KexiDB::PreparedStatement Class Reference

#include <preparedstatement.h>

Inheritance diagram for KexiDB::PreparedStatement:

Public Types
enum	StatementType { SelectStatement , InsertStatement }
typedef TDESharedPtr< PreparedStatement >	Ptr

Public Member Functions
	PreparedStatement (StatementType type, ConnectionInternal &conn, FieldList &fields, const TQStringList &where=TQStringList())
PreparedStatement &	operator<< (const TQVariant &value)
void	clearArguments ()
virtual bool	execute ()=0

Protected Member Functions
TQCString	generateStatementString ()

Protected Attributes
StatementType	m_type
FieldList *	m_fields
TQValueList< TQVariant >	m_args
TQStringList *	m_where
Field::List *	m_whereFields

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 TQVariant& 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.

Member Typedef Documentation

Ptr

typedef TDESharedPtr<PreparedStatement> KexiDB::PreparedStatement::Ptr

Definition at line 76 of file preparedstatement.h.

Member Enumeration Documentation

StatementType

enum KexiDB::PreparedStatement::StatementType

Defines type of the prepared statement.

Enumerator
SelectStatement	SELECT statement will be prepared end executed.
InsertStatement	INSERT statement will be prepared end executed.

Definition at line 79 of file preparedstatement.h.

Constructor & Destructor Documentation

PreparedStatement()

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

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

Definition at line 28 of file preparedstatement.cpp.

~PreparedStatement()

PreparedStatement::~PreparedStatement ( )

virtual

Definition at line 39 of file preparedstatement.cpp.

Member Function Documentation

clearArguments()

void PreparedStatement::clearArguments

(

)

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

Definition at line 132 of file preparedstatement.cpp.

execute()

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.

generateStatementString()

TQCString PreparedStatement::generateStatementString ( )

protected

Todo:

is this portable across backends?

Todo:

only tables and trivial queries supported for select...

Todo:

only tables supported for insert; what about views?

Definition at line 45 of file preparedstatement.cpp.

operator<<()

PreparedStatement & PreparedStatement::operator<<

(

const TQVariant &

value

)

Appends argument value to the statement.

Definition at line 113 of file preparedstatement.cpp.

Member Data Documentation

m_args

TQValueList<TQVariant> KexiDB::PreparedStatement::m_args

protected

Definition at line 110 of file preparedstatement.h.

m_fields

FieldList* KexiDB::PreparedStatement::m_fields

protected

Definition at line 109 of file preparedstatement.h.

m_type

StatementType KexiDB::PreparedStatement::m_type

protected

Definition at line 108 of file preparedstatement.h.

m_where

TQStringList* KexiDB::PreparedStatement::m_where

protected

Definition at line 111 of file preparedstatement.h.

m_whereFields

Field::List* KexiDB::PreparedStatement::m_whereFields

protected

Definition at line 112 of file preparedstatement.h.

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

• preparedstatement.h
• preparedstatement.cpp