Hive 去除 CSV 字段中的双引号

问题

在 AWS 中，可以开启详细账单的功能。开启详细账单后，AWS 每天会多次将详细的账单数据存入到指定的 S3 bucket 中[1]。
账单数据是一个 CSV 文件，示例如下：

"InvoiceID","PayerAccountId","LinkedAccountId","RecordType","ProductName","RateId","SubscriptionId","PricingPlanId","UsageType","Operation","AvailabilityZone","ReservedInstance","ItemDescription","UsageStartDate","UsageEndDate","UsageQuantity","Rate","Cost"
"Estimated","xxxxxxxxxxxx","xxxxxxxxxxxx","LineItem","Amazon Simple Queue Service","16850885","1846142824","1292565","CNN1-Requests-Tier1","GetQueueAttributes","","N","First 1,000,000 Amazon SQS Requests per month are free","2019-01-01 00:00:00","2019-01-01 01:00:00","60.0000000000","0.0000000000","0.0000000000"
"Estimated","xxxxxxxxxxxx","xxxxxxxxxxxx","LineItem","Amazon Simple Queue Service","16850885","1846142824","1292565","CNN1-Requests-Tier1","GetQueueUrl","","N","First 1,000,000 Amazon SQS Requests per month are free","2019-01-01 00:00:00","2019-01-01 01:00:00","180.0000000000","0.0000000000","0.0000000000"

第一行是每个字段的名字，后面的行是相应的数据。

如果想用 Hive 进行分析，按照如下方式建表，得到的每一个字段内容都会包含双引号，不方便分析。

hive > CREATE EXTERNAL TABLE IF NOT EXISTS
 aws_bill (
 InvoiceID string,
 PayerAccountId string,
 LinkedAccountId string,
 RecordType string,
 ProductName string,
 RateId string,
 SubscriptionId string,
 PricingPlanId string,
 UsageType string,
 Operation string,
 AvailabilityZone string,
 ReservedInstance string,
 ItemDescription string,
 UsageStartDate string,
 UsageEndDate string,
 UsageQuantity double,
 Rate double,
 Cost double
)
 ROW FORMAT DELIMITED FIELDS TERMINATED BY ','
 LOCATION 's3://feichashao-hadoop/bill/';

hive> select * from aws_bill
"Estimated","xxxxxxxxxxxx","xxxxxxxxxxxx","LineItem","Amazon Simple Queue Service","16850885","1846142824","1292565","CNN1-Requests-Tier1","GetQueueAttributes","","N","First 1,000,000 Amazon SQS Requests per month are free","2019-01-01 00:00:00","2019-01-01 01:00:00",NULL,NULL,NULL

而期望的结果是，字段中不含有双引号，如

Estimated       xxxxxxxxxxxx    xxxxxxxxxxxx    LineItem        Amazon Simple Queue Service     16850885        1846142824      1292565CNN1-Requests-Tier1      GetQueueAttributes              N       First 1,000,000 Amazon SQS Requests per month are free  2019-01-01 00:00:00     2019-01-01 01:00:00     60.0000000000   0.0000000000    0.0000000000

方法一：CSV Serde

Hive 没有原生的方法来去除字段中的双引号。不过我们可以在建表的时候，使用 CSV Serde[2]。
建表的方法如下：

Hive > CREATE EXTERNAL TABLE IF NOT EXISTS
 aws_bill_serde (
 InvoiceID string,
 PayerAccountId string,
    [...省略...]
 Cost double)
 ROW FORMAT SERDE 'org.apache.hadoop.hive.serde2.OpenCSVSerde'
 LOCATION 's3://feichashao-hadoop/bill/';

这样建表，select * from aws_bill_serde 得到的结果没有双引号。

不过，用 SERDE 建表的话，无论我们指定数据类是 string 还是 double, describe table 时看到的类型全都是 string. 如果要做运算会变得不方便。

hive> describe aws_bill_serde;
OK
invoiceid               string                  from deserializer
payeraccountid          string                  from deserializer
linkedaccountid         string                  from deserializer
recordtype              string                  from deserializer
productname             string                  from deserializer
rateid                  string                  from deserializer
subscriptionid          string                  from deserializer
pricingplanid           string                  from deserializer
usagetype               string                  from deserializer
operation               string                  from deserializer
availabilityzone        string                  from deserializer
reservedinstance        string                  from deserializer
itemdescription         string                  from deserializer
usagestartdate          string                  from deserializer
usageenddate            string                  from deserializer
usagequantity           string                  from deserializer
cost                    string                  from deserializer

方法二：预处理 CSV 文件

既然不想要双引号，那就预先处理 csv 文件，把双引号从根本上去除。
使用 sed 命令可以实现：

$ sed 's/"//g'  old.csv > new.csv

参考文档

[1] https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/billing-getting-started.html
[2] https://cwiki.apache.org/confluence/display/Hive/CSV+Serde