MERGE INTO

Function

This command is used to query another table based on the join condition of a table or subquery. If UPDATE or DELETE is executed for the table matching the join condition, and INSERT is executed if the join condition is not met. This command completes the synchronization requiring only one full table scan, delivering higher efficiency than INSERT plus UPDATE.

Syntax

MERGE INTO tableIdentifier AS target_alias

USING (sub_query | tableIdentifier) AS source_alias

ON <merge_condition>

[ WHEN MATCHED [ AND <condition> ] THEN <matched_action> ]

[ WHEN MATCHED [ AND <condition> ] THEN <matched_action> ]

[ WHEN NOT MATCHED [ AND <condition> ] THEN <not_matched_action> ]

<merge_condition> =A equal bool condition

<matched_action> =

DELETE |

UPDATE SET * |

UPDATE SET column1 = expression1 [, column2 = expression2 ...]

<not_matched_action> =

INSERT * |

INSERT (column1 [, column2 ...]) VALUES (value1 [, value2 ...])

Parameter Description

Precautions

1. The merge-on condition supports only primary key columns currently.
2. In earlier versions, only some fields in the COW table can be updated, and the updated values must contain pre-merged columns. All fields in the MOR table must be provided in the Update syntax.

Examples

• Some fields are updated.

  create table h0(id int, comb int, name string, price int) using hudi options(primaryKey = 'id', preCombineField = 'comb');
  create table s0(id int, comb int, name string, price int) using hudi options(primaryKey = 'id', preCombineField = 'comb');
  insert into h0 values(1, 1, 1, 1);
  insert into s0 values(1, 1, 1, 1);
  insert into s0 values(2, 2, 2, 2);
  //Writing Method 1
  merge into h0 using s0
  on h0.id = s0.id
  when matched then update set h0.id = s0.id, h0.comb = s0.comb, price = s0.price * 2;
  //Writing Method 2
  merge into h0 using s0
  on h0.id = s0.id
  when matched then update set id = s0.id,
  name = h0.name,
  comb = s0.comb + h0.comb,
  price = s0.price + h0.price;

• Default Field Updates and Inserts.

  create table h0(id int, comb int, name string, price int, flag boolean) using hudi options(primaryKey = 'id', preCombineField = 'comb');
  create table s0(id int, comb int, name string, price int, flag boolean) using hudi options(primaryKey = 'id', preCombineField = 'comb');
  insert into h0 values(1, 1, 1, 1, false);
  insert into s0 values(1, 2, 1, 1, true);
  insert into s0 values(2, 2, 2, 2, false);
  
  merge into h0 as target
  using (
  select id, comb, name, price, flag from s0
  ) source
  on target.id = source.id
  when matched then update set *
  when not matched then insert *;

• Multi-condition update and deletion.

  create table h0(id int, comb int, name string, price int, flag boolean) using hudi options(primaryKey = 'id', preCombineField = 'comb');
  create table s0(id int, comb int, name string, price int, flag boolean) using hudi options(primaryKey = 'id', preCombineField = 'comb');
  insert into h0 values(1, 1, 1, 1, false);
  insert into h0 values(2, 2, 1, 1, false);
  insert into s0 values(1, 1, 1, 1, true);
  insert into s0 values(2, 2, 2, 2, false);
  insert into s0 values(3, 3, 3, 3, false);
  
  merge into h0
  using (
  select id, comb, name, price, flag from s0
  ) source
  on h0.id = source.id
  when matched and flag = false then update set id = source.id, comb = h0.comb + source.comb, price = source.price * 2
  when matched and flag = true then delete
  when not matched then insert *;

System Response

You can view the result in driver logs or on the client.