Skip to content

Latest commit

 

History

History
806 lines (595 loc) · 34.7 KB

flink-getting-started.md

File metadata and controls

806 lines (595 loc) · 34.7 KB
title url menu
Enabling Iceberg in Flink
flink
main
parent weight
Flink
100

Flink

Apache Iceberg supports both Apache Flink's DataStream API and Table API. See the Multi-Engine Support#apache-flink page for the integration of Apache Flink.

Feature support Flink Notes
SQL create catalog ✔️
SQL create database ✔️
SQL create table ✔️
SQL create table like ✔️
SQL alter table ✔️ Only support altering table properties, column and partition changes are not supported
SQL drop_table ✔️
SQL select ✔️ Support both streaming and batch mode
SQL insert into ✔️ ️ Support both streaming and batch mode
SQL insert overwrite ✔️ ️
DataStream read ✔️ ️
DataStream append ✔️ ️
DataStream overwrite ✔️ ️
Metadata tables ️ Support Java API but does not support Flink SQL
Rewrite files action ✔️ ️

Preparation when using Flink SQL Client

To create iceberg table in flink, we recommend to use Flink SQL Client because it's easier for users to understand the concepts.

Step.1 Downloading the flink 1.11.x binary package from the apache flink download page. We now use scala 2.12 to archive the apache iceberg-flink-runtime jar, so it's recommended to use flink 1.11 bundled with scala 2.12.

FLINK_VERSION=1.11.1
SCALA_VERSION=2.12
APACHE_FLINK_URL=archive.apache.org/dist/flink/
wget ${APACHE_FLINK_URL}/flink-${FLINK_VERSION}/flink-${FLINK_VERSION}-bin-scala_${SCALA_VERSION}.tgz
tar xzvf flink-${FLINK_VERSION}-bin-scala_${SCALA_VERSION}.tgz

Step.2 Start a standalone flink cluster within hadoop environment.

# HADOOP_HOME is your hadoop root directory after unpack the binary package.
export HADOOP_CLASSPATH=`$HADOOP_HOME/bin/hadoop classpath`

# Start the flink standalone cluster
./bin/start-cluster.sh

Step.3 Start the flink SQL client.

We've created a separate flink-runtime module in iceberg project to generate a bundled jar, which could be loaded by flink SQL client directly.

If we want to build the flink-runtime bundled jar manually, please just build the iceberg project and it will generate the jar under <iceberg-root-dir>/flink-runtime/build/libs. Of course, we could also download the flink-runtime jar from the apache official repository.

# HADOOP_HOME is your hadoop root directory after unpack the binary package.
export HADOOP_CLASSPATH=`$HADOOP_HOME/bin/hadoop classpath`

./bin/sql-client.sh embedded -j <flink-runtime-directory>/iceberg-flink-runtime-xxx.jar shell

By default, iceberg has included hadoop jars for hadoop catalog. If we want to use hive catalog, we will need to load the hive jars when opening the flink sql client. Fortunately, apache flink has provided a bundled hive jar for sql client. So we could open the sql client as the following:

# HADOOP_HOME is your hadoop root directory after unpack the binary package.
export HADOOP_CLASSPATH=`$HADOOP_HOME/bin/hadoop classpath`

# download Iceberg dependency
ICEBERG_VERSION=0.11.1
MAVEN_URL=https://repo1.maven.org/maven2
ICEBERG_MAVEN_URL=${MAVEN_URL}/org/apache/iceberg
ICEBERG_PACKAGE=iceberg-flink-runtime
wget ${ICEBERG_MAVEN_URL}/${ICEBERG_PACKAGE}/${ICEBERG_VERSION}/${ICEBERG_PACKAGE}-${ICEBERG_VERSION}.jar

# download the flink-sql-connector-hive-${HIVE_VERSION}_${SCALA_VERSION}-${FLINK_VERSION}.jar
HIVE_VERSION=2.3.6
SCALA_VERSION=2.11
FLINK_VERSION=1.11.0
FLINK_CONNECTOR_URL=${MAVEN_URL}/org/apache/flink
FLINK_CONNECTOR_PACKAGE=flink-sql-connector-hive
wget ${FLINK_CONNECTOR_URL}/${FLINK_CONNECTOR_PACKAGE}-${HIVE_VERSION}_${SCALA_VERSION}/${FLINK_VERSION}/${FLINK_CONNECTOR_PACKAGE}-${HIVE_VERSION}_${SCALA_VERSION}-${FLINK_VERSION}.jar

# open the SQL client.
/path/to/bin/sql-client.sh embedded \
    -j ${ICEBERG_PACKAGE}-${ICEBERG_VERSION}.jar \
    -j ${FLINK_CONNECTOR_PACKAGE}-${HIVE_VERSION}_${SCALA_VERSION}-${FLINK_VERSION}.jar \
    shell

Preparation when using Flink's Python API

Install the Apache Flink dependency using pip

pip install apache-flink==1.11.1

In order for pyflink to function properly, it needs to have access to all Hadoop jars. For pyflink we need to copy those Hadoop jars to the installation directory of pyflink, which can be found under <PYTHON_ENV_INSTALL_DIR>/site-packages/pyflink/lib/ (see also a mention of this on the Flink ML). We can use the following short Python script to copy all Hadoop jars (you need to make sure that HADOOP_HOME points to your Hadoop installation):

import os
import shutil
import site


def copy_all_hadoop_jars_to_pyflink():
    if not os.getenv("HADOOP_HOME"):
        raise Exception("The HADOOP_HOME env var must be set and point to a valid Hadoop installation")

    jar_files = []

    def find_pyflink_lib_dir():
        for dir in site.getsitepackages():
            package_dir = os.path.join(dir, "pyflink", "lib")
            if os.path.exists(package_dir):
                return package_dir
        return None

    for root, _, files in os.walk(os.getenv("HADOOP_HOME")):
        for file in files:
            if file.endswith(".jar"):
                jar_files.append(os.path.join(root, file))

    pyflink_lib_dir = find_pyflink_lib_dir()

    num_jar_files = len(jar_files)
    print(f"Copying {num_jar_files} Hadoop jar files to pyflink's lib directory at {pyflink_lib_dir}")
    for jar in jar_files:
        shutil.copy(jar, pyflink_lib_dir)


if __name__ == '__main__':
    copy_all_hadoop_jars_to_pyflink()

Once the script finished, you should see output similar to

Copying 645 Hadoop jar files to pyflink's lib directory at <PYTHON_DIR>/lib/python3.8/site-packages/pyflink/lib

Now we need to provide a file:// path to the iceberg-flink-runtime jar, which we can either get by building the project and looking at <iceberg-root-dir>/flink-runtime/build/libs, or downloading it from the Apache official repository. Third-party libs can be added to pyflink via env.add_jars("file:///my/jar/path/connector.jar") / table_env.get_config().get_configuration().set_string("pipeline.jars", "file:///my/jar/path/connector.jar"), which is also mentioned in the official docs. In our example we're using env.add_jars(..) as shown below:

import os

from pyflink.datastream import StreamExecutionEnvironment

env = StreamExecutionEnvironment.get_execution_environment()
iceberg_flink_runtime_jar = os.path.join(os.getcwd(), "iceberg-flink-runtime-{{% icebergVersion %}}.jar")

env.add_jars("file://{}".format(iceberg_flink_runtime_jar))

Once we reached this point, we can then create a StreamTableEnvironment and execute Flink SQL statements. The below example shows how to create a custom catalog via the Python Table API:

from pyflink.table import StreamTableEnvironment
table_env = StreamTableEnvironment.create(env)
table_env.execute_sql("CREATE CATALOG my_catalog WITH ("
                      "'type'='iceberg', "
                      "'catalog-impl'='com.my.custom.CatalogImpl', "
                      "'my-additional-catalog-config'='my-value')")

For more details, please refer to the Python Table API.

Creating catalogs and using catalogs.

Flink 1.11 support to create catalogs by using flink sql.

Catalog Configuration

A catalog is created and named by executing the following query (replace <catalog_name> with your catalog name and <config_key>=<config_value> with catalog implementation config):

CREATE CATALOG <catalog_name> WITH (
  'type'='iceberg',
  `<config_key>`=`<config_value>`
);

The following properties can be set globally and are not limited to a specific catalog implementation:

  • type: Must be iceberg. (required)
  • catalog-type: hive or hadoop for built-in catalogs, or left unset for custom catalog implementations using catalog-impl. (Optional)
  • catalog-impl: The fully-qualified class name of a custom catalog implementation. Must be set if catalog-type is unset. (Optional)
  • property-version: Version number to describe the property version. This property can be used for backwards compatibility in case the property format changes. The current property version is 1. (Optional)
  • cache-enabled: Whether to enable catalog cache, default value is true

Hive catalog

This creates an iceberg catalog named hive_catalog that can be configured using 'catalog-type'='hive', which loads tables from a hive metastore:

CREATE CATALOG hive_catalog WITH (
  'type'='iceberg',
  'catalog-type'='hive',
  'uri'='thrift://localhost:9083',
  'clients'='5',
  'property-version'='1',
  'warehouse'='hdfs://nn:8020/warehouse/path'
);

The following properties can be set if using the Hive catalog:

  • uri: The Hive metastore's thrift URI. (Required)
  • clients: The Hive metastore client pool size, default value is 2. (Optional)
  • warehouse: The Hive warehouse location, users should specify this path if neither set the hive-conf-dir to specify a location containing a hive-site.xml configuration file nor add a correct hive-site.xml to classpath.
  • hive-conf-dir: Path to a directory containing a hive-site.xml configuration file which will be used to provide custom Hive configuration values. The value of hive.metastore.warehouse.dir from <hive-conf-dir>/hive-site.xml (or hive configure file from classpath) will be overwrote with the warehouse value if setting both hive-conf-dir and warehouse when creating iceberg catalog.
  • hadoop-conf-dir: Path to a directory containing core-site.xml and hdfs-site.xml configuration files which will be used to provide custom Hadoop configuration values.

Hadoop catalog

Iceberg also supports a directory-based catalog in HDFS that can be configured using 'catalog-type'='hadoop':

CREATE CATALOG hadoop_catalog WITH (
  'type'='iceberg',
  'catalog-type'='hadoop',
  'warehouse'='hdfs://nn:8020/warehouse/path',
  'property-version'='1'
);

The following properties can be set if using the Hadoop catalog:

  • warehouse: The HDFS directory to store metadata files and data files. (Required)

We could execute the sql command USE CATALOG hive_catalog to set the current catalog.

Custom catalog

Flink also supports loading a custom Iceberg Catalog implementation by specifying the catalog-impl property. Here is an example:

CREATE CATALOG my_catalog WITH (
  'type'='iceberg',
  'catalog-impl'='com.my.custom.CatalogImpl',
  'my-additional-catalog-config'='my-value'
);

Create through YAML config

Catalogs can be registered in sql-client-defaults.yaml before starting the SQL client. Here is an example:

catalogs: 
  - name: my_catalog
    type: iceberg
    catalog-type: hadoop
    warehouse: hdfs://nn:8020/warehouse/path

Create through SQL Files

Since the sql-client-defaults.yaml file was removed in flink 1.14, SQL Client supports the -i startup option to execute an initialization SQL file to setup environment when starting up the SQL Client. An example of such a file is presented below.

-- define available catalogs
CREATE CATALOG hive_catalog WITH (
  'type'='iceberg',
  'catalog-type'='hive',
  'uri'='thrift://localhost:9083',
  'warehouse'='hdfs://nn:8020/warehouse/path'
);

USE CATALOG hive_catalog;

using -i <init.sql> option to initialize SQL Client session

/path/to/bin/sql-client.sh -i /path/to/init.sql

DDL commands

CREATE DATABASE

By default, iceberg will use the default database in flink. Using the following example to create a separate database if we don't want to create tables under the default database:

CREATE DATABASE iceberg_db;
USE iceberg_db;

CREATE TABLE

CREATE TABLE `hive_catalog`.`default`.`sample` (
    id BIGINT COMMENT 'unique id',
    data STRING
);

Table create commands support the most commonly used flink create clauses now, including:

  • PARTITION BY (column1, column2, ...) to configure partitioning, apache flink does not yet support hidden partitioning.
  • COMMENT 'table document' to set a table description.
  • WITH ('key'='value', ...) to set table configuration which will be stored in apache iceberg table properties.

Currently, it does not support computed column, primary key and watermark definition etc.

PARTITIONED BY

To create a partition table, use PARTITIONED BY:

CREATE TABLE `hive_catalog`.`default`.`sample` (
    id BIGINT COMMENT 'unique id',
    data STRING
) PARTITIONED BY (data);

Apache Iceberg support hidden partition but apache flink don't support partitioning by a function on columns, so we've no way to support hidden partition in flink DDL now, we will improve apache flink DDL in future.

CREATE TABLE LIKE

To create a table with the same schema, partitioning, and table properties as another table, use CREATE TABLE LIKE.

CREATE TABLE `hive_catalog`.`default`.`sample` (
    id BIGINT COMMENT 'unique id',
    data STRING
);

CREATE TABLE  `hive_catalog`.`default`.`sample_like` LIKE `hive_catalog`.`default`.`sample`;

For more details, refer to the Flink CREATE TABLE documentation.

ALTER TABLE

Iceberg only support altering table properties in flink 1.11 now.

ALTER TABLE `hive_catalog`.`default`.`sample` SET ('write.format.default'='avro')

ALTER TABLE .. RENAME TO

ALTER TABLE `hive_catalog`.`default`.`sample` RENAME TO `hive_catalog`.`default`.`new_sample`;

DROP TABLE

To delete a table, run:

DROP TABLE `hive_catalog`.`default`.`sample`;

Querying with SQL

Iceberg support both streaming and batch read in flink now. we could execute the following sql command to switch the execute type from 'streaming' mode to 'batch' mode, and vice versa:

-- Execute the flink job in streaming mode for current session context
SET execution.runtime-mode = streaming;

-- Execute the flink job in batch mode for current session context
SET execution.runtime-mode = batch;

Flink batch read

If want to check all the rows in iceberg table by submitting a flink batch job, you could execute the following sentences:

-- Execute the flink job in batch mode for current session context
SET execution.runtime-mode = batch;
SELECT * FROM sample       ;

Flink streaming read

Iceberg supports processing incremental data in flink streaming jobs which starts from a historical snapshot-id:

-- Submit the flink job in streaming mode for current session.
SET execution.runtime-mode = streaming;

-- Enable this switch because streaming read SQL will provide few job options in flink SQL hint options.
SET table.dynamic-table-options.enabled=true;

-- Read all the records from the iceberg current snapshot, and then read incremental data starting from that snapshot.
SELECT * FROM sample /*+ OPTIONS('streaming'='true', 'monitor-interval'='1s')*/ ;

-- Read all incremental data starting from the snapshot-id '3821550127947089987' (records from this snapshot will be excluded).
SELECT * FROM sample /*+ OPTIONS('streaming'='true', 'monitor-interval'='1s', 'start-snapshot-id'='3821550127947089987')*/ ;

Those are the options that could be set in flink SQL hint options for streaming job:

  • monitor-interval: time interval for consecutively monitoring newly committed data files (default value: '10s').
  • start-snapshot-id: the snapshot id that streaming job starts from.

FLIP-27 source for SQL

Here are the SQL settings for the FLIP-27 source, which is only available for Flink 1.14 or above. All other SQL settings and options documented above are applicable to the FLIP-27 source.

-- Opt in the FLIP-27 source. Default is false.
SET table.exec.iceberg.use-flip27-source = true;

Writing with SQL

Iceberg support both INSERT INTO and INSERT OVERWRITE in flink 1.11 now.

INSERT INTO

To append new data to a table with a flink streaming job, use INSERT INTO:

INSERT INTO `hive_catalog`.`default`.`sample` VALUES (1, 'a');
INSERT INTO `hive_catalog`.`default`.`sample` SELECT id, data from other_kafka_table;

INSERT OVERWRITE

To replace data in the table with the result of a query, use INSERT OVERWRITE in batch job (flink streaming job does not support INSERT OVERWRITE). Overwrites are atomic operations for Iceberg tables.

Partitions that have rows produced by the SELECT query will be replaced, for example:

INSERT OVERWRITE sample VALUES (1, 'a');

Iceberg also support overwriting given partitions by the select values:

INSERT OVERWRITE `hive_catalog`.`default`.`sample` PARTITION(data='a') SELECT 6;

For a partitioned iceberg table, when all the partition columns are set a value in PARTITION clause, it is inserting into a static partition, otherwise if partial partition columns (prefix part of all partition columns) are set a value in PARTITION clause, it is writing the query result into a dynamic partition. For an unpartitioned iceberg table, its data will be completely overwritten by INSERT OVERWRITE.

UPSERT

Iceberg supports UPSERT based on the primary key when writing data into v2 table format. There are two ways to enable upsert.

  1. Enable the UPSERT mode as table-level property write.upsert.enabled. Here is an example SQL statement to set the table property when creating a table. It would be applied for all write paths to this table (batch or streaming) unless overwritten by write options as described later.
CREATE TABLE `hive_catalog`.`default`.`sample` (
  `id`  INT UNIQUE COMMENT 'unique id',
  `data` STRING NOT NULL,
 PRIMARY KEY(`id`) NOT ENFORCED
) with ('format-version'='2', 'write.upsert.enabled'='true');
  1. Enabling UPSERT mode using upsert-enabled in the [write options](#Write options) provides more flexibility than a table level config. Note that you still need to use v2 table format and specify the primary key when creating the table.
INSERT INTO tableName /*+ OPTIONS('upsert-enabled'='true') */
...

{{< hint info >}} OVERWRITE and UPSERT can't be set together. In UPSERT mode, if the table is partitioned, the partition fields should be included in equality fields. {{< /hint >}}

Reading with DataStream

Iceberg support streaming or batch read in Java API now.

Batch Read

This example will read all records from iceberg table and then print to the stdout console in flink batch job:

StreamExecutionEnvironment env = StreamExecutionEnvironment.createLocalEnvironment();
TableLoader tableLoader = TableLoader.fromHadoopTable("hdfs://nn:8020/warehouse/path");
DataStream<RowData> batch = FlinkSource.forRowData()
     .env(env)
     .tableLoader(tableLoader)
     .streaming(false)
     .build();

// Print all records to stdout.
batch.print();

// Submit and execute this batch read job.
env.execute("Test Iceberg Batch Read");

Streaming read

This example will read incremental records which start from snapshot-id '3821550127947089987' and print to stdout console in flink streaming job:

StreamExecutionEnvironment env = StreamExecutionEnvironment.createLocalEnvironment();
TableLoader tableLoader = TableLoader.fromHadoopTable("hdfs://nn:8020/warehouse/path");
DataStream<RowData> stream = FlinkSource.forRowData()
     .env(env)
     .tableLoader(tableLoader)
     .streaming(true)
     .startSnapshotId(3821550127947089987L)
     .build();

// Print all records to stdout.
stream.print();

// Submit and execute this streaming read job.
env.execute("Test Iceberg Streaming Read");

There are other options that we could set by Java API, please see the [FlinkSource#Builder](../../../javadoc/{{% icebergVersion %}}/org/apache/iceberg/flink/source/FlinkSource.html).

Reading with DataStream (FLIP-27 source)

FLIP-27 source interface was introduced in Flink 1.12. It aims to solve several shortcomings of the old SourceFunction streaming source interface. It also unifies the source interfaces for both batch and streaming executions. Most source connectors (like Kafka, file) in Flink repo have migrated to the FLIP-27 interface. Flink is planning to deprecate the old SourceFunction interface in the near future.

A FLIP-27 based Flink IcebergSource is added in iceberg-flink module for Flink 1.14 or above. The FLIP-27 IcebergSource is currently an experimental feature.

Batch Read

This example will read all records from iceberg table and then print to the stdout console in flink batch job:

StreamExecutionEnvironment env = StreamExecutionEnvironment.createLocalEnvironment();
TableLoader tableLoader = TableLoader.fromHadoopTable("hdfs://nn:8020/warehouse/path");

IcebergSource<RowData> source = IcebergSource.forRowData()
    .tableLoader(tableLoader)
    .assignerFactory(new SimpleSplitAssignerFactory())
    .build();

DataStream<RowData> batch = env.fromSource(
    source,
    WatermarkStrategy.noWatermarks(),
    "My Iceberg Source",
    TypeInformation.of(RowData.class));

// Print all records to stdout.
batch.print();

// Submit and execute this batch read job.
env.execute("Test Iceberg Batch Read");

Streaming read

This example will start the streaming read from the latest table snapshot (inclusive). Every 60s, it polls Iceberg table to discover new append-only snapshots. CDC read is not supported yet.

StreamExecutionEnvironment env = StreamExecutionEnvironment.createLocalEnvironment();
TableLoader tableLoader = TableLoader.fromHadoopTable("hdfs://nn:8020/warehouse/path");

IcebergSource source = IcebergSource.forRowData()
    .tableLoader(tableLoader)
    .assignerFactory(new SimpleSplitAssignerFactory())
    .streaming(true)
    .streamingStartingStrategy(StreamingStartingStrategy.INCREMENTAL_FROM_LATEST_SNAPSHOT)
    .monitorInterval(Duration.ofSeconds(60))
    .build()

DataStream<RowData> stream = env.fromSource(
    source,
    WatermarkStrategy.noWatermarks(),
    "My Iceberg Source",
    TypeInformation.of(RowData.class));

// Print all records to stdout.
stream.print();

// Submit and execute this streaming read job.
env.execute("Test Iceberg Streaming Read");

There are other options that we could set by Java API, please see the [IcebergSource#Builder](../../../javadoc/{{% icebergVersion %}}/org/apache/iceberg/flink/source/IcebergSource.html).

Writing with DataStream

Iceberg support writing to iceberg table from different DataStream input.

Appending data.

we have supported writing DataStream<RowData> and DataStream<Row> to the sink iceberg table natively.

StreamExecutionEnvironment env = ...;

DataStream<RowData> input = ... ;
Configuration hadoopConf = new Configuration();
TableLoader tableLoader = TableLoader.fromHadoopTable("hdfs://nn:8020/warehouse/path", hadoopConf);

FlinkSink.forRowData(input)
    .tableLoader(tableLoader)
    .build();

env.execute("Test Iceberg DataStream");

The iceberg API also allows users to write generic DataStream<T> to iceberg table, more example could be found in this unit test.

Overwrite data

To overwrite the data in existing iceberg table dynamically, we could set the overwrite flag in FlinkSink builder.

StreamExecutionEnvironment env = ...;

DataStream<RowData> input = ... ;
Configuration hadoopConf = new Configuration();
TableLoader tableLoader = TableLoader.fromHadoopTable("hdfs://nn:8020/warehouse/path", hadoopConf);

FlinkSink.forRowData(input)
    .tableLoader(tableLoader)
    .overwrite(true)
    .build();

env.execute("Test Iceberg DataStream");

Upsert data

To upsert the data in existing iceberg table, we could set the upsert flag in FlinkSink builder. The table must use v2 table format and have a primary key.

StreamExecutionEnvironment env = ...;

DataStream<RowData> input = ... ;
Configuration hadoopConf = new Configuration();
TableLoader tableLoader = TableLoader.fromHadoopTable("hdfs://nn:8020/warehouse/path", hadoopConf);

FlinkSink.forRowData(input)
    .tableLoader(tableLoader)
    .upsert(true)
    .build();

env.execute("Test Iceberg DataStream");

{{< hint info >}} OVERWRITE and UPSERT can't be set together. In UPSERT mode, if the table is partitioned, the partition fields should be included in equality fields. {{< /hint >}}

Write options

Flink write options are passed when configuring the FlinkSink, like this:

FlinkSink.Builder builder = FlinkSink.forRow(dataStream, SimpleDataUtil.FLINK_SCHEMA)
    .table(table)
    .tableLoader(tableLoader)
    .set("write-format", "orc")
    .set(FlinkWriteOptions.OVERWRITE_MODE, "true");

For Flink SQL, write options can be passed in via SQL hints like this:

INSERT INTO tableName /*+ OPTIONS('upsert-enabled'='true') */
...
Flink option Default Description
write-format Table write.format.default File format to use for this write operation; parquet, avro, or orc
target-file-size-bytes As per table property Overrides this table's write.target-file-size-bytes
upsert-enabled Table write.upsert.enabled Overrides this table's write.upsert.enabled
overwrite-enabled false Overwrite the table's data, overwrite mode shouldn't be enable when configuring to use UPSERT data stream.
distribution-mode Table write.distribution-mode Overrides this table's write.distribution-mode
compression-codec Table write.(fileformat).compression-codec Overrides this table's compression codec for this write
compression-level Table write.(fileformat).compression-level Overrides this table's compression level for Parquet and Avro tables for this write
compression-strategy Table write.orc.compression-strategy Overrides this table's compression strategy for ORC tables for this write

Inspecting tables.

Iceberg does not support inspecting table in flink sql now, we need to use iceberg's Java API to read iceberg's meta data to get those table information.

Rewrite files action.

Iceberg provides API to rewrite small files into large files by submitting flink batch job. The behavior of this flink action is the same as the spark's rewriteDataFiles.

import org.apache.iceberg.flink.actions.Actions;

TableLoader tableLoader = TableLoader.fromHadoopTable("hdfs://nn:8020/warehouse/path");
Table table = tableLoader.loadTable();
RewriteDataFilesActionResult result = Actions.forTable(table)
        .rewriteDataFiles()
        .execute();

For more doc about options of the rewrite files action, please see [RewriteDataFilesAction](../../../javadoc/{{% icebergVersion %}}/org/apache/iceberg/flink/actions/RewriteDataFilesAction.html)

Type conversion

Iceberg's integration for Flink automatically converts between Flink and Iceberg types. When writing to a table with types that are not supported by Flink, like UUID, Iceberg will accept and convert values from the Flink type.

Flink to Iceberg

Flink types are converted to Iceberg types according to the following table:

Flink Iceberg Notes
boolean boolean
tinyint integer
smallint integer
integer integer
bigint long
float float
double double
char string
varchar string
string string
binary binary
varbinary fixed
decimal decimal
date date
time time
timestamp timestamp without timezone
timestamp_ltz timestamp with timezone
array list
map map
multiset map
row struct
raw Not supported
interval Not supported
structured Not supported
timestamp with zone Not supported
distinct Not supported
null Not supported
symbol Not supported
logical Not supported

Iceberg to Flink

Iceberg types are converted to Flink types according to the following table:

Iceberg Flink
boolean boolean
struct row
list array
map map
integer integer
long bigint
float float
double double
date date
time time
timestamp without timezone timestamp(6)
timestamp with timezone timestamp_ltz(6)
string varchar(2147483647)
uuid binary(16)
fixed(N) binary(N)
binary varbinary(2147483647)
decimal(P, S) decimal(P, S)

Future improvement.

There are some features that we do not yet support in the current flink iceberg integration work:

  • Don't support creating iceberg table with hidden partitioning. Discussion in flink mail list.
  • Don't support creating iceberg table with computed column.
  • Don't support creating iceberg table with watermark.
  • Don't support adding columns, removing columns, renaming columns, changing columns. FLINK-19062 is tracking this.