DataSourceStrategy Execution Planning Strategy¶

DataSourceStrategy is an execution planning strategy (of SparkPlanner) that plans LogicalRelation logical operators as RowDataSourceScanExec physical operators (possibly under FilterExec and ProjectExec logical operators).

Executing Rule¶

apply(
  plan: LogicalPlan): Seq[SparkPlan]

apply plans the given LogicalPlan into a corresponding SparkPlan.

pruneFilterProject¶

pruneFilterProject(
  relation: LogicalRelation,
  projects: Seq[NamedExpression],
  filterPredicates: Seq[Expression],
  scanBuilder: (Seq[Attribute], Array[Filter]) => RDD[InternalRow]): SparkPlan

pruneFilterProject pruneFilterProjectRaw (with scanBuilder ignoring the Seq[Expression] input argument).

pruneFilterProject is used when:

• DataSourceStrategy execution planning strategy is executed (with LogicalRelations over a PrunedFilteredScan or a PrunedScan)

Selecting Catalyst Expressions Convertible to Data Source Filter Predicates¶

selectFilters(
  relation: BaseRelation,
  predicates: Seq[Expression]): (Seq[Expression], Seq[Filter], Set[Filter])

selectFilters builds a map of Catalyst predicate expressions (from the input predicates) that can be translated to a data source filter predicate.

selectFilters then requests the input BaseRelation for unhandled filters (out of the convertible ones that selectFilters built the map with).

In the end, selectFilters returns a 3-element tuple with the following:

1. Inconvertible and unhandled Catalyst predicate expressions

2. All converted data source filters

3. Pushed-down data source filters (that the input BaseRelation can handle)

selectFilters is used when DataSourceStrategy execution planning strategy is executed (and creates a RowDataSourceScanExec physical operator).

Translating Catalyst Expression into Data Source Filter Predicate¶

translateFilter(
  predicate: Expression,
  supportNestedPredicatePushdown: Boolean): Option[Filter]

translateFilter translateFilterWithMapping (with the input parameters and an undefined (None) translatedFilterToExpr).

translateFilter is used when:

• FileSourceScanExec physical operator is requested for the pushedDownFilters
• DataSourceStrategy execution planning strategy is requested to selectFilters
• FileSourceStrategy execution planning strategy is executed
• DataSourceV2Strategy execution planning strategy is executed
• V2Writes is requested to apply

translateFilterWithMapping¶

translateFilterWithMapping(
  predicate: Expression,
  translatedFilterToExpr: Option[mutable.HashMap[sources.Filter, Expression]],
  nestedPredicatePushdownEnabled: Boolean): Option[Filter]

translateFilterWithMapping translates the input Catalyst Expression to a Data Source Filter predicate.

translateFilterWithMapping branches off based on the given predicate expression:

• For Ands, translateFilterWithMapping translateFilterWithMapping with the left and right expressions and creates a And filter

• For Ors, translateFilterWithMapping translateFilterWithMapping with the left and right expressions and creates a Or filter

• For Nots, translateFilterWithMapping translateFilterWithMapping with the child expression and creates a Not filter

• For all the other cases, translateFilterWithMapping translateLeafNodeFilter and, if successful, adds the filter and the predicate expression to translatedFilterToExpr collection

translateFilterWithMapping is used when:

• DataSourceStrategy is requested to translateFilter
• PushDownUtils is requested to pushFilters

translateLeafNodeFilter¶

translateLeafNodeFilter(
  predicate: Expression,
  pushableColumn: PushableColumnBase): Option[Filter]

translateLeafNodeFilter translates a given Catalyst Expression into a corresponding Filter predicate if possible. If not, translateFilter returns None.

RDD Conversion (Converting RDD of Rows to Catalyst RDD of InternalRows)¶

toCatalystRDD(
  relation: LogicalRelation,
  output: Seq[Attribute],
  rdd: RDD[Row]): RDD[InternalRow]
toCatalystRDD(
  relation: LogicalRelation,
  rdd: RDD[Row]) // <1>

toCatalystRDD branches off per the needConversion flag of the BaseRelation of the input LogicalRelation:

• when true, toCatalystRDD converts the objects inside Rows to Catalyst types.

• otherwise, toCatalystRDD casts the input RDD[Row] to an RDD[InternalRow] (using Java's asInstanceOf operator)

toCatalystRDD is used when DataSourceStrategy execution planning strategy is executed (for all kinds of BaseRelations).

Creating RowDataSourceScanExec Physical Operator for LogicalRelation¶

pruneFilterProjectRaw(
  relation: LogicalRelation,
  projects: Seq[NamedExpression],
  filterPredicates: Seq[Expression],
  scanBuilder: (Seq[Attribute], Seq[Expression], Seq[Filter]) => RDD[InternalRow]): SparkPlan

pruneFilterProjectRaw converts the given LogicalRelation leaf logical operator into a RowDataSourceScanExec leaf physical operator with the LogicalRelation leaf logical operator (possibly as a child of a FilterExec and a ProjectExec unary physical operators).

Internally, pruneFilterProjectRaw splits the input filterPredicates expressions to select the Catalyst expressions that can be converted to data source filter predicates (and handled by the underlying BaseRelation of the LogicalRelation).

pruneFilterProjectRaw combines all expressions that are neither convertible to data source filters nor can be handled by the relation using And binary expression (that creates a so-called filterCondition that will eventually be used to create a FilterExec physical operator if non-empty).

pruneFilterProjectRaw creates a RowDataSourceScanExec leaf physical operator.

Demo¶

import org.apache.spark.sql.execution.datasources.DataSourceStrategy
val strategy = DataSourceStrategy(spark.sessionState.conf)

import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
val plan: LogicalPlan = ???

val sparkPlan = strategy(plan).head