Package org.apache.druid.math.expr

Class Expr.BindingAnalysis

java.lang.Object

org.apache.druid.math.expr.Expr.BindingAnalysis

Enclosing interface:

Expr

public static class Expr.BindingAnalysis
extends Object

Information about the context in which IdentifierExpr are used in a greater Expr, listing the 'free variables' (total set of required input columns or values) and distinguishing between which identifiers are used as scalar inputs and which are used as array inputs. This type is primarily used at query time when creating expression column selectors to decide if an expression can properly deal with a multi-valued column input, and also to determine if certain optimizations can be taken. Current implementations of Expr.analyzeInputs() provide context about Function and ApplyFunction arguments which are direct children IdentifierExpr as scalar or array typed. This is defined by Function.getScalarInputs(List), Function.getArrayInputs(List) and ApplyFunction.getArrayInputs(List). Identifiers that are nested inside of argument expressions which are other expression types will not be considered to belong directly to that function, and so are classified by the context their children are using them as instead. This means in rare cases and mostly for "questionable" expressions which we still allow to function 'correctly', these lists might not be fully reliable without a complete type inference system in place. Due to this shortcoming, boolean values hasInputArrays() and isOutputArray() are provided to allow functions to explicitly declare that they utilize array typed values, used when determining if some types of optimizations can be applied when constructing the expression column value selector.

See Also:

Function.getScalarInputs(java.util.List<org.apache.druid.math.expr.Expr>), Function.getArrayInputs(java.util.List<org.apache.druid.math.expr.Expr>), ApplyFunction.getArrayInputs(java.util.List<org.apache.druid.math.expr.Expr>), Parser.applyUnappliedBindings(org.apache.druid.math.expr.Expr, org.apache.druid.math.expr.Expr.BindingAnalysis, java.util.List<java.lang.String>), Parser.applyUnapplied(org.apache.druid.math.expr.Expr, java.util.List<java.lang.String>), Parser.liftApplyLambda(org.apache.druid.math.expr.ApplyFunctionExpr, java.util.List<java.lang.String>), ExpressionSelectors.makeDimensionSelector(org.apache.druid.segment.ColumnSelectorFactory, org.apache.druid.math.expr.Expr, org.apache.druid.query.extraction.ExtractionFn), ExpressionSelectors.makeColumnValueSelector(org.apache.druid.segment.ColumnSelectorFactory, org.apache.druid.math.expr.Expr)

Field Summary

Fields

Modifier and Type	Field	Description
static Expr.BindingAnalysis	EMTPY

Constructor Summary

Constructors

Constructor	Description
BindingAnalysis()

Method Summary

Modifier and Type	Method	Description
Set<String>	getArrayBindings()	Set of IdentifierExpr.binding which are used as array inputs to operators, functions, and apply functions.
Set<org.apache.druid.math.expr.IdentifierExpr>	getFreeVariables()	Total set of 'free' inputs of an Expr, that are not supplied by a LambdaExpr binding
Set<String>	getRequiredBindings()	Get the set of required column inputs to evaluate an expression (IdentifierExpr.binding)
List<String>	getRequiredBindingsList()	Get the list of required column inputs to evaluate an expression (IdentifierExpr.binding)
boolean	hasInputArrays()	Returns true if any expression in the expression tree has any array inputs.
boolean	isOutputArray()	Returns true if any expression in this expression tree produces array outputs as reported by Function.hasArrayOutput() or ApplyFunction.hasArrayOutput(LambdaExpr)
Expr.BindingAnalysis	with(Expr other)	Combine with Expr.BindingAnalysis from Expr.analyzeInputs()
Expr.BindingAnalysis	with(Expr.BindingAnalysis other)	Combine (union) another Expr.BindingAnalysis
Expr.BindingAnalysis	withScalarArguments(Set<Expr> scalarArguments)	Add set of arguments as scalarVariables that are *directly* IdentifierExpr, else they are ignored.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

EMTPY

public static final Expr.BindingAnalysis EMTPY

Constructor Detail

BindingAnalysis

public BindingAnalysis()

Method Detail

getRequiredBindingsList

public List<String> getRequiredBindingsList()

Get the list of required column inputs to evaluate an expression (IdentifierExpr.binding)

getRequiredBindings

public Set<String> getRequiredBindings()

Get the set of required column inputs to evaluate an expression (IdentifierExpr.binding)

getArrayBindings

public Set<String> getArrayBindings()

Set of IdentifierExpr.binding which are used as array inputs to operators, functions, and apply functions.

getFreeVariables

public Set<org.apache.druid.math.expr.IdentifierExpr> getFreeVariables()

Total set of 'free' inputs of an Expr, that are not supplied by a LambdaExpr binding

hasInputArrays

public boolean hasInputArrays()

Returns true if any expression in the expression tree has any array inputs. Note that in some cases, this can be true and getArrayBindings() or getArrayVariables() can be empty. This is because these collections contain identifiers/bindings which were classified as either scalar or array inputs based on the context of their usage by Expr.analyzeInputs(), where as this value and isOutputArray() are set based on information reported by Function.hasArrayInputs(), Function.hasArrayOutput(), and ApplyFunction.hasArrayOutput(LambdaExpr), without regards to identifiers or anything else.

isOutputArray

public boolean isOutputArray()

Returns true if any expression in this expression tree produces array outputs as reported by Function.hasArrayOutput() or ApplyFunction.hasArrayOutput(LambdaExpr)

with

public Expr.BindingAnalysis with(Expr other)

Combine with Expr.BindingAnalysis from Expr.analyzeInputs()

with

public Expr.BindingAnalysis with(Expr.BindingAnalysis other)

Combine (union) another Expr.BindingAnalysis

withScalarArguments

public Expr.BindingAnalysis withScalarArguments(Set<Expr> scalarArguments)

Add set of arguments as scalarVariables that are *directly* IdentifierExpr, else they are ignored.