BulkDelete

This method deletes rows from the database in bulk, matched by the defined qualifiers. It is supported for MySqlConnector. MySqlConnector also has a dedicated BulkDeleteByKey operation for deleting by primary key.

This page documents the MySqlConnector-specific arguments and examples. For the SQL Server implementation, see BulkDelete (SQL Server); for Oracle, see BulkDelete (Oracle).

Call Flow Diagram

The diagram below shows the flow when calling this operation.

flowchart TD
    Client["Client<br/>(RepoDB)"] -->|BulkDelete| Source["Entities /<br/>DataTable /<br/>DbDataReader"]
    Source --> Pseudo["Create Pseudo Table<br/>(Physical)"]
    Pseudo --> BulkCopy["MySqlBulkCopy"]
    BulkCopy -->|Write| PseudoTable[("Pseudo Table")]
    PseudoTable -->|"DELETE ... INNER JOIN<br/>ON qualifiers"| Table[("Target Table")]
    PseudoTable -->|Drop| Cleanup(["Pseudo Table Dropped"])

Use Case

Use this method to delete rows at high speed. It leverages the native bulk operation from MySqlConnector via the MySqlBulkCopy class.

For deleting 1,000 or more rows, prefer this method over DeleteAll.

A pseudo (staging) table is created under a transaction context. The library writes to it via BulkInsert internally, then cascades the deletions to the target table via a DELETE ... INNER JOIN matched on the qualifiers — see Operations (MySqlConnector) for the underlying mechanics.

Special Arguments

The qualifiers, bulkCopyTimeout, batchSize and pseudoTableType arguments are available for this operation.

qualifiers defines the fields used to match existing rows, corresponding to the ON clause of the join. Defaults to the primary column if not specified.

bulkCopyTimeout overrides the command timeout, in seconds.

batchSize overrides the number of rows sent to the server per batch. When not set, all items are sent at once.

pseudoTableType (via MySqlConnectorBulkImportPseudoTableType) controls the kind of staging table used internally.

Every pseudoTableType value currently resolves to Physical at runtime — see Operations (MySqlConnector) for details.

Caveats

This operation creates a pseudo-temporary table internally under a transaction context. The database user must have permission to create tables, or a MySqlException will be thrown.

Usability

The following example retrieves all inactive people, then bulk-deletes them from the Person table.

using (var connection = new MySqlConnection(connectionString))
{
    var people = connection.Query<Person>(e => e.IsActive == false);
    var deletedRows = connection.BulkDelete<Person>(people);
}

To specify a batch size:

using (var connection = new MySqlConnection(connectionString))
{
    var deletedRows = connection.BulkDelete<Person>(people, batchSize: 100);
}

When batchSize is not set, all rows are sent to the server in a single batch.

DataTable

using (var connection = new MySqlConnection(connectionString))
{
    var table = ConvertToDataTable(people);
    var deletedRows = connection.BulkDelete("Person", table);
}

Dictionary/ExpandoObject

using (var sourceConnection = new MySqlConnection(sourceConnectionString))
{
    var result = sourceConnection.QueryAll("Person");
    using (var destinationConnection = new MySqlConnection(destinationConnectionString))
    {
        var deletedRows = destinationConnection.BulkDelete("Person", result);
    }
}

DataReader

using (var sourceConnection = new MySqlConnection(sourceConnectionString))
{
    using (var reader = sourceConnection.ExecuteReader("SELECT * FROM Person"))
    {
        using (var destinationConnection = new MySqlConnection(destinationConnectionString))
        {
            var rows = destinationConnection.BulkDelete("Person", reader);
        }
    }
}

Targeting a Table

To target a specific table, pass the literal table name.

using (var connection = new MySqlConnection(connectionString))
{
    var deletedRows = connection.BulkDelete("Person", people);
}

Field Qualifiers

By default, the primary column is used as the qualifier. To override, pass a list of Field objects in the qualifiers argument.

using (var connection = new MySqlConnection(connectionString))
{
    var deletedRows = connection.BulkDelete<Person>(people,
        qualifiers: e => new { e.LastName, e.DateOfBirth });
}

Use indexed columns from the target table as qualifiers to maximize performance.

Async Method

An equivalent BulkDeleteAsync method is also available.

using (var connection = new MySqlConnection(connectionString))
{
    var people = connection.Query<Person>(e => e.IsActive == false);
    var deletedRows = await connection.BulkDeleteAsync<Person>(people);
}