BulkInsertOrUpdateAsync performance questions

[Balint Kulcsar]

Hi Guys!

I need some help regarding to BulkInsertOrUpdateAsync operation, I could not find any performance benchmarks related to BulkInsertOrUpdateAsync, however I think it not as fast as I would expect from SQL MERGE operation. I am using Azure MS SQL server with 200 DTU and for 250k records the BulkInsertOrUpdateAsync tooks arround 6 minues for the first run (when basically all records are new so it does only insert), and when we load again the same records with some changes it tooks 2 minutes. If course increasing the MS DB's DTU would help the performance, but first I want to optimize the BulkInsertOrUpdateAsync as much as possible.

So my question is that is 6 mins normal to load 250k records with BulkInsertOrUpdateAsync with 200 DTU Azure SQL? Can I improve its perfomance with configuration? I cannot find any config in BulkConfig which might can help.

Code for the merge operation:

public virtual async Task BulkMergeAsync(
    IEnumerable<T> entities,
    BulkConfig? bulkConfig = null,
    CancellationToken cancellationToken = default)
{
    try
    {
        if (bulkConfig == null)
        {
            bulkConfig = new BulkConfig();
        }

        bulkConfig.CalculateStats = true;
        bulkConfig.BulkCopyTimeout = 0;

        await _dbContext.BulkInsertOrUpdateAsync(entities, bulkConfig, cancellationToken: cancellationToken);

        if (bulkConfig.StatsInfo != null)
        {
            _logger.LogInformation($"Record inserted: {bulkConfig.StatsInfo.StatsNumberInserted}, Record updated: {bulkConfig.StatsInfo.StatsNumberUpdated}");
        }
    }
    catch (Exception ex)
    {
        _logger.LogError($"Error during BulkInsertOrUpdate: {ex.Message}");
        throw;
    }        
}

[Balint Kulcsar]

I was able to find out that not the MERGE operation is slow, but the INSERT to the temporary created table.
Is there a way to omit the COLLATE in the insert statement?

[Boris Djurdjevic]

Both Insert or Update should be done much faster, as you check from ReadMe stats even 1 mil. is under a minute.
But that is done on local Sql, not sure about Azure, still should not be over 1 min.
Where did you find COLLATE statement in the code ?

[Balint Kulcsar]

I've changed the pricing model from DTU based to vCore based, it became much faster, however it's still not fast enough.
I've tested the operations with 2 million records:

80 vCores - 55 seconds - insert
80 vCores - 190 seconds - merge
16 vCores - 58 seconds - insert
16 vCores - 206 second - merge
8 vCores - 100 seconds - insert
8 vCores - 300 seconds - merge

I've profiled the SQL statements generated by the library and I saw there is a COLLATE function for every column:

insert bulk <table> (<column1> NVarChar(40) COLLATE SQL_Latin1_General_CP1_CI_AS, <column2> NVarChar(100) COLLATE SQL_Latin1_General_CP1_CI_AS ....)

This may can cause performance issues.