chore: display schema for datasets being compared

Author: comphead

fuzz-testing/src/main/scala/org/apache/comet/fuzz/ComparisonTool.scala

@@ -117,6 +117,12 @@ object ComparisonTool {
             // Compare the results
             if (QueryComparison.assertSameRows(sparkRows, cometRows, output)) {
               output.write(s"Subfolder $subfolderName: ${sparkRows.length} rows matched\n\n")
+            } else {
+              // Output schema if dataframes are not equal
+              QueryComparison.showSchema(
+                output,
+                sparkDf.schema.treeString,
+                cometDf.schema.treeString)
             }
           } catch {
             case e: Exception =>

fuzz-testing/src/main/scala/org/apache/comet/fuzz/QueryRunner.scala

@@ -156,14 +156,10 @@ object QueryComparison {
         val r = cometRows(i)
 
         // Check the schema is equal for first row only
-        if (i == 0) {
-          showSchema(output, l.schema.treeString, r.schema.treeString)
+        if (i == 0 && l.schema != r.schema) {
+          output.write("[ERROR] Spark produced different schema than Comet.\n")
 
-          if (l.schema != r.schema) {
-            output.write("[ERROR] Spark produced different schema than Comet.\n")
-
-            return false
-          }
+          return false
         }
 
         assert(l.length == r.length)