read_statestore table-valued function

Applies to: Databricks SQL Databricks Runtime 14.3 and above

A table valued function for reading records from the state store of streaming queries. The returned relation only supports running as a batch query.

Syntax

read_statestore ( path [, option_key => option_value ] [ ... ] )

Arguments

read_statestore requires named parameter invocation for its optional parameters.

• path: A STRING literal. The path of the streaming query checkpoint location.
• option_key: The name of the option to configure. You need to use backticks (`) for options that contain dots (.).
• option_value: A constant expression to set the option to. Accepts literals and scalar functions.

All option_values are case-insensitive.

option_key	Type	Default	Description
batchId	BIGINT	latest batch id	Represents the target batch to read from. This option is used when users want to perform time-travel. The batch should be committed but not yet cleaned up.
OperatorId	BIGINT	0	Represents the target operator to read from. This option is used when the query is using multiple stateful operators.
storeName	STRING	'DEFAULT'	Represents the target side to read from. This option is used when users want to read the state from stream-stream join.
joinSide	STRING	'None'	Represents the target side to read from. This option is used when users want to read the state from stream-stream join. One of: 'Left', 'Right', 'None'.

Returns

The function returns a result set with the following columns.

注記

The nested columns for key and value heavily depend on the input schema of the stateful operator and the type of operator.

Name	Data type	Nullable	Standard	Description
id	STRUCT	No	Key row of the stateful operator stored in the state checkpoint.
value	STRUCT	Yes	Value row of the stateful operator stored in the state checkpoint.
partition_id	INTEGER	No	The partition that contains the record.
shardId	STRING	No	A unique identifier for the shard where the data was read from.
sequenceNumber	BIGINT	No	The unique identifier of the record within its shard.
approximateArrivalTimestamp	TIMESTAMP	No	The approximate time that the record was inserted into the stream.

Examples

SQL

- Read from state
> SELECT * FROM read_statestore('/checkpoint/path');

– Read from state with storeName option
> SELECT * FROM read_statestore(
      '/checkpoint/path',
      operatorId => 0,
      batchId => 2,
      storeName => 'default'
  );

– Read from state with joinSide option

> SELECT * FROM read_statestore(
      '/checkpoint/path',
      joinSide => 'left'
  );

Related functions

• read_files table-valued function
• read_kafka table-valued function
• read_kinesis streaming table-valued function