[GitHub] [carbondata] ajantha-bhat commented on a change in pull request #3504: [CARBONDATA-3614] Support Alter table properties set/unset for longstring columns

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ajantha-bhat commented on a change in pull request #3504: [CARBONDATA-3614] Support Alter table properties set/unset for longstring columns
URL: https://github.com/apache/carbondata/pull/3504#discussion_r356961867
 
 

 ##########
 File path: core/src/main/java/org/apache/carbondata/core/util/CarbonUtil.java
 ##########
 @@ -3396,4 +3398,105 @@ public static CarbonFile createTempFolderForIndexServer(String tablePath, String
       return file;
     }
   }
+
+  /**
+   * For alter table tableProperties of long string, modify ColumnSchema
+   * set operation:
+   * a. reset the current varchar datatype to string
+   * b. reorder back to original order (consider sort column and original schema ordinal)
+   * c. set the new columns to varchar
+   * d. reorder new varchar columns to be after dimensions
+   * <p>
+   * unset operation:
+   * a. reset the current varchar datatype to string
+   * b. reorder back to original order (consider sort column and original schema ordinal)
+   *
+   * @param columns                 list of column schema from thrift
+   * @param longStringColumnsString comma separated long string columns to be set, empty for unset
+   * @return updated columnSchema list
+   */
+  public static List<org.apache.carbondata.format.ColumnSchema> reorderColumnsForLongString(
+      List<org.apache.carbondata.format.ColumnSchema> columns, String longStringColumnsString) {
+    // find the end of the dimension index [which can be start of complex or measure columns or end]
+    // if doesn't find any complex are measure column, last element is the dimension end.
+    int dimensionEnd = columns.size() - 1;
+    int sortColumnEnd = -1;
+    for (int i = 0; i < columns.size(); i++) {
+      // if it is complex or measure, then previous index is dimension end
+      if ((columns.get(i).getData_type() == org.apache.carbondata.format.DataType.ARRAY
+          || columns.get(i).getData_type() == org.apache.carbondata.format.DataType.STRUCT
+          || columns.get(i).getData_type() == org.apache.carbondata.format.DataType.MAP || (!columns
+          .get(i).isDimension()))) {
+        dimensionEnd = i - 1;
+        break;
+      } else {
+        // update sort columns end
+        if (columns.get(i).getColumnProperties() != null) {
+          String isSortColumn =
+              columns.get(i).getColumnProperties().get(CarbonCommonConstants.SORT_COLUMNS);
+          if ((isSortColumn != null) && (isSortColumn.equalsIgnoreCase("true"))) {
+            sortColumnEnd = i;
+          }
+        }
+      }
+    }
+    List<org.apache.carbondata.format.ColumnSchema> sortColumns = null;
+    List<org.apache.carbondata.format.ColumnSchema> dimColumns = null;
+    List<org.apache.carbondata.format.ColumnSchema> otherColumns = null;
+    if (sortColumnEnd != -1) {
+      // sort columns will always be present first
+      sortColumns = columns.subList(0, sortColumnEnd + 1);
+      dimColumns = columns.subList(sortColumnEnd + 1, dimensionEnd + 1);
+    } else {
+      dimColumns = columns.subList(0, dimensionEnd + 1);
+    }
+    otherColumns = columns.subList(dimensionEnd + 1, columns.size());
+    // clear the varchar type in dims
+    boolean isResetDone = false;
+    for (org.apache.carbondata.format.ColumnSchema col : dimColumns) {
+      if (col.data_type == org.apache.carbondata.format.DataType.VARCHAR) {
+        col.data_type = org.apache.carbondata.format.DataType.STRING;
+        isResetDone = true;
+      }
+    }
 
 Review comment:
   yes. done.

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