UnresolvedOrdinal Unevaluable Leaf Expression

UnresolvedOrdinal is a leaf expression that represents a single integer literal in Sort logical operators (in SortOrder ordering expressions) and in Aggregate logical operators (in grouping expressions) in a logical plan.

UnresolvedOrdinal is created when SubstituteUnresolvedOrdinals logical resolution rule is executed.

// Note "order by 1" clause
val sqlText = "select id from VALUES 1, 2, 3 t1(id) order by 1"
val logicalPlan = spark.sql(sqlText).queryExecution.logical
scala> println(logicalPlan.numberedTreeString)
00 'Sort [1 ASC NULLS FIRST], true
01 +- 'Project ['id]
02    +- 'SubqueryAlias t1
03       +- 'UnresolvedInlineTable [id], [List(1), List(2), List(3)]

import org.apache.spark.sql.catalyst.analysis.SubstituteUnresolvedOrdinals
val rule = new SubstituteUnresolvedOrdinals(spark.sessionState.conf)

val logicalPlanWithUnresolvedOrdinals = rule.apply(logicalPlan)
scala> println(logicalPlanWithUnresolvedOrdinals.numberedTreeString)
00 'Sort [unresolvedordinal(1) ASC NULLS FIRST], true
01 +- 'Project ['id]
02    +- 'SubqueryAlias t1
03       +- 'UnresolvedInlineTable [id], [List(1), List(2), List(3)]

import org.apache.spark.sql.catalyst.plans.logical.Sort
val sortOp = logicalPlanWithUnresolvedOrdinals.collect { case s: Sort => s }.head
val sortOrder = sortOp.order.head

import org.apache.spark.sql.catalyst.analysis.UnresolvedOrdinal
val unresolvedOrdinalExpr = sortOrder.child.asInstanceOf[UnresolvedOrdinal]
scala> println(unresolvedOrdinalExpr)

UnresolvedOrdinal takes a single ordinal integer when created.

UnresolvedOrdinal is an unevaluable expression and cannot be evaluated (i.e. produce a value given an internal row).

An unevaluable expression cannot be evaluated to produce a value (neither in interpreted nor code-generated expression evaluations) and has to be resolved (replaced) to some other expressions or logical operators at analysis or optimization phases or they fail analysis.

UnresolvedOrdinal can never be resolved (and is replaced at analysis phase).

UnresolvedOrdinal is resolved when ResolveOrdinalInOrderByAndGroupBy logical resolution rule is executed.

UnresolvedOrdinal has no representation in SQL.

UnresolvedOrdinal in GROUP BY ordinal position is not allowed for a select list with a star (*).

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