Operations · 3 min read

BulkDelete

This method deletes rows from the database in bulk, matched by the defined qualifiers. It is supported for Db2. Db2 also has a dedicated BulkDeleteByKey operation for deleting by primary key.

This page documents the Db2-specific arguments and examples. For the SQL Server implementation, see BulkDelete (SQL Server).

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 + Truncate<br/>Pseudo Table (Physical)"]
    Pseudo --> BulkCopy["DB2BulkCopy"]
    BulkCopy -->|Write| PseudoTable[("Pseudo Table<br/>(qualifier columns only)")]
    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 the native bulk operation from the IBM Data Server .NET Provider via the DB2BulkCopy class.

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

A pseudo (staging) table is created (and truncated) under a transaction context. The library writes to it via BulkInsert internally, then cascades the deletions to the target table via a correlated EXISTS subquery — see Operations (Db2) 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 Db2BulkImportPseudoTableType) controls the kind of staging table used internally.

Every pseudoTableType value currently resolves to Physical at runtime — see Operations (Db2) 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 DB2Exception will be thrown.

The DB2BulkCopy load into the staging table does not participate in the caller-supplied transaction — only the surrounding staging-table DDL and the final DELETE against the real table do.

Usability

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

using (var connection = new DB2Connection(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 DB2Connection(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 DB2Connection(connectionString))
{
    var table = ConvertToDataTable(people);
    var deletedRows = connection.BulkDelete("Person", table);
}

Dictionary/ExpandoObject

using (var sourceConnection = new DB2Connection(sourceConnectionString))
{
    var result = sourceConnection.QueryAll("Person");
    using (var destinationConnection = new DB2Connection(destinationConnectionString))
    {
        var deletedRows = destinationConnection.BulkDelete("Person", result);
    }
}

DataReader

using (var sourceConnection = new DB2Connection(sourceConnectionString))
{
    using (var reader = sourceConnection.ExecuteReader("SELECT * FROM Person"))
    {
        using (var destinationConnection = new DB2Connection(destinationConnectionString))
        {
            var rows = destinationConnection.BulkDelete("Person", reader);
        }
    }
}

Targeting a Table

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

using (var connection = new DB2Connection(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 DB2Connection(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 DB2Connection(connectionString))
{
    var people = connection.Query<Person>(e => e.IsActive == false);
    var deletedRows = await connection.BulkDeleteAsync<Person>(people);
}