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org.apache.spark.sql.catalyst.optimizer

DecorrelateInnerQuery

object DecorrelateInnerQuery extends PredicateHelper

Decorrelate the inner query by eliminating outer references and create domain joins. The implementation is based on the paper: Unnesting Arbitrary Queries by Thomas Neumann and Alfons Kemper. https://dl.gi.de/handle/20.500.12116/2418.

A correlated subquery can be viewed as a "dependent" nested loop join between the outer and the inner query. For each row produced by the outer query, we bind the OuterReferences in in the inner query with the corresponding values in the row, and then evaluate the inner query.

Dependent Join :- Outer Query +- Inner Query

If the OuterReferences are bound to the same value, the inner query will return the same result. Based on this, we can reduce the times to evaluate the inner query by first getting all distinct values of the OuterReferences.

Normal Join :- Outer Query +- Dependent Join :- Inner Query +- Distinct Aggregate (outer_ref1, outer_ref2, ...) +- Outer Query

The distinct aggregate of the outer references is called a "domain", and the dependent join between the inner query and the domain is called a "domain join". We need to push down the domain join through the inner query until there is no outer reference in the sub-tree and the domain join will turn into a normal join.

The decorrelation function returns a new query plan with optional placeholder DomainJoinss added and a list of join conditions with the outer query. DomainJoins need to be rewritten into actual inner join between the inner query sub-tree and the outer query.

E.g. decorrelate an inner query with equality predicates:

SELECT (SELECT MIN(b) FROM t1 WHERE t2.c = t1.a) FROM t2

Aggregate [] [min(b)] Aggregate [a] [min(b), a] +- Filter (outer(c) = a) => +- Relation [t1] +- Relation [t1]

Join conditions: [c = a]

E.g. decorrelate an inner query with non-equality predicates:

SELECT (SELECT MIN(b) FROM t1 WHERE t2.c > t1.a) FROM t2

Aggregate [] [min(b)] Aggregate [c'] [min(b), c'] +- Filter (outer(c) > a) => +- Filter (c' > a) +- Relation [t1] +- DomainJoin [c'] +- Relation [t1]

Join conditions: [c <=> c']

Linear Supertypes
PredicateHelper, Logging, AliasHelper, AnyRef, Any
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  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  4. def apply(innerPlan: LogicalPlan, outerPlan: LogicalPlan, handleCountBug: Boolean = false): (LogicalPlan, Seq[Expression])
  5. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  6. def buildBalancedPredicate(expressions: Seq[Expression], op: (Expression, Expression) ⇒ Expression): Expression

    Builds a balanced output predicate in bottom up approach, by applying binary operator op pair by pair on input predicates exprs recursively.

    Builds a balanced output predicate in bottom up approach, by applying binary operator op pair by pair on input predicates exprs recursively. Example: exprs = [a, b, c, d], op = And, returns (a And b) And (c And d) exprs = [a, b, c, d, e, f], op = And, returns ((a And b) And (c And d)) And (e And f)

    Attributes
    protected
    Definition Classes
    PredicateHelper
  7. def canEvaluate(expr: Expression, plan: LogicalPlan): Boolean

    Returns true if expr can be evaluated using only the output of plan.

    Returns true if expr can be evaluated using only the output of plan. This method can be used to determine when it is acceptable to move expression evaluation within a query plan.

    For example consider a join between two relations R(a, b) and S(c, d).

    - canEvaluate(EqualTo(a,b), R) returns true - canEvaluate(EqualTo(a,c), R) returns false - canEvaluate(Literal(1), R) returns true as literals CAN be evaluated on any plan

    Attributes
    protected
    Definition Classes
    PredicateHelper
  8. def canEvaluateWithinJoin(expr: Expression): Boolean

    Returns true iff expr could be evaluated as a condition within join.

    Returns true iff expr could be evaluated as a condition within join.

    Attributes
    protected
    Definition Classes
    PredicateHelper
  9. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  10. def deduplicate(innerPlan: LogicalPlan, conditions: Seq[Expression], outerOutputSet: AttributeSet): (LogicalPlan, Seq[Expression])

    Deduplicate the inner and the outer query attributes and return an aliased subquery plan and join conditions if duplicates are found.

    Deduplicate the inner and the outer query attributes and return an aliased subquery plan and join conditions if duplicates are found. Duplicated attributes can break the structural integrity when joining the inner and outer plan together.

  11. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  12. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  13. def extractPredicatesWithinOutputSet(condition: Expression, outputSet: AttributeSet): Option[Expression]

    Returns a filter that its reference is a subset of outputSet and it contains the maximum constraints from condition.

    Returns a filter that its reference is a subset of outputSet and it contains the maximum constraints from condition. This is used for predicate pushdown. When there is no such filter, None is returned.

    Attributes
    protected
    Definition Classes
    PredicateHelper
  14. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  15. def findExpressionAndTrackLineageDown(exp: Expression, plan: LogicalPlan): Option[(Expression, LogicalPlan)]

    Find the origin of where the input references of expression exp were scanned in the tree of plan, and if they originate from a single leaf node.

    Find the origin of where the input references of expression exp were scanned in the tree of plan, and if they originate from a single leaf node. Returns optional tuple with Expression, undoing any projections and aliasing that has been done along the way from plan to origin, and the origin LeafNode plan from which all the exp

    Definition Classes
    PredicateHelper
  16. def getAliasMap(exprs: Seq[NamedExpression]): AttributeMap[Alias]
    Attributes
    protected
    Definition Classes
    AliasHelper
  17. def getAliasMap(plan: Aggregate): AttributeMap[Alias]
    Attributes
    protected
    Definition Classes
    AliasHelper
  18. def getAliasMap(plan: Project): AttributeMap[Alias]
    Attributes
    protected
    Definition Classes
    AliasHelper
  19. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  20. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  21. def initializeLogIfNecessary(isInterpreter: Boolean, silent: Boolean): Boolean
    Attributes
    protected
    Definition Classes
    Logging
  22. def initializeLogIfNecessary(isInterpreter: Boolean): Unit
    Attributes
    protected
    Definition Classes
    Logging
  23. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  24. def isNullIntolerant(expr: Expression): Boolean
    Attributes
    protected
    Definition Classes
    PredicateHelper
  25. def isTraceEnabled(): Boolean
    Attributes
    protected
    Definition Classes
    Logging
  26. def log: Logger
    Attributes
    protected
    Definition Classes
    Logging
  27. def logDebug(msg: ⇒ String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  28. def logDebug(msg: ⇒ String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  29. def logError(msg: ⇒ String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  30. def logError(msg: ⇒ String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  31. def logInfo(msg: ⇒ String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  32. def logInfo(msg: ⇒ String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  33. def logName: String
    Attributes
    protected
    Definition Classes
    Logging
  34. def logTrace(msg: ⇒ String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  35. def logTrace(msg: ⇒ String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  36. def logWarning(msg: ⇒ String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  37. def logWarning(msg: ⇒ String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  38. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  39. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  40. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  41. def outputWithNullability(output: Seq[Attribute], nonNullAttrExprIds: Seq[ExprId]): Seq[Attribute]
    Attributes
    protected
    Definition Classes
    PredicateHelper
  42. def replaceAlias(expr: Expression, aliasMap: AttributeMap[Alias]): Expression

    Replace all attributes, that reference an alias, with the aliased expression

    Replace all attributes, that reference an alias, with the aliased expression

    Attributes
    protected
    Definition Classes
    AliasHelper
  43. def replaceAliasButKeepName(expr: NamedExpression, aliasMap: AttributeMap[Alias]): NamedExpression

    Replace all attributes, that reference an alias, with the aliased expression, but keep the name of the outermost attribute.

    Replace all attributes, that reference an alias, with the aliased expression, but keep the name of the outermost attribute.

    Attributes
    protected
    Definition Classes
    AliasHelper
  44. def rewriteDomainJoins(outerPlan: LogicalPlan, innerPlan: LogicalPlan, conditions: Seq[Expression]): LogicalPlan

    Rewrite all DomainJoins in the inner query to actual joins with the outer query.

  45. def splitConjunctivePredicates(condition: Expression): Seq[Expression]
    Attributes
    protected
    Definition Classes
    PredicateHelper
  46. def splitDisjunctivePredicates(condition: Expression): Seq[Expression]
    Attributes
    protected
    Definition Classes
    PredicateHelper
  47. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  48. def toString(): String
    Definition Classes
    AnyRef → Any
  49. def trimAliases(e: Expression): Expression
    Attributes
    protected
    Definition Classes
    AliasHelper
  50. def trimNonTopLevelAliases[T <: Expression](e: T): T
    Attributes
    protected
    Definition Classes
    AliasHelper
  51. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  52. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  53. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()

Inherited from PredicateHelper

Inherited from Logging

Inherited from AliasHelper

Inherited from AnyRef

Inherited from Any

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