BulkDelete

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

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["ClickHouseBulkCopy"]
    BulkCopy -->|Write| PseudoTable[("Pseudo Table")]
    PseudoTable -->|"ALTER TABLE ... DELETE<br/>WHERE qualifiers"| Table[("Target Table")]
    PseudoTable -->|Drop| Cleanup(["Pseudo Table Dropped"])

Use Case

Use this method to delete rows at high speed. It leverages this package’s internal ClickHouseBulkCopy class (see Operations (ClickHouse)).

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

A pseudo (staging) table is created for the call. The library writes to it via ClickHouseBulkCopy, then cascades the deletions to the target table via an ALTER TABLE ... DELETE mutation matched on the qualifiers — see Operations (ClickHouse) for the underlying mechanics.

The reported result is the number of rows staged, not a confirmed post-mutation count — see No Reliable Affected-Row Count.

Special Arguments

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

qualifiers defines the fields used to match existing rows. Defaults to the primary column if not specified.

bulkCopyTimeout is accepted for API parity with other providers, but currently has no effect.

batchSize overrides the number of rows sent to the server per batch. When not set, the driver’s own default (100,000) is used.

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

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

Usability

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

using (var connection = new ClickHouseConnection(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 ClickHouseConnection(connectionString))
{
    var deletedRows = connection.BulkDelete<Person>(people, batchSize: 1000);
}

DataTable

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

DataReader

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

Targeting a Table

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

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

Async Method

An equivalent BulkDeleteAsync method is also available.

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