dsl

A collection of implicit conversions that create a DSL for constructing catalyst data structures.

scala> import org.apache.spark.sql.catalyst.dsl.expressions._

// Standard operators are added to expressions.
scala> import org.apache.spark.sql.catalyst.expressions.Literal
scala> Literal(1) + Literal(1)
res0: org.apache.spark.sql.catalyst.expressions.Add = (1 + 1)

// There is a conversion from 'symbols to unresolved attributes.
scala> 'a.attr
res1: org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute = 'a

// These unresolved attributes can be used to create more complicated expressions.
scala> 'a === 'b
res2: org.apache.spark.sql.catalyst.expressions.EqualTo = ('a = 'b)

// SQL verbs can be used to construct logical query plans.
scala> import org.apache.spark.sql.catalyst.plans.logical._
scala> import org.apache.spark.sql.catalyst.dsl.plans._
scala> LocalRelation('key.int, 'value.string).where('key === 1).select('value).analyze
res3: org.apache.spark.sql.catalyst.plans.logical.LogicalPlan =
Project [value#3]
 Filter (key#2 = 1)
  LocalRelation [key#2,value#3], []