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.
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.