BulkDelete

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

This page documents the Vertica-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 Pseudo Table<br/>(Auto/Memory/Physical) +<br/>Index on qualifiers"]
    Pseudo --> Stream["VerticaCopyStream<br/>(COPY ... FROM STDIN)"]
    Stream -->|Write| PseudoTable[("Pseudo Table<br/>(qualifier columns only)")]
    PseudoTable -->|"DELETE FROM Target<br/>WHERE EXISTS (SELECT 1 FROM<br/>Pseudo S WHERE qualifiers match)"| Table[("Target Table")]
    PseudoTable -->|Drop| Cleanup(["Pseudo Table Dropped"])

Use Case

Use this method to delete rows at high speed. It leverages VerticaCopyStream, Vertica.Data’s native COPY ... FROM STDIN streaming API.

For deleting 1,000 or more rows, prefer this method over DeleteAll — Vertica’s IsMultiStatementExecutable setting is false, so DeleteAll issues one round trip per row when deleting by a list of keys.

A pseudo (staging) table, containing only the qualifier columns and indexed on them, is created for every call. The library streams into it via a COPY load internally, then cascades the deletions to the target table via a correlated EXISTS subquery — see Operations (Vertica) 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. Defaults to the primary or identity 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 VerticaBulkImportPseudoTableType) controls the kind of staging table used internally.

Caveats

This operation creates a pseudo (staging) table for every call — a per-call, uniquely-named TABLE or GLOBAL TEMPORARY TABLE, per pseudoTableType. The database user must have permission to create tables, or a VerticaException will be thrown.

Usability

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

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

Dictionary/ExpandoObject

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

DataReader

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

Targeting a Table

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

using (var connection = new VerticaConnection(connectionString))
{
    var deletedRows = connection.BulkDelete("\"Person\"", people);
}

Field Qualifiers

By default, the primary or identity column is used as the qualifier. To override, pass a list of Field objects in the qualifiers argument.

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

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