Configuring garbage collection

This page shows you how to view, set, and update garbage collection policies in Cloud Bigtable. Before you read this page, you should be familiar with garbage collection.

Before you use the cbt command-line tool, follow the setup instructions, including the steps to create a .cbtrc file.

Viewing current garbage collection policies

You can use either the Cloud Console or the cbt tool to view a column family's garbage collection policies.

Console

To view the current garbage collection policy for a column family:

  1. Open the list of Bigtable instances in the Cloud Console.

    Open the instance list

  2. Click the instance whose tables you want to view.

  3. Click Tables in the left pane.

    The Tables page displays a list of tables in the instance.

  4. Click Edit in the table's row.

  5. Click Open next to the column family that you want to view.

  6. When you are finished viewing the garbage collection policy, click Cancel to exit.

cbt

You can look up the current garbage collection policies for a given table by running the following command, substituting a valid table ID for TABLE_ID:

cbt ls TABLE_ID

Setting garbage collection policies

You can set garbage collection policies using the Google Cloud Console, the cbt command-line tool, or the Cloud Bigtable client libraries.

Garbage collection based on age

The following section shows how to set the maximum age for data in a column family.

Console

To set an expiration time for cells in a column family:

  1. Open the list of Bigtable instances in the Cloud Console.

    Open the instance list

  2. Click the instance whose tables you want to view.

  3. Click Tables in the left pane.

    The Tables page displays a list of tables in the instance.

  4. Click Edit.

  5. Click Open next to the column family that you want to edit.

  6. Select Age based policy.

  7. Enter the age by entering a number in the Max age text box and using the Unit dropdown to select the unit of time.

    For example, to retain a column family's data for 30 minutes, enter 30 and choose minutes.

  8. Click Save.

cbt

This example creates a column family named cf1, then sets the maximum age for data in the column family to five days. This tells Bigtable to remove all data with timestamps older than five days in all columns in this column family.

cbt createfamily your-table cf1
cbt setgcpolicy your-table cf1 maxage=5d

Go

bigtable/garbagecollection/create_family_gc_max_age.go 
import (
	"context"
	"fmt"
	"io"
	"time"

	"cloud.google.com/go/bigtable"
)

func createFamilyGCMaxAge(w io.Writer, projectID, instanceID string, tableName string) error {
	// projectID := "my-project-id"
	// instanceID := "my-instance-id"
	// tableName := "my-table-name"

	ctx := context.Background()

	adminClient, err := bigtable.NewAdminClient(ctx, projectID, instanceID)
	if err != nil {
		return fmt.Errorf("bigtable.NewAdminClient: %v", err)
	}
	defer adminClient.Close()

	columnFamilyName := "cf1"
	if err := adminClient.CreateColumnFamily(ctx, tableName, columnFamilyName); err != nil {
		return fmt.Errorf("CreateColumnFamily(%s): %v", columnFamilyName, err)
	}

	// Set a garbage collection policy of 5 days.
	maxAge := time.Hour * 24 * 5
	policy := bigtable.MaxAgePolicy(maxAge)
	if err := adminClient.SetGCPolicy(ctx, tableName, columnFamilyName, policy); err != nil {
		return fmt.Errorf("SetGCPolicy(%s): %v", policy, err)
	}

	fmt.Fprintf(w, "created column family %s with policy: %v\n", columnFamilyName, policy)
	return nil
}

HBase

This code sample is coming soon.

Java

samples/snippets/src/main/java/com/example/bigtable/TableAdminExample.java 
// Creates a column family with GC policy : maximum age
// where age = current time minus cell timestamp

// Defines the GC rule to retain data with max age of 5 days.
DurationRule maxAgeRule = GCRULES.maxAge(5, TimeUnit.DAYS);

// Creates column family with given GC rule.
try {
  // ModifyColumnFamiliesRequest can be used both for adding and modifying families, here it is
  // being used to add a family
  ModifyColumnFamiliesRequest columnFamiliesRequest =
      ModifyColumnFamiliesRequest.of(tableId).addFamily(COLUMN_FAMILY_1, maxAgeRule);
  adminClient.modifyFamilies(columnFamiliesRequest);
  System.out.println("Created column family: " + COLUMN_FAMILY_1);
} catch (AlreadyExistsException e) {
  System.err.println(
      "Failed to create column family with rule, already exists: " + e.getMessage());
}

Python

samples/tableadmin/tableadmin.py 
    print('Creating column family cf1 with with MaxAge GC Rule...')
    # Create a column family with GC policy : maximum age
    # where age = current time minus cell timestamp

    # Define the GC rule to retain data with max age of 5 days
    max_age_rule = column_family.MaxAgeGCRule(datetime.timedelta(days=5))

    column_family1 = table.column_family('cf1', max_age_rule)
    column_family1.create()
    print('Created column family cf1 with MaxAge GC Rule.')

C#

bigtable/api/TableAdminExample/TableAdmin.cs 
// Create a column family with GC policy : maximum age
// where age = current time minus cell timestamp
// Initialize request argument(s).
// Define the GC rule to retain data with max age of 5 days
GcRule MaxAgeRule = new GcRule { MaxAge = Duration.FromTimeSpan(TimeSpan.FromDays(5.0)) };

// Column family to create
ColumnFamily columnFamily = new ColumnFamily { GcRule = MaxAgeRule };

TableName tableName = new TableName(projectId, instanceId, tableId);

// Modification to create column family
ModifyColumnFamiliesRequest.Types.Modification modification = new ModifyColumnFamiliesRequest.Types.Modification
{
    Create = columnFamily,
    Id = "cf1"
};

ModifyColumnFamiliesRequest request = new ModifyColumnFamiliesRequest
{
    TableName = tableName,
    Modifications = { modification }
};
try
{
    // Make the request
    Table response = bigtableTableAdminClient.ModifyColumnFamilies(request);
    Console.WriteLine("Created column family");
    // Print table information.
    GetTable(tableId);
}
catch (Exception ex)
{
    Console.WriteLine($"Error creating column family {ex.Message}");
}

C++

google/cloud/bigtable/examples/table_admin_snippets.cc 
namespace cbt = ::google::cloud::bigtable;
using ::google::cloud::StatusOr;
[](cbt::TableAdmin admin, std::string const& table_id,
   std::string const& family_name) {
  StatusOr<google::bigtable::admin::v2::Table> schema =
      admin.ModifyColumnFamilies(
          table_id,
          {cbt::ColumnFamilyModification::Create(
              family_name, cbt::GcRule::MaxAge(std::chrono::hours(5 * 24)))});

  if (!schema) throw std::runtime_error(schema.status().message());
  std::cout << "Schema modified to: " << schema->DebugString() << "\n";
}

Node.js

samples/tableadmin.js 
// Create a column family with GC policy : maximum age
// where age = current time minus cell timestamp

// Define the GC rule to retain data with max age of 5 days
const maxAgeRule = {
  rule: {
    age: {
      // Value must be atleast 1 millisecond
      seconds: 60 * 60 * 24 * 5,
      nanos: 0,
    },
  },
};

let [family] = await table.createFamily('cf1', maxAgeRule);
console.log(`Created column family ${family.id}`);

PHP

bigtable/src/create_family_gc_max_age.php 
use Google\Cloud\Bigtable\Admin\V2\ModifyColumnFamiliesRequest\Modification;
use Google\Cloud\Bigtable\Admin\V2\BigtableTableAdminClient;
use Google\Cloud\Bigtable\Admin\V2\ColumnFamily;
use Google\Cloud\Bigtable\Admin\V2\GcRule;
use Google\Protobuf\Duration;

/**
 * Create a new column family with a max age GC rule
 *
 * @param string $projectId The Google Cloud project ID
 * @param string $instanceId The ID of the Bigtable instance where the table resides
 * @param string $tableId The ID of the table in which the rule needs to be created
 */
function create_family_gc_max_age(
    string $projectId,
    string $instanceId,
    string $tableId
): void {
    $tableAdminClient = new BigtableTableAdminClient();

    $tableName = $tableAdminClient->tableName($projectId, $instanceId, $tableId);

    print('Creating column family cf1 with MaxAge GC Rule...' . PHP_EOL);
    // Create a column family with GC policy : maximum age
    // where age = current time minus cell timestamp

    $columnFamily1 = new ColumnFamily();
    $duration = new Duration();
    $duration->setSeconds(3600 * 24 * 5);
    $MaxAgeRule = (new GcRule())->setMaxAge($duration);
    $columnFamily1->setGcRule($MaxAgeRule);

    $columnModification = new Modification();
    $columnModification->setId('cf1');
    $columnModification->setCreate($columnFamily1);
    $tableAdminClient->modifyColumnFamilies($tableName, [$columnModification]);
    print('Created column family cf1 with MaxAge GC Rule.' . PHP_EOL);
}

Ruby

google-cloud-bigtable/samples/tableadmin.rb 
# Create a column family with GC policy : maximum age
# where age = current time minus cell timestamp
# NOTE: Age value must be atleast 1 millisecond
max_age_rule = Google::Cloud::Bigtable::GcRule.max_age 60 * 60 * 24 * 5
column_families = table.column_families do |cfs|
  cfs.add "cf1", gc_rule: max_age_rule
end
family = column_families["cf1"]

Garbage collection based on the number of versions

The following section shows how to create a column family with a garbage collection policy that states the number of versions of the data, or number of cells, to keep.

Console

To set the number of cells, or versions, to retain in a column family:

  1. Open the list of Bigtable instances in the Cloud Console.

    Open the instance list

  2. Click the instance whose tables you want to view.

  3. Click Tables in the left pane.

    The Tables page displays a list of tables in the instance.

  4. Click Edit in the table's row.

  5. Click Open next to the column family that you want to edit.

  6. Select Version based policy.

  7. Enter the number of cells to retain in every column in the column family.

  8. Click Save.

cbt

This example creates a column family named cf2, then sets the number of versions to keep in the column family to two. This tells Bigtable to remove all but the two most recent cells in all columns in this column family.

cbt createfamily your-table cf2
cbt setgcpolicy your-table cf2 maxversions=2

This example sets a policy to remove all cells except the newest one.

cbt setgcpolicy your-table cf2 maxversions=1

Go

bigtable/garbagecollection/create_family_gc_max_versions.go 
import (
	"context"
	"fmt"
	"io"

	"cloud.google.com/go/bigtable"
)

func createFamilyGCMaxVersions(w io.Writer, projectID, instanceID string, tableName string) error {
	// projectID := "my-project-id"
	// instanceID := "my-instance-id"
	// tableName := "my-table-name"

	ctx := context.Background()

	adminClient, err := bigtable.NewAdminClient(ctx, projectID, instanceID)
	if err != nil {
		return fmt.Errorf("bigtable.NewAdminClient: %v", err)
	}
	defer adminClient.Close()

	columnFamilyName := "cf2"
	if err := adminClient.CreateColumnFamily(ctx, tableName, columnFamilyName); err != nil {
		return fmt.Errorf("CreateColumnFamily(%s): %v", columnFamilyName, err)
	}

	// Set a garbage collection policy of 2 versions.
	policy := bigtable.MaxVersionsPolicy(2)
	if err := adminClient.SetGCPolicy(ctx, tableName, columnFamilyName, policy); err != nil {
		return fmt.Errorf("SetGCPolicy(%s): %v", policy, err)
	}

	fmt.Fprintf(w, "created column family %s with policy: %v\n", columnFamilyName, policy)
	return nil
}

HBase

This code sample is coming soon.

Java

samples/snippets/src/main/java/com/example/bigtable/TableAdminExample.java 
// Creates a column family with GC policy : most recent N versions
// where 1 = most recent version

// Defines the GC policy to retain only the most recent 2 versions.
VersionRule versionRule = GCRULES.maxVersions(2);

// Creates column family with given GC rule.
try {
  // ModifyColumnFamiliesRequest can be used both for adding and modifying families, here it is
  // being used to add a family
  ModifyColumnFamiliesRequest columnFamiliesRequest =
      ModifyColumnFamiliesRequest.of(tableId).addFamily(COLUMN_FAMILY_2, versionRule);
  adminClient.modifyFamilies(columnFamiliesRequest);
  System.out.println("Created column family: " + COLUMN_FAMILY_2);
} catch (AlreadyExistsException e) {
  System.err.println(
      "Failed to create column family with rule, already exists: " + e.getMessage());
}

Python

samples/tableadmin/tableadmin.py 
    print('Creating column family cf2 with max versions GC rule...')
    # Create a column family with GC policy : most recent N versions
    # where 1 = most recent version

    # Define the GC policy to retain only the most recent 2 versions
    max_versions_rule = column_family.MaxVersionsGCRule(2)

    column_family2 = table.column_family('cf2', max_versions_rule)
    column_family2.create()
    print('Created column family cf2 with Max Versions GC Rule.')

C#

bigtable/api/TableAdminExample/TableAdmin.cs 
// Create a column family with GC policy : most recent N versions
// where 1 = most recent version
// Initialize request argument(s).
// Define the GC policy to retain only the most recent 2 versions
GcRule maxVersionsRule = new GcRule { MaxNumVersions = 2 };

// Column family to create
ColumnFamily columnFamily = new ColumnFamily { GcRule = maxVersionsRule };

TableName tableName = new TableName(projectId, instanceId, tableId);

// Modification to create column family
ModifyColumnFamiliesRequest.Types.Modification modification = new ModifyColumnFamiliesRequest.Types.Modification
{
    Create = columnFamily,
    Id = "cf2"
};

ModifyColumnFamiliesRequest request = new ModifyColumnFamiliesRequest
{
    TableName = tableName,
    Modifications = { modification }
};
try
{
    // Make the request
    Table response = bigtableTableAdminClient.ModifyColumnFamilies(request);
    Console.WriteLine("Created column family");
}
catch (Exception ex)
{
    Console.WriteLine($"Error creating column family {ex.Message}");
}

C++

google/cloud/bigtable/examples/table_admin_snippets.cc 
namespace cbt = ::google::cloud::bigtable;
using ::google::cloud::StatusOr;
[](cbt::TableAdmin admin, std::string const& table_id,
   std::string const& family_name) {
  StatusOr<google::bigtable::admin::v2::Table> schema =
      admin.ModifyColumnFamilies(
          table_id, {cbt::ColumnFamilyModification::Create(
                        family_name, cbt::GcRule::MaxNumVersions(2))});

  if (!schema) throw std::runtime_error(schema.status().message());
  std::cout << "Schema modified to: " << schema->DebugString() << "\n";
}

Node.js

samples/tableadmin.js 
// Create a column family with GC policy : most recent N versions
// where 1 = most recent version

// Define the GC policy to retain only the most recent 2 versions
const maxVersionsRule = {
  rule: {
    versions: 2,
  },
};

// Create a column family with given GC rule
[family] = await table.createFamily('cf2', maxVersionsRule);
console.log(`Created column family ${family.id}`);

PHP

bigtable/src/create_family_gc_max_versions.php 
use Google\Cloud\Bigtable\Admin\V2\ModifyColumnFamiliesRequest\Modification;
use Google\Cloud\Bigtable\Admin\V2\BigtableTableAdminClient;
use Google\Cloud\Bigtable\Admin\V2\ColumnFamily;
use Google\Cloud\Bigtable\Admin\V2\GcRule;

/**
 * Create a new column family with a max versions GC rule
 *
 * @param string $projectId The Google Cloud project ID
 * @param string $instanceId The ID of the Bigtable instance where the table resides
 * @param string $tableId The ID of the table in which the rule needs to be created
 */
function create_family_gc_max_versions(
    string $projectId,
    string $instanceId,
    string $tableId
): void {
    $tableAdminClient = new BigtableTableAdminClient();

    $tableName = $tableAdminClient->tableName($projectId, $instanceId, $tableId);

    print('Creating column family cf2 with max versions GC rule...' . PHP_EOL);
    $columnFamily2 = new ColumnFamily();
    $maxVersionRule = (new GcRule())->setMaxNumVersions(2);
    $columnFamily2->setGCRule($maxVersionRule);

    $columnModification = new Modification();
    $columnModification->setId('cf2');
    $columnModification->setCreate($columnFamily2);
    $tableAdminClient->modifyColumnFamilies($tableName, [$columnModification]);

    print('Created column family cf2 with Max Versions GC Rule.' . PHP_EOL);
}

Ruby

google-cloud-bigtable/samples/tableadmin.rb 
# Create a column family with GC policy : most recent N versions
# where 1 = most recent version
max_versions_rule = Google::Cloud::Bigtable::GcRule.max_versions 2
column_families = table.column_families do |cfs|
  cfs.add "cf2", gc_rule: max_versions_rule
end
family = column_families["cf2"]

Garbage collection based on multiple criteria

The following section demonstrate how to create a column family with an intersection garbage collection policy.

Console

To set an intersection garbage collection policy for cells in a column family:

  1. Open the list of Bigtable instances in the Cloud Console.

    Open the instance list

  2. Click the instance whose tables you want to view.

  3. Click Tables in the left pane.

    The Tables page displays a list of tables in the instance.

  4. Click Edit in the table's row.

  5. Click Open next to the column family that you want to edit.

  6. Select Custom policy.

  7. Enter a garbage collection rule in the text area, setting values for maxage, maxversions, or both. Acceptable age units are ms, s, m, h, and d, which stand for milliseconds, seconds, minutes, hours, and days.

    For example, to remove cells that are older than five days and older than the two most recent cells, enter the following. Cells must meet both criteria to be removed.

     maxage=5d and maxversions=2

  8. Click Save.

cbt

This example creates a column family named cf4, then sets a garbage collection policy that removes cells that are older than five days and older than the two most recent cells for all columns in the column family. Cells must meet both criteria to be removed.

cbt createfamily your-table cf4
cbt setgcpolicy your-table cf4 maxage=5d and maxversions=2

This example sets a policy that removes all cells more than 14 days old except the newest one.

cbt setgcpolicy your-table cf4 maxage=14d and maxversion=1

Go

bigtable/garbagecollection/create_family_gc_intersect.go 
import (
	"context"
	"fmt"
	"io"
	"time"

	"cloud.google.com/go/bigtable"
)

func createFamilyGCIntersect(w io.Writer, projectID, instanceID string, tableName string) error {
	// projectID := "my-project-id"
	// instanceID := "my-instance-id"
	// tableName := "my-table-name"

	ctx := context.Background()

	adminClient, err := bigtable.NewAdminClient(ctx, projectID, instanceID)
	if err != nil {
		return fmt.Errorf("bigtable.NewAdminClient: %v", err)
	}
	defer adminClient.Close()

	columnFamilyName := "cf4"
	if err := adminClient.CreateColumnFamily(ctx, tableName, columnFamilyName); err != nil {
		return fmt.Errorf("CreateColumnFamily(%s): %v", columnFamilyName, err)
	}

	// GC rule: Drop cells older than 5 days AND older than the most recent 2 versions
	maxAge := time.Hour * 24 * 5
	maxAgePolicy := bigtable.MaxAgePolicy(maxAge)
	policy := bigtable.IntersectionPolicy(bigtable.MaxVersionsPolicy(2), maxAgePolicy)
	if err := adminClient.SetGCPolicy(ctx, tableName, columnFamilyName, policy); err != nil {
		return fmt.Errorf("SetGCPolicy(%s): %v", policy, err)
	}

	fmt.Fprintf(w, "created column family %s with policy: %v\n", columnFamilyName, policy)
	return nil
}

HBase

This code sample is coming soon.

Java

samples/snippets/src/main/java/com/example/bigtable/TableAdminExample.java 
// Creates a column family with GC policy to drop data that matches all conditions.

// Defines a GC rule to drop cells older than 5 days AND older than the most recent 2 versions.
DurationRule maxAgeRule = GCRULES.maxAge(5, TimeUnit.DAYS);
VersionRule versionRule = GCRULES.maxVersions(2);
IntersectionRule intersectionRule = GCRULES.intersection().rule(maxAgeRule).rule(versionRule);

// Creates column family with given GC rule.
try {
  // ModifyColumnFamiliesRequest can be used both for adding and modifying families, here it is
  // being used to add a family
  ModifyColumnFamiliesRequest columnFamiliesRequest =
      ModifyColumnFamiliesRequest.of(tableId).addFamily(COLUMN_FAMILY_4, intersectionRule);
  adminClient.modifyFamilies(columnFamiliesRequest);
  System.out.println("Created column family: " + COLUMN_FAMILY_4);
} catch (AlreadyExistsException e) {
  System.err.println(
      "Failed to create column family with rule, already exists: " + e.getMessage());
}

Python

samples/tableadmin/tableadmin.py 
    print('Creating column family cf4 with Intersection GC rule...')
    # Create a column family with GC policy to drop data that matches
    # all conditions
    # GC rule: Drop cells older than 5 days AND older than the most
    # recent 2 versions
    intersection_rule = column_family.GCRuleIntersection([
        column_family.MaxAgeGCRule(datetime.timedelta(days=5)),
        column_family.MaxVersionsGCRule(2)])

    column_family4 = table.column_family('cf4', intersection_rule)
    column_family4.create()
    print('Created column family cf4 with Intersection GC rule.')

C#

bigtable/api/TableAdminExample/TableAdmin.cs 
// Create a column family with GC policy to drop data that matches all conditions.
// Initialize request argument(s).
// GC rule: Drop cells older than 5 days AND older than the most recent 2 versions.
GcRule.Types.Intersection intersectionRule = new GcRule.Types.Intersection
{
    Rules =
    {
        new GcRule { MaxNumVersions = 2 },
        new GcRule { MaxAge = Duration.FromTimeSpan(TimeSpan.FromDays(5)) }
    }
};
GcRule gcRule = new GcRule { Intersection = intersectionRule };

// Column family to create
ColumnFamily columnFamily = new ColumnFamily { GcRule = gcRule };

TableName tableName = new TableName(projectId, instanceId, tableId);

// Modification to create column family
ModifyColumnFamiliesRequest.Types.Modification modification = new ModifyColumnFamiliesRequest.Types.Modification
{
    Create = columnFamily,
    Id = "cf4"
};

ModifyColumnFamiliesRequest request = new ModifyColumnFamiliesRequest
{
    TableName = tableName,
    Modifications = { modification }
};
try
{
    // Make the request
    Table response = bigtableTableAdminClient.ModifyColumnFamilies(request);
    Console.WriteLine("Created column family");
}
catch (Exception ex)
{
    Console.WriteLine($"Error creating column family {ex.Message}");
}

C++

google/cloud/bigtable/examples/table_admin_snippets.cc 
namespace cbt = ::google::cloud::bigtable;
using ::google::cloud::StatusOr;
[](cbt::TableAdmin admin, std::string const& table_id,
   std::string const& family_name) {
  StatusOr<google::bigtable::admin::v2::Table> schema =
      admin.ModifyColumnFamilies(
          table_id,
          {cbt::ColumnFamilyModification::Create(
              family_name,
              cbt::GcRule::Intersection(
                  cbt::GcRule::MaxNumVersions(1),
                  cbt::GcRule::MaxAge(5 * std::chrono::hours(24))))});

  if (!schema) throw std::runtime_error(schema.status().message());
  std::cout << "Schema modified to: " << schema->DebugString() << "\n";
}

Node.js

samples/tableadmin.js 
// Create a column family with GC policy to drop data that matches all conditions

// GC rule: Drop cells older than 5 days AND older than the most recent 2 versions
const intersectionRule = {
  rule: {
    versions: 2,
    age: {
      seconds: 60 * 60 * 24 * 5,
      nanos: 0,
    },
    intersection: true,
  },
};
[family] = await table.createFamily('cf4', intersectionRule);
console.log(`Created column family ${family.id}`);

PHP

bigtable/src/create_family_gc_intersection.php 
use Google\Cloud\Bigtable\Admin\V2\GcRule\Intersection as GcRuleIntersection;
use Google\Cloud\Bigtable\Admin\V2\ModifyColumnFamiliesRequest\Modification;
use Google\Cloud\Bigtable\Admin\V2\BigtableTableAdminClient;
use Google\Cloud\Bigtable\Admin\V2\ColumnFamily;
use Google\Cloud\Bigtable\Admin\V2\GcRule;
use Google\Protobuf\Duration;

/**
 * Create a new column family with an intersection GC rule
 *
 * @param string $projectId The Google Cloud project ID
 * @param string $instanceId The ID of the Bigtable instance where the table resides
 * @param string $tableId The ID of the table in which the rule needs to be created
 */
function create_family_gc_intersection(
    string $projectId,
    string $instanceId,
    string $tableId
): void {
    $tableAdminClient = new BigtableTableAdminClient();

    $tableName = $tableAdminClient->tableName($projectId, $instanceId, $tableId);

    print('Creating column family cf4 with Intersection GC rule...' . PHP_EOL);
    $columnFamily4 = new ColumnFamily();

    $intersectionRule = new GcRuleIntersection();
    $intersectionArray = [
        (new GcRule())->setMaxAge((new Duration())->setSeconds(3600 * 24 * 5)),
        (new GcRule())->setMaxNumVersions(2)
    ];
    $intersectionRule->setRules($intersectionArray);

    $intersection = new GcRule();
    $intersection->setIntersection($intersectionRule);

    $columnFamily4->setGCRule($intersection);

    $columnModification = new Modification();
    $columnModification->setId('cf4');
    $columnModification->setCreate($columnFamily4);
    $tableAdminClient->modifyColumnFamilies($tableName, [$columnModification]);

    print('Created column family cf4 with Union GC rule' . PHP_EOL);
}

Ruby

google-cloud-bigtable/samples/tableadmin.rb 
# Create a column family with GC policy to drop data that matches at least
# one condition
max_age_rule = Google::Cloud::Bigtable::GcRule.max_age 60 * 60 * 24 * 5
max_versions_rule = Google::Cloud::Bigtable::GcRule.max_versions 2
intersection_gc_rule = Google::Cloud::Bigtable::GcRule.intersection max_age_rule, max_versions_rule
column_families = table.column_families do |cfs|
  cfs.add "cf4", gc_rule: intersection_gc_rule
end
family = column_families["cf4"]

The following section shows how to create a column family that has a union garbage collection policy.

Console

To set a union garbage collection policy for cells in a column family:

  1. Open the list of Bigtable instances in the Cloud Console.

    Open the instance list

  2. Click the instance whose tables you want to view.

  3. Click Tables in the left pane.

    The Tables page displays a list of tables in the instance.

  4. Click Edit in the table's row.

  5. Click Open next to the column family that you want to edit.

  6. Select Custom policy.

  7. Enter a garbage collection rule in the text area, setting values for maxage, maxversions, or both. Acceptable age units are ms, s, m, h, and d, which stand for milliseconds, seconds, minutes, hours, and days.

    For example, to remove cells that are more than five days old or are older than the two most recent cells, enter the following. Cells must meet either criteria to be removed.

     maxage=5d or maxversions=2

  8. Click Save.

cbt

This example creates a column family named cf3, then sets a garbage collection policy that removes cells that are more than five days old or are older than the two most recent cells. Cells must meet either conditions to be removed.

cbt createfamily your-table cf3
cbt setgcpolicy your-table cf3 maxage=5d or maxversions=2

This example sets a policy that removes all cell values except the newest one, but removes even the newest cell if it is more than one second old.

cbt setgcpolicy your-table cf3 maxversions=1 or maxage=1s

Go

bigtable/garbagecollection/create_family_gc_union.go 
import (
	"context"
	"fmt"
	"io"
	"time"

	"cloud.google.com/go/bigtable"
)

func createFamilyGCUnion(w io.Writer, projectID, instanceID string, tableName string) error {
	// projectID := "my-project-id"
	// instanceID := "my-instance-id"
	// tableName := "my-table-name"

	ctx := context.Background()

	adminClient, err := bigtable.NewAdminClient(ctx, projectID, instanceID)
	if err != nil {
		return fmt.Errorf("bigtable.NewAdminClient: %v", err)
	}
	defer adminClient.Close()

	columnFamilyName := "cf3"
	if err := adminClient.CreateColumnFamily(ctx, tableName, columnFamilyName); err != nil {
		return fmt.Errorf("CreateColumnFamily(%s): %v", columnFamilyName, err)
	}

	// Define a GC rule to drop cells older than 5 days or not the most recent version
	maxAge := time.Hour * 24 * 5
	maxAgePolicy := bigtable.MaxAgePolicy(maxAge)
	policy := bigtable.UnionPolicy(bigtable.MaxVersionsPolicy(2), maxAgePolicy)
	if err := adminClient.SetGCPolicy(ctx, tableName, columnFamilyName, policy); err != nil {
		return fmt.Errorf("SetGCPolicy(%s): %v", policy, err)
	}

	fmt.Fprintf(w, "created column family %s with policy: %v\n", columnFamilyName, policy)
	return nil
}

HBase

This code sample is coming soon.

Java

samples/snippets/src/main/java/com/example/bigtable/TableAdminExample.java 
// Creates a column family with GC policy to drop data that matches at least one condition.

// Defines a list of GC rules to drop cells older than 5 days OR not the most recent
// version.
UnionRule unionRule =
    GCRULES.union().rule(GCRULES.maxAge(5, TimeUnit.DAYS)).rule(GCRULES.maxVersions(1));

// Creates column family with given GC rule.
try {
  // ModifyColumnFamiliesRequest can be used both for adding and modifying families, here it is
  // being used to add a family
  ModifyColumnFamiliesRequest columnFamiliesRequest =
      ModifyColumnFamiliesRequest.of(tableId).addFamily(COLUMN_FAMILY_3, unionRule);
  adminClient.modifyFamilies(columnFamiliesRequest);
  System.out.println("Created column family: " + COLUMN_FAMILY_3);
} catch (AlreadyExistsException e) {
  System.err.println(
      "Failed to create column family with rule, already exists: " + e.getMessage());
}

Python

samples/tableadmin/tableadmin.py 
    print('Creating column family cf3 with union GC rule...')
    # Create a column family with GC policy to drop data that matches
    # at least one condition.
    # Define a GC rule to drop cells older than 5 days or not the
    # most recent version
    union_rule = column_family.GCRuleUnion([
        column_family.MaxAgeGCRule(datetime.timedelta(days=5)),
        column_family.MaxVersionsGCRule(2)])

    column_family3 = table.column_family('cf3', union_rule)
    column_family3.create()
    print('Created column family cf3 with Union GC rule')

C#

bigtable/api/TableAdminExample/TableAdmin.cs 
// Create a column family with GC policy to drop data that matches at least one condition.
// Initialize request argument(s).
// Define a GC rule to drop cells older than 5 days or not the most recent version.
GcRule.Types.Union unionRule = new GcRule.Types.Union
{
    Rules =
    {
        new GcRule { MaxNumVersions = 1 },
        new GcRule { MaxAge = Duration.FromTimeSpan(TimeSpan.FromDays(5)) }
    }
};
GcRule gcRule = new GcRule { Union = unionRule };

// Column family to create
ColumnFamily columnFamily = new ColumnFamily { GcRule = gcRule };

TableName tableName = new TableName(projectId, instanceId, tableId);

// Modification to create column family
ModifyColumnFamiliesRequest.Types.Modification modification = new ModifyColumnFamiliesRequest.Types.Modification
{
    Create = columnFamily,
    Id = "cf3"
};

ModifyColumnFamiliesRequest request = new ModifyColumnFamiliesRequest
{
    TableName = tableName,
    Modifications = { modification }
};
try
{
    // Make the request
    Table response = bigtableTableAdminClient.ModifyColumnFamilies(request);
    Console.WriteLine("Created column family");
}
catch (Exception ex)
{
    Console.WriteLine($"Error creating column family {ex.Message}");
}

C++

google/cloud/bigtable/examples/table_admin_snippets.cc 
namespace cbt = ::google::cloud::bigtable;
using ::google::cloud::StatusOr;
[](cbt::TableAdmin admin, std::string const& table_id,
   std::string const& family_name) {
  StatusOr<google::bigtable::admin::v2::Table> schema =
      admin.ModifyColumnFamilies(
          table_id,
          {cbt::ColumnFamilyModification::Create(
              family_name,
              cbt::GcRule::Union(
                  cbt::GcRule::MaxNumVersions(1),
                  cbt::GcRule::MaxAge(5 * std::chrono::hours(24))))});

  if (!schema) throw std::runtime_error(schema.status().message());
  std::cout << "Schema modified to: " << schema->DebugString() << "\n";
}

Node.js

samples/tableadmin.js 
// Create a column family with GC policy to drop data that matches at least one condition.

// Define a GC rule to drop cells older than 5 days or not the most recent version
const unionRule = {
  rule: {
    versions: 1,
    age: {
      seconds: 60 * 60 * 24 * 5,
      nanos: 0,
    },
    union: true,
  },
};

[family] = await table.createFamily('cf3', unionRule);
console.log(`Created column family ${family.id}`);

PHP

bigtable/src/create_family_gc_union.php 
use Google\Cloud\Bigtable\Admin\V2\ModifyColumnFamiliesRequest\Modification;
use Google\Cloud\Bigtable\Admin\V2\GcRule\Union as GcRuleUnion;
use Google\Cloud\Bigtable\Admin\V2\BigtableTableAdminClient;
use Google\Cloud\Bigtable\Admin\V2\ColumnFamily;
use Google\Cloud\Bigtable\Admin\V2\GcRule;
use Google\Protobuf\Duration;

/**
 * Create a new column family with a union GC rule
 *
 * @param string $projectId The Google Cloud project ID
 * @param string $instanceId The ID of the Bigtable instance where the table resides
 * @param string $tableId The ID of the table in which the rule needs to be created
 */
function create_family_gc_union(
    string $projectId,
    string $instanceId,
    string $tableId
): void {
    $tableAdminClient = new BigtableTableAdminClient();

    $tableName = $tableAdminClient->tableName($projectId, $instanceId, $tableId);

    print('Creating column family cf3 with union GC rule...' . PHP_EOL);
    // Create a column family with GC policy to drop data that matches
    // at least one condition.
    // Define a GC rule to drop cells older than 5 days or not the
    // most recent version

    $columnFamily3 = new ColumnFamily();

    $ruleUnion = new GcRuleUnion();
    $ruleUnionArray = [
        (new GcRule())->setMaxNumVersions(2),
        (new GcRule())->setMaxAge((new Duration())->setSeconds(3600 * 24 * 5))
    ];
    $ruleUnion->setRules($ruleUnionArray);
    $union = new GcRule();
    $union->setUnion($ruleUnion);

    $columnFamily3->setGCRule($union);

    $columnModification = new Modification();
    $columnModification->setId('cf3');
    $columnModification->setCreate($columnFamily3);
    $tableAdminClient->modifyColumnFamilies($tableName, [$columnModification]);

    print('Created column family cf3 with Union GC rule.' . PHP_EOL);
}

Ruby

google-cloud-bigtable/samples/tableadmin.rb 
# Create a column family with GC policy to drop data that matches at least
# one condition
max_age_rule = Google::Cloud::Bigtable::GcRule.max_age 60 * 60 * 24 * 5
max_versions_rule = Google::Cloud::Bigtable::GcRule.max_versions 2
union_gc_rule = Google::Cloud::Bigtable::GcRule.union max_age_rule, max_versions_rule
column_families = table.column_families do |cfs|
  cfs.add "cf3", gc_rule: union_gc_rule
end
family = column_families["cf3"]

The following section shows how to create a column family that has a nested garbage collection policy. A nested garbage collection policy has a combination of union and intersection rules.

Console

To set a nested garbage collection policy for cells in a column family:

  1. Open the list of Bigtable instances in the Cloud Console.

    Open the instance list

  2. Click the instance whose tables you want to view.

  3. Click Tables in the left pane.

    The Tables page displays a list of tables in the instance.

  4. Click Edit in the table's row.

  5. Click Open next to the column family that you want to edit.

  6. Select Custom policy.

  7. Enter a garbage collection rule in the text area, setting values for maxage, maxversions, or both. Acceptable age units are ms, s, m, h, and d, which stand for milliseconds, seconds, minutes, hours, and days.

    For example, to keep the two newest cells even if they are more than one minute old, or keep the ten newest cells as long as they are less than one minute old, enter the following:

     (maxage=1m and maxversions=2) or maxversions=10

  8. Click Save.

cbt

This example creates a column family named cf5, then sets a garbage collection policy that removes cells in the column family that meet either of the following conditions:

  • Older than the ten most recent cells
  • More than one minute old and older than the two most recent cells

In other words, this policy keeps the two newest cells even if they are more than one minute old, or keeps the ten newest cells as long as they are less than one minute old.

cbt createfamily your-table cf5
cbt setgcpolicy your-table cf5 "(maxage=1m and maxversions=2) or
maxversions=10"

Go

bigtable/garbagecollection/create_family_gc_nested.go 
import (
	"context"
	"fmt"
	"io"
	"time"

	"cloud.google.com/go/bigtable"
)

func createFamilyGCNested(w io.Writer, projectID, instanceID string, tableName string) error {
	// projectID := "my-project-id"
	// instanceID := "my-instance-id"
	// tableName := "my-table-name"

	ctx := context.Background()

	adminClient, err := bigtable.NewAdminClient(ctx, projectID, instanceID)
	if err != nil {
		return fmt.Errorf("bigtable.NewAdminClient: %v", err)
	}
	defer adminClient.Close()

	columnFamilyName := "cf5"
	if err := adminClient.CreateColumnFamily(ctx, tableName, columnFamilyName); err != nil {
		return fmt.Errorf("CreateColumnFamily(%s): %v", columnFamilyName, err)
	}

	// Create a nested GC rule:
	// Drop cells that are either older than the 10 recent versions
	// OR
	// Drop cells that are older than a month AND older than the 2 recent versions
	maxAge := time.Hour * 24 * 5
	maxAgePolicy := bigtable.MaxAgePolicy(maxAge)
	policy := bigtable.UnionPolicy(
		bigtable.MaxVersionsPolicy(10),
		bigtable.IntersectionPolicy(
			bigtable.MaxVersionsPolicy(2),
			maxAgePolicy))
	if err := adminClient.SetGCPolicy(ctx, tableName, columnFamilyName, policy); err != nil {
		return fmt.Errorf("SetGCPolicy(%s): %v", policy, err)
	}

	fmt.Fprintf(w, "created column family %s with policy: %v\n", columnFamilyName, policy)
	return nil
}

HBase

This code sample is coming soon.

Java

samples/snippets/src/main/java/com/example/bigtable/TableAdminExample.java 
// Creates a nested GC rule:
// Drop cells that are either older than the 10 recent versions
// OR
// Drop cells that are older than a month AND older than the 2 recent versions
VersionRule versionRule1 = GCRULES.maxVersions(10);
VersionRule versionRule2 = GCRULES.maxVersions(2);
DurationRule maxAgeRule = GCRULES.maxAge(30, TimeUnit.DAYS);
IntersectionRule intersectionRule = GCRULES.intersection().rule(maxAgeRule).rule(versionRule2);
UnionRule unionRule = GCRULES.union().rule(intersectionRule).rule(versionRule1);

// Creates column family with given GC rule.
try {
  // ModifyColumnFamiliesRequest can be used both for adding and modifying families, here it is
  // being used to add a family
  ModifyColumnFamiliesRequest columnFamiliesRequest =
      ModifyColumnFamiliesRequest.of(tableId).addFamily(COLUMN_FAMILY_5, unionRule);
  adminClient.modifyFamilies(columnFamiliesRequest);
  System.out.println("Created column family: " + COLUMN_FAMILY_5);
} catch (AlreadyExistsException e) {
  System.err.println(
      "Failed to create column family with rule, already exists: " + e.getMessage());
}

Python

samples/tableadmin/tableadmin.py 
    print('Creating column family cf5 with a Nested GC rule...')
    # Create a column family with nested GC policies.
    # Create a nested GC rule:
    # Drop cells that are either older than the 10 recent versions
    # OR
    # Drop cells that are older than a month AND older than the
    # 2 recent versions
    rule1 = column_family.MaxVersionsGCRule(10)
    rule2 = column_family.GCRuleIntersection([
        column_family.MaxAgeGCRule(datetime.timedelta(days=30)),
        column_family.MaxVersionsGCRule(2)])

    nested_rule = column_family.GCRuleUnion([rule1, rule2])

    column_family5 = table.column_family('cf5', nested_rule)
    column_family5.create()
    print('Created column family cf5 with a Nested GC rule.')

C#

bigtable/api/TableAdminExample/TableAdmin.cs 
// Create a nested GC rule:
// Drop cells that are either older than the 10 recent versions
// OR
// Drop cells that are older than 5 days AND older than the 2 recent versions.
// Initialize request argument(s).
GcRule.Types.Intersection intersectionRule = new GcRule.Types.Intersection
{
    Rules =
    {
        new GcRule { MaxNumVersions = 2 },
        new GcRule { MaxAge = Duration.FromTimeSpan(TimeSpan.FromDays(5)) }
    }
};

GcRule.Types.Union nestedRule = new GcRule.Types.Union
{
    Rules =
    {
        new GcRule { MaxNumVersions = 10 },
        new GcRule { Intersection = intersectionRule }
    }
};

GcRule gcRule = new GcRule { Union = nestedRule };

// Column family to create
ColumnFamily columnFamily = new ColumnFamily { GcRule = gcRule };

TableName tableName = new TableName(projectId, instanceId, tableId);

// Modification to create column family
ModifyColumnFamiliesRequest.Types.Modification modification = new ModifyColumnFamiliesRequest.Types.Modification
{
    Create = columnFamily,
    Id = "cf5"
};

ModifyColumnFamiliesRequest request = new ModifyColumnFamiliesRequest
{
    TableName = tableName,
    Modifications = { modification }
};
try
{
    // Make the request
    Table response = bigtableTableAdminClient.ModifyColumnFamilies(request);
    Console.WriteLine("Created column family");
}
catch (Exception ex)
{
    Console.WriteLine($"Error creating column family {ex.Message}");
}

C++

google/cloud/bigtable/examples/table_admin_snippets.cc 
namespace cbt = ::google::cloud::bigtable;
using ::google::cloud::StatusOr;
[](cbt::TableAdmin admin, std::string const& table_id,
   std::string const& family_name) {
  StatusOr<google::bigtable::admin::v2::Table> schema =
      admin.ModifyColumnFamilies(
          table_id,
          {cbt::ColumnFamilyModification::Create(
              family_name,
              cbt::GcRule::Union(
                  cbt::GcRule::MaxNumVersions(10),
                  cbt::GcRule::Intersection(
                      cbt::GcRule::MaxNumVersions(1),
                      cbt::GcRule::MaxAge(5 * std::chrono::hours(24)))))});

  if (!schema) throw std::runtime_error(schema.status().message());
  std::cout << "Schema modified to: " << schema->DebugString() << "\n";
}

Node.js

samples/tableadmin.js 
// Create a nested GC rule:
// Drop cells that are either older than the 10 recent versions
// OR
// Drop cells that are older than a month AND older than the 2 recent versions
const nestedRule = {
  union: true,
  versions: 10,
  rule: {
    versions: 2,
    age: {
      // one month
      seconds: 60 * 60 * 24 * 30,
      nanos: 0,
    },
  },
};

[family] = await table.createFamily('cf5', nestedRule);
console.log(`Created column family ${family.id}`);

PHP

bigtable/src/create_family_gc_nested.php 
use Google\Cloud\Bigtable\Admin\V2\GcRule\Intersection as GcRuleIntersection;
use Google\Cloud\Bigtable\Admin\V2\ModifyColumnFamiliesRequest\Modification;
use Google\Cloud\Bigtable\Admin\V2\GcRule\Union as GcRuleUnion;
use Google\Cloud\Bigtable\Admin\V2\BigtableTableAdminClient;
use Google\Cloud\Bigtable\Admin\V2\ColumnFamily;
use Google\Cloud\Bigtable\Admin\V2\GcRule;
use Google\Protobuf\Duration;

/**
 * Create a new column family with a nested GC rule
 *
 * @param string $projectId The Google Cloud project ID
 * @param string $instanceId The ID of the Bigtable instance where the table resides
 * @param string $tableId The ID of the table in which the rule needs to be created
 */
function create_family_gc_nested(
    string $projectId,
    string $instanceId,
    string $tableId
): void {
    $tableAdminClient = new BigtableTableAdminClient();

    $tableName = $tableAdminClient->tableName($projectId, $instanceId, $tableId);

    print('Creating column family cf5 with a Nested GC rule...' . PHP_EOL);
    // Create a column family with nested GC policies.
    // Create a nested GC rule:
    // Drop cells that are either older than the 10 recent versions
    // OR
    // Drop cells that are older than a month AND older than the
    // 2 recent versions
    $columnFamily5 = new ColumnFamily();
    $rule1 = (new GcRule())->setMaxNumVersions(10);

    $rule2Intersection = new GcRuleIntersection();
    $rule2Duration1 = new Duration();
    $rule2Duration1->setSeconds(3600 * 24 * 30);
    $rule2Array = [
        (new GcRule())->setMaxAge($rule2Duration1),
        (new GcRule())->setMaxNumVersions(2)
    ];
    $rule2Intersection->setRules($rule2Array);
    $rule2 = new GcRule();
    $rule2->setIntersection($rule2Intersection);

    $nestedRule = new GcRuleUnion();
    $nestedRule->setRules([
        $rule1,
        $rule2
    ]);
    $nestedRule = (new GcRule())->setUnion($nestedRule);

    $columnFamily5->setGCRule($nestedRule);

    $columnModification = new Modification();
    $columnModification->setId('cf5');
    $columnModification->setCreate($columnFamily5);
    $tableAdminClient->modifyColumnFamilies($tableName, [$columnModification]);

    print('Created column family cf5 with a Nested GC rule.' . PHP_EOL);
}

Ruby

google-cloud-bigtable/samples/tableadmin.rb 
# Create a nested GC rule:
# Drop cells that are either older than the 10 recent versions
# OR
# Drop cells that are older than a month AND older than the 2 recent versions
max_versions_rule1 = Google::Cloud::Bigtable::GcRule.max_versions 10
max_age_rule = Google::Cloud::Bigtable::GcRule.max_age 60 * 60 * 24 * 5
max_versions_rule2 = Google::Cloud::Bigtable::GcRule.max_versions 2
intersection_gc_rule = Google::Cloud::Bigtable::GcRule.intersection max_age_rule, max_versions_rule2
nested_gc_rule = Google::Cloud::Bigtable::GcRule.union max_versions_rule1, intersection_gc_rule

Updating a garbage collection policy

The following section demonstrates how to modify an existing garbage collection policy.

Console

To update the garbage collection policy for a column family:

  1. Open the list of Bigtable instances in the Cloud Console.

    Open the instance list

  2. Click the instance whose tables you want to view.

  3. Click Tables in the left pane.

    The Tables page displays a list of tables in the instance.

  4. Click Edit in the table's row.

  5. Click Open next to the column family that you want to edit.

  6. Set the policy.

  7. Click Save.

cbt

cbt setgcpolicy your-table cf1 maxage=1d

Go

This code sample is coming soon.

HBase

This code sample is coming soon.

Java

samples/snippets/src/main/java/com/example/bigtable/TableAdminExample.java 
// Updates the column family metadata to update the GC rule.
// Updates a column family GC rule.
VersionRule versionRule = GCRULES.maxVersions(1);
try {
  // ModifyColumnFamiliesRequest can be used both for adding and modifying families, here it is
  // being used to modify a family
  // Updates column family with given GC rule.
  ModifyColumnFamiliesRequest updateRequest =
      ModifyColumnFamiliesRequest.of(tableId).updateFamily(COLUMN_FAMILY_1, versionRule);
  adminClient.modifyFamilies(updateRequest);
  System.out.printf("Column family %s GC rule updated%n", COLUMN_FAMILY_1);
} catch (NotFoundException e) {
  System.err.println("Failed to modify a non-existent column family: " + e.getMessage());
}

Python

samples/tableadmin/tableadmin.py 
print('Updating column family cf1 GC rule...')
# Update the column family cf1 to update the GC rule
column_family1 = table.column_family(
    'cf1',
    column_family.MaxVersionsGCRule(1))
column_family1.update()
print('Updated column family cf1 GC rule\n')

C#

bigtable/api/TableAdminExample/TableAdmin.cs 
// Update the column family metadata to update the GC rule.
// Initialize request argument(s).
// Updated column family GC rule.
GcRule maxVersionsRule = new GcRule { MaxNumVersions = 1 };

// Column family to create
ColumnFamily columnFamily = new ColumnFamily { GcRule = maxVersionsRule };

TableName tableName = new TableName(projectId, instanceId, tableId);

// Modification to update column family
ModifyColumnFamiliesRequest.Types.Modification modification = new ModifyColumnFamiliesRequest.Types.Modification
{
    Update = columnFamily,
    Id = "cf1"
};

ModifyColumnFamiliesRequest request = new ModifyColumnFamiliesRequest
{
    TableName = tableName,
    Modifications = { modification }
};
try
{
    // Make the request
    Table response = bigtableTableAdminClient.ModifyColumnFamilies(request);
    Console.WriteLine("Updated column family");
}
catch (Exception ex)
{
    Console.WriteLine($"Error updating column family {ex.Message}");
}

C++

google/cloud/bigtable/examples/table_admin_snippets.cc 
namespace cbt = ::google::cloud::bigtable;
using ::google::cloud::StatusOr;
[](cbt::TableAdmin admin, std::string const& table_id,
   std::string const& family_name) {
  StatusOr<google::bigtable::admin::v2::Table> schema =
      admin.ModifyColumnFamilies(
          table_id, {cbt::ColumnFamilyModification::Update(
                        family_name, cbt::GcRule::MaxNumVersions(1))});

  if (!schema) throw std::runtime_error(schema.status().message());
  std::cout << "Schema modified to: " << schema->DebugString() << "\n";
}

Node.js

samples/tableadmin.js 
// Update the column family metadata to update the GC rule

// Create a reference to the column family
family = table.family('cf1');

// Update a column family GC rule
const updatedMetadata = {
  rule: {
    versions: 1,
  },
};

const [apiResponse] = await family.setMetadata(updatedMetadata);
console.log(`Updated GC rule: ${JSON.stringify(apiResponse)}`);

PHP

bigtable/src/update_gc_rule.php 
use Google\Cloud\Bigtable\Admin\V2\ModifyColumnFamiliesRequest\Modification;
use Google\Cloud\Bigtable\Admin\V2\BigtableTableAdminClient;
use Google\Cloud\Bigtable\Admin\V2\ColumnFamily;
use Google\Cloud\Bigtable\Admin\V2\GcRule;
use Google\ApiCore\ApiException;

/**
 * Update the GC Rule for an existing column family in the table
 *
 * @param string $projectId The Google Cloud project ID
 * @param string $instanceId The ID of the Bigtable instance
 * @param string $tableId The ID of the table where the rule needs to be updated
 * @param string $familyId The ID of the column family
 */
function update_gc_rule(
    string $projectId,
    string $instanceId,
    string $tableId,
    string $familyId = 'cf3'
): void {
    $tableAdminClient = new BigtableTableAdminClient();
    $tableName = $tableAdminClient->tableName($projectId, $instanceId, $tableId);
    $columnFamily1 = new ColumnFamily();

    printf('Updating column family %s GC rule...' . PHP_EOL, $familyId);
    $columnFamily1->setGcRule((new GcRule())->setMaxNumVersions(1));
    // Update the column family with ID $familyId to update the GC rule
    $columnModification = new Modification();
    $columnModification->setId($familyId);
    $columnModification->setUpdate($columnFamily1);

    try {
        $tableAdminClient->modifyColumnFamilies($tableName, [$columnModification]);
    } catch (ApiException $e) {
        if ($e->getStatus() === 'NOT_FOUND') {
            printf('Column family %s does not exist.' . PHP_EOL, $familyId);
            return;
        }
        throw $e;
    }

    printf('Print column family %s GC rule after update...' . PHP_EOL, $familyId);
    printf('Column Family: ' . $familyId . PHP_EOL);
    printf('%s' . PHP_EOL, $columnFamily1->serializeToJsonString());
}

Ruby

google-cloud-bigtable/samples/tableadmin.rb 
gc_rule = Google::Cloud::Bigtable::GcRule.max_versions 1
column_families = table.column_families do |cfs|
  cfs.update "cf1", gc_rule: gc_rule
end
p column_families["cf1"]

What's next