CODEWITHSUNDEEP
c++databaseperformancestructcopy
Jak
Jak

Reputation: 499

Copying column info in C++

I have to copy column info from a database to a struct, the problem is that it takes over 5000 iterations and is very slow. Is there any better way?

The code used is in the .h file:

struct sFieldDef
{
CString m_strQualifier;
CString m_strOwner;
CString m_strTableName;
CString m_strColumnName;
int  m_nDataType;
CString m_strTypeName;
long m_lPrecision;
long m_lLength;
int m_nScale;
int m_nRadix;
int m_nNullable;
};

The code used in the .cpp file:

sFieldDef sTempField;
CColumns rsColumns(m_pDatabase);
rsColumns.Open(CRecordset::snapshot);

while( !rsColumns.IsEOF() )
{
sTempField.m_strQualifier=rsColumns.m_strQualifier;
sTempField.m_strOwner=rsColumns.m_strOwner;
sTempField.m_strTableName=rsColumns.m_strTableName;
sTempField.m_strColumnName=rsColumns.m_strColumnName;
sTempField.m_nDataType=rsColumns.m_nDataType;
sTempField.m_strTypeName=rsColumns.m_strTypeName;
sTempField.m_lPrecision=rsColumns.m_lPrecision;
sTempField.m_lLength=rsColumns.m_lLength;
sTempField.m_nScale=rsColumns.m_nScale;
sTempField.m_nRadix=rsColumns.m_nRadix;
sTempField.m_nNullable=rsColumns.m_nNullable;
pArrFiels->Add(sTempField);
rsColumns.MoveNext();
}

Upvotes: 0

Views: 128

Answers (1)

iavr
iavr

Reputation: 7637

You seem to be copying and storing everything in an array of structs, where each struct has identical members with the corresponding record. Usually we use arrays through iterators. So why not provide an iterator to your record-set and avoid copying altogether? You could roughly start like this:

template <typename RS>
class rs_iterator
{
   RS& rs;
public:
   rs_iterator(RS& rs) : rs{rs} { }
   const RS& operator*() { return rs; }
   rs_iterator& operator++() { return rs.MoveNext(), *this; }
   // ...
}

So you not only provide a convenient and standard interface to an array-like data source like a record-set, but you can use it directly in STL-like algorithms requiring bidirectional iterators.

If your CRecordset supports random access, then so would your iterator, easily. Otherwise, random access provision by itself is a good reason to copy (e.g. to sort columns).

Upvotes: 1

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