[SPARK-17034][SQL] Minor code cleanup for UnresolvedOrdinal

## What changes were proposed in this pull request?
I was looking at the code for UnresolvedOrdinal and made a few small changes to make it slightly more clear:

1. Rename the rule to SubstituteUnresolvedOrdinals which is more consistent with other rules that start with verbs. Note that this is still inconsistent with CTESubstitution and WindowsSubstitution.
2. Broke the test suite down from a single test case to three test cases.

## How was this patch tested?
This is a minor cleanup.

Author: petermaxlee <petermaxlee@gmail.com>

Closes #14672 from petermaxlee/SPARK-17034.

1 files changed, 13 insertions, 11 deletions

diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/UnresolvedOrdinalSubstitutionSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/SubstituteUnresolvedOrdinalsSuite.scala
index 23995e96e1..3c429ebce1 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/UnresolvedOrdinalSubstitutionSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/SubstituteUnresolvedOrdinalsSuite.scala
@@ -23,20 +23,21 @@ import org.apache.spark.sql.catalyst.dsl.plans._
 import org.apache.spark.sql.catalyst.expressions.Literal
 import org.apache.spark.sql.catalyst.SimpleCatalystConf
 
-class UnresolvedOrdinalSubstitutionSuite extends AnalysisTest {
-
-  test("test rule UnresolvedOrdinalSubstitution, replaces ordinal in order by or group by") {
-    val a = testRelation2.output(0)
-    val b = testRelation2.output(1)
-    val conf = new SimpleCatalystConf(caseSensitiveAnalysis = true)
+class SubstituteUnresolvedOrdinalsSuite extends AnalysisTest {
+  private lazy val conf = SimpleCatalystConf(caseSensitiveAnalysis = true)
+  private lazy val a = testRelation2.output(0)
+  private lazy val b = testRelation2.output(1)
 
+  test("unresolved ordinal should not be unresolved") {
     // Expression OrderByOrdinal is unresolved.
     assert(!UnresolvedOrdinal(0).resolved)
+  }
 
+  test("order by ordinal") {
     // Tests order by ordinal, apply single rule.
     val plan = testRelation2.orderBy(Literal(1).asc, Literal(2).asc)
     comparePlans(
-      new UnresolvedOrdinalSubstitution(conf).apply(plan),
+      new SubstituteUnresolvedOrdinals(conf).apply(plan),
       testRelation2.orderBy(UnresolvedOrdinal(1).asc, UnresolvedOrdinal(2).asc))
 
     // Tests order by ordinal, do full analysis
@@ -44,14 +45,15 @@ class UnresolvedOrdinalSubstitutionSuite extends AnalysisTest {
 
     // order by ordinal can be turned off by config
     comparePlans(
-      new UnresolvedOrdinalSubstitution(conf.copy(orderByOrdinal = false)).apply(plan),
+      new SubstituteUnresolvedOrdinals(conf.copy(orderByOrdinal = false)).apply(plan),
       testRelation2.orderBy(Literal(1).asc, Literal(2).asc))
+  }
 
-
+  test("group by ordinal") {
     // Tests group by ordinal, apply single rule.
     val plan2 = testRelation2.groupBy(Literal(1), Literal(2))('a, 'b)
     comparePlans(
-      new UnresolvedOrdinalSubstitution(conf).apply(plan2),
+      new SubstituteUnresolvedOrdinals(conf).apply(plan2),
       testRelation2.groupBy(UnresolvedOrdinal(1), UnresolvedOrdinal(2))('a, 'b))
 
     // Tests group by ordinal, do full analysis
@@ -59,7 +61,7 @@ class UnresolvedOrdinalSubstitutionSuite extends AnalysisTest {
 
     // group by ordinal can be turned off by config
     comparePlans(
-      new UnresolvedOrdinalSubstitution(conf.copy(groupByOrdinal = false)).apply(plan2),
+      new SubstituteUnresolvedOrdinals(conf.copy(groupByOrdinal = false)).apply(plan2),
       testRelation2.groupBy(Literal(1), Literal(2))('a, 'b))
   }
 }