How to extract where clause as array in spark sql? - regex

Question

I am trying to extract where clause from SQL query.
Multiple conditions in where clause should be in form array. Please help me.
Sample Input String:
select * from table where col1=1 and (col2 between 1 and 10 or col2 between 190 and 200) and col2 is not null
Output Expected:
Array("col1=1", "(col2 between 1 and 10 or col2 between 190 and 200)", "col2 is not null")
Thanks in advance.
EDIT:
My question here is like... I would like to split all the conditions as separate items... let's say my query is like
select * from table where col1=1 and (col2 between 1 and 10 or col2 between 190 and 200) and col2 is not null
The output I'm expecting is like
List("col1=1", "col2 between 1 and 10", "col2 between 190 and 200", "col2 is not null")
The thing is the query may have multiple levels of conditions like
select * from table where col1=1 and (col2 =2 or(col3 between 1 and 10 or col3 is between 190 and 200)) and col4='xyz'
in output each condition should be a separate item
List("col1=1","col2=2", "col3 between 1 and 10", "col3 between 190 and 200", "col4='xyz'")

Answer 1

I wouldn't use Regex for this. Here's an alternative way to extract your conditions based on Catalyst's Logical Plan :
val plan = df.queryExecution.logical
val predicates: Seq[Expression] = plan.children.collect{case f: Filter =>
f.condition.productIterator.flatMap{
case And(l,r) => Seq(l,r)
case o:Predicate => Seq(o)
}
}.toList.flatten
println(predicates)
Output :
List(('col1 = 1), ((('col2 >= 1) && ('col2 <= 10)) || (('col2 >= 190) && ('col2 <= 200))), isnotnull('col2))
Here the predicates are still Expressions and hold information (tree representation).
EDIT :
As asked in comment, here's a String (user friendly I hope) representation of the predicates :)
val plan = df.queryExecution.logical
val predicates: Seq[Expression] = plan.children.collect{case f: Filter =>
f.condition.productIterator.flatMap{
case o:Predicate => Seq(o)
}
}.toList.flatten
def stringifyExpressions(expression: Expression): Seq[String] = {
expression match{
case And(l,r) => (l,r) match {
case (gte: GreaterThanOrEqual,lte: LessThanOrEqual) => Seq(s"""${gte.left.toString} between ${gte.right.toString} and ${lte.right.toString}""")
case (_,_) => Seq(l,r).flatMap(stringifyExpressions)
}
case Or(l,r) => Seq(Seq(l,r).flatMap(stringifyExpressions).mkString("(",") OR (", ")"))
case eq: EqualTo => Seq(s"${eq.left.toString} = ${eq.right.toString}")
case inn: IsNotNull => Seq(s"${inn.child.toString} is not null")
case p: Predicate => Seq(p.toString)
}
}
val stringRepresentation = predicates.flatMap{stringifyExpressions}
println(stringRepresentation)
New Output :
List('col1 = 1, ('col2 between 1 and 10) OR ('col2 between 190 and 200), 'col2 is not null)
You can keep playing with the recursive stringifyExpressions method if you want to customize the output.
EDIT 2 : In response to your own edit :
You can change the Or / EqualTo cases to the following
def stringifyExpressions(expression: Expression): Seq[String] = {
expression match{
case And(l,r) => (l,r) match {
case (gte: GreaterThanOrEqual,lte: LessThanOrEqual) => Seq(s"""${gte.left.toString} between ${gte.right.toString} and ${lte.right.toString}""")
case (_,_) => Seq(l,r).flatMap(stringifyExpressions)
}
case Or(l,r) => Seq(l,r).flatMap(stringifyExpressions)
case EqualTo(l,r) =>
val prettyLeft = if(l.resolved && l.dataType == StringType) s"'${l.toString}'" else l.toString
val prettyRight = if(r.resolved && r.dataType == StringType) s"'${r.toString}'" else r.toString
Seq(s"$prettyLeft=$prettyRight")
case inn: IsNotNull => Seq(s"${inn.child.toString} is not null")
case p: Predicate => Seq(p.toString)
}
}
This gives the 4 elements List :
List('col1=1, 'col2 between 1 and 10, 'col2 between 190 and 200, 'col2 is not null)
For the second example :
select * from table where col1=1 and (col2 =2 or (col3 between 1 and 10 or col3 between 190 and 200)) and col4='xyz'
You'd get this output (List[String] with 5 elements) :
List('col1=1, 'col2=2, 'col3 between 1 and 10, 'col3 between 190 and 200, 'col4='xyz')
Additional note: If you want to print the attribute names without the starting quote, you can handle it by printing this instead of toString :
node.asInstanceOf[UnresolvedAttribute].name