NHibernate does not seems doing Bulk Inserting into PostgreSQL - nhibernate

Question

I am interfacing with a PostgreSQL database with NHibernate.
Background
I made some simple tests...it seems it's taking 2 seconds to persist 300 records.
I have a Perl program with identical functionality, but issue direct SQL instead, takes only 70% of the time.
I am not sure if this is expected. I thought C#/NHibernate would be faster or at least on par.
Questions
One of my observation is that (with show_sql turned on), the NHibernate is issuing INSERTs a few hundreds times, instead of doing bulk INSERT that take cares of multiple rows. And note I am assigning the primary key myself, not using the "native" generator.
Is that expected? Is there anyway I could make it issue bulk INSERT statement instead? It seems to me that this could be one of the area I could speed up the performance.

Answer 1

As stachu found out correctly: NHibernate does not have *BatchingBatcher(Factory) for PostgreSQL(Npgsql)
As stachu askes: Did anybody managed to force Nhibarnate to do batch inserts to PostgreSQL
I wrote a Batcher that doesn't use any Npgsql batching stuff, but does manipulate the SQL String "oldschool style" (INSERT INTO [..] VALUES (...),(...), ...)
using System;
using System.Collections;
using System.Data;
using System.Diagnostics;
using System.Text;
using Npgsql;
namespace NHibernate.AdoNet
{
public class PostgresClientBatchingBatcherFactory : IBatcherFactory
{
public virtual IBatcher CreateBatcher(ConnectionManager connectionManager, IInterceptor interceptor)
{
return new PostgresClientBatchingBatcher(connectionManager, interceptor);
}
}
/// <summary>
/// Summary description for PostgresClientBatchingBatcher.
/// </summary>
public class PostgresClientBatchingBatcher : AbstractBatcher
{
private int batchSize;
private int countOfCommands = 0;
private int totalExpectedRowsAffected;
private StringBuilder sbBatchCommand;
private int m_ParameterCounter;
private IDbCommand currentBatch;
public PostgresClientBatchingBatcher(ConnectionManager connectionManager, IInterceptor interceptor)
: base(connectionManager, interceptor)
{
batchSize = Factory.Settings.AdoBatchSize;
}
private string NextParam()
{
return ":p" + m_ParameterCounter++;
}
public override void AddToBatch(IExpectation expectation)
{
if(expectation.CanBeBatched && !(CurrentCommand.CommandText.StartsWith("INSERT INTO") && CurrentCommand.CommandText.Contains("VALUES")))
{
//NonBatching behavior
IDbCommand cmd = CurrentCommand;
LogCommand(CurrentCommand);
int rowCount = ExecuteNonQuery(cmd);
expectation.VerifyOutcomeNonBatched(rowCount, cmd);
currentBatch = null;
return;
}
totalExpectedRowsAffected += expectation.ExpectedRowCount;
log.Info("Adding to batch");
int len = CurrentCommand.CommandText.Length;
int idx = CurrentCommand.CommandText.IndexOf("VALUES");
int endidx = idx + "VALUES".Length + 2;
if (currentBatch == null)
{
// begin new batch.
currentBatch = new NpgsqlCommand();
sbBatchCommand = new StringBuilder();
m_ParameterCounter = 0;
string preCommand = CurrentCommand.CommandText.Substring(0, endidx);
sbBatchCommand.Append(preCommand);
}
else
{
//only append Values
sbBatchCommand.Append(", (");
}
//append values from CurrentCommand to sbBatchCommand
string values = CurrentCommand.CommandText.Substring(endidx, len - endidx - 1);
//get all values
string[] split = values.Split(',');
ArrayList paramName = new ArrayList(split.Length);
for (int i = 0; i < split.Length; i++ )
{
if (i != 0)
sbBatchCommand.Append(", ");
string param = null;
if (split[i].StartsWith(":")) //first named parameter
{
param = NextParam();
paramName.Add(param);
}
else if(split[i].StartsWith(" :")) //other named parameter
{
param = NextParam();
paramName.Add(param);
}
else if (split[i].StartsWith(" ")) //other fix parameter
{
param = split[i].Substring(1, split[i].Length-1);
}
else
{
param = split[i]; //first fix parameter
}
sbBatchCommand.Append(param);
}
sbBatchCommand.Append(")");
//rename & copy parameters from CurrentCommand to currentBatch
int iParam = 0;
foreach (NpgsqlParameter param in CurrentCommand.Parameters)
{
param.ParameterName = (string)paramName[iParam++];
NpgsqlParameter newParam = /*Clone()*/new NpgsqlParameter(param.ParameterName, param.NpgsqlDbType, param.Size, param.SourceColumn, param.Direction, param.IsNullable, param.Precision, param.Scale, param.SourceVersion, param.Value);
currentBatch.Parameters.Add(newParam);
}
countOfCommands++;
//check for flush
if (countOfCommands >= batchSize)
{
DoExecuteBatch(currentBatch);
}
}
protected override void DoExecuteBatch(IDbCommand ps)
{
if (currentBatch != null)
{
//Batch command now needs its terminator
sbBatchCommand.Append(";");
countOfCommands = 0;
log.Info("Executing batch");
CheckReaders();
//set prepared batchCommandText
string commandText = sbBatchCommand.ToString();
currentBatch.CommandText = commandText;
LogCommand(currentBatch);
Prepare(currentBatch);
int rowsAffected = 0;
try
{
rowsAffected = currentBatch.ExecuteNonQuery();
}
catch (Exception e)
{
if(Debugger.IsAttached)
Debugger.Break();
throw;
}
Expectations.VerifyOutcomeBatched(totalExpectedRowsAffected, rowsAffected);
totalExpectedRowsAffected = 0;
currentBatch = null;
sbBatchCommand = null;
m_ParameterCounter = 0;
}
}
protected override int CountOfStatementsInCurrentBatch
{
get { return countOfCommands; }
}
public override int BatchSize
{
get { return batchSize; }
set { batchSize = value; }
}
}
}

Answer 2

I also found that NHibernate is not doing batch inserts into PostgreSQL.
I identified two possible reasons:
1) Npgsql driver does not support batch inserts/updates (see forum)
2) NHibernate does not have *BatchingBatcher(Factory) for PostgreSQL(Npgsql). I tried using Devart dotConnect driver with NHibernate (I wrote custom driver for NHibernate) but it still did not worked.
I suppose this driver should also implement IEmbeddedBatcherFactoryProvider interface, but it seems not trivial for me (using one for Oracle did not worked ;) )
Did anybody managed to force Nhibarnate to do batch inserts to PostgreSQL or can confirm my conclusion?