kexi

KexiDB::PreparedStatement Class Reference

#include <preparedstatement.h>

Inheritance diagram for KexiDB::PreparedStatement:

KexiDB::MySqlPreparedStatement KexiDB::pqxxPreparedStatement KexiDB::SQLitePreparedStatement List of all members.

Detailed Description

Prepared database command for optimizing sequences of multiple database actions.

Currently INSERT and SELECT statements are supported. For example, wher using PreparedStatement for INSERTs, you can gain about 30% speedup compared to using multiple connection.insertRecord(*tabelSchema, dbRowBuffer).

To use PreparedStatement, create is using KexiDB::Connection:prepareStatement(), providing table schema; set up arguments using operator << ( const QVariant& value ); and call execute() when ready. PreparedStatement objects are accessed using KDE shared pointers, i.e KexiDB::PreparedStatement::Ptr, so you do not need to remember about destroying them. However, when underlying Connection object is destroyed, PreparedStatement should not be used.

Let's assume tableSchema contains two columns NUMBER integer and TEXT text. Following code inserts 10000 records with random numbers and text strings obtained elsewhere using getText(i).

    bool insertMultiple(KexiDB::Connection &conn, KexiDB::TableSchema& tableSchema)
    {
        KexiDB::PreparedStatement::Ptr prepared = conn.prepareStatement(
            KexiDB::PreparedStatement::InsertStatement, tableSchema);
        for (i=0; i<10000; i++) {
            prepared << rand() << getText(i);
            if (!prepared.execute())
                return false;
            prepared.clearArguments();
        }
        return true;
    }

If you do not call clearArguments() after every insert, you can insert the same value multiple times using execute() what increases efficiency even more.

Another use case is inserting large objects (BLOBs or CLOBs). Depending on database backend, you can avoid escaping BLOBs. See KexiFormView::storeData() for example use.

Definition at line 73 of file preparedstatement.h.


Public Types

typedef KSharedPtr< PreparedStatementPtr
enum  StatementType { SelectStatement, InsertStatement }

Public Member Functions

 PreparedStatement (StatementType type, ConnectionInternal &conn, FieldList &fields, const QStringList &where=QStringList())
virtual ~PreparedStatement ()
PreparedStatementoperator<< (const QVariant &value)
void clearArguments ()
virtual bool execute ()=0

Protected Member Functions

QCString generateStatementString ()

Protected Attributes

StatementType m_type
FieldListm_fields
QValueList< QVariant > m_args
QStringList * m_where
Field::Listm_whereFields

Member Enumeration Documentation

enum KexiDB::PreparedStatement::StatementType
 

Defines type of the prepared statement.

Enumerator:
SelectStatement  SELECT statement wil be prepared end executed.
InsertStatement  INSERT statement wil be prepared end executed.

Definition at line 79 of file preparedstatement.h.


Constructor & Destructor Documentation

PreparedStatement::PreparedStatement StatementType  type,
ConnectionInternal &  conn,
FieldList fields,
const QStringList &  where = QStringList()
 

Creates Prepared statement. In your code use KexiDB::Connection:prepareStatement() instead.

Definition at line 28 of file preparedstatement.cpp.


Member Function Documentation

void PreparedStatement::clearArguments  ) 
 

Clears arguments of the prepared statement. Usually used after execute().

Definition at line 121 of file preparedstatement.cpp.

virtual bool KexiDB::PreparedStatement::execute  )  [pure virtual]
 

Executes the prepared statement. In most cases you will need to clear arguments after executing, using clearArguments(). A number arguments set up for the statement must be the same as a number of fields defined in the underlying database table.

Returns:
false on failure. Detailed error status can be obtained from KexiDB::Connection object used to create this statement.

Implemented in KexiDB::MySqlPreparedStatement, KexiDB::pqxxPreparedStatement, and KexiDB::SQLitePreparedStatement.

QCString PreparedStatement::generateStatementString  )  [protected]
 

Todo:
is this portable across backends?

Definition at line 45 of file preparedstatement.cpp.

PreparedStatement & PreparedStatement::operator<< const QVariant &  value  ) 
 

Appends argument value to the statement.

Definition at line 102 of file preparedstatement.cpp.


The documentation for this class was generated from the following files:
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