解决hue/hiveserver2对于hive date类型显示为NULL的问题

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：

-- ::, WARN  [main]: data.JsonSerDe (JsonSerDe.java:deserialize()) - Error [java.io.IOException: Start of Array expected] parsing json text [{"count":,"usage":,"pkg":{"weight":,"type":"apple"},"languages":["German","French","Italian"],"store":{"fruit":[{"weight":,"type":"apple"},{"weight":,"type":"pear"}]}}].
-- ::, ERROR [main]: CliDriver (SessionState.java:printError()) - 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:)
        at org.apache.hadoop.hive.ql.exec.FetchOperator.pushRow(FetchOperator.java:)
        at org.apache.hadoop.hive.ql.exec.FetchTask.fetch(FetchTask.java:)
        at org.apache.hadoop.hive.ql.Driver.getResults(Driver.java:)
        at org.apache.hadoop.hive.cli.CliDriver.processLocalCmd(CliDriver.java:)
        at org.apache.hadoop.hive.cli.CliDriver.processCmd(CliDriver.java:)
        at org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:)
        at org.apache.hadoop.hive.cli.CliDriver.executeDriver(CliDriver.java:)
        at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:)
        at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:)
        at java.lang.reflect.Method.invoke(Method.java:)
        at org.apache.hadoop.util.RunJar.run(RunJar.java:)
        at org.apache.hadoop.util.RunJar.main(RunJar.java:)
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:)
        at org.apache.hadoop.hive.ql.exec.FetchOperator.getNextRow(FetchOperator.java:)
        ...  more
Caused by: java.io.IOException: Start of Array expected
        at org.apache.hive.hcatalog.data.JsonSerDe.extractCurrentField(JsonSerDe.java:)
        at org.apache.hive.hcatalog.data.JsonSerDe.extractCurrentField(JsonSerDe.java:)
        at org.apache.hive.hcatalog.data.JsonSerDe.populateRecord(JsonSerDe.java:)
        at org.apache.hive.hcatalog.data.JsonSerDe.deserialize(JsonSerDe.java:)
        ...  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[],store['fruit'][]['type'] from json_nested_test_openx;
OK
Failed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: Error evaluating store['fruit'][]['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。