Java API Quickstart
Create a table
Tables are created using either a Catalog
or an implementation of the Tables
interface.
Using a Hive catalog
The Hive catalog connects to a Hive metastore to keep track of Iceberg tables. You can initialize a Hive catalog with a name and some properties. (see: Catalog properties)
Note: Currently, setConf
is always required for hive catalogs, but this will change in the future.
import org.apache.iceberg.hive.HiveCatalog;
HiveCatalog catalog = new HiveCatalog();
catalog.setConf(spark.sparkContext().hadoopConfiguration()); // Configure using Spark's Hadoop configuration
Map <String, String> properties = new HashMap<String, String>();
properties.put("warehouse", "...");
properties.put("uri", "...");
catalog.initialize("hive", properties);
The Catalog
interface defines methods for working with tables, like createTable
, loadTable
, renameTable
, and dropTable
. HiveCatalog
implements the Catalog
interface.
To create a table, pass an Identifier
and a Schema
along with other initial metadata:
import org.apache.iceberg.Table;
import org.apache.iceberg.catalog.TableIdentifier;
TableIdentifier name = TableIdentifier.of("logging", "logs");
Table table = catalog.createTable(name, schema, spec);
// or to load an existing table, use the following line
// Table table = catalog.loadTable(name);
The logs schema and partition spec are created below.
Using a Hadoop catalog
A Hadoop catalog doesn't need to connect to a Hive MetaStore, but can only be used with HDFS or similar file systems that support atomic rename. Concurrent writes with a Hadoop catalog are not safe with a local FS or S3. To create a Hadoop catalog:
import org.apache.hadoop.conf.Configuration;
import org.apache.iceberg.hadoop.HadoopCatalog;
Configuration conf = new Configuration();
String warehousePath = "hdfs://host:8020/warehouse_path";
HadoopCatalog catalog = new HadoopCatalog(conf, warehousePath);
Like the Hive catalog, HadoopCatalog
implements Catalog
, so it also has methods for working with tables, like createTable
, loadTable
, and dropTable
.
This example creates a table with Hadoop catalog:
import org.apache.iceberg.Table;
import org.apache.iceberg.catalog.TableIdentifier;
TableIdentifier name = TableIdentifier.of("logging", "logs");
Table table = catalog.createTable(name, schema, spec);
// or to load an existing table, use the following line
// Table table = catalog.loadTable(name);
The logs schema and partition spec are created below.
Using Hadoop tables
Iceberg also supports tables that are stored in a directory in HDFS. Concurrent writes with a Hadoop tables are not safe when stored in the local FS or S3. Directory tables don't support all catalog operations, like rename, so they use the Tables
interface instead of Catalog
.
To create a table in HDFS, use HadoopTables
:
import org.apache.hadoop.conf.Configuration;
import org.apache.iceberg.hadoop.HadoopTables;
import org.apache.iceberg.Table;
Configuration conf = new Configuration();
HadoopTables tables = new HadoopTables(conf);
Table table = tables.create(schema, spec, table_location);
// or to load an existing table, use the following line
// Table table = tables.load(table_location);
Danger
Hadoop tables shouldn't be used with file systems that do not support atomic rename. Iceberg relies on rename to synchronize concurrent commits for directory tables.
Tables in Spark
Spark uses both HiveCatalog
and HadoopTables
to load tables. Hive is used when the identifier passed to load
or save
is not a path, otherwise Spark assumes it is a path-based table.
To read and write to tables from Spark see:
Schemas
Create a schema
This example creates a schema for a logs
table:
import org.apache.iceberg.Schema;
import org.apache.iceberg.types.Types;
Schema schema = new Schema(
Types.NestedField.required(1, "level", Types.StringType.get()),
Types.NestedField.required(2, "event_time", Types.TimestampType.withZone()),
Types.NestedField.required(3, "message", Types.StringType.get()),
Types.NestedField.optional(4, "call_stack", Types.ListType.ofRequired(5, Types.StringType.get()))
);
When using the Iceberg API directly, type IDs are required. Conversions from other schema formats, like Spark, Avro, and Parquet will automatically assign new IDs.
When a table is created, all IDs in the schema are re-assigned to ensure uniqueness.
Convert a schema from Avro
To create an Iceberg schema from an existing Avro schema, use converters in AvroSchemaUtil
:
import org.apache.avro.Schema;
import org.apache.avro.Schema.Parser;
import org.apache.iceberg.avro.AvroSchemaUtil;
Schema avroSchema = new Parser().parse("{\"type\": \"record\" , ... }");
Schema icebergSchema = AvroSchemaUtil.toIceberg(avroSchema);
Convert a schema from Spark
To create an Iceberg schema from an existing table, use converters in SparkSchemaUtil
:
import org.apache.iceberg.spark.SparkSchemaUtil;
Schema schema = SparkSchemaUtil.schemaForTable(sparkSession, table_name);
Partitioning
Create a partition spec
Partition specs describe how Iceberg should group records into data files. Partition specs are created for a table's schema using a builder.
This example creates a partition spec for the logs
table that partitions records by the hour of the log event's timestamp and by log level:
import org.apache.iceberg.PartitionSpec;
PartitionSpec spec = PartitionSpec.builderFor(schema)
.hour("event_time")
.identity("level")
.build();
For more information on the different partition transforms that Iceberg offers, visit this page.
Branching and Tagging
Creating branches and tags
New branches and tags can be created via the Java library's ManageSnapshots API.
/* Create a branch test-branch which is retained for 1 week, and the latest 2 snapshots on test-branch will always be retained.
Snapshots on test-branch which are created within the last hour will also be retained. */
String branch = "test-branch";
table.manageSnapshots()
.createBranch(branch, 3)
.setMinSnapshotsToKeep(branch, 2)
.setMaxSnapshotAgeMs(branch, 3600000)
.setMaxRefAgeMs(branch, 604800000)
.commit();
// Create a tag historical-tag at snapshot 10 which is retained for a day
String tag = "historical-tag"
table.manageSnapshots()
.createTag(tag, 10)
.setMaxRefAgeMs(tag, 86400000)
.commit();
Committing to branches
Writing to a branch can be performed by specifying toBranch
in the operation. For the full list refer to UpdateOperations.
// Append FILE_A to branch test-branch
String branch = "test-branch";
table.newAppend()
.appendFile(FILE_A)
.toBranch(branch)
.commit();
// Perform row level updates on "test-branch"
table.newRowDelta()
.addRows(DATA_FILE)
.addDeletes(DELETES)
.toBranch(branch)
.commit();
// Perform a rewrite operation replacing small_file_1 and small_file_2 on "test-branch" with compacted_file.
table.newRewrite()
.rewriteFiles(ImmutableSet.of(small_file_1,small_file_2), ImmutableSet.of(compacted_file))
.toBranch(branch)
.commit();
Reading from branches and tags
Reading from a branch or tag can be done as usual via the Table Scan API, by passing in a branch or tag in the useRef
API. When a branch is passed in, the snapshot that's used is the head of the branch. Note that currently reading from a branch and specifying an asOfSnapshotId
in the scan is not supported.
// Read from the head snapshot of test-branch
TableScan branchRead = table.newScan().useRef("test-branch");
// Read from the snapshot referenced by audit-tag
Table tagRead = table.newScan().useRef("audit-tag");
Replacing and fast forwarding branches and tags
The snapshots which existing branches and tags point to can be updated via the replace
APIs. The fast forward operation is similar to git fast-forwarding. Fast forward can be used to advance a target branch to the head of a source branch or a tag when the target branch is an ancestor of the source. For both fast forward and replace, retention properties of the target branch are maintained by default.
// Update "test-branch" to point to snapshot 4
table.manageSnapshots()
.replaceBranch(branch, 4)
.commit()
String tag = "audit-tag";
// Replace "audit-tag" to point to snapshot 3 and update its retention
table.manageSnapshots()
.replaceBranch(tag, 4)
.setMaxRefAgeMs(1000)
.commit()
Updating retention properties
Retention properties for branches and tags can be updated as well.
Use the setMaxRefAgeMs for updating the retention property of the branch or tag itself. Branch snapshot retention properties can be updated via the setMinSnapshotsToKeep
and setMaxSnapshotAgeMs
APIs.
String branch = "test-branch";
// Update retention properties for test-branch
table.manageSnapshots()
.setMinSnapshotsToKeep(branch, 10)
.setMaxSnapshotAgeMs(branch, 7200000)
.setMaxRefAgeMs(branch, 604800000)
.commit();
// Update retention properties for test-tag
table.manageSnapshots()
.setMaxRefAgeMs("test-tag", 604800000)
.commit();
Removing branches and tags
Branches and tags can be removed via the removeBranch
and removeTag
APIs respectively