Package org.apache.beam.sdk.io.clickhouse

Class ClickHouseIO

java.lang.Object

org.apache.beam.sdk.io.clickhouse.ClickHouseIO

public class ClickHouseIO
extends Object

An IO to write to ClickHouse.

Writing to ClickHouse

To write to ClickHouse, use write(String, String), which writes elements from input PCollection. It's required that your ClickHouse cluster already has table you are going to insert into.

 pipeline
   .apply(...)
   .apply(
     ClickHouseIO.<POJO>write("jdbc:clickhouse:localhost:8123/default", "my_table"));
 

Optionally, you can provide connection settings, for instance, specify insert block size with ClickHouseIO.Write.withMaxInsertBlockSize(long), or configure number of retries with ClickHouseIO.Write.withMaxRetries(int).

Deduplication

Deduplication is performed by ClickHouse if inserting to ReplicatedMergeTree or Distributed table on top of ReplicatedMergeTree. Without replication, inserting into regular MergeTree can produce duplicates, if insert fails, and then successfully retries. However, each block is inserted atomically, and you can configure block size with ClickHouseIO.Write.withMaxInsertBlockSize(long).

Deduplication is performed using checksums of inserted blocks.

Mapping between Beam and ClickHouse types

ClickHouse	Beam
TableSchema.TypeName.FLOAT32	Schema.TypeName.FLOAT
TableSchema.TypeName.FLOAT64	Schema.TypeName.DOUBLE
TableSchema.TypeName.FIXEDSTRING	FixedBytes
TableSchema.TypeName.INT8	Schema.TypeName.BYTE
TableSchema.TypeName.INT16	Schema.TypeName.INT16
TableSchema.TypeName.INT32	Schema.TypeName.INT32
TableSchema.TypeName.INT64	Schema.TypeName.INT64
TableSchema.TypeName.STRING	Schema.TypeName.STRING
TableSchema.TypeName.UINT8	Schema.TypeName.INT16
TableSchema.TypeName.UINT16	Schema.TypeName.INT32
TableSchema.TypeName.UINT32	Schema.TypeName.INT64
TableSchema.TypeName.UINT64	Schema.TypeName.INT64
TableSchema.TypeName.DATE	Schema.TypeName.DATETIME
TableSchema.TypeName.DATETIME	Schema.TypeName.DATETIME
TableSchema.TypeName.ARRAY	Schema.TypeName.ARRAY
TableSchema.TypeName.ENUM8	Schema.TypeName.STRING
TableSchema.TypeName.ENUM16	Schema.TypeName.STRING
TableSchema.TypeName.BOOL	Schema.TypeName.BOOLEAN
TableSchema.TypeName.TUPLE	Schema.TypeName.ROW

Nullable row columns are supported through Nullable type in ClickHouse. Low cardinality hint is supported through LowCardinality DataType in ClickHouse.

Nested rows should be unnested using Select.flattenedSchema(). Type casting should be done using Cast before ClickHouseIO.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ClickHouseIO.Write<T>	A PTransform to write to ClickHouse.

Field Summary

Fields

Modifier and Type	Field	Description
static final Duration	DEFAULT_INITIAL_BACKOFF
static final Duration	DEFAULT_MAX_CUMULATIVE_BACKOFF
static final long	DEFAULT_MAX_INSERT_BLOCK_SIZE
static final int	DEFAULT_MAX_RETRIES

Constructor Summary

Constructors

Constructor	Description
ClickHouseIO()

Method Summary

Modifier and Type	Method	Description
static TableSchema	getTableSchema(String jdbcUrl, String table)	Returns TableSchema for a given table.
static <T> ClickHouseIO.Write<T>	write(String jdbcUrl, String table)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

DEFAULT_MAX_INSERT_BLOCK_SIZE

public static final long DEFAULT_MAX_INSERT_BLOCK_SIZE

See Also:

• Constant Field Values

DEFAULT_MAX_RETRIES

public static final int DEFAULT_MAX_RETRIES

See Also:

• Constant Field Values

DEFAULT_MAX_CUMULATIVE_BACKOFF

public static final Duration DEFAULT_MAX_CUMULATIVE_BACKOFF

DEFAULT_INITIAL_BACKOFF

public static final Duration DEFAULT_INITIAL_BACKOFF

Constructor Details

ClickHouseIO

public ClickHouseIO()

Method Details

write

public static <T> ClickHouseIO.Write<T> write(String jdbcUrl,
 String table)

getTableSchema

public static TableSchema getTableSchema(String jdbcUrl,
 String table)

Returns TableSchema for a given table.

Parameters:

jdbcUrl - jdbc connection url

table - table name

Returns:

table schema