Hive Merge詳解

參考

https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DML#LanguageManualDML-Merge

https://community.cloudera.com/t5/Community-Articles/Hive-ACID-Merge-by-Example/ta-p/245402

 

說明

Hive在2.2版本之後開始支持Merge操作，並且Merge只能在支持ACID的表上執行

 

語法

MERGE INTO <target table> AS T USING <source expression/table> AS S
ON <boolean expression1>
WHEN MATCHED [AND <boolean expression2>] THEN UPDATE SET <set clause list>
WHEN MATCHED [AND <boolean expression3>] THEN DELETE
WHEN NOT MATCHED [AND <boolean expression4>] THEN INSERT VALUES<value list>

 

建表語句

CREATE DATABASE merge_data;

CREATE TABLE merge_data.transactions(
 ID int,
 TranValue string,
 last_update_user string)
PARTITIONED BY (tran_date string)
CLUSTERED BY (ID) into 5 buckets 
STORED AS ORC TBLPROPERTIES ('transactional'='true');

CREATE TABLE merge_data.merge_source(
 ID int,
 TranValue string,
 tran_date string)
STORED AS ORC;

 

導入數據

INSERT INTO merge_data.merge_source VALUES 
(1, 'value_01', '20170410'),
(4, NULL, '20170410'),
(7, 'value_77777', '20170413'),
(8, NULL, '20170413'),
(8, 'value_08', '20170415'),
(11, 'value_11', '20170415');

INSERT INTO merge_data.transactions PARTITION (tran_date) VALUES
(1, 'value_01', 'creation', '20170410'),
(2, 'value_02', 'creation', '20170410'),
(3, 'value_03', 'creation', '20170410'),
(4, 'value_04', 'creation', '20170410'),
(5, 'value_05', 'creation', '20170413'),
(6, 'value_06', 'creation', '20170413'),
(7, 'value_07', 'creation', '20170413'),
(8, 'value_08', 'creation', '20170413'),
(9, 'value_09', 'creation', '20170413'),
(10, 'value_10','creation', '20170413');

 

在導入目標表數據會遇到以下問題 

錯誤一：

FAILED: SemanticException [Error 10096]: Dynamic partition strict mode requires at least one static partition column. To turn this off set hive.exec.dynamic.partition.mode=nonstrict

set hive.exec.dynamic.partition.mode=nonstrict;

錯誤二：

FAILED: SemanticException [Error 10265]: This command is not allowed on an ACID table merge_data.transactions with a non-ACID transaction manager. Failed command: INSERT INTO merge_data.transactions PARTITION (tran_date) VALUES

set hive.txn.manager=org.apache.hadoop.hive.ql.lockmgr.DbTxnManager;

錯誤三：

FAILED: RuntimeException [Error 10264]: To use DbTxnManager you must set hive.support.concurrency=true
Exception in thread "main" java.lang.NullPointerException
    at org.apache.hadoop.hive.ql.Driver.releaseLocksAndCommitOrRollback(Driver.java:1186)
    at org.apache.hadoop.hive.ql.Driver.compileInternal(Driver.java:1324)
    at org.apache.hadoop.hive.ql.Driver.runInternal(Driver.java:1457)
    at org.apache.hadoop.hive.ql.Driver.run(Driver.java:1237)
    at org.apache.hadoop.hive.ql.Driver.run(Driver.java:1227)
    at org.apache.hadoop.hive.cli.CliDriver.processLocalCmd(CliDriver.java:233)
    at org.apache.hadoop.hive.cli.CliDriver.processCmd(CliDriver.java:184)
    at org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:403)
    at org.apache.hadoop.hive.cli.CliDriver.executeDriver(CliDriver.java:821)
    at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:759)
    at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:686)
    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)

set hive.support.concurrency=true;

修改完以上三個參數之後，導入數據成功

 

Merge操作

MERGE INTO merge_data.transactions AS T 
USING merge_data.merge_source AS S
ON T.ID = S.ID and T.tran_date = S.tran_date
WHEN MATCHED AND (T.TranValue != S.TranValue AND S.TranValue IS NOT NULL) THEN UPDATE SET
     TranValue = S.TranValue
    ,last_update_user = 'merge_update'
WHEN MATCHED AND S.TranValue IS NULL THEN DELETE
WHEN NOT MATCHED THEN INSERT VALUES (
    S.ID
    , S.TranValue
    , 'merge_insert'
    , S.tran_date
);

 

查看結果

至此，我們就完美實現了Hive的Merge操作！ 

 

擴展delete操作

既然我們已經是事務表了那讓我們試一試刪除操作

 從臨時表導入數據

insert into table merge_data.transactions PARTITION (tran_date)
select ID,TranValue,last_update_user,tran_date from merge_data.transactions_tmp
cluster by id;

cluster by (id) - 指定getPartition以哪個字段來進行hash散列，並且排序字段也是指定的字段，默認以正序進行排序
distribute by(uid) – 指定getPartition以哪個字段來進行hash散列
sort by(uid asc) – 指定排序字段，以及排序規則