---
{
    "title": "Sql Interception",
    "language": "en"
}
---

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# SQL Block Rule

This function is only used to limit the query statement, and does not limit the execution of the explain statement.
Support SQL block rule by user level:

1. by regex way to deny specify SQL

2. by setting partition_num, tablet_num, cardinality, check whether a sql reaches one of the limitations
    - partition_num, tablet_num, cardinality could be set together, and once reach one of them, the sql will be blocked.

## Rule

SQL block rule CRUD
- create SQL block rule,For more creation syntax see[CREATE SQL BLOCK RULE](../sql-manual/sql-reference/Data-Definition-Statements/Create/CREATE-SQL-BLOCK-RULE.md)
    - sql：Regex pattern，Special characters need to be translated, "NULL" by default
    - sqlHash: Sql hash value, Used to match exactly, We print it in fe.audit.log, This parameter is the only choice between sql and sql, "NULL" by default
    - partition_num: Max number of partitions will be scanned by a scan node, 0L by default
    - tablet_num: Max number of tablets will be scanned by a scan node, 0L by default
    - cardinality: An inaccurate number of scan rows of a scan node, 0L by default
    - global: Whether global(all users)is in effect, false by default
    - enable：Whether to enable block rule，true by default
```sql
CREATE SQL_BLOCK_RULE test_rule 
PROPERTIES(
  "sql"="select * from order_analysis",
  "global"="false",
  "enable"="true",
  "sqlHash"=""
)
```
When we execute the sql that we defined in the rule just now, an exception error will be returned. An example is as follows:
```sql
mysql> select * from order_analysis;
ERROR 1064 (HY000): errCode = 2, detailMessage = sql match regex sql block rule: order_analysis_rule
```

- create test_rule2, limits the maximum number of scanning partitions to 30 and the maximum scanning cardinality to 10 billion rows. As shown in the following example:
```sql
CREATE SQL_BLOCK_RULE test_rule2 PROPERTIES("partition_num" = "30", "cardinality"="10000000000","global"="false","enable"="true")
```

- show configured SQL block rules, or show all rules if you do not specify a rule name,Please see the specific grammar [SHOW SQL BLOCK RULE](../sql-manual/sql-reference/Show-Statements/SHOW-SQL-BLOCK-RULE.md)

```sql
SHOW SQL_BLOCK_RULE [FOR RULE_NAME]
```
- alter SQL block rule，Allows changes sql/sqlHash/global/enable/partition_num/tablet_num/cardinality anyone,Please see the specific grammar[ALTER SQL BLOCK  RULE](../sql-manual/sql-reference/Data-Definition-Statements/Alter/ALTER-SQL-BLOCK-RULE.md)
    - sql and sqlHash cannot be set both. It means if sql or sqlHash is set in a rule, another property will never be allowed to be altered
    - sql/sqlHash and partition_num/tablet_num/cardinality cannot be set together. For example, partition_num is set in a rule, then sql or sqlHash will never be allowed to be altered.
```sql
ALTER SQL_BLOCK_RULE test_rule PROPERTIES("sql"="select \\* from test_table","enable"="true")
```

```
ALTER SQL_BLOCK_RULE test_rule2 PROPERTIES("partition_num" = "10","tablet_num"="300","enable"="true")
```

- drop SQL block rule，Support multiple rules, separated by `,`,Please see the specific grammar[DROP SQL BLOCK RULR](../sql-manual/sql-reference/Data-Definition-Statements/Drop/DROP-SQL-BLOCK-RULE.md)
```sql
DROP SQL_BLOCK_RULE test_rule1,test_rule2
```

## User bind rules
If global=false is configured, the rules binding for the specified user needs to be configured, with multiple rules separated by ', '
```sql
SET PROPERTY [FOR 'jack'] 'sql_block_rules' = 'test_rule1,test_rule2'
```