Package org.apache.spark.sql.connector.write

Interface RowLevelOperation

All Known Subinterfaces:
SupportsDelta
@Experimental public interface RowLevelOperation
A logical representation of a data source DELETE, UPDATE, or MERGE operation that requires rewriting data.
Since:
3.3.0

  • Method Details

    • description

      default String description()
      Returns the description associated with this row-level operation.

    • command

      RowLevelOperation.Command command()
      Returns the SQL command that is being performed.

    • newScanBuilder

      ScanBuilder newScanBuilder(CaseInsensitiveStringMap options)
      Returns a ScanBuilder to configure a Scan for this row-level operation.

      Data sources fall into two categories: those that can handle a delta of rows and those that need to replace groups (e.g. partitions, files). Data sources that handle deltas allow Spark to quickly discard unchanged rows and have no requirements for input scans. Data sources that replace groups of rows can discard deleted rows but need to keep unchanged rows to be passed back into the source. This means that scans for such data sources must produce all rows in a group if any are returned. Some data sources will avoid pushing filters into files (file granularity), while others will avoid pruning files within a partition (partition granularity).

      For example, if a data source can only replace partitions, all rows from a partition must be returned by the scan, even if a filter can narrow the set of changes to a single file in the partition. Similarly, a data source that can swap individual files must produce all rows from files where at least one record must be changed, not just rows that must be changed.

      Data sources that replace groups of data (e.g. files, partitions) may prune entire groups using provided data source filters when building a scan for this row-level operation. However, such data skipping is limited as not all expressions can be converted into data source filters and some can only be evaluated by Spark (e.g. subqueries). Since rewriting groups is expensive, Spark allows group-based data sources to filter groups at runtime. The runtime filtering enables data sources to narrow down the scope of rewriting to only groups that must be rewritten. If the row-level operation scan implements SupportsRuntimeV2Filtering, Spark will execute a query at runtime to find which records match the row-level condition. The runtime group filter subquery will leverage a regular batch scan, which isn't required to produce all rows in a group if any are returned. The information about matching records will be passed back into the row-level operation scan, allowing data sources to discard groups that don't have to be rewritten.

    • newWriteBuilder

      WriteBuilder newWriteBuilder(LogicalWriteInfo info)
      Returns a WriteBuilder to configure a Write for this row-level operation.

      Note that Spark will first configure the scan and then the write, allowing data sources to pass information from the scan to the write. For example, the scan can report which condition was used to read the data that may be needed by the write under certain isolation levels. Implementations may capture the built scan or required scan information and then use it while building the write.

    • requiredMetadataAttributes

      default NamedReference[] requiredMetadataAttributes()
      Returns metadata attributes that are required to perform this row-level operation.

      Data sources that can use this method to project metadata columns needed for writing the data back (e.g. metadata columns for grouping data).