[CARBONDATA-3134] fixed null values when cachelevel is set as blocklet

Problem:
For each blocklet an object of SegmentPropertiesAndSchemaHolder is created to store the schema used for query. This object is created only if no other blocklet has the same schema. To check the schema we are comparing List<ColumnSchema>, as the equals method in ColumnSchema does not check for columnUniqueId therefore this check is failing and the new restructured blocklet is using the schema of the old blocklet. Due to this the newly added column is being ignored as the old blocklet schema specifies that the column is delete(alter drop).

Solution:
Instead of checking the equality through equals and hashcode, write a new implementation for both and check based on columnUniqueId.

core/src/main/java/org/apache/carbondata/core/datastore/block/SegmentPropertiesAndSchemaHolder.java

@@ -18,6 +18,8 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
+import java.util.Comparator;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -332,13 +334,42 @@ public void clear() {
       }
       SegmentPropertiesAndSchemaHolder.SegmentPropertiesWrapper other =
           (SegmentPropertiesAndSchemaHolder.SegmentPropertiesWrapper) obj;
-      return tableIdentifier.equals(other.tableIdentifier) && columnsInTable
-          .equals(other.columnsInTable) && Arrays
+      return tableIdentifier.equals(other.tableIdentifier) && checkColumnSchemaEquality(
+          columnsInTable, other.columnsInTable) && Arrays
           .equals(columnCardinality, other.columnCardinality);
     }
 
+    private boolean checkColumnSchemaEquality(List<ColumnSchema> obj1, List<ColumnSchema> obj2) {
+      List<ColumnSchema> clonedObj1 = new ArrayList<>();
+      List<ColumnSchema> clonedObj2 = new ArrayList<>();
+      clonedObj1.addAll(obj1);
+      clonedObj2.addAll(obj2);
+      Collections.sort(clonedObj1, new Comparator<ColumnSchema>() {
+        @Override public int compare(ColumnSchema o1, ColumnSchema o2) {
+          return o1.getColumnUniqueId().compareTo(o2.getColumnUniqueId());
+        }
+      });
+      Collections.sort(clonedObj2, new Comparator<ColumnSchema>() {
+        @Override public int compare(ColumnSchema o1, ColumnSchema o2) {
+          return o1.getColumnUniqueId().compareTo(o2.getColumnUniqueId());
+        }
+      });
+      boolean exists = true;
+      for (int i = 0; i < obj1.size(); i++) {
+        if (!clonedObj1.get(i).equalsWithColumnId(clonedObj2.get(i))) {
+          exists = false;
+          break;
+        }
+      }
+      return exists;
+    }
+
     @Override public int hashCode() {
-      return tableIdentifier.hashCode() + columnsInTable.hashCode() + Arrays
+      int hashCode = 0;
+      for (ColumnSchema columnSchema: columnsInTable) {
+        hashCode += columnSchema.hashCodeWithColumnId();
+      }
+      return tableIdentifier.hashCode() + hashCode + Arrays
           .hashCode(columnCardinality);
     }
 

core/src/main/java/org/apache/carbondata/core/metadata/schema/table/column/ColumnSchema.java

@@ -297,6 +297,10 @@ public void setParentColumnTableRelations(
     return result;
   }
 
+  public int hashCodeWithColumnId() {
+    return hashCode() + ((columnUniqueId == null) ? 0 : columnUniqueId.hashCode());
+  }
+
   /**
    * Overridden equals method for columnSchema
    */
@@ -334,25 +338,14 @@ public void setParentColumnTableRelations(
    * @param obj
    * @return
    */
-  public boolean equalsWithStrictCheck(Object obj) {
+  public boolean equalsWithColumnId(Object obj) {
     if (!this.equals(obj)) {
       return false;
     }
     ColumnSchema other = (ColumnSchema) obj;
-    if (!columnUniqueId.equals(other.columnUniqueId) ||
-        (isDimensionColumn != other.isDimensionColumn) ||
-        (isSortColumn != other.isSortColumn)) {
-      return false;
-    }
-    if (encodingList.size() != other.encodingList.size()) {
+    if (!columnUniqueId.equals(other.columnUniqueId)) {
       return false;
     }
-    for (int i = 0; i < encodingList.size(); i++) {
-      if (encodingList.get(i).compareTo(other.encodingList.get(i)) != 0) {
-        return false;
-      }
-    }
-
     return true;
   }
 

integration/spark-common-test/src/test/scala/org/apache/carbondata/spark/testsuite/standardpartition/StandardPartitionTableQueryTestCase.scala

@@ -440,7 +440,7 @@ test("Creation of partition table should fail if the colname in table schema and
   test("validate data in partition table after dropping and adding a column") {
     sql("drop table if exists par")
     sql("create table par(name string) partitioned by (age double) stored by " +
-              "'carbondata'")
+              "'carbondata' TBLPROPERTIES('cache_level'='blocklet')")
     sql(s"load data local inpath '$resourcesPath/uniqwithoutheader.csv' into table par options" +
         s"('header'='false')")
     sql("alter table par drop columns(name)")