spark-sql-Projection.adoc

Projection Contract — Functions to Produce InternalRow for InternalRow

Projection is a contract of Scala functions that produce an internal binary row for a given internal row.

Projection: InternalRow => InternalRow

Projection can optionally be initialized with the current partition index (which by default does nothing).

initialize(partitionIndex: Int): Unit = {}

Note	initialize is overriden by InterpretedProjection and InterpretedMutableProjection projections that are used in interpreted expression evaluation.

Table 1. Projections

Projection	Description
UnsafeProjection
InterpretedProjection
IdentityProjection
MutableProjection
InterpretedMutableProjection	Appears not to be used anymore