UPDATE|V4.2.0| docs|Distributed Database

UPDATE

Last Updated：2025-12-02 03:06:22 Updated

The UPDATE operator is used to modify data rows in a data table that meet specified conditions.

OceanBase Database supports the UPDATE and DISTRIBUTED UPDATE operators.

UPDATE

The UPDATE statement is used to update data in a partition of a table.

In the following example, Q1 updates all rows in the t1 table that meet the c2 = '100' condition and sets the value of the c2 column to 200.

--Oracle mode:

obclient> CREATE TABLE t1 (c1 INT PRIMARY KEY, c2 VARCHAR2(10));
Query OK, 0 rows affected

obclient> CREATE TABLE t2 (c1 INT PRIMARY KEY, c2 VARCHAR2(10)) PARTITION BY
        HASH(c1) PARTITIONS 10;
Query OK, 0 rows affected

obclient> CREATE TABLE t3 (c1 INT PRIMARY KEY, c2 VARCHAR2(10));
Query OK, 0 rows affected

obclient> CREATE INDEX IDX_t3_c2 ON t3 (c2) PARTITION BY HASH(c2) PARTITIONS 3;
Query OK, 0 rows affected

--MySQL mode:

obclient> CREATE TABLE t1 (c1 INT PRIMARY KEY, c2 INT);
Query OK, 0 rows affected

obclient> CREATE TABLE t2 (c1 INT PRIMARY KEY, c2 INT) PARTITION BY
        HASH(c1) PARTITIONS 10;
Query OK, 0 rows affected

obclient> CREATE TABLE t3 (c1 INT PRIMARY KEY, c2 INT);
Query OK, 0 rows affected

obclient> CREATE INDEX IDX_t3_c2 ON t3 (c2) PARTITION BY HASH(c2) PARTITIONS 3;
Query OK, 0 rows affected

Q1:
obclient> EXPLAIN UPDATE t1 SET c2 = '200' WHERE c2 = '100';

Query Plan:
======================================
|ID|OPERATOR            |NAME|EST. ROWS|COST  |
-----------------------------------------------
|0 |EXCHANGE IN REMOTE  |    |990      |109687|
|1 | EXCHANGE OUT REMOTE|    |990      |109687|
|2 |  UPDATE            |    |990      |109687|
|3 |   TABLE SCAN       |T1  |990      |108697|
===============================================

Outputs & filters:
-------------------------------------
  0 - output(nil), filter(nil)
  1 - output(nil), filter(nil)
  2 - output(nil), filter(nil), table_columns([{T1: ({T1: (T1.C1, T1.C2)})}]),
      update([T1.C2=?])
  3 - output([T1.C1], [T1.C2], [?]), filter([T1.C2 = '100']),
      access([T1.C2], [T1.C1]), partitions(p0)

In the execution plan of the preceding example, the outputs & filters section details the output information of the UPDATE operator:

Information	Meaning
output	The expressions output by the operator.
filter	The filter conditions on the operator. Since the `UPDATE` operator has no `filter` in the example, this is `nil`. For update statements, the predicates in `WHERE` are pushed down to the base table. For example, `c2 = '100'` in Q1 is pushed down to operator 1.
table_columns	The columns of the data tables involved in the update operation.
update	All assignment expressions in the update operation.

Here are more examples of the UPDATE operator:

Q2 updates all data rows in the t1 table and sets the value of the c2 column to 200.
Q3 updates the data rows in the partitioned t2 table that meet the c1='100' condition and sets the value of the c2 column to 150.
Q4 updates the data rows in the partitioned t2 table that meet the c2 ='100' condition and sets the value of the c2 column to rpad(t2.c2, 10, '9'). As shown in the execution plan, the UPDATE operator is placed under the EXCHANGE operator, so operators 2 and 3 will be scheduled as a task at the partition level. During execution, operator 4 scans the data in the t2 partition that meets the c2 = '100' condition, and operator 3, which is the UPDATE operator, will only update the data that was scanned in the corresponding partition.

Q2: 
obclient> EXPLAIN UPDATE t1 SET c2 = '200';

Query Plan:
======================================
|ID|OPERATOR            |NAME|EST. ROWS|COST  |
-----------------------------------------------
|0 |EXCHANGE IN REMOTE  |    |100000   |161860|
|1 | EXCHANGE OUT REMOTE|    |100000   |161860|
|2 |  UPDATE            |    |100000   |161860|
|3 |   TABLE SCAN       |T1  |100000   |61860 |
===============================================

Outputs & filters:
-------------------------------------
  0 - output(nil), filter(nil)
  1 - output(nil), filter(nil)
  2 - output(nil), filter(nil), table_columns([{T1: ({T1: (T1.C1, T1.C2)})}]),
      update([T1.C2=?])
  3 - output([T1.C1], [T1.C2], [?]), filter(nil),
      access([T1.C2], [T1.C1]), partitions(p0)

     
Q3: 
obclient> EXPLAIN UPDATE t2 SET t2.c2 = '150' WHERE t2.c1 = '100';

Query Plan:
===================================
|ID|OPERATOR  |NAME|EST. ROWS|COST|
-----------------------------------
|0 |UPDATE    |    |1        |53  |
|1 | TABLE GET|T2  |1        |52  |
===================================

Outputs & filters:
-------------------------------------
  0 - output(nil), filter(nil), table_columns([{T2: ({T2: (T2.C1, T2.C2)})}]),
      update([T2.C2=?])
  1 - output([T2.C1], [T2.C2], [?]), filter(nil),
      access([T2.C1], [T2.C2]), partitions(p5)
      

Q4: 
obclient> EXPLAIN UPDATE t2 SET t2.c2 = RPAD(t2.c2, 10, '9')  WHERE t2.c2 = '100';

Query Plan:
===============================================
|ID|OPERATOR               |NAME    |EST. ROWS|COST   |
-------------------------------------------------------
|0 |PX COORDINATOR         |        |9900     |1096793|
|1 | EXCHANGE OUT DISTR    |:EX10000|9900     |1096793|
|2 |  PX PARTITION ITERATOR|        |9900     |1096793|
|3 |   UPDATE              |        |9900     |1096793|
|4 |    TABLE SCAN         |T2      |9900     |1086893|
=======================================================

Outputs & filters:
-------------------------------------
  0 - output(nil), filter(nil)
  1 - output(nil), filter(nil), dop=1
  2 - output(nil), filter(nil)
  3 - output(nil), filter(nil), table_columns([{T2: ({T2: (T2.C1, T2.C2)})}]),
      update([T2.C2=column_conv(VARCHAR,utf8mb4_bin,length:10,NULL,RPAD(T2.C2, 10, ?))])
  4 - output([T2.C1], [T2.C2], [column_conv(VARCHAR,utf8mb4_bin,length:10,NULL,RPAD(T2.C2, 10, ?))]), filter([T2.C2 = '100']),
      access([T2.C1], [T2.C2]), partitions(p[0-9])

Distributed update

The DISTRIBUTED UPDATE operator updates data in multiple partitions of a table. For example, Q5 updates all data rows in the t3 table that meet the condition c2 < '100' and sets the value of the c2 column to 200. Although t3 is a non-partitioned table, it has a global index named idx_t3_c2. Therefore, each data row exists in multiple partitions.

Q5: 
obclient> EXPLAIN UPDATE t3 SET c2 = '200' WHERE c2 < '100';
+--------------------------------------------------------------------------------------------------------+
| Query Plan                                                                                             |
+--------------------------------------------------------------------------------------------------------+
| =======================================================================                                |
| |ID|OPERATOR                      |NAME         |EST.ROWS|EST.TIME(us)|                                |
| -----------------------------------------------------------------------                                |
| |0 |DISTRIBUTED UPDATE            |             |1       |61          |                                |
| |1 |└─DISTRIBUTED TABLE RANGE SCAN|T3(IDX_T3_C2)|1       |6           |                                |
| =======================================================================                                |
| Outputs & filters:                                                                                     |
| -------------------------------------                                                                  |
|   0 - output(nil), filter(nil)                                                                         |
|       table_columns([{T3: ({T3: (T3.C1, T3.C2)}, {IDX_T3_C2: (T3.C2, T3.C1)})}]),                      |
|       update([T3.C2=column_conv(VARCHAR2,utf8mb4_bin,length:10,NULL,cast('200', VARCHAR2(1048576 )))]) |
|   1 - output([T3.C1], [T3.C2]), filter(nil), rowset=256                                                |
|       access([T3.C1], [T3.C2]), partitions(p[0-2])                                                     |
|       is_index_back=false, is_global_index=true,                                                       |
|       range_key([T3.C2], [T3.C1]), range(MIN,MIN ; 100,MIN),                                           |
|       range_cond([T3.C2 < cast('100', VARCHAR2(1048576 ))])                                            |
+--------------------------------------------------------------------------------------------------------+

Here are more examples of DISTRIBUTED UPDATE:

Q6 updates the data rows in the t2 partitioned table that meet the condition c1 = 100 and sets the value of the c1 column to 101. Since the updated column is the primary key, the updated data rows may be located in different partitions from the original data rows. Therefore, the DISTRIBUTED UPDATE operator is required for the update.

Q6: 
obclient> EXPLAIN UPDATE t2 SET t2.c1 = 101 WHERE t2.c1 = 100;
+------------------------------------------------------------------+
| Query Plan                                                       |
+------------------------------------------------------------------+
| ==================================================               |
| |ID|OPERATOR          |NAME|EST.ROWS|EST.TIME(us)|               |
| --------------------------------------------------               |
| |0 |DISTRIBUTED UPDATE|    |1       |34          |               |
| |1 |└─TABLE GET       |T2  |1       |3           |               |
| ==================================================               |
| Outputs & filters:                                               |
| -------------------------------------                            |
|   0 - output(nil), filter(nil)                                   |
|       table_columns([{T2: ({T2: (T2.C1, T2.C2)})}]),             |
|       update([T2.C1=column_conv(NUMBER,PS:(-1,0),NOT NULL,101)]) |
|   1 - output([T2.C1], [T2.C2]), filter(nil), rowset=256          |
|       access([T2.C1], [T2.C2]), partitions(p5)                   |
|       is_index_back=false, is_global_index=false,                |
|       range_key([T2.C1]), range[100 ; 100],                      |
|       range_cond([T2.C1 = 100])                                  |
+------------------------------------------------------------------+

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