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BulkDelete


This method is used to delete the target rows from the database by bulk. It is only supporting the SQL Server RDBMS.

Call Flow Diagram

The diagram below shows the flow when calling this operation.

Use Case

This method is very useful if you are deleting multiple rows from the database in a very speedy manner. It is high-performant in nature as it is using the real bulk operation natively from ADO.NET (via SqlBulkCopy class).

If you are working to delete a range of rows from 1000 or more, then use this method over the DeleteAll operation.

Special Arguments

The arguments qualifiers and usePhysicalPseudoTempTable is provided on this operation.

The qualifiers is used to define the qualifier fields to be used in the operation. It usually refers to the WHERE expression of the SQL Statement. If not given, the primary column will be used.

The usePhysicalPseudoTempTable is used to define whether a physical pseudo-table will be created during the operation. By default, a temporary table (i.e.: #TableName) is used.

Please be noted that it is not recommended to enable the usePhysicalPseudoTempTable argument if you are to work with parallelism. Ensure to always utilize the session-based non-physical pseudo-temporary table when working with parallelism.

Caveats

RepoDB is automatically setting the value of the options argument to SqlBulkCopyOptions.KeepIdentity when calling this method and if you have not passed any qualifiers and if your table has an IDENTITY primary key column. The same logic will apply if there is no primary key but has an IDENTITY column defined in the table.

In addition, when calling this method, the library is creating a pseudo temporary table behind the scene. It requires your user to have the correct privilege to create a table in the database, otherwise a SqlException will be thrown.

Usability

Let us say you are retrieving all the inactive people from the database.

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

Then, below is the code that bulk-deletes all those inactive rows from the [dbo].[Person] table.

using (var connection = new SqlConnection(connectionString))
{
    var deletedRows = connection.BulkDelete<Person>(people);
}

And below if you would like to specify the batch size.

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

By default, the batch size is 10, equals to Constant.DefaultBatchOperationSize value.

DataTable

Below is the sample code to bulk-delete via data table.

using (var connection = new SqlConnection(connectionString))
{
    var table = ConvertToDataTable(people);
    var deletedRows = connection.BulkDelete<Person>(table);
}

Dictionary/ExpandoObject

Below is the sample code to bulk-delete via Dictionary<string, object> or ExpandoObject.

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

DataReader

Below is the sample code to bulk-delete via DbDataReader.

using (var sourceConnection = new SqlConnection(sourceConnectionString))
{
    using (var reader = sourceConnection.ExecuteReader("SELECT * FROM [dbo].[Person];"))
    {
        using (var destinationConnection = new SqlConnection(destinationConnectionString))
        {
            var rows = destinationConnection.BulkDelete<Person>(reader);
        }
    }
}

Targeting a Table

You can also target a specific table by passing the literal table and field name like below.

using (var connection = new SqlConnection(connectionString))
{
    var deletedRows = connection.BulkDelete("[dbo].[Person]", people);
}

Field Qualifiers

By default, this operation is using the primary column as the qualifier. You can override the qualifiers by simply passing the list of Field object in the qualifiers argument.

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

Or by parsing the field expression.

When using the qualifiers, we recommend that you use the list of columns that has the correct index from the original table.

Table Hints

To pass a hint, simply write the table-hints and pass it in the hints argument.

using (var connection = new SqlConnection(connectionString))
{
    var deletedRows = connection.BulkDelete("[dbo].[Person]",
        people,
        hints: "WITH (TABLOCK)");
}

Or, you can use the SqlServerTableHints class.

using (var connection = new SqlConnection(connectionString))
{
    var deletedRows = connection.BulkDelete("[dbo].[Person]",
        people,
        hints: SqlServerTableHints.TabLock);
}

Physical Temporary Table

To use a physical pseudo-temporary table, simply pass true in the usePhysicalPseudoTempTable argument.

using (var connection = new SqlConnection(connectionString))
{
    var deletedRows = connection.BulkDelete("[dbo].[Person]",
        people,
        usePhysicalPseudoTempTable: true);
}

By using the actual pseudo physical temporary table, it will further help you maximize the performance over using the normal temporary table. However, you need to be aware that the table is shared to any call, so parallelism may fail on this scenario.