Changes related to following tracker items:

[2025916] ODBC binds empty string as null?
[2000408] DynamicAny non-initialized state support
[1981130] pointless comparison of unsigned integer with zero

and some refactoring.

Warning: only tested on Windows.

Data/src/AbstractExtraction.cpp

@@ -47,7 +47,9 @@ AbstractExtraction::AbstractExtraction(Poco::UInt32 limit,
 	_pExtractor(0), 
 	_limit(limit),
 	_position(position),
-	_bulk(bulk)
+	_bulk(bulk),
+	_emptyStringIsNull(false),
+	_forceEmptyString(false)
 {
 }
 
@@ -57,4 +59,16 @@ AbstractExtraction::~AbstractExtraction()
 }
 
 
+template <>
+bool AbstractExtraction::isValueNull(const std::string& str, bool deflt)
+{
+	if (getForceEmptyString()) return false;
+
+	if (getEmptyStringIsNull() && str.empty())
+		return true;
+
+	return deflt;
+}
+
+
 } } // namespace Poco::Data

Data/src/MetaColumn.cpp

@@ -59,7 +59,6 @@ MetaColumn::MetaColumn(std::size_t position,
 	_type(type),
 	_nullable(nullable)
 {
-	poco_assert(position >= 0);
 }
 
 

Data/src/RecordSet.cpp

@@ -93,6 +93,8 @@ RecordSet::~RecordSet()
 
 DynamicAny RecordSet::value(std::size_t col, std::size_t row) const
 {
+	if (isNull(col, row)) return DynamicAny();
+
 	switch (columnType(col))
 	{
 		case MetaColumn::FDT_BOOL:      return value<bool>(col, row);
@@ -119,6 +121,8 @@ DynamicAny RecordSet::value(std::size_t col, std::size_t row) const
 
 DynamicAny RecordSet::value(const std::string& name, std::size_t row) const
 {
+	if (isNull(metaColumn(name).position(), row)) return DynamicAny();
+
 	switch (columnType(name))
 	{
 		case MetaColumn::FDT_BOOL:      return value<bool>(name, row);

Data/src/StatementImpl.cpp

@@ -364,6 +364,12 @@ void StatementImpl::addExtract(AbstractExtraction* pExtraction)
 	if (pos >= _extractors.size()) 
 		_extractors.resize(pos + 1);
 
+	pExtraction->setEmptyStringIsNull(
+		_rSession.getFeature("emptyStringIsNull"));
+
+	pExtraction->setForceEmptyString(
+		_rSession.getFeature("forceEmptyString"));
+
 	_extractors[pos].push_back(pExtraction);
 }