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Data Check in the Sharding Scenario
Learn the data check in the sharding scenario.
/docs/dev/sync-diff-inspector/shard-diff/
/docs/dev/reference/tools/sync-diff-inspector/shard-diff/

Data Check in the Sharding Scenario

sync-diff-inspector supports data check in the sharding scenario. Assume that you use the TiDB Data Migration tool to replicate data from multiple MySQL instances into TiDB, you can use sync-diff-inspector to check upstream and downstream data.

For scenarios where the number of upstream sharded tables is small and the naming rules of sharded tables do not have a pattern as shown below, you can use Datasource config to configure table-0, set corresponding rules and configure the tables that have the mapping relationship between the upstream and downstream databases. This configuration method requires setting all sharded tables.

shard-table-replica-1

Below is a complete example of the sync-diff-inspector configuration.

# Diff Configuration.

######################### Global config #########################

# The number of goroutines created to check data. The number of connections between upstream and downstream databases are slightly greater than this value
check-thread-count = 4

# If enabled, SQL statements is exported to fix inconsistent tables
export-fix-sql = true

# Only compares the table structure instead of the data
check-struct-only = false

######################### Datasource config #########################
[data-sources.mysql1]
    host = "127.0.0.1"
    port = 3306
    user = "root"
    password = ""

    route-rules = ["rule1"]

[data-sources.mysql2]
    host = "127.0.0.1"
    port = 3306
    user = "root"
    password = ""

    route-rules = ["rule2"]

[data-sources.tidb0]
    host = "127.0.0.1"
    port = 4000
    user = "root"
    password = ""

########################### Routes ###########################
[routes.rule1]
schema-pattern = "test"        # Matches the schema name of the data source. Supports the wildcards "*" and "?"
table-pattern = "table-[1-2]"  # Matches the table name of the data source. Supports the wildcards "*" and "?"
target-schema = "test"         # The name of the schema in the target database
target-table = "table-0"       # The name of the target table

[routes.rule2]
schema-pattern = "test"      # Matches the schema name of the data source. Supports the wildcards "*" and "?"
table-pattern = "table-3"    # Matches the table name of the data source. Supports the wildcards "*" and "?"
target-schema = "test"       # The name of the schema in the target database
target-table = "table-0"     # The name of the target table

######################### Task config #########################
[task]
    output-dir = "./output"

    source-instances = ["mysql1", "mysql2"]

    target-instance = "tidb0"

    # The tables of downstream databases to be compared. Each table needs to contain the schema name and the table name, separated by '.'
    target-check-tables = ["test.table-0"]

You can use table-rules for configuration when there are a large number of upstream sharded tables and the naming rules of all sharded tables have a pattern, as shown below:

shard-table-replica-2

Below is a complete example of the sync-diff-inspector configuration.

# Diff Configuration.
######################### Global config #########################

# The number of goroutines created to check data. The number of connections between upstream and downstream databases are slightly greater than this value.
check-thread-count = 4

# If enabled, SQL statements is exported to fix inconsistent tables.
export-fix-sql = true

# Only compares the table structure instead of the data.
check-struct-only = false

######################### Datasource config #########################
[data-sources.mysql1]
    host = "127.0.0.1"
    port = 3306
    user = "root"
    password = ""

[data-sources.mysql2]
    host = "127.0.0.1"
    port = 3306
    user = "root"
    password = ""

[data-sources.tidb0]
    host = "127.0.0.1"
    port = 4000
    user = "root"
    password = ""

########################### Routes ###########################
[routes.rule1]
schema-pattern = "test"      # Matches the schema name of the data source. Supports the wildcards "*" and "?"
table-pattern = "table-*"    # Matches the table name of the data source. Supports the wildcards "*" and "?"
target-schema = "test"       # The name of the schema in the target database
target-table = "table-0"     # The name of the target table

######################### Task config #########################
[task]
    output-dir = "./output"
    source-instances = ["mysql1", "mysql2"]

    target-instance = "tidb0"

    # The tables of downstream databases to be compared. Each table needs to contain the schema name and the table name, separated by '.'
    target-check-tables = ["test.table-0"]

Note

If test.table-0 exists in the upstream database, the downstream database also compares this table.