[HUDI-3513] Make sure Column Stats does not fail in case it fails to load previous Index Table state (#5015)

Author: Alexey Kudinkin

hudi-client/hudi-spark-client/src/main/java/org/apache/hudi/index/columnstats/ColumnStatsIndexHelper.java

@@ -24,6 +24,7 @@
 import org.apache.hudi.common.model.HoodieColumnRangeMetadata;
 import org.apache.hudi.common.model.HoodieFileFormat;
 import org.apache.hudi.common.util.BaseFileUtils;
+import org.apache.hudi.common.util.Option;
 import org.apache.hudi.common.util.ParquetUtils;
 import org.apache.hudi.common.util.collection.Pair;
 import org.apache.hudi.exception.HoodieException;
@@ -304,21 +305,28 @@ public static void updateColumnStatsIndexFor(
       if (validIndexTables.isEmpty()) {
         finalColStatsIndexDf = newColStatsIndexDf;
       } else {
-        // NOTE: That Parquet schema might deviate from the original table schema (for ex,
-        //       by upcasting "short" to "integer" types, etc), and hence we need to re-adjust it
-        //       prior to merging, since merging might fail otherwise due to schemas incompatibility
-        finalColStatsIndexDf =
-            tryMergeMostRecentIndexTableInto(
-                sparkSession,
-                newColStatsIndexDf,
-                // Load current most recent col-stats-index table
-                sparkSession.read().load(
-                    new Path(indexFolderPath, validIndexTables.get(validIndexTables.size() - 1)).toString()
-                )
-            );
-
-        // Clean up all index tables (after creation of the new index)
-        tablesToCleanup.addAll(validIndexTables);
+        Path latestIndexTablePath = new Path(indexFolderPath, validIndexTables.get(validIndexTables.size() - 1));
+
+        Option<Dataset<Row>> existingIndexTableOpt =
+            tryLoadExistingIndexTable(sparkSession, latestIndexTablePath);
+
+        if (!existingIndexTableOpt.isPresent()) {
+          finalColStatsIndexDf = newColStatsIndexDf;
+        } else {
+          // NOTE: That Parquet schema might deviate from the original table schema (for ex,
+          //       by upcasting "short" to "integer" types, etc), and hence we need to re-adjust it
+          //       prior to merging, since merging might fail otherwise due to schemas incompatibility
+          finalColStatsIndexDf =
+              tryMergeMostRecentIndexTableInto(
+                  sparkSession,
+                  newColStatsIndexDf,
+                  // Load current most recent col-stats-index table
+                  existingIndexTableOpt.get()
+              );
+
+          // Clean up all index tables (after creation of the new index)
+          tablesToCleanup.addAll(validIndexTables);
+        }
       }
 
       // Persist new col-stats-index table
@@ -349,6 +357,17 @@ public static void updateColumnStatsIndexFor(
     }
   }
 
+  @Nonnull
+  private static Option<Dataset<Row>> tryLoadExistingIndexTable(@Nonnull SparkSession sparkSession, @Nonnull Path indexTablePath) {
+    try {
+      Dataset<Row> indexTableDataset = sparkSession.read().load(indexTablePath.toUri().toString());
+      return Option.of(indexTableDataset);
+    } catch (Exception e) {
+      LOG.error(String.format("Failed to load existing Column Stats index table from (%s)", indexTablePath), e);
+      return Option.empty();
+    }
+  }
+
   @Nonnull
   private static Dataset<Row> tryMergeMostRecentIndexTableInto(
       @Nonnull SparkSession sparkSession,