Operations · 3 min read

BulkDelete

This method deletes rows from the database in bulk, matched by the defined qualifiers. It is supported for DuckDB. DuckDB 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/>(TEMP by default,<br/>qualifier columns only)"]
    Pseudo --> Appender["DuckDbBulkAppender"]
    Appender -->|Write| PseudoTable[("Pseudo Table")]
    PseudoTable -->|"DELETE ... WHERE EXISTS<br/>(SELECT 1 ... JOIN ON qualifiers)"| Table[("Target Table")]
    PseudoTable -->|Drop| Cleanup(["Pseudo Table Dropped"])

Use Case

Use this method to delete rows at high speed. It leverages DuckDB.NET’s native DuckDBAppender via the DuckDbBulkAppender wrapper.

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

A pseudo (staging) table — holding only the qualifier columns — is always created first. The library writes to it via DuckDbBulkAppender internally, then cascades the deletions to the target table via a correlated EXISTS subquery — see Operations (DuckDB) 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 WHERE clause. 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 DuckDbBulkImportPseudoTableType) controls the kind of staging table used internally.

Auto currently behaves exactly like Memory (a TEMP table) — see Operations (DuckDB) for details.

Caveats

This operation creates a pseudo-temporary table internally. The database user must have permission to create tables, or the underlying DuckDBException will surface from the create-table statement.

Usability

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

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

Dictionary/ExpandoObject

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

DataReader

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

Targeting a Table

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

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