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https://issues.apache.org/jira/browse/KYLIN-4810?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Xiaoxiang Yu closed KYLIN-4810.
-------------------------------
Released at kylin 3.1.2
> TrieDictionary is not correctly build
> -------------------------------------
>
> Key: KYLIN-4810
> URL: https://issues.apache.org/jira/browse/KYLIN-4810
> Project: Kylin
> Issue Type: Bug
> Components: Job Engine
> Affects Versions: v2.3.2
> Reporter: ShengJun Zheng
> Assignee: ShengJun Zheng
> Priority: Critical
> Labels: Dictionary
> Fix For: v3.1.2
>
>
> Hi, recently, I've met a problem in our product environment: Segments failed
> to merge because TrieDictionaryForest was disordered
> {code:java}
> java.lang.IllegalStateException: Invalid input data. Unordered data cannot be
> split into multi trees
> at
> org.apache.kylin.dict.TrieDictionaryForestBuilder.addValue(TrieDictionaryForestBuilder.java:92)
> at
> org.apache.kylin.dict.TrieDictionaryForestBuilder.addValue(TrieDictionaryForestBuilder.java:78)
> at
> org.apache.kylin.dict.DictionaryGenerator$StringTrieDictForestBuilder.addValue(DictionaryGenerator.java:214)
> at
> org.apache.kylin.dict.DictionaryGenerator.buildDictionary(DictionaryGenerator.java:81)
> at
> org.apache.kylin.dict.DictionaryGenerator.buildDictionary(DictionaryGenerator.java:65)
> at
> org.apache.kylin.dict.DictionaryGenerator.mergeDictionaries(DictionaryGenerator.java:106)
> {code}
> After some analysis, we found out when there is large values in a
> dict-encoded column, iterating over a single TrieDictionaryTree will get
> unordered data.
>
> Digging into the source code, the root cause is as described:
> # Kylin will split a TrieTree Node into two parts when a single nodes's
> value length is more than 255 bytes
> # Then, these tow parts of value will be added to build the TrieTree. In
> fact the splitted two parts should not be used as new values to add to the
> TrieTree.
> # Step 2 will cause the TrieDictionaryTree build more leave nodes，and the
> extra leaf nodes will be 'end-value' of dictionary tree;
> # It has no impact to the correctness of the dict tree itself, except for
> adding some additional nodes .
> # But If you spit a UTF-8 word, you will get unordered data when iterating
> over the tree ( Something todo with Java UTF-8 String Serialize/Deserialize
> implementations. Please Refer to JDK sun.nio.cs.UTF_8.class)
> How to re-produce ? Run test code :
> {code:java}
> TrieDictionaryForestBuilder builder = new TrieDictionaryForestBuilder(new
> StringBytesConverter());
> String longUrl =
> "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx你好~~~";
> builder.addValue(longUrl);
> TrieDictionaryForest<String> dict = builder.build();
> TrieDictionaryForestBuilder mergeBuild = new TrieDictionaryForestBuilder(new
> StringBytesConverter());
> for (int i = dict.getMinId(); i <= dict.getMaxId(); i++) {
> String str = dict.getValueFromId(i);
> System.out.println("add value into merge tree");
> mergeBuild.addValue(str);
> }
> The log output of this test code is:
> add value into merge tree
> add value into merge tree
> 16:59:36 [main] INFO
> org.apache.kylin.dict.TrieDictionaryForestBuilder.addValue(TrieDictionaryForestBuilder.java:127)
> values not in ascending order, previous
> 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx\xEF\xBF\xBD',
> current
> 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx\xE4\xBD\xA0\xE5\xA5\xBD~~~'
> {code}
> We can see from the test code's output：
> # We only add 1 value but the tire dictionary tree turn out to have 2 end
> vlaues
> # Iterating over the TrieDictionary Tree got unordered data
> We address this problem by
> # classify values which is a whole column value, which is splitted value,
> # not mark splitted value as end-value of a TrieTree Node.
> I wonder if there is something wrong, thanks.
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