BoundReference Leaf Expression — Reference to Value in Internal Binary Row

BoundReference is a leaf expression that is a reference to a value in internal binary row at a specified position and of specified data type.

BoundReference holds the following:

  • Ordinal, i.e. the position

  • DataType

  • Flag whether the value can be nullable or not

import org.apache.spark.sql.catalyst.expressions.BoundReference
import org.apache.spark.sql.types.LongType
val boundRef = BoundReference(ordinal = 0, dataType = LongType, nullable = true)

scala> println(boundRef.toString)
input[0, bigint, true]

// create an InternalRow using ExpressionEncoder
import org.apache.spark.sql.catalyst.encoders.ExpressionEncoder
import spark.implicits.newLongEncoder
val longExprEnc = newLongEncoder.asInstanceOf[ExpressionEncoder[Long]]
val row = longExprEnc.toRow(5)

val five = boundRef.eval(row).asInstanceOf[Long]

eval Method

eval(input: InternalRow): Any
Note
eval is a part of Expression Contract to evaluate a Catalyst expression to a JVM object for a given internal binary row.

eval gives the value at position in the input internal binary row that is of a correct type.

Internally, eval returns null if the value at the position is null.

Otherwise, eval uses the methods of InternalRow per the defined data type to access the value.

Table 1. eval’s DataType to InternalRow’s Methods Mapping (in execution order)
DataType InternalRow’s Method

BooleanType

getBoolean

ByteType

getByte

ShortType

getShort

IntegerType

getInt

DateType

getInt

LongType

getLong

TimestampType

getLong

FloatType

getFloat

DoubleType

getDouble

StringType

getUTF8String

BinaryType

getBinary

CalendarIntervalType

getInterval

DecimalType

getDecimal

StructType

getStruct

ArrayType

getArray

MapType

getMap

others

get(ordinal, dataType)

Generating Java Source Code — doGenCode Method

doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode
Note
doGenCode is a part of Expression Contract.

doGenCode…​FIXME

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