hadoop - Hive中 'Stored as InputFormat, OutputFormat'和 'Stored as'的区别

Question

如果表是 ORC，则执行 show create table 然后执行生成的 create table 语句时出现问题。

使用 show create table，您会得到:

STORED AS INPUTFORMAT
  ‘org.apache.hadoop.hive.ql.io.orc.OrcInputFormat’
OUTPUTFORMAT
  ‘org.apache.hadoop.hive.ql.io.orc.OrcOutputFormat’

但是，如果您使用这些子句创建表，则在选择时会出现转换错误。错误喜欢:

Failed with exception java.io.IOException:java.lang.ClassCastException: org.apache.hadoop.hive.ql.io.orc.OrcStruct cannot be cast to org.apache.hadoop.io.BinaryComparable

要解决此问题，只需将 create table 语句更改为 STORED AS ORC

但是，正如类似问题中的答案所说: What is the difference between 'InputFormat, OutputFormat' & 'Stored as' in Hive? .

我想不通原因。

Answer 1

STORED AS 意味着 3 件事:

1. 服务器端
2. 输入格式
3. 输出格式

您只定义了最后 2 个，留下 SERDE 由 hive.default.serde 定义

hive.default.serde
Default Value: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe
Added in: Hive 0.14 with HIVE-5976
The default SerDe Hive will use for storage formats that do not specify a SerDe.
Storage formats that currently do not specify a SerDe include 'TextFile, RcFile'.

演示

hive.default.serde

set hive.default.serde;

---

hive.default.serde=org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe

存储为 ORC

create table mytable (i int) 
stored as orc;

show create table mytable;

---

请注意，SERDE 是 'org.apache.hadoop.hive.ql.io.orc.OrcSerde'

CREATE TABLE `mytable`(
  `i` int)
ROW FORMAT SERDE 
  'org.apache.hadoop.hive.ql.io.orc.OrcSerde' 
STORED AS INPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.orc.OrcInputFormat' 
OUTPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.orc.OrcOutputFormat'
LOCATION
  'file:/home/cloudera/local_db/mytable'
TBLPROPERTIES (
  'COLUMN_STATS_ACCURATE'='{\"BASIC_STATS\":\"true\"}', 
  'numFiles'='0', 
  'numRows'='0', 
  'rawDataSize'='0', 
  'totalSize'='0', 
  'transient_lastDdlTime'='1496982059')

---

存储为输入格式...输出格式...

create table mytable2 (i int) 
STORED AS 
INPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.orc.OrcInputFormat' 
OUTPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.orc.OrcOutputFormat'
;

show create table mytable2
;

---

请注意，SERDE 是 'org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe'

CREATE TABLE `mytable2`(
  `i` int)
ROW FORMAT SERDE 
  'org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe' 
STORED AS INPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.orc.OrcInputFormat' 
OUTPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.orc.OrcOutputFormat'
LOCATION
  'file:/home/cloudera/local_db/mytable2'
TBLPROPERTIES (
  'COLUMN_STATS_ACCURATE'='{\"BASIC_STATS\":\"true\"}', 
  'numFiles'='0', 
  'numRows'='0', 
  'rawDataSize'='0', 
  'totalSize'='0', 
  'transient_lastDdlTime'='1496982426')