ALTER TABLE

Purpose

This statement is used to modify the structure of an existing table, such as changing the table and its attributes, adding columns, changing columns and their attributes, and deleting columns.

Syntax

alter_table_stmt:
    ALTER TABLE table_name alter_table_action_list;

alter_table_action_list:
    alter_table_action [, alter_table_action ...]

alter_table_action:
      ADD [COLUMN] column_definition
          [ opt_position_column ]
    | ADD [COLUMN] (column_definition_list)
    | ADD [CONSTRAINT [constraint_name]] UNIQUE {INDEX | KEY}
          [index_name] index_desc
    | ADD [CONSTRAINT [constraint_name]] FOREIGN KEY
          [index_name] index_desc
          REFERENCES reference_definition
          [match_action][opt_reference_option_list]
    | ADD PRIMARY KEY (column_name)
    | ADD CONSTRAINT [constraint_name] CHECK (expression)[[NOT] ENFORCED]
    | ADD PARTITION (range_partition_list)
    | ADD {INDEX | KEY} [index_name] [index_type] (key_part,...) [index_option_list][index_column_group_option]
    | ADD FULLTEXT [INDEX | KEY] [index_name](column_name, [column_name ...]) [WITH PARSER tokenizer_option] [PARSER_PROPERTIES[=](parser_properties_list)] [LOCAL]
    | ADD COLUMN GROUP([all columns, ]each column) [DELAYED]
    | ALTER [COLUMN] column_name {
          SET DEFAULT const_value
        | DROP DEFAULT
      }
    | ALTER {CHECK | CONSTRAINT} symbol [NOT] ENFORCED
    | ALTER INDEX index_name [VISIBLE | INVISIBLE] [STORAGE_CACHE_POLICY = {"hot"|"auto"|"none"}]
    | CHANGE [COLUMN] column_name column_definition
    | DROP [COLUMN] column_name [, DROP COLUMN column_name ...]
    | DROP {PARTITION | SUBPARTITION} partition_name_list
    | DROP TABLEGROUP
    | DROP FOREIGN KEY fk_name
    | DROP PRIMARY KEY [, ADD PRIMARY KEY (column)]
    | DROP CHECK constraint_name
    | DROP COLUMN GROUP([all columns, ]each column)
    | MODIFY [COLUMN] column_definition
    | RENAME COLUMN old_col_name [TO|AS] new_col_name
    | RENAME [TO|AS] table_name
    | RENAME {INDEX | KEY} old_index_name [TO|AS] new_index_name
    | [SET] table_option_list
    | TRUNCATE {PARTITION | SUBPARTITION} partition_name_list
    | EXCHANGE PARTITION partition_name WITH TABLE origin_table_name WITHOUT VALIDATION
    | REORGANIZE PARTITION partition_name INTO (split_range_partition_list)
    | PARTITION BY {RANGE [COLUMNS]([column_name_list]) [SIZE('size_value')] [range_partition_list]
                   | partition_option}
    | MODIFY PARTITION partition_name ADD SUBPARTITION (add_subpartition_option)
    | ALTER {PARTITION | SUBPARTITION} partition_name STORAGE_CACHE_POLICY = {"hot" | "auto" | "none"}
    | FORCE

column_definition_list:
    column_definition [, column_definition ...]

column_definition:
    column_name data_type
    [DEFAULT const_value] [AUTO_INCREMENT]
    [NULL | NOT NULL] [[PRIMARY] KEY] [UNIQUE [KEY]] [COMMENT string_value] [SKIP_INDEX(skip_index_option_list)] [ opt_position_column ]

skip_index_option_list:
    skip_index_option [,skip_index_option ...]

skip_index_option:
    MIN_MAX
    | SUM

opt_position_column:
    FIRST | BEFORE | AFTER column_name

index_desc:
   (column_desc_list) [index_type] [index_option_list]

match_action:
   MATCH {SIMPLE | FULL | PARTIAL}

opt_reference_option_list:
   reference_option [,reference_option ...]

reference_option:
   ON {DELETE | UPDATE} {RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT}

column_desc_list:
    column_desc [, column_desc ...]

column_desc:
     column_name [(length)] [ASC | DESC]

key_part:
    {index_col_name [(length)] | (expr)} [ASC | DESC]

index_type:
    USING BTREE

index_option_list:
    index_option [ index_option ...]

index_option:
     [GLOBAL | LOCAL]
    | block_size
    | compression
    | STORING(column_name_list)
    | COMMENT string_value
    | STORAGE_CACHE_POLICY (storage_cache_policy_option)

index_column_group_option:
    WITH COLUMN GROUP([all columns, ]each column)

tokenizer_option:
    SPACE
    | NGRAM
    | BENG
    | IK
    | NGRAM2

parser_properties_list:
    parser_properties, [parser_properties]

parser_properties:
    min_token_size = int_value
    | max_token_size = int_value
    | ngram_token_size = int_value
    | ik_mode = 'char_value'
    | min_ngram_size = int_value
    | max_ngram_size = int_value

table_option_list:
    table_option [ table_option ...]

table_option:
      TABLEGROUP = tablegroup_name
    | block_size
    | lob_inrow_threshold [=] num
    | compression
    | AUTO_INCREMENT [=] INT_VALUE
    | COMMENT string_value
    | parallel_clause
    | TABLE_MODE [=] 'table_mode_value'
    | AUTO_INCREMENT_CACHE_SIZE [=] INT_VALUE
    | READ {ONLY | WRITE}
    | DUPLICATE_SCOPE= 'none | cluster'
    | enable_macro_block_bloom_filter [=] {True | False}
    | DYNAMIC_PARTITION_POLICY [=] (dynamic_partition_policy_list)
    | SEMISTRUCT_ENCODING_TYPE [=] 'encoding' # This parameter is deprecated in Version V4.4.1. Use SEMISTRUCT_PROPERTIES instead.
    | SEMISTRUCT_PROPERTIES [=] (encoding_type=encoding|none[,freq_threshold=INT_VALUE])
    | STORAGE_CACHE_POLICY (storage_cache_policy_option)

parallel_clause:
    {NOPARALLEL | PARALLEL integer}

table_mode_value:
    NORMAL
    | QUEUING
    | MODERATE
    | SUPER
    | EXTREME

dynamic_partition_policy_list:
    dynamic_partition_policy_option [, dynamic_partition_policy_option ...]

dynamic_partition_policy_option:
    ENABLE = {true | false}
    | PRECREATE_TIME = {'-1' | '0' | 'n {hour | day | week | month | year}'}
    | EXPIRE_TIME = {'-1' | '0' | 'n {hour | day | week | month | year}'}

partition_option:
      PARTITION BY HASH(expression)
      [subpartition_option] PARTITIONS partition_count
    | PARTITION BY KEY([column_name_list])
      [subpartition_option] PARTITIONS partition_count
    | PARTITION BY RANGE {(expression) | COLUMNS (column_name_list)}
      [subpartition_option] (range_partition_list)

subpartition_option:
      SUBPARTITION BY HASH(expression)
      SUBPARTITIONS subpartition_count
    | SUBPARTITION BY KEY(column_name_list)
      SUBPARTITIONS subpartition_count
    | SUBPARTITION BY RANGE {(expression) | COLUMNS (column_name_list)}
      (range_subpartition_list)

storage_cache_policy_option:
    GLOBAL = {"hot" | "auto" | "none"}
    | timeline_strategy_list

timeline_strategy_list:
    BOUNDARY_COLUMN = column_name [,BOUNDARY_COLUMN_UNIT = {"s"| "ms"}] ,HOT_RETENTON = intnum retention_time_unit

retention_time_unit:
    YEAR
    | MONTH
    | WEEK
    | DAY
    | HOUR
    | MINUTE

split_range_partition_list:
    PARTITION split_partition_name VALUES LESS THAN (value)
    [, PARTITION split_partition_name VALUES LESS THAN (value) ...]
     , PARTITION split_partition_name VALUES LESS THAN (source_value)

range_partition_list:
    range_partition [, range_partition ...]

range_partition:
    PARTITION partition_name
    VALUES LESS THAN {(expression_list) | MAXVALUE}
    [STORAGE_CACHE_POLICY = {"hot" | "auto" | "none"}]

range_subpartition_list:
    range_subpartition [, range_subpartition ...]

range_subpartition:
    SUBPARTITION subpartition_name
    VALUES LESS THAN {(expression_list) | MAXVALUE}
    [STORAGE_CACHE_POLICY = {"hot" | "auto" | "none"}]

expression_list:
    expression [, expression ...]

column_name_list:
    column_name [, column_name ...]

partition_name_list:
    partition_name [, partition_name ...]

partition_count | subpartition_count:
    INT_VALUE

add_subpartition_option:
    {SUBPARTITION subpartition_name VALUES LESS THAN range_partition_expr
        [, SUBPARTITION subpartition_name VALUES LESS THAN range_partition_expr] ...}
    | {SUBPARTITION subpartition_name VALUES IN list_partition_expr
        [, SUBPARTITION subpartition_name VALUES IN list_partition_expr] ...}

Parameters

table_mode_value

• NORMAL: The default value. In this mode, the probability of triggering a major compaction after a data dump is very low.
• QUEUING: In this mode, the probability of triggering a major compaction after a data dump is low.
• MODERATE: In this mode, the probability of triggering a major compaction after a data dump is moderate.
• SUPER: In this mode, the probability of triggering a major compaction after a data dump is high.
• EXTREME: In this mode, the probability of triggering a major compaction after a data dump is very high.

For more information about major compactions, see Adaptive major compactions.

tokenizer_option

• SPACE: The default value. In this mode, the text is tokenized by spaces. You can specify the following parameters:

  Parameter	Value range
  min_token_size	[1, 16]
  max_token_size	[10, 84]

• NGRAM: In this mode, the text is tokenized based on N-grams (Chinese). You can specify the following parameters:

  Parameter	Value range
  ngram_token_size	[1, 10]

• NGRAM2: In this mode, the text is tokenized into continuous characters of length between min_ngram_size and max_ngram_size. You can specify the following parameters:

  Parameter	Value range
  min_ngram_size	[1, 16]
  max_ngram_size	[1, 16]

• BENG: In this mode, the text is tokenized based on basic English (Beng). You can specify the following parameters:

  Parameter	Value range
  min_token_size	[1, 16]
  max_token_size	[10, 84]

• IK: In this mode, the text is tokenized based on the IK (Chinese) tokenizer. Currently, only the utf-8 character set is supported. You can specify the following parameter:

  Parameter	Value range
  ik_mode	smart max_word

You can use the TOKENIZE function to view the tokenization result of the text in the specified tokenizer and JSON format.

parser_properties

• min_token_size: The minimum token length. Default value: 3. Value range: 1 to 16.

• max_token_size: The maximum token length. Default value: 84. Value range: 10 to 84.

• ngram_token_size: The N-gram token length. This parameter is valid only for the NGRAM tokenizer. Default value: 2. Value range: 1 to 10.

• ik_mode: The tokenization mode of the IK tokenizer. Valid values:

  • smart: The default value. The dictionary is used to improve the accuracy of tokenization. The boundaries of the dictionary are prioritized, which may reduce unnecessary expansions.
  • max_word: The dictionary is used to identify the defined words, but it does not affect the maximum expansion of tokenization. Even if the dictionary contains defined words, the max_word mode still attempts to split the text into more words.

• min_ngram_size: The minimum token length. Value range: [1,16].

• max_ngram_size: The maximum token length. Value range: [1,16].

Here is an example:

1. Create a table named tbl1.

   CREATE TABLE tbl1 (col1 VARCHAR(200), col2 TEXT);
   

2. Add a full-text index named fidx to the tbl1 table.

   ALTER TABLE tbl1 ADD FULLTEXT INDEX fidx(col2) WITH PARSER ik PARSER_PROPERTIES=(ik_mode='max_word');
   

dynamic_partition_policy_option

• ENABLE = {true | false}: Specifies whether to enable dynamic partition management. Valid values:

  • true: The default value. Dynamic partition management is enabled.
  • false: Dynamic partition management is disabled.

• PRECREATE_TIME = {'-1' | '0' | 'n {hour | day | week | month | year}'}: Specifies the precreation time. When dynamic partition management is scheduled, partitions are precreated so that the upper bound of the maximum partition > now() + precreate_time. Valid values:

  • -1: The default value. No partitions are precreated.
  • 0: Only the current partition is precreated.
  • n {hour | day | week | month | year}: Partitions are precreated for the specified time span. For example, 3 hour indicates that partitions for the last 3 hours are precreated.

  Note

  • When multiple partitions are to be precreated, the interval between the boundaries of adjacent partitions is TIME_UNIT.
  • The boundary of the first precreated partition is the ceiling of the upper bound of the existing maximum partition, rounded up to the nearest multiple of TIME_UNIT.

• EXPIRE_TIME = {'-1' | '0' | 'n {hour | day | week | month | year}'}: Optional. Specifies the partition expiration time. When dynamic partition management is scheduled, all partitions whose upper bound < now() - expire_time are deleted. Valid values:

  • -1: The default value. Partitions never expire.
  • 0: All partitions except the current one expire.
  • n {hour | day | week | month | year}: The partition expiration time. For example, 1 day indicates that a partition expires after 1 day.

For more information about dynamic partition tables, see Modify a dynamic partition table.

Here is an example:

ALTER TABLE tbl2 SET DYNAMIC_PARTITION_POLICY(
    ENABLE = true,
    PRECREATE_TIME = '1 day',
    EXPIRE_TIME = '-1'
);

storage_cache_policy

Different attributes in storage_cache_policy_option are defined in the key-value format. The semantics of each attribute are described as follows:

• GLOBAL = {"hot" | "auto"| "none"}: specifies the hot cache strategy for the data of the entire table. Valid values:

  • hot: indicates that all data in the specified table is hot data. If the cache disk space is sufficient, all data in the table will be cached to the local cloud disk.
  • auto: indicates that the hot data in the specified table is automatically identified by the system.
  • none: indicates that the strategy of the index follows the value of STORAGE_CACHE_POLICY of the primary table.

    Notice

    The none attribute can be used only for indexes.

• timeline_strategy_list: specifies the list of time axis strategy parameters. Parameters are separated by commas. The hot cache time axis strategy supports a mechanism to determine whether partition data is hot data based on time. The system automatically adjusts the partition data on the local cache disk based on the configured strategy.

  Note

  A time axis is a partitioning range that is used to cache hot data. When a certain time condition is met, the data in the partition is considered hot data. When you use the time axis strategy, note the following:

  • Only Range-partitioned tables (with Range partitioning as the primary or secondary partitioning) support the time axis strategy. This is because the system needs to determine whether the data has expired based on time, but it cannot determine the time for a double Range partition.
  • When you use the time axis strategy, the partition expression can contain only column names. Expressions are not supported. For example, PARTITION BY RANGE COLUMNS(expr(col3)) is not supported.
  • BOUNDARY_COLUMN must be a partition key. If the partition key contains multiple columns, BOUNDARY_COLUMN must be the first column, which is used to determine whether the partition has expired.

• BOUNDARY_COLUMN = column_name: specifies the column used to determine hot data. Integer types (BIGINT or INT, in the Unix timestamp format) and time types (TIMESTAMP, DATE, DATETIME, or YEAR) are supported.

  • If the BOUNDARY_COLUMN is of an integer type, the table can be partitioned by Range or Range Columns.
  • If the BOUNDARY_COLUMN is of a time type, the table can be partitioned only by Range Columns.

• BOUNDARY_COLUMN_UNIT = {"s" | "ms"}: specifies the time unit of the BOUNDARY_COLUMN parameter. This parameter can be set only when the BOUNDARY_COLUMN is of an integer type. If the integer value is used as a timestamp, you must specify the timestamp unit. Otherwise, the system may incorrectly parse the timestamp. Valid values:

  • If the partition column is of the INT type, the value of BOUNDARY_COLUMN_UNIT can be only s.

  • If the partition column is of the BIGINT type, the value of BOUNDARY_COLUMN_UNIT can be s or ms.

    Notice

    If the timestamp is not in the Unix timestamp format, the system cannot correctly identify the time represented by the INT type.

• HOT_RETENTION = intnum retention_time_unit: specifies the time range of hot data.

  • intnum: specifies an integer.

  • retention_time_unit: specifies the time unit. Valid values:

    • YEAR: specifies a year.
    • MONTH: specifies a month.
    • WEEK: specifies a week.
    • DAY: specifies a day.
    • HOUR: specifies an hour.
    • MINUTE: specifies a minute.

partition_storage_cache_policy

• STORAGE_CACHE_POLICY = {"hot" | "auto" | "none"}: specifies whether the data in the partition is hot data. Valid values:
  • hot: indicates that the partition is hot data. If the cache disk space is sufficient, all data in the partition will be cached to the local cloud disk.
  • auto: indicates that the hot data in the partition is automatically identified by the system.
  • none: the default value. Indicates that the strategy of the partition follows the value of STORAGE_CACHE_POLICY of the primary table.

Examples

Add and drop columns

Create a sample table named tbl1 and execute the DESCRIBE command to view the table information.

obclient> CREATE TABLE tbl1 (c1 INT(11) PRIMARY KEY,c2 VARCHAR(50));
Query OK, 0 rows affected

obclient> DESCRIBE tbl1;
+-------+------------+----------+--------+---------+-------+
| Field | Type       | Null     | Key    | Default | Extra |
+-------+------------+----------+--------+---------+-------+
| c1    | int(11)    | NO       | PRI    | NULL    |       |
| c2    | varchar(50)| YES      |        | NULL    |       |
+-------+------------+----------+--------+---------+-------+

• Add the c3 column and execute the DESCRIBE command to view the table information.

  obclient> ALTER TABLE tbl1 ADD c3 INT;
  Query OK, 1 row affected
  
  obclient> DESCRIBE tbl1;
  +-------+------------+----------+--------+---------+-------+
  | Field | Type       | Null     | Key    | Default | Extra |
  +-------+------------+----------+--------+---------+-------+
  | c1    | int(11)    | NO       | PRI    | NULL    |       |
  | c2    | varchar(50)| YES      |        | NULL    |       |
  | c3    | int(11)    | YES      |        | NULL    |       |
  +-------+------------+----------+--------+---------+-------+
  3 row affected
  

• Drop the c3 column and execute the DESCRIBE command to view the table information.

  obclient> ALTER TABLE tbl1 DROP c3;
  Query OK, 1 row affected
  
  obclient> DESCRIBE tbl1;
  +-------+------------+----------+--------+---------+-------+
  | Field | Type       | Null     | Key    | Default | Extra |
  +-------+------------+----------+--------+---------+-------+
  | c1    | int(11)    | NO       | PRI    | NULL    |       |
  | c2    | varchar(50)| YES      |        | NULL    |       |
  +-------+------------+----------+--------+---------+-------+
  2 row affected
  

• Rename the c2 column to c3 in the tbl1 table and execute the DESCRIBE command to view the table information.

  obclient> ALTER TABLE tbl1 CHANGE COLUMN c2 c3 VARCHAR(50);
  Query OK, 1 row affected
  
  obclient> DESCRIBE tbl1;
  +-------+------------+----------+--------+---------+-------+
  | Field | Type       | Null     | Key    | Default | Extra |
  +-------+------------+----------+--------+---------+-------+
  | c1    | int(11)    | NO       | PRI    | NULL    |       |
  | c3    | varchar(50)| YES      |        | NULL    |       |
  +-------+------------+----------+--------+---------+-------+
  2 rows affected
  

• Add the c4 column to the tbl1 table and set it as the first column of the table. Then, execute the DESCRIBE command to view the table information.

  obclient> ALTER TABLE tbl1 ADD COLUMN c4 INTEGER FIRST;
  Query OK, 1 row affected
  
  obclient> DESCRIBE tbl1;
  +-------+------------+----------+--------+---------+-------+
  | Field | Type       | Null     | Key    | Default | Extra |
  +-------+------------+----------+--------+---------+-------+
  | c4    | int(11)    | YES      |        | NULL    |       |
  | c1    | int(11)    | NO       | PRI    | NULL    |       |
  | c3    | varchar(50)| YES      |        | NULL    |       |
  +-------+------------+----------+--------+---------+-------+
  3 row affected
  

• Add the c2 column after the c1 column in the tbl1 table and execute the DESCRIBE command to view the table information.

  obclient> ALTER TABLE tbl1 ADD COLUMN c2 INTEGER AFTER c1;
  Query OK, 1 row affected
  
  obclient> DESCRIBE tbl1;
  +-------+------------+----------+--------+---------+-------+
  | Field | Type       | Null     | Key    | Default | Extra |
  +-------+------------+----------+--------+---------+-------+
  | c4    | int(11)    | YES      |        | NULL    |       |
  | c1    | int(11)    | NO       | PRI    | NULL    |       |
  | c2    | int(11)    | YES      |        | NULL    |       |
  | c3    | varchar(50)| YES      |        | NULL    |       |
  +-------+------------+----------+--------+---------+-------+
  4 row affected
  

• Add the c5 column before the c4 column in the tbl1 table and execute the DESCRIBE command to view the table information.

  obclient> ALTER TABLE tbl1 ADD COLUMN c5 INT BEFORE c4;
  Query OK, 1 row affected
  
  obclient> DESCRIBE tbl1;
  +-------+------------+----------+--------+---------+-------+
  | Field | Type       | Null     | Key    | Default | Extra |
  +-------+------------+----------+--------+---------+-------+
  | c5    | int(11)    | YES      |        | NULL    |       |
  | c4    | int(11)    | YES      |        | NULL    |       |
  | c1    | int(11)    | NO       | PRI    | NULL    |       |
  | c2    | int(11)    | YES      |        | NULL    |       |
  | c3    | varchar(50)| YES      |        | NULL    |       |
  +-------+------------+----------+--------+---------+-------+
  5 row affected
  

• Add the fk1 foreign key constraint to the tbl2 table. When an UPDATE operation affects the key values in the parent table that match the rows in the child table, execute the SET NULL operation.

  obclient> CREATE TABLE tbl2(c1 INT PRIMARY KEY,c2 INT);
  Query OK, 0 row affected
  obclient> CREATE TABLE tbl3(c1 INT PRIMARY KEY,c2 INT);
  Query OK, 0 row affected
  obclient> ALTER TABLE tbl2 ADD CONSTRAINT fk1 FOREIGN KEY (c2) REFERENCES tbl3(c1) ON UPDATE SET NULL;
  Query OK, 0 row affected
  

• Drop the fk1 foreign key constraint from the tbl3 table.

  obclient> ALTER TABLE tbl2 DROP FOREIGN KEY fk1;
  Query OK, 0 row affected
  

• Drop the primary key from the tbl2 table.

  obclient> ALTER TABLE tbl2 DROP PRIMARY KEY;
  Query OK, 0 row affected
  

Index operations

• Rename the ind1 index in the tbl2 table to ind2.

  obclient> CREATE TABLE tbl2(c1 INT(11) PRIMARY KEY,c2 INT(50));
  Query OK, 0 row affected
  
  obclient> CREATE INDEX ind1 ON tbl2 (c2 ASC);
  Query OK, 0 row affected
  obclient> ALTER TABLE tbl2 RENAME INDEX ind1 TO ind2;
  Query OK, 0 row affected
  

• Create an index named ind3 on the tbl2 table, referencing the c1 and c2 columns.

  obclient> ALTER TABLE tbl2 ADD INDEX ind3 (c1,c2);
  Query OK, 0 row affected
  

  You can execute the SHOW INDEX statement to view the created index.

  obclient> SHOW INDEX FROM tbl2;
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+
  | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment   | Index_comment | Visible |
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+
  | tbl2  |          0 | PRIMARY  |            1 | c1          | A         |        NULL | NULL     | NULL   |      | BTREE      | available |               | YES     |
  | tbl2  |          1 | ind2     |            1 | c2          | A         |        NULL | NULL     | NULL   |  YES | BTREE      | available |               | YES     |
  | tbl2  |          1 | ind3     |            1 | c1          | A         |        NULL | NULL     | NULL   |      | BTREE      | available |               | YES     |
  | tbl2  |          1 | ind3     |            2 | c2          | A         |        NULL | NULL     | NULL   |  YES | BTREE      | available |               | YES     |
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+
  4 rows in set
  

• Drop the ind2 index from the tbl2 table.

  obclient> ALTER TABLE tbl2 DROP INDEX ind2;
  Query OK, 0 row affected
  

  Note

  In actual O&M scenarios, you can use the preceding methods to perform atomic index changes.

• Add three function indexes to the t1_func table. One of the indexes is named i2, and the other two are automatically generated by the system with names in the format of functional_index followed by a number.

  obclient> ALTER TABLE t1_func ADD INDEX ((CONCAT(c1,'a')));
  Query OK, 0 rows affected
  obclient> ALTER TABLE t1_func ADD INDEX ((c1+1));
  Query OK, 0 rows affected
  obclient> ALTER TABLE t1_func ADD INDEX i2 ((CONCAT(c1,'a')));
  Query OK, 0 rows affected
  obclient> SHOW CREATE TABLE t1_func;
  +---------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | Table   | Create Table                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
  +---------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | t1_func | CREATE TABLE `t1_func` (
  `c1` int(11) DEFAULT NULL,
  `c2` int(11) DEFAULT NULL,
  KEY `i1` (((`c1` + `c2`) < 1)) BLOCK_SIZE 16384 LOCAL,
  KEY `functional_index` (concat(`c1`,'a')) BLOCK_SIZE 16384 LOCAL,
  KEY `functional_index_2` ((`c1` + 1)) BLOCK_SIZE 16384 LOCAL,
  KEY `i2` (concat(`c1`,'a')) BLOCK_SIZE 16384 LOCAL
  ) DEFAULT CHARSET = utf8mb4 ROW_FORMAT = DYNAMIC COMPRESSION = 'zstd_1.3.8' REPLICA_NUM = 1 BLOCK_SIZE = 16384 USE_BLOOM_FILTER = FALSE TABLET_SIZE = 134217728 PCTFREE = 0 |
  +---------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  1 row in set
  

• Create a columnstore index on the table.

  1. Execute the following SQL statement to create the tbl3 table.

     CREATE TABLE tbl3 (col1 INT, col2 VARCHAR(50));
     

  2. Create a columnstore index named idx1_tbl3 on the tbl3 table, referencing the col1 column.

     ALTER TABLE tbl3 ADD INDEX idx1_tbl3 (col1) WITH COLUMN GROUP(each column);
     

• Modify the index to be invisible.

  Note

  After an index is set to invisible, you can see the /*!80000 INVISIBLE */ tag in the table structure.

  1. Create the tbl4 table.

     CREATE TABLE tbl4 (col1 INT PRIMARY KEY, col2 INT, col3 INT);
     

  2. Create an index named idx1_tbl4.

     CREATE INDEX idx1_tbl4 ON tbl4(col2);
     

  3. Modify the idx1_tbl4 index to be invisible.

     ALTER TABLE tbl4 ALTER INDEX idx1_tbl4 INVISIBLE;
     

  4. View the structure of the tbl4 table again.

     SHOW CREATE TABLE tbl4;
     

     The return result is as follows:

     +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
     | Table | Create Table                                                                                                                                                                                                                                                                                                                                                                                                              |
     +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
     | tbl4  | CREATE TABLE `tbl4` (
       `col1` int(11) NOT NULL,
       `col2` int(11) DEFAULT NULL,
       `col3` int(11) DEFAULT NULL,
       PRIMARY KEY (`col1`),
       KEY `idx1_tbl4` (`col2`) BLOCK_SIZE 16384 LOCAL /*!80000 INVISIBLE */
     ) DEFAULT CHARSET = utf8mb4 ROW_FORMAT = DYNAMIC COMPRESSION = 'zstd_1.3.8' REPLICA_NUM = 1 BLOCK_SIZE = 16384 USE_BLOOM_FILTER = FALSE TABLET_SIZE = 134217728 PCTFREE = 0 WITH COLUMN GROUP(each column) |
     +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
     1 row in set
     

Partition operations

• Clear all data in the M202001 and M202002 partitions of the t_log_part_by_range partitioned table.

  obclient> CREATE TABLE t_log_part_by_range (
      log_id      bigint NOT NULL
      , log_value varchar(50)
      , log_date  timestamp NOT NULL
  ) PARTITION BY RANGE(UNIX_TIMESTAMP(log_date))
  (
      PARTITION M202001 VALUES LESS THAN(UNIX_TIMESTAMP('2020/02/01'))
      , PARTITION M202002 VALUES LESS THAN(UNIX_TIMESTAMP('2020/03/01'))
      , PARTITION M202003 VALUES LESS THAN(UNIX_TIMESTAMP('2020/04/01'))
      , PARTITION M202004 VALUES LESS THAN(UNIX_TIMESTAMP('2020/05/01'))
      , PARTITION M202005 VALUES LESS THAN(UNIX_TIMESTAMP('2020/06/01'))
  );
  Query OK, 0 rows affected
  
  obclient> ALTER TABLE t_log_part_by_range TRUNCATE PARTITION M202001, M202002;
  Query OK, 0 rows affected
  

• Add a partition named M202006 to the t_log_part_by_range partitioned table.

  obclient> CREATE TABLE t_log_part_by_range (
      log_id      bigint NOT NULL
      , log_value varchar(50)
      , log_date  timestamp NOT NULL
  ) PARTITION BY RANGE(UNIX_TIMESTAMP(log_date))
  (
      PARTITION M202001 VALUES LESS THAN(UNIX_TIMESTAMP('2020/02/01'))
      , PARTITION M202002 VALUES LESS THAN(UNIX_TIMESTAMP('2020/03/01'))
      , PARTITION M202003 VALUES LESS THAN(UNIX_TIMESTAMP('2020/04/01'))
      , PARTITION M202004 VALUES LESS THAN(UNIX_TIMESTAMP('2020/05/01'))
      , PARTITION M202005 VALUES LESS THAN(UNIX_TIMESTAMP('2020/06/01'))
  );
  Query OK, 0 rows affected
  
  obclient> ALTER TABLE t_log_part_by_range ADD PARTITION
           (PARTITION M202006 VALUES LESS THAN(UNIX_TIMESTAMP('2020/07/01'))
           );
  

Change the parallelism

• Change the parallelism of the tbl3 table to 2.

  obclient> ALTER TABLE tbl3 PARALLEL 2;
  

  In addition to using the ALTER TABLE table_name PARALLEL int; statement to change the parallelism of a table, you can also use the PARALLEL hint. The syntax is as follows: alter /*+ parallel(int) */ table.

Operations related to column types

• Modify the ordinary column col1 of the tbl4 table to an auto-increment column.

  obclient> CREATE TABLE tbl4 (col1 BIGINT(10) NOT NULL,col2 INT);
  Query OK, 0 rows affected
  
  obclient> ALTER TABLE tbl4 MODIFY col1 BIGINT(10) AUTO_INCREMENT;
  Query OK, 0 rows affected
  

• Add the col1 column as the primary key of the tbl4 table, and then change the primary key to col2.

  obclient> ALTER TABLE tbl4 ADD PRIMARY KEY (col1);
  Query OK, 0 rows affected
  
  obclient> ALTER TABLE tbl4 DROP PRIMARY KEY,ADD PRIMARY KEY (`col2`);
  Query OK, 0 rows affected
  

• Add a CHECK constraint.

  obclient> CREATE TABLE tbl7(col1 VARCHAR(10),col2 VARCHAR(10));
  Query OK, 0 rows affected
  
  obclient> ALTER TABLE tbl7 ADD CONSTRAINT my_check CHECK (col1> col2) ;
  Query OK, 0 rows affected
  

• Remove the CHECK constraint from the tbl7 table.

  obclient> ALTER TABLE tbl7 DROP CHECK my_check;
  Query OK, 0 rows affected
  

• Modify the column type to NOT NULL.

  obclient> CREATE TABLE dept(
      deptno           NUMBER(2,0),
      dname            VARCHAR(14),
      location         VARCHAR(13),
      CONSTRAINT pk_dept PRIMARY KEY(deptno)
  );
  Query OK, 0 rows affected
  
  obclient> CREATE TABLE emp(
      empno         NUMBER(4,0) NOT NULL,
      empname       VARCHAR(10) NOT NULL,
      job           VARCHAR(9) NOT NULL,
      mgr           NUMBER(4,0) NOT NULL,
      hiredate      DATE NOT NULL,
      sal           NUMBER(7,2) DEFAULT NULL,
      comm          NUMBER(7,2) DEFAULT NULL,
      deptno        NUMBER(2,0) DEFAULT NULL,
      CONSTRAINT PK_emp PRIMARY KEY (empno),
      CONSTRAINT FK_deptno  FOREIGN KEY (deptno)  REFERENCES dept (deptno)
  );
  Query OK, 0 rows affected
  
  obclient> ALTER TABLE emp MODIFY deptno NUMBER(2,0) DEFAULT '12' NOT NULL;
  Query OK, 0 rows affected
  

Rename a column and add a NOT NULL constraint

obclient> ALTER TABLE test_alter1 MODIFY COLUMN `C1` varchar(10) NOT NULL;
Query OK, 0 rows affected (2.421 sec)

Add NOT NULL constraints to two columns

Execute the following command to add NOT NULL constraints to the C1 and c2 columns:

obclient> ALTER TABLE test_alter4 MODIFY COLUMN c1 varchar(10) NOT NULL, MODIFY COLUMN c2 varchar(10) NOT NULL;
Query OK, 0 rows affected (2.605 sec)

Change the column type of a column with a prefix index

1. Execute the following command to create a table named test_alter5 that contains a column named c1 of the CHAR(20) data type and has a prefix index named idx_c1 on the c1 column:

   obclient> CREATE TABLE test_alter5 (c1 char(20), KEY idx_c1(c1(10)));
   

2. Execute the following command to change the data type of the c1 column to varchar(20):

   obclient> ALTER TABLE test_alter5 MODIFY COLUMN c1 varchar(20);
   

Change the foreign key constraint rules

1. Execute the following command to create a table named t1 and add a unique constraint to the integer column c1:

   obclient> CREATE TABLE t1(c1 int unique key);
   

2. Execute the following command to create a table named t2 that contains an integer column named c1 and define a foreign key constraint:

   obclient> CREATE TABLE t2(c1 int, CONSTRAINT fk_cst_test FOREIGN KEY (c1) REFERENCES t1(c1) on update set null on delete no action);
   

3. Execute the following command to query the INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS system table and obtain the update and delete rules of the foreign key constraint named fk_cst_test:

   obclient> SELECT update_rule, delete_rule FROM information_schema.referential_constraints WHERE CONSTRAINT_NAME = 'fk_cst_test';
   

   The return result is as follows:

   +-------------+-------------+
   | update_rule | delete_rule |
   +-------------+-------------+
   | SET NULL    | NO ACTION   |
   +-------------+-------------+
   

   • UPDATE_RULE: SET NULL indicates that the foreign key is set to NULL when the value of the primary key is updated.
   • DELETE_RULE: NO ACTION indicates that the constraint is checked when the primary key is deleted, and the operation may be blocked.

Rename a column

• The RENAME COLUMN operation does not change the column definition. It only modifies the column name. If the target name already exists in the table, the RENAME COLUMN operation will return an error. However, if you rename the column back to its original name, no error will be returned.

  obclient> CREATE TABLE tbl8 (a INT, b INT);
  Query OK, 0 rows affected
  
  obclient> ALTER TABLE tbl8 RENAME COLUMN a TO b;
  ERROR 1060 (42S21): Duplicate column name 'b'
  
  obclient> ALTER TABLE tbl8 RENAME COLUMN a TO a;
  Query OK, 0 rows affected
  

• If an index is created on the column that you want to rename, the RENAME COLUMN operation can be executed normally, and the index definition will be automatically updated.

  obclient> CREATE TABLE tbl9 (a INT, b INT, index idx_a(a));
  Query OK, 0 rows affected
  
  obclient> SHOW INDEX FROM tbl9;
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+------------+
  | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment   | Index_comment | Visible | Expression |
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+------------+
  | tbl9  |          1 | idx_a    |            1 | a           | A         |        NULL | NULL     | NULL   | YES  | BTREE      | available |               | YES     | NULL       |
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+------------+
  1 row in set
  
  obclient> ALTER TABLE tbl9 RENAME COLUMN a TO c;
  Query OK, 0 rows affected
  
  obclient> SHOW INDEX FROM tbl9;
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+------------+
  | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment   | Index_comment | Visible | Expression |
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+------------+
  | tbl9  |          1 | idx_a    |            1 | c           | A         |        NULL | NULL     | NULL   | YES  | BTREE      | available |               | YES     | NULL       |
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+------------+
  1 row in set
  

• If the column that you want to rename is referenced by a prefix index, the RENAME COLUMN operation can be executed normally, and the prefix index will be automatically updated.

  DROP TABLE tbl9;
  obclient> CREATE TABLE tbl9 (c1 INT PRIMARY KEY, c2 BLOB, c3 INT, INDEX i1 (c2(10)));
  Query OK, 0 rows affected
  
  obclient> ALTER TABLE tbl9 RENAME COLUMN c2 TO c2_, RENAME COLUMN c1 TO c2_1;
  DESC tbl9;
  Query OK, 0 rows affected
  
  obclient> SHOW INDEX FROM tbl9;
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+------------+
  | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment   | Index_comment | Visible | Expression |
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+------------+
  | tbl9  |          0 | PRIMARY  |            1 | c2_1        | A         |        NULL | NULL     | NULL   |      | BTREE      | available |               | YES     | NULL       |
  | tbl9  |          1 | i1       |            1 | c2_         | A         |        NULL | 10       | NULL   | YES  | BTREE      | available |               | YES     | NULL       |
  +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+------------+
  2 rows in set
  

• If a foreign key constraint is defined on the column that you want to rename, the RENAME COLUMN operation can be executed normally, and the foreign key constraint will be automatically updated.

  obclient> CREATE TABLE tbl10 (a INT PRIMARY KEY);
  Query OK, 0 rows affected
  
  obclient> CREATE TABLE tbl11(b INT, FOREIGN KEY (b) REFERENCES tbl10(a));
  
  obclient> SHOW CREATE TABLE tbl11;
  +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | Table | Create Table                                                                                                                                                                                                                                                                                                                                                      |
  +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | tbl11 | CREATE TABLE `tbl11` (
  `b` int(11) DEFAULT NULL,
  CONSTRAINT `tbl11_OBFK_1694681944513338` FOREIGN KEY (`b`) REFERENCES `test`.`tbl10`(`a`) ON UPDATE RESTRICT ON DELETE RESTRICT
  ) DEFAULT CHARSET = utf8mb4 ROW_FORMAT = DYNAMIC COMPRESSION = 'zstd_1.3.8' REPLICA_NUM = 1 BLOCK_SIZE =  16384 USE_BLOOM_FILTER = FALSE TABLET_SIZE = 134217728 PCTFREE = 0 |
  +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  1 row in set
  
  obclient> ALTER TABLE tbl10 RENAME COLUMN a TO c;
  Query OK, 0 rows affected
  
  obclient> SHOW CREATE TABLE tbl11;
  +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | Table | Create Table                                                                                                                                                                                                                                                                                                                                                      |
  +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | tbl11 | CREATE TABLE `tbl11` (
  `b` int(11) DEFAULT NULL,
  CONSTRAINT `tbl11_OBFK_1694681944513338` FOREIGN KEY (`b`) REFERENCES `test`.`tbl10`(`c`) ON UPDATE RESTRICT ON DELETE RESTRICT
  ) DEFAULT CHARSET = utf8mb4 ROW_FORMAT = DYNAMIC COMPRESSION = 'zstd_1.3.8' REPLICA_NUM = 1 BLOCK_SIZE = 16384 USE_BLOOM_FILTER = FALSE TABLET_SIZE = 134217728 PCTFREE = 0 |
  +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  1 row in set
  

OceanBase Database does not support modifying or automatically updating the following scenarios:

• If the column that you want to rename is referenced by a generated list expression, the column name cannot be modified, and an error will be returned when the RENAME COLUMN operation is executed.

  obclient> CREATE TABLE tbl12(a INT, b INT AS (a + 1), c INT, d INT, CONSTRAINT d_check CHECK(d > 0)) PARTITION BY HASH(c + 1) PARTITIONS 2;
  
  obclient> ALTER TABLE tbl12 RENAME COLUMN a TO e;
  ERROR 3108 (HY000): Column 'a' has a generated column dependency
  

• If the column that you want to rename is referenced by a partitioning expression, the column name cannot be modified, and an error will be returned when the RENAME COLUMN operation is executed.

  obclient> ALTER TABLE tbl12 RENAME COLUMN c TO e;
  ERROR 3855 (HY000): Column 'c' has a partitioning function dependency and cannot be dropped or renamed.
  

• If the column that you want to rename is referenced by a CHECK constraint, the column name cannot be modified, and an error will be returned when the RENAME COLUMN operation is executed.

  obclient> ALTER TABLE tbl12 RENAME COLUMN d TO e;
  ERROR 3959 (HY000): Check constraint 'd_check' uses column 'd', hence column cannot be dropped or renamed.
  

• If the column that you want to rename is referenced by a function-based index, the column name cannot be modified, and an error will be returned when the RENAME COLUMN operation is executed.

  DROP TABLE IF EXISTS tbl12;
  obclient> CREATE TABLE tbl12(i INT, INDEX ((i+1)));
  Query OK, 0 rows affected
  
  obclient> ALTER TABLE tbl12 RENAME COLUMN i TO j;
  ERROR 3837 (HY000): Column 'i' has a functional index dependency and cannot be dropped or renamed.
  

• If the column that you want to rename is referenced by a view, the RENAME COLUMN operation will succeed, but querying the view will return an error. You need to manually modify the view definition.

  obclient> CREATE TABLE tbl13(a INT);
  Query OK, 0 rows affected
  
  obclient> CREATE VIEW v1 AS SELECT a + 1 FROM tbl13;
  Query OK, 0 rows affected
  
  obclient> SELECT * FROM v1;
  Empty set
  
  obclient> ALTER TABLE tbl13 RENAME COLUMN a TO b;
  Query OK, 0 rows affected
  
  obclient> SELECT * FROM v1;
  ERROR 1356 (42S22): View 'test.v1' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them
  

• If the column that you want to rename is referenced by a stored procedure, the RENAME COLUMN operation will succeed, but the CALL procedure will return an error. You need to manually modify the stored procedure.

  obclient> CREATE TABLE tbl14(a INT);
  Query OK, 0 rows affected
  
  obclient> CREATE PROCEDURE proc() SELECT a + 1 FROM tbl14;
  Query OK, 0 rows affected
  
  obclient> CALL proc();
  Empty set
  
  obclient> ALTER TABLE tbl14 RENAME COLUMN a TO b;
  Query OK, 0 rows affected
  
  obclient> CALL proc();
  ERROR 1054 (42S22): Unknown column 'a' in 'field list'
  

Modify the columnstore attribute of a table

1. Run the following SQL statement to create a table named tbl1.

   CREATE TABLE tbl1 (col1 INT PRIMARY KEY, col2 VARCHAR(50));
   

2. Change the table tbl1 to a rowstore and columnstore redundant table, and then delete the rowstore and columnstore redundant attributes.

   ALTER TABLE tbl1 ADD COLUMN GROUP(all columns, each column);
   

   ALTER TABLE tbl1 DROP COLUMN GROUP(all columns, each column);
   

3. Change the table tbl1 to a columnstore table, and then delete the columnstore attribute.

   ALTER TABLE tbl1 ADD COLUMN GROUP(each column);
   

   ALTER TABLE tbl1 DROP COLUMN GROUP(each column);
   

Modify the Skip Index attribute of a column

Run the following SQL statement to create a table named test_skidx.

CREATE TABLE test_skidx(
  col1 INT SKIP_INDEX(MIN_MAX, SUM),
  col2 FLOAT SKIP_INDEX(MIN_MAX),
  col3 VARCHAR(1024) SKIP_INDEX(MIN_MAX),
  col4 CHAR(10)
  );

• Change the Skip Index attribute of column col2 in the test_skidx table to the SUM Skip Index type.

  ALTER TABLE test_skidx MODIFY COLUMN col2 FLOAT SKIP_INDEX(SUM);
  

• Add the Skip Index attribute to a new column in the test_skidx table. Add the MIN_MAX Skip Index type to column col4 in the test_skidx table.

  ALTER TABLE test_skidx MODIFY COLUMN col4 CHAR(10) SKIP_INDEX(MIN_MAX);
  

• Delete the Skip Index attribute of a column in the test_skidx table. Delete the Skip Index attribute of column col1 in the test_skidx table.

  ALTER TABLE test_skidx MODIFY COLUMN col1 INT SKIP_INDEX();
  

  or

  ALTER TABLE test_skidx MODIFY COLUMN col1 INT;
  

Modify the table attribute

Disable the persistent macroblock-level Bloom filter for the tb table.

ALTER TABLE tb SET enable_macro_block_bloom_filter = False;

Modify the STORAGE_CACHE_POLICY at the table level

• Change the hot cache of the tbl1 table to be automatically identified by the system.

  ALTER TABLE tbl1 SET STORAGE_CACHE_POLICY (GLOBAL = "auto");
  

• Change the data in the tbl2 table to be hot data that is within two months of the current time, based on the col3 column.

  ALTER TABLE tbl2 SET STORAGE_CACHE_POLICY (BOUNDARY_COLUMN = col3, HOT_RETENTION = 2 MONTH); 
  

Modify the STORAGE_CACHE_POLICY at the partition level

• Add a partition named p2 to the tbl3 table. The hot data in partition p2 that needs to be cached to the local disk is automatically identified by the system.

  ALTER TABLE tbl3 ADD PARTITION (PARTITION p2 VALUES LESS THAN(300) STORAGE_CACHE_POLICY = "auto");
  

• Change the data in the existing partition p1 of the tbl3 table to hot data.

  ALTER TABLE tbl3 ALTER PARTITION p1 STORAGE_CACHE_POLICY = 'hot';
  

• Change the data in the subpartition sp3 of the tbl4 table to hot data that needs to be cached to the local disk. This data is automatically identified by the system.

  ALTER TABLE tbl4 ALTER SUBPARTITON sp3 STORAGE_CACHE_POLICY = 'auto';
  

References

Change a table