseId)
      throws InterruptedException, ExecutionException {
    try (Spanner spanner =
        SpannerOptions.newBuilder()
            .setProjectId(projectId)
            .build()
            .getService();
        DatabaseAdminClient databaseAdminClient = spanner.createDatabaseAdminClient()) {
      // Wait for the operation to finish.
      // This will throw an ExecutionException if the operation fails.
      databaseAdminClient.updateDatabaseDdlAsync(
          DatabaseName.of(projectId, instanceId, databaseId),
          ImmutableList.of("ALTER TABLE Venues ADD COLUMN VenueDetails JSON")).get();
      System.out.printf("Successfully added column `VenueDetails`%n");
    }
  }
}

Node.js


/**
 * TODO(developer): Uncomment the following lines before running the sample.
 */
// const projectId = 'my-project-id';
// const instanceId = 'my-instance';
// const databaseId = 'my-database';

// Imports the Google Cloud client library
const {Spanner} = require('@google-cloud/spanner');

// creates a client
const spanner = new Spanner({
  projectId: projectId,
});

const databaseAdminClient = spanner.getDatabaseAdminClient();

const request = ['ALTER TABLE Venues ADD COLUMN VenueDetails JSON'];

// Alter existing table to add a column.
const [operation] = await databaseAdminClient.updateDatabaseDdl({
  database: databaseAdminClient.databasePath(
    projectId,
    instanceId,
    databaseId
  ),
  statements: request,
});

console.log(`Waiting for operation on ${databaseId} to complete...`);

await operation.promise();

console.log(
  `Added VenueDetails column to Venues table in database ${databaseId}.`
);

PHP

use Google\Cloud\Spanner\Admin\Database\V1\Client\DatabaseAdminClient;
use Google\Cloud\Spanner\Admin\Database\V1\UpdateDatabaseDdlRequest;

/**
 * Adds a JSON column to a table.
 * Example:
 * ```
 * add_json_column($projectId, $instanceId, $databaseId);
 * ```
 *
 * @param string $projectId The Google Cloud project ID.
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function add_json_column(string $projectId, string $instanceId, string $databaseId): void
{
    $databaseAdminClient = new DatabaseAdminClient();
    $databaseName = DatabaseAdminClient::databaseName($projectId, $instanceId, $databaseId);

    $request = new UpdateDatabaseDdlRequest([
        'database' => $databaseName,
        'statements' => ['ALTER TABLE Venues ADD COLUMN VenueDetails JSON']
    ]);

    $operation = $databaseAdminClient->updateDatabaseDdl($request);

    print('Waiting for operation to complete...' . PHP_EOL);
    $operation->pollUntilComplete();

    printf('Added VenueDetails as a JSON column in Venues table' . PHP_EOL);
}

Python

def add_json_column(instance_id, database_id):
    """Adds a new JSON column to the Venues table in the example database."""
    # instance_id = "your-spanner-instance"
    # database_id = "your-spanner-db-id"

    from google.cloud.spanner_admin_database_v1.types import spanner_database_admin

    spanner_client = spanner.Client()
    database_admin_api = spanner_client.database_admin_api

    request = spanner_database_admin.UpdateDatabaseDdlRequest(
        database=database_admin_api.database_path(
            spanner_client.project, instance_id, database_id
        ),
        statements=["ALTER TABLE Venues ADD COLUMN VenueDetails JSON"],
    )

    operation = database_admin_api.update_database_ddl(request)

    print("Waiting for operation to complete...")
    operation.result(OPERATION_TIMEOUT_SECONDS)

    print(
        'Altered table "Venues" on database {} on instance {}.'.format(
            database_id, instance_id
        )
    )

Ruby

# project_id  = "Your Google Cloud project ID"
# instance_id = "Your Spanner instance ID"
# database_id = "Your Spanner database ID"

require "google/cloud/spanner"
require "google/cloud/spanner/admin/database"

db_admin_client = Google::Cloud::Spanner::Admin::Database.database_admin

database_path = db_admin_client.database_path project: project_id,
                                              instance: instance_id,
                                              database: database_id

statements = ["ALTER TABLE Venues ADD COLUMN VenueDetails JSON"]
job = db_admin_client.update_database_ddl database: database_path,
                                          statements: statements
job.wait_until_done!

puts "Added VenueDetails column to Venues table in database #{database_id}"