BulkDeleteByKey

This method deletes rows from the database using a list of primary keys in bulk. It is supported for RepoDb.MySql.BulkOperations, targeting the MySql.Data driver.

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

Call Flow Diagram

The diagram below shows the flow when calling this operation.

flowchart TD
    Client["Client<br/>(RepoDB)"] -->|BulkDeleteByKey| Keys["Primary Keys<br/>IEnumerable&lt;TPrimaryKey&gt;"]
    Keys --> Pseudo["Create Pseudo Table<br/>(Physical, key column only)"]
    Pseudo --> BulkCopy["MySqlBulkCopy<br/>(LOAD DATA LOCAL INFILE)"]
    BulkCopy -->|Write| PseudoTable[("Pseudo Table<br/>(key column only)")]
    PseudoTable -->|"DELETE ... INNER JOIN<br/>ON key"| Table[("Target Table")]
    PseudoTable -->|Drop| Cleanup(["Pseudo Table Dropped"])

Use Case

Use this method to delete rows by primary key at high speed. It leverages this package’s internal MySqlBulkCopy class (LOAD DATA LOCAL INFILE-based, see Operations (MySQL)).

Prefer this method over BulkDelete when you only have the primary keys of the rows to delete (not the full entities). The pseudo table used internally only ever stages the one key column, making this the lightest of the bulk operations, and it’s named distinctly from BulkDelete’s so the two never collide even against the same real table.

Special Arguments

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

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 MySqlBulkImportPseudoTableType) controls the kind of staging table used internally.

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

BulkDeleteByKey has no qualifiers argument of its own, since the key values themselves are the match criteria.

Caveats

This operation creates a pseudo-temporary table for each call. The database user must have permission to create tables, or a MySqlException will be thrown. Because CREATE TABLE/DROP TABLE are DDL, each call implicitly commits any other pending work on the connection — see The Staging Table Lifecycle.

Usability

Pass the target table name and the list of primary keys to the operation.

using (var connection = new MySqlConnection(connectionString))
{
    var primaryKeys = connection.Query<Person>(p => p.IsActive == false).Select(p => p.Id);
    var deletedRows = connection.BulkDeleteByKey("Person", primaryKeys);
}

It returns the number of rows deleted from the underlying table.

To specify a batch size:

using (var connection = new MySqlConnection(connectionString))
{
    var primaryKeys = connection.Query<Person>(p => p.IsActive == false).Select(p => p.Id);
    var deletedRows = connection.BulkDeleteByKey("Person",
        primaryKeys,
        batchSize: 100);
}

If batchSize is not set, all items in the collection are sent at once.

DataReader

using (var sourceConnection = new MySqlConnection(sourceConnectionString))
{
    using (var reader = sourceConnection.ExecuteReader("SELECT Id FROM Person WHERE (IsActive = 0)"))
    {
        var primaryKeys = new List<int>();
        while (reader.Read())
        {
            primaryKeys.Add(reader.GetInt32(0));
        }
        using (var destinationConnection = new MySqlConnection(destinationConnectionString))
        {
            var deletedRows = destinationConnection.BulkDeleteByKey("Person", primaryKeys);
        }
    }
}

Async Method

An equivalent BulkDeleteByKeyAsync method is also available.

using (var connection = new MySqlConnection(connectionString))
{
    var primaryKeys = connection.Query<Person>(p => p.IsActive == false).Select(p => p.Id);
    var deletedRows = await connection.BulkDeleteByKeyAsync("Person", primaryKeys);
}