BulkUpdate

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

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/>(Physical)"]
    Pseudo --> BulkCopy["ClickHouseBulkCopy"]
    BulkCopy -->|Write| PseudoTable[("Pseudo Table")]
    PseudoTable -->|"ALTER TABLE ... UPDATE<br/>WHERE qualifiers<br/>(no anti-join insert)"| Table[("Target Table")]
    PseudoTable -->|Drop| Cleanup(["Pseudo Table Dropped"])

Use Case

Use this method to update rows at high speed. It leverages this package’s internal ClickHouseBulkCopy class (see Operations (ClickHouse)).

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

A pseudo (staging) table is created for the call. The library writes to it via ClickHouseBulkCopy, then cascades the changes to the target table via a single ALTER TABLE ... UPDATE mutation — unlike BulkMerge, staged rows with no matching target row are left as-is, not inserted. See Operations (ClickHouse) for the underlying mechanics.

The reported result is the number of rows staged, not a confirmed post-mutation count — see No Reliable Affected-Row Count.

Special Arguments

The qualifiers, mappings, bulkCopyTimeout, batchSize and pseudoTableType arguments are available for this operation.

qualifiers defines the fields used to match existing rows. Defaults to the primary column if not specified.

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

bulkCopyTimeout is accepted for API parity with other providers, but currently has no effect.

batchSize overrides the number of rows sent to the server per batch. When not set, the driver’s own default (100,000) is used.

pseudoTableType (via ClickHouseBulkImportPseudoTableType) controls the kind of staging table used internally.

Every pseudoTableType value currently resolves to Physical at runtime — see Operations (ClickHouse) for details.

There are no identity-related arguments — this operation never generates or reads back identity values. If every staged column is also a qualifier (nothing left to update), the operation short-circuits and returns 0 without touching the database.

Usability

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

using (var connection = new ClickHouseConnection(connectionString))
{
    var updatedRows = connection.BulkUpdate(people);
}

To specify a batch size:

using (var connection = new ClickHouseConnection(connectionString))
{
    var updatedRows = connection.BulkUpdate(people, batchSize: 1000);
}

DataTable

using (var connection = new ClickHouseConnection(connectionString))
{
    var table = ConvertToDataTable(people);
    var updatedRows = connection.BulkUpdate("Person", table);
}

DataReader

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

To bulk-update via DataEntityDataReader:

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

Column Mappings

Add column mappings using the ClickHouseBulkInsertMapItem class.

var mappings = new List<ClickHouseBulkInsertMapItem>();

// Add the mappings
mappings.Add(new ClickHouseBulkInsertMapItem("SourceId", "DestinationId"));
mappings.Add(new ClickHouseBulkInsertMapItem("SourceName", "DestinationName"));

// Execute
using (var connection = new ClickHouseConnection(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 ClickHouseConnection(connectionString))
{
    var people = GetPeople(10000);
    var updatedRows = connection.BulkUpdate("Person", people);
}

Async Method

An equivalent BulkUpdateAsync method is also available.

using (var connection = new ClickHouseConnection(connectionString))
{
    var updatedRows = await connection.BulkUpdateAsync(people);
}