com.google.cloud.spanner.watcher

Interface ShardProvider

All Known Implementing Classes:

FixedShardProvider, NotNullShardProvider, TimebasedShardProvider

public interface ShardProvider

Interface for providing a shard id for Spanner Table Change watchers. The shard id will be used by the change watcher when querying the table for the most recent changes. This can be used to prevent full table scans when polling a table.

See https://cloud.google.com/spanner/docs/schema-design#fix_hash_the_key for more information on how logical shards should be implemented in Cloud Spanner.

Method Summary

Modifier and Type	Method and Description
void	appendShardFilter(com.google.cloud.spanner.Statement.Builder statementBuilder) Appends the required sharding filter to the given statement.
default String	getColumnName() Returns the name of the column that this shard provider uses.
com.google.cloud.spanner.Value	getShardValue() Returns the (fixed) value that is used by this ShardProvider.

Method Detail

appendShardFilter

void appendShardFilter(com.google.cloud.spanner.Statement.Builder statementBuilder)

Appends the required sharding filter to the given statement. This could be an SQL fragment or one or more parameters or a combination of both.

getShardValue

@Nullable
com.google.cloud.spanner.Value getShardValue()

Returns the (fixed) value that is used by this ShardProvider. This value will be passed to the CommitTimestampRepository to indicate the last seen commit timestamp for a certain shard. This value will be null if the ShardProvider does not use a fixed value.

getColumnName

@Nullable
default String getColumnName()

Returns the name of the column that this shard provider uses.