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BulkMerge

This method merges all rows from the client application into the database in bulk — inserting new rows and updating existing ones based on the defined qualifiers. It is supported for SAP HANA.

This page documents the SAP HANA-specific arguments and examples. For the SQL Server implementation, see BulkMerge (SQL Server).

Call Flow Diagram

The diagram below shows the flow when calling this operation.

flowchart TD
    Client["Client<br/>(RepoDB)"] -->|BulkMerge| Source["Entities /<br/>DataTable /<br/>DbDataReader"]
    Source --> Pseudo["Create Pseudo Table<br/>(deterministic name) +<br/>Index on qualifiers"]
    Pseudo --> Loader["Buffered row-by-row<br/>parameterized INSERT"]
    Loader -->|Write| PseudoTable[("Pseudo Table")]
    PseudoTable --> Decision{"identityBehavior ==<br/>ReturnIdentity?"}
    Decision -->|NO| Merge["MERGE INTO ... USING ...<br/>WHEN MATCHED THEN UPDATE<br/>WHEN NOT MATCHED THEN INSERT<br/>(single statement)"]
    Decision -->|YES| Step1["Copy existing identity onto<br/>matched pseudo rows"]
    Step1 --> Step2["Assign fresh, gap-free identity<br/>to unmatched pseudo rows<br/>(correlated COUNT)"]
    Step2 --> Step3["MERGE INTO ... (identity<br/>inserted explicitly)"]
    Merge --> Table[("Target Table")]
    Step3 --> Table
    Step3 -->|"SELECT identity FROM Pseudo<br/>ORDER BY row-order"| Client
    PseudoTable -->|Drop| Cleanup(["Pseudo Table Dropped"])

Use Case

Use this method to merge rows against SAP HANA without hand-rolling the row-by-row loop yourself.

SAP HANA has no native bulk-load API, so writing into the pseudo table is a client-buffered loop of single-row, parameterized INSERT statements — one round trip per row. The cascading MERGE against the real table, however, is a single native statement.

A pseudo (staging) table, indexed on the qualifier columns, is created under a deterministic name for every call. The library writes to it row-by-row internally, then cascades the changes to the target table — see Operations (SAP HANA) for the underlying mechanics and its concurrency caveat.

Special Arguments

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

qualifiers defines the fields used to match existing rows, corresponding to the ON clause. Defaults to the primary or identity column if not specified.

mappings (via SapHanaBulkInsertMapItem) defines explicit column mappings between the source properties and the destination columns, with an optional HanaDbType override per mapping. When omitted, columns are auto-mapped by name (case-insensitive).

bulkCopyTimeout overrides the command timeout, in seconds, applied to each row’s INSERT while staging.

batchSize overrides how many rows are buffered client-side between flushes (default 500) — it does not change the number of round trips.

identityBehavior (via SapHanaBulkImportIdentityBehavior) controls whether newly generated identity values are set back on the data entities. Disabled (KeepIdentity) by default.

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

The DbDataReader overload has no identityBehavior argument, for the same reason as BulkInsert’s reader overload.

Identity Setting Alignment

When identityBehavior is ReturnIdentity, resolving every pseudo row’s final identity value is a three-step sequence, run once every row has already been staged:

  1. Assign matched identities. For every pseudo row that already has a match in the target table (by the qualifier columns), copy that row’s existing identity value onto the pseudo row.
  2. Assign fresh identities to unmatched rows. For every pseudo row with no match, assign (seed - 1) + (its rank among the unmatched rows, by load order) — computed via a correlated COUNT(*) rather than a window function, deliberately kept as plain, portable ANSI SQL.
  3. Merge. Run the real MERGE, now inserting the identity column explicitly (with its pre-assigned value from steps 1–2) instead of leaving SAP HANA to auto-generate it.

Every row’s identity is then read back via a SELECT ordered by the pseudo table’s row-order column.

Per the library’s own source comments, step 2’s correlated-COUNT rank computation is the least-verified statement in the whole provider. Verify this specifically — including its behavior under concurrent writers to the same table — before relying on BulkMerge with ReturnIdentity in production.

Usability

Given a list of Person models containing both existing and new rows, the following example bulk-merges them into the Person table.

using (var connection = new HanaConnection(connectionString))
{
    var mergedRows = connection.BulkMerge(people);
}

To specify a batch size:

using (var connection = new HanaConnection(connectionString))
{
    var mergedRows = connection.BulkMerge(people, batchSize: 100);
}

DataTable

using (var connection = new HanaConnection(connectionString))
{
    var table = ConvertToDataTable(people);
    var mergedRows = connection.BulkMerge("\"Person\"", table);
}

Dictionary/ExpandoObject

using (var sourceConnection = new HanaConnection(sourceConnectionString))
{
    var result = sourceConnection.QueryAll("\"Person\"");
    using (var destinationConnection = new HanaConnection(destinationConnectionString))
    {
        var mergedRows = destinationConnection.BulkMerge("\"Person\"", result,
            qualifiers: Field.From("Name"));
    }
}

DataReader

using (var sourceConnection = new HanaConnection(sourceConnectionString))
{
    using (var reader = sourceConnection.ExecuteReader("SELECT * FROM \"Person\" WHERE \"Age\" > 18"))
    {
        using (var destinationConnection = new HanaConnection(destinationConnectionString))
        {
            var rows = destinationConnection.BulkMerge("\"Person\"", reader);
        }
    }
}

To bulk-merge via DataEntityDataReader:

using (var connection = new HanaConnection(connectionString))
{
    var people = GetPeople(10000);
    using (var reader = new DataEntityDataReader<Person>(people))
    {
        var mergedRows = connection.BulkMerge("\"Person\"", reader);
    }
}

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 HanaConnection(connectionString))
{
    var people = GetPeople(10000);
    var mergedRows = connection.BulkMerge<Person>(people,
        qualifiers: e => new { e.Name });
}

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

Column Mappings

Add column mappings using the SapHanaBulkInsertMapItem class.

var mappings = new List<SapHanaBulkInsertMapItem>();

// Add the mappings
mappings.Add(new SapHanaBulkInsertMapItem("SourceId", "DestinationId"));
mappings.Add(new SapHanaBulkInsertMapItem("SourceName", "DestinationName"));
mappings.Add(new SapHanaBulkInsertMapItem("SourceAge", "DestinationAge"));
mappings.Add(new SapHanaBulkInsertMapItem("SourceCreatedDateUtc", "DestinationCreatedDateUtc"));

// Execute
using (var connection = new HanaConnection(connectionString))
{
    var people = GetPeople(10000);
    var mergedRows = connection.BulkMerge(people,
        mappings: mappings);
}

Targeting a Table

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

using (var connection = new HanaConnection(connectionString))
{
    var people = GetPeople(10000);
    var mergedRows = connection.BulkMerge("\"Person\"", people);
}

Async Method

An equivalent BulkMergeAsync method is also available.

using (var connection = new HanaConnection(connectionString))
{
    var mergedRows = await connection.BulkMergeAsync(people);
}