Operations · 4 min read

BulkUpdate

This method updates existing rows in the database in bulk, matched by the defined qualifiers. It is supported for DuckDB.

Call Flow Diagram

The diagram below shows the flow when calling this operation.

flowchart TD
    Client["Client<br/>(RepoDB)"] -->|BulkUpdate| Source["Entities /<br/>DataTable /<br/>DbDataReader"]
    Source --> Pseudo["Create Pseudo Table<br/>(TEMP by default)"]
    Pseudo --> Appender["DuckDbBulkAppender"]
    Appender -->|Write| PseudoTable[("Pseudo Table")]
    PseudoTable -->|"UPDATE ... FROM ...<br/>(no unmatched-row insert)"| Table[("Target Table")]
    PseudoTable -->|Drop| Cleanup(["Pseudo Table Dropped"])

Use Case

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

For updating 1,000 or more rows, prefer this method over UpdateAll.

A pseudo (staging) table is always created first. The library writes to it via DuckDbBulkAppender internally, then cascades the changes to the target table via a plain UPDATE ... FROM statement — staged rows with no matching target row are left as-is, not inserted. See Operations (DuckDB) for the underlying mechanics.

Special Arguments

The qualifiers, mappings, 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.

mappings (via DuckDbBulkInsertMapItem) defines explicit column mappings between the source properties and the destination columns. When omitted, columns are auto-mapped by name (case-insensitive).

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

Given a list of Person models, the following example bulk-updates rows in the Person table.

using (var connection = new DuckDBConnection(ConnectionString))
{
    var updatedRows = connection.BulkUpdate(people);
}

To specify a batch size:

using (var connection = new DuckDBConnection(ConnectionString))
{
    var updatedRows = connection.BulkUpdate(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 updatedRows = connection.BulkUpdate("Person", table);
}

Dictionary/ExpandoObject

using (var sourceConnection = new DuckDBConnection(sourceConnectionString))
{
    var result = sourceConnection.QueryAll("Person");
    using (var destinationConnection = new DuckDBConnection(destinationConnectionString))
    {
        var updatedRows = destinationConnection.BulkUpdate("Person", result,
            qualifiers: Field.From("LastName", "DateOfBirth"));
    }
}

DataReader

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

To bulk-update via DataEntityDataReader:

using (var connection = new DuckDBConnection(ConnectionString))
{
    var people = GetPeople(10000);
    using (var reader = new DataEntityDataReader<Person>(people))
    {
        var updatedRows = connection.BulkUpdate("Person", reader);
    }
}

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 people = GetPeople(10000);
    var updatedRows = connection.BulkUpdate<Person>(people,
        qualifiers: e => new { e.LastName, e.DateOfBirth });
}

Use indexed columns from the target table as qualifiers to maximize performance.

Column Mappings

Add column mappings using the DuckDbBulkInsertMapItem class.

var mappings = new List<DuckDbBulkInsertMapItem>();

// Add the mappings
mappings.Add(new DuckDbBulkInsertMapItem("SourceId", "DestinationId"));
mappings.Add(new DuckDbBulkInsertMapItem("SourceName", "DestinationName"));
mappings.Add(new DuckDbBulkInsertMapItem("SourceIsActive", "DestinationIsActive"));

// Execute
using (var connection = new DuckDBConnection(ConnectionString))
{
    var people = GetPeople(10000);
    var updatedRows = connection.BulkUpdate(people,
        mappings: mappings);
}

Targeting a Table

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

using (var connection = new DuckDBConnection(ConnectionString))
{
    var people = GetPeople(10000);
    var updatedRows = connection.BulkUpdate("Person", people);
}

Async Method

An equivalent BulkUpdateAsync method is also available.

using (var connection = new DuckDBConnection(ConnectionString))
{
    var updatedRows = await connection.BulkUpdateAsync(people);
}