[HUDI-5038] Increase default num_instants to fetch for incremental source (#6955)

Author: yihua

hudi-utilities/src/main/java/org/apache/hudi/utilities/sources/HoodieIncrSource.java

@@ -52,7 +52,7 @@ public static class Config {
      * {@value #NUM_INSTANTS_PER_FETCH} allows the max number of instants whose changes can be incrementally fetched.
      */
     static final String NUM_INSTANTS_PER_FETCH = "hoodie.deltastreamer.source.hoodieincr.num_instants";
-    static final Integer DEFAULT_NUM_INSTANTS_PER_FETCH = 1;
+    static final Integer DEFAULT_NUM_INSTANTS_PER_FETCH = 5;
 
     /**
      * {@value #HOODIE_SRC_PARTITION_FIELDS} specifies partition fields that needs to be added to source table after

hudi-utilities/src/test/java/org/apache/hudi/utilities/functional/TestHoodieDeltaStreamer.java

@@ -2101,6 +2101,7 @@ public void testHoodieIncrFallback() throws Exception {
     HoodieDeltaStreamer.Config downstreamCfg =
         TestHelpers.makeConfigForHudiIncrSrc(tableBasePath, downstreamTableBasePath,
             WriteOperationType.BULK_INSERT, true, null);
+    downstreamCfg.configs.add("hoodie.deltastreamer.source.hoodieincr.num_instants=1");
     new HoodieDeltaStreamer(downstreamCfg, jsc).sync();
 
     insertInTable(tableBasePath, 9, WriteOperationType.UPSERT);
@@ -2112,6 +2113,8 @@ public void testHoodieIncrFallback() throws Exception {
       downstreamCfg.configs = new ArrayList<>();
     }
 
+    // Remove source.hoodieincr.num_instants config
+    downstreamCfg.configs.remove(downstreamCfg.configs.size() - 1);
     downstreamCfg.configs.add(DataSourceReadOptions.INCREMENTAL_FALLBACK_TO_FULL_TABLE_SCAN_FOR_NON_EXISTING_FILES().key() + "=true");
     //Adding this conf to make testing easier :)
     downstreamCfg.configs.add("hoodie.deltastreamer.source.hoodieincr.num_instants=10");