Set encoding, start/stop/rollback transaction (PG driver)

[bishop]

1. Add function SetEncoding
2. Make functions (SoftStartTransaction, SoftCommit, SoftRollback) exported from dll

[bishop]

pg header

[bishop]

ogrpgdatasource

[bishop]

ogrpgtablelayer

[Even Rouault]

Please attach patches to existing files instead of full files.

And please make those patches against GDAL SVN trunk for new features, which resides at ​http://svn.osgeo.org/gdal/trunk/gdal (http://trac.osgeo.org/gdal/browser)

[bishop]

Replying to bishop: Sorry, but I'm a newbie, so can you provide some instructions, to do it, or point me of some kind of faq.

[Even Rouault]

Assuming that you're somehow familiar with subversion, otherwise please read a user manual of it or some tutorial

1. Checkout the trunk repository with :

svn checkout ​http://svn.osgeo.org/gdal/trunk/gdal (or with any graphical interface that exists)

2. Apply your changes; Build; Test
3. svn diff > name_of_the_patch.patch

As Frank says try to isolate each functionnal change to make a separate patch.

[bishop]

According to new option "PGCLIENTENCODING" this ticket can be closed.

[Even Rouault]

Why is it necessary to export the transaction functions at the OGRPGDataSource level ? They are already exposed at the OGRLayer level.

[bishop]

There is necessary to make some changes in several tables (layers) and if some change return error to roll back all operations. This is very important in related tables too

[bishop]

SetEncoding & exoprts some functions

[bishop]

I updated patch to current svn tranc. I also want to note that using PGCLIENTENCODING environment variable is not a good way. Because SetEncoding method returns OGRErr and log some info. So developer can manage this situation in program logic.

[Even Rouault]

Adding new exported method is not a good solution as it implies people to use C++ and depend on the non-installed private headers of the driver.

1) OGRPGDataSource::SetEncoding(const char* Encoding) is probably unnecessary. You can call poDS->ExecuteSQL("SET client_encoding TO blahblah") and install before an error handler with CPLPushErrorHandler() to track any error issued by the server.

2) Exporting SoftStartTransaction(), SoftCommit(), SoftRollback() and FlushSoftTransaction() is probably not a good solution either. It would be more interesting if could provide a small Python script or C/C++ code that demonstrates the problems that lead you to call them explicitely. This way perhaps we could perhaps make the driver more clever to call itself those functions when it's needed, without requiring the user to mess with that.

[bishop]

1) I tested poDS->ExecuteSQL("SET client_encoding TO blahblah") - it's works 2) As I wrote I need make changes in several tables and if it will be some errors to Rollback all changes For example:

void CreateDoubleFeatures()
{
	OGRLayer* pLayer1 = m_pOGRPGDataSource->GetLayerByName("layer1");
	if(pLayer1 == NULL)
		return;
	OGRLayer* pLayer2 = m_pOGRPGDataSource->GetLayerByName("pLayer2");
	if(pLayer2 == NULL)
		return;

	//start transactions
	m_pOGRPGDataSource->SoftStartTransaction();
	
	OGRFeature *pFeature1 = OGRFeature::CreateFeature( pLayer1->GetLayerDefn() );

	pFeature1->SetField("someid", 0);
	pFeature1->SetField("sometext", "some text");

	if( pFeature1->CreateFeature( pFeature1 ) != OGRERR_NONE )
	{
		m_pOGRPGDataSource->SoftRollback();
		return;
	}
	OGRFeature::DestroyFeature( pFeature1 );

	OGRFeature *pFeature2 = OGRFeature::CreateFeature( pLayer2->GetLayerDefn() );

	pFeature2->SetField("somedata", 1.1);
	pFeature1->SetField("sometext", "over some text");

	if( pFeature2->CreateFeature( pFeature2 ) != OGRERR_NONE )
	{
		m_pOGRPGDataSource->SoftRollback();
		return;
	}
	OGRFeature::DestroyFeature( pFeature2 );
	
	//stop transactions
	m_pOGRPGDataSource->SoftCommit();
}

[bishop]

It's make sense to change PG driver documentation to explain the way to set encoding

CPLPushErrorHandler(); poDS->ExecuteSQL("SET client_encoding TO blahblah"); CPLPopErrorHandler();

[Even Rouault]

r17603 /trunk/gdal/ogr/ogrsf_frmts/pg/drv_pg.html: PG driver : document how to set client_encoding with a SQL request instead of environmenet variable (#2556)

[Jukka Rahkonen]

Fixed 5 years ago.