[KYLIN-3920] Don't merge same dictionaries when merge dictionary

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Won't Fix
• Affects Version/s: v2.5.2
• Component/s: Others
• Assignee: Unassigned
• Reporter: Yuzhang QIU
• Created: 28/Mar/19 08:28
• Updated: 08/Apr/19 03:26
• Resolved: 08/Apr/19 03:26

Description

Hi team:
I found DictionaryManager will pass some dictionaries to DictionaryGenerator to merge them when there is different one among them. But If there are 3 dictionaries

{Dic1, Dic1, Dic2}

in 3 segments, kylin may don't need to merge Dic1 and Dic1, which won't add same value into new dictionary twice.
If I misunderstand the merge job logic, please feel free to correct me!
Here is the code snapshot at DictionaryManager.java:251

```
boolean identicalSourceDicts = true;
for (int i = 1; i < dicts.size(); ++i) {
if (!dicts.get(0).getDictionaryObject().equals(dicts.get.getDictionaryObject()))

{ identicalSourceDicts = false; break; }

}

if (identicalSourceDicts)

{ logger.info("Use one of the merging dictionaries directly"); return dicts.get(0); }

else

{ Dictionary<String> newDict = DictionaryGenerator.mergeDictionaries(DataType.getType(newDictInfo.getDataType()), dicts); return trySaveNewDict(newDict, newDictInfo); }

```