[HUDI-2550] Expand File-Group candidates list for appending for MOR tables (#3986)

hudi-client/hudi-client-common/src/main/java/org/apache/hudi/config/HoodieWriteConfig.java

@@ -354,6 +354,12 @@ public class HoodieWriteConfig extends HoodieConfig {
       .withDocumentation("When enabled, we allow duplicate keys even if inserts are routed to merge with an existing file (for ensuring file sizing)."
           + " This is only relevant for insert operation, since upsert, delete operations will ensure unique key constraints are maintained.");
 
+  public static final ConfigProperty<Integer> MERGE_SMALL_FILE_GROUP_CANDIDATES_LIMIT = ConfigProperty
+      .key("hoodie.merge.small.file.group.candidates.limit")
+      .defaultValue(1)
+      .withDocumentation("Limits number of file groups, whose base file satisfies small-file limit, to consider for appending records during upsert operation. "
+          + "Only applicable to MOR tables");
+
   public static final ConfigProperty<Integer> CLIENT_HEARTBEAT_INTERVAL_IN_MS = ConfigProperty
       .key("hoodie.client.heartbeat.interval_in_ms")
       .defaultValue(60 * 1000)
@@ -1035,6 +1041,10 @@ public class HoodieWriteConfig extends HoodieConfig {
     return getBoolean(MERGE_ALLOW_DUPLICATE_ON_INSERTS_ENABLE);
   }
 
+  public int getSmallFileGroupCandidatesLimit() {
+    return getInt(MERGE_SMALL_FILE_GROUP_CANDIDATES_LIMIT);
+  }
+
   public EngineType getEngineType() {
     return engineType;
   }
@@ -2116,6 +2126,11 @@ public class HoodieWriteConfig extends HoodieConfig {
       return this;
     }
 
+    public Builder withMergeSmallFileGroupCandidatesLimit(int limit) {
+      writeConfig.setValue(MERGE_SMALL_FILE_GROUP_CANDIDATES_LIMIT, String.valueOf(limit));
+      return this;
+    }
+
     public Builder withHeartbeatIntervalInMs(Integer heartbeatIntervalInMs) {
       writeConfig.setValue(CLIENT_HEARTBEAT_INTERVAL_IN_MS, String.valueOf(heartbeatIntervalInMs));
       return this;