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用户报在Hue中执行一条sql：select admission_date, discharge_date,birth_date from hm_004_20170309141149.inpatient_visit limit 20; 返回的结果中date类型的列全部显示为null，可是在hive客户端中能正常显示。

验证一下：beeline -u jdbc:hive2://0.0.0.0:10000 -e "select admission_date, discharge_date,birth_date from hm_004_20170309141149.inpatient_visit limit 20;"

 怀疑是hiveserver2的问题，可查询另一个包含date的表，却显示正常：select part_dt from default.kylin_sales limit 50;

于是怀疑是serde的问题，hm_004_20170309141149.inpatient_visit用的是org.openx.data.jsonserde.JsonSerDe，default.kylin_sales用的是TextInputFormat.

这个JsonSerDe看着有点怪，一查果然是第三方的，同事之前引入 。已向开发者报问题： https://github.com/rcongiu/Hive-JSON-Serde/issues/187 

官方自带的是org.apache.hive.hcatalog.data.JsonSerDe( https://cwiki.apache.org/confluence/display/Hive/SerDe), 位于$HIVE_HOME/hcatalog/share/hcatalog/hive-hcatalog-core-1.2.1.jar， 用此jar测试：

CREATE EXTERNAL TABLE `default.inpatient_visit`(
  `age_m` int COMMENT 'from deserializer', 
  `discharge_date` date COMMENT 'from deserializer', 
  `address_code` string COMMENT 'from deserializer', 
  `admission_date` date COMMENT 'from deserializer', 
  `visit_dept_name` string COMMENT 'from deserializer', 
  `birth_date` date COMMENT 'from deserializer', 
  `outcome` string COMMENT 'from deserializer', 
  `age` int COMMENT 'from deserializer')
ROW FORMAT SERDE 
  'org.apache.hive.hcatalog.data.JsonSerDe' 
STORED AS INPUTFORMAT 
  'org.apache.hadoop.mapred.TextInputFormat' 
OUTPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'
LOCATION
  'hdfs://xxxx/user/hive/warehouse/xx.db/inpatient_visit';

本地测试beeline -u jdbc:hive2://0.0.0.0:10000 -e "add jar /home/work/hive/hcatalog/share/hcatalog/hive-hcatalog-core-1.2.1.jar;select admission_date, discharge_date,birth_date from default.inpatient_visit limit 20;"

 

在Hue中测试：

 

---

 

【测试系统自带JsonSerDe是否功能一样】

CREATE TABLE json_nested_test (
    count string,
    usage string,
    pkg map<string,string>,
    languages array<string>,
    store map<string,array<map<string,string>>>)
ROW FORMAT SERDE 'org.apache.hive.hcatalog.data.JsonSerDe'
STORED AS TEXTFILE;

遇到个报错：

2017-04-25 15:46:38,655 WARN  [main]: data.JsonSerDe (JsonSerDe.java:deserialize(181)) - Error [java.io.IOException: Start of Array expected] parsing json text [{"count":2,"usage":91273,"pkg":{"weight":8,"type":"apple"},"languages":["German","French","Italian"],"store":{"fruit":[{"weight":8,"type":"apple"},{"weight":9,"type":"pear"}]}}].
2017-04-25 15:46:38,656 ERROR [main]: CliDriver (SessionState.java:printError(960)) - Failed with exception java.io.IOException:org.apache.hadoop.hive.serde2.SerDeException: java.io.IOException: Start of Array expected
java.io.IOException: org.apache.hadoop.hive.serde2.SerDeException: java.io.IOException: Start of Array expected
        at org.apache.hadoop.hive.ql.exec.FetchOperator.getNextRow(FetchOperator.java:507)
        at org.apache.hadoop.hive.ql.exec.FetchOperator.pushRow(FetchOperator.java:414)
        at org.apache.hadoop.hive.ql.exec.FetchTask.fetch(FetchTask.java:140)
        at org.apache.hadoop.hive.ql.Driver.getResults(Driver.java:1670)
        at org.apache.hadoop.hive.cli.CliDriver.processLocalCmd(CliDriver.java:233)
        at org.apache.hadoop.hive.cli.CliDriver.processCmd(CliDriver.java:165)
        at org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:376)
        at org.apache.hadoop.hive.cli.CliDriver.executeDriver(CliDriver.java:736)
        at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:681)
        at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:621)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
        at org.apache.hadoop.util.RunJar.main(RunJar.java:136)
Caused by: org.apache.hadoop.hive.serde2.SerDeException: java.io.IOException: Start of Array expected
        at org.apache.hive.hcatalog.data.JsonSerDe.deserialize(JsonSerDe.java:183)
        at org.apache.hadoop.hive.ql.exec.FetchOperator.getNextRow(FetchOperator.java:488)
        ... 15 more
Caused by: java.io.IOException: Start of Array expected
        at org.apache.hive.hcatalog.data.JsonSerDe.extractCurrentField(JsonSerDe.java:332)
        at org.apache.hive.hcatalog.data.JsonSerDe.extractCurrentField(JsonSerDe.java:356)
        at org.apache.hive.hcatalog.data.JsonSerDe.populateRecord(JsonSerDe.java:218)
        at org.apache.hive.hcatalog.data.JsonSerDe.deserialize(JsonSerDe.java:174)
        ... 16 more

经过多轮测试（具体测试过程见：http://www.cnblogs.com/aprilrain/p/6916359.html），发现这个SerDe对于复杂些的嵌套会报此错，例如map<string,array<string>>

CREATE TABLE s6 (
    store map<string,array<string>>
)
ROW FORMAT SERDE 'org.apache.hive.hcatalog.data.JsonSerDe'
STORED AS TEXTFILE;
load data local inpath '/home/work/s6.txt' overwrite into table s6;
select * from s6;
6s.txt的内容
{"store":{"fruit":["weight","8","type","apple"]}}
{"store":{"fruit":["weight","9","type","orange"]}}

向社区报了一个issue: https://issues.apache.org/jira/browse/HIVE-16526

另外还有问题：不支持数据文件中的空行： https://issues.apache.org/jira/browse/HIVE-15475，见下面的例子

---

org.openx.data.jsonserde.JsonSerDe 不支持空行的例子：

CREATE TABLE json_nested_test_openx (
    count string,
    usage string,
    pkg map<string,string>,
    languages array<string>,
    store map<string,array<map<string,string>>>)
ROW FORMAT SERDE 'org.openx.data.jsonserde.JsonSerDe'
STORED AS TEXTFILE;

hive> select pkg['weight'],languages[0],store['fruit'][0]['type'] from json_nested_test_openx;
OK
Failed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: Error evaluating store['fruit'][0]['type']

解决：以上错误是由于数据文件的最后一行多了一个空行，去掉空行即可解决。