MehulBatra commented on code in PR #1640: URL: https://github.com/apache/fluss/pull/1640#discussion_r2322529271
########## website/docs/streaming-lakehouse/integrate-data-lakes/iceberg.md: ########## @@ -0,0 +1,343 @@ +--- +title: Iceberg +sidebar_position: 2 +--- + +# Iceberg + +[Apache Iceberg](https://iceberg.apache.org/) is an open table format for huge analytic datasets. It provides ACID transactions, schema evolution, and efficient data organization for data lakes. +To integrate Fluss with Iceberg, you must enable lakehouse storage and configure Iceberg as the lakehouse storage. For more details, see [Enable Lakehouse Storage](maintenance/tiered-storage/lakehouse-storage.md#enable-lakehouse-storage). + +## Introduction + +When a table is created or altered with the option `'table.datalake.enabled' = 'true'` and configured with Iceberg as the datalake format, Fluss will automatically create a corresponding Iceberg table with the same table path. +The schema of the Iceberg table matches that of the Fluss table, except for the addition of three system columns at the end: `__bucket`, `__offset`, and `__timestamp`. +These system columns help Fluss clients consume data from Iceberg in a streaming fashion, such as seeking by a specific bucket using an offset or timestamp. + +```sql title="Flink SQL" +USE CATALOG fluss_catalog; + +CREATE TABLE fluss_order_with_lake ( + `order_key` BIGINT, + `cust_key` INT NOT NULL, + `total_price` DECIMAL(15, 2), + `order_date` DATE, + `order_priority` STRING, + `clerk` STRING, + `ptime` AS PROCTIME(), + PRIMARY KEY (`order_key`) NOT ENFORCED + ) WITH ( + 'table.datalake.enabled' = 'true', + 'table.datalake.freshness' = '30s' +); +``` + +Then, the datalake tiering service continuously tiers data from Fluss to Iceberg. The parameter `table.datalake.freshness` controls the frequency that Fluss writes data to Iceberg tables. By default, the data freshness is 3 minutes. +For primary key tables, changelogs are also generated in the Iceberg format, enabling stream-based consumption via Iceberg APIs. Primary key tables use merge-on-read (MOR) strategy for efficient updates and deletes. + +Since Fluss version 0.8, you can also specify Iceberg table properties when creating a datalake-enabled Fluss table by using the `iceberg.` prefix within the Fluss table properties clause. + +```sql title="Flink SQL" +CREATE TABLE fluss_order_with_lake ( + `order_key` BIGINT, + `cust_key` INT NOT NULL, + `total_price` DECIMAL(15, 2), + `order_date` DATE, + `order_priority` STRING, + `clerk` STRING, + `ptime` AS PROCTIME(), + PRIMARY KEY (`order_key`) NOT ENFORCED + ) WITH ( + 'table.datalake.enabled' = 'true', + 'table.datalake.freshness' = '30s', + 'table.datalake.auto-maintenance' = 'true', + 'iceberg.write.format.default' = 'parquet', + 'iceberg.commit.retry.num-retries' = '5' +); +``` + +For example, you can specify the Iceberg property `write.format.default` to change the file format of the Iceberg table, or set `commit.retry.num-retries` to configure retry behavior for commits. The `table.datalake.auto-maintenance` option (true by default) enables automatic maintenance tasks such as file compaction and snapshot expiration. + +## Table Types and Bucketing Strategy + +Fluss uses a special bucketing strategy when integrating with Iceberg to ensure data distribution consistency between Fluss and Iceberg layers. This enables efficient data access and future union read capabilities. + +### Bucket Strategy + +When Iceberg is configured as the datalake format, Fluss uses `IcebergBucketingFunction` to bucket data following Iceberg's bucketing strategy. This ensures: +- **Data distribution consistency**: The same record goes to the same bucket in both Fluss and Iceberg +- **Efficient data access**: You can quickly locate data for a specific Fluss bucket within Iceberg +- **Dynamic enablement**: Tables can be enabled for datalake without rewriting existing data + +### Primary Key Tables + +Primary key tables in Fluss are mapped to Iceberg tables with: +- **Primary key constraints**: The Iceberg table maintains the same primary key definition +- **Merge-on-read (MOR) strategy**: Updates and deletes are handled efficiently using Iceberg's MOR capabilities +- **Required bucket keys**: Primary key tables must have exactly one bucket key defined +- **Bucket partitioning**: Automatically partitioned by the bucket key using Iceberg's bucket transform + +```sql title="Primary Key Table Example" +CREATE TABLE user_profiles ( + `user_id` BIGINT, + `username` STRING, + `email` STRING, + `last_login` TIMESTAMP, + `profile_data` STRING, + PRIMARY KEY (`user_id`) NOT ENFORCED +) WITH ( + 'table.datalake.enabled' = 'true', + 'bucket.num' = '4', + 'bucket.key' = 'user_id' +); +``` + +**Corresponding Iceberg table structure:** +```sql +CREATE TABLE user_profiles ( + user_id BIGINT, + username STRING, + email STRING, + last_login TIMESTAMP, + profile_data STRING, + __bucket INT, + __offset BIGINT, + __timestamp TIMESTAMP_LTZ, + PRIMARY KEY (user_id) NOT ENFORCED +) PARTITIONED BY (bucket(user_id, 4)) +SORTED BY (__offset ASC); +``` + +### Log Tables (Append-Only) + +Log tables support different bucketing configurations: + +#### No Bucket Key +For log tables without a configured bucket key, Iceberg uses identity partitioning on the `__bucket` system column: + +```sql title="Log Table without Bucket Key" +CREATE TABLE access_logs ( + `timestamp` TIMESTAMP, + `user_id` BIGINT, + `action` STRING, + `ip_address` STRING +) WITH ( + 'table.datalake.enabled' = 'true', + 'bucket.num' = '3' +); +``` + +**Corresponding Iceberg table:** +```sql +CREATE TABLE access_logs ( + timestamp TIMESTAMP, + user_id BIGINT, + action STRING, + ip_address STRING, + __bucket INT, + __offset BIGINT, + __timestamp TIMESTAMP_LTZ +) PARTITIONED BY (IDENTITY(__bucket)) +SORTED BY (__offset ASC); +``` + +#### Single Bucket Key +For log tables with one bucket key, Iceberg uses bucket partitioning: + +```sql title="Log Table with Bucket Key" +CREATE TABLE order_events ( + `order_id` BIGINT, + `item_id` BIGINT, + `amount` INT, + `event_time` TIMESTAMP +) WITH ( + 'table.datalake.enabled' = 'true', + 'bucket.num' = '5', + 'bucket.key' = 'order_id' +); +``` + +**Corresponding Iceberg table:** +```sql +CREATE TABLE order_events ( + order_id BIGINT, + item_id BIGINT, + amount INT, + event_time TIMESTAMP, + __bucket INT, + __offset BIGINT, + __timestamp TIMESTAMP_LTZ +) PARTITIONED BY (bucket(order_id, 5)) +SORTED BY (__offset ASC); +``` + +### Partitioned Tables + +For Fluss partitioned tables, Iceberg first partitions by Fluss partition keys, then by bucket keys: + +```sql title="Partitioned Table Example" +CREATE TABLE daily_sales ( + `sale_id` BIGINT, + `amount` DECIMAL(10,2), + `customer_id` BIGINT, + `sale_date` STRING, + PRIMARY KEY (`sale_id`) NOT ENFORCED +) PARTITIONED BY (`sale_date`) +WITH ( + 'table.datalake.enabled' = 'true', + 'bucket.num' = '4', + 'bucket.key' = 'sale_id' +); +``` + +**Corresponding Iceberg table:** +```sql +CREATE TABLE daily_sales ( + sale_id BIGINT, + amount DECIMAL(10,2), + customer_id BIGINT, + sale_date STRING, + __bucket INT, + __offset BIGINT, + __timestamp TIMESTAMP_LTZ, + PRIMARY KEY (sale_id) NOT ENFORCED +) PARTITIONED BY (IDENTITY(sale_date), bucket(sale_id, 4)) +SORTED BY (__offset ASC); +``` + +## Read Tables + +### Reading with Apache Flink + +For a table with the option `'table.datalake.enabled' = 'true'` and Iceberg configured as the lakehouse storage, you can read data stored in Iceberg using the `$lake` suffix in the table name. + +#### Read Data Only in Iceberg + +To read only data stored in Iceberg, use the `$lake` suffix in the table name: + +```sql title="Flink SQL" +-- Read from Iceberg +SELECT COUNT(*) FROM orders$lake; +``` + +```sql title="Flink SQL" +-- Query system tables +SELECT * FROM orders$lake$snapshots; +``` + +When you specify the `$lake` suffix, the table behaves like a standard Iceberg table with full Iceberg capabilities including time travel, system tables, and more. + +#### Union Read Limitations + +**Important**: Iceberg does not currently support union read of data from both Fluss and Iceberg layers. You can only read data from: +- **Fluss layer only**: Query the table directly without `$lake` suffix (real-time data) Review Comment: got it yes, currently Without $lake suffix: Reads all data from Fluss (both historical and fresh) - not separated by boundary With $lake suffix: Reads only tiered data from Iceberg. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@fluss.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
