1 /* This file is part of the KDE project 2 Copyright (C) 2005-2016 Jarosław Staniek <staniek@kde.org> 3 4 This library is free software; you can redistribute it and/or 5 modify it under the terms of the GNU Library General Public 6 License as published by the Free Software Foundation; either 7 version 2 of the License, or (at your option) any later version. 8 9 This library is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 Library General Public License for more details. 13 14 You should have received a copy of the GNU Library General Public License 15 along with this library; see the file COPYING.LIB. If not, write to 16 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 17 * Boston, MA 02110-1301, USA. 18 */ 19 20 #ifndef KDB_PREPAREDSTATEMENT_H 21 #define KDB_PREPAREDSTATEMENT_H 22 23 #include <QVariant> 24 #include <QStringList> 25 #include <QSharedData> 26 27 #include "KDbField.h" 28 #include "KDbResult.h" 29 30 class KDbFieldList; 31 class KDbPreparedStatementInterface; 32 33 //! Prepared statement paraneters used in KDbPreparedStatement::execute() 34 typedef QList<QVariant> KDbPreparedStatementParameters; 35 36 /*! @short Prepared database command for optimizing sequences of multiple database actions 37 38 Currently INSERT and SELECT statements are supported. 39 For example when using KDbPreparedStatement for INSERTs, 40 you can gain about 30% speedup compared to using multiple 41 connection.insertRecord(*tabelSchema, dbRecordBuffer). 42 43 To use KDbPreparedStatement, create is using KDbConnection:prepareStatement(), 44 providing table schema; set up parameters using operator << ( const QVariant& value ); 45 and call execute() when ready. KDbPreparedStatement objects are accessed 46 using KDE shared pointers, i.e KDbPreparedStatement, so you do not need 47 to remember about destroying them. However, when underlying KDbConnection object 48 is destroyed, KDbPreparedStatement should not be used. 49 50 Let's assume tableSchema contains two columns NUMBER integer and TEXT text. 51 Following code inserts 10000 records with random numbers and text strings 52 obtained elsewhere using getText(i). 53 @code 54 bool insertMultiple(KDbConnection* conn, KDbTableSchema* tableSchema) 55 { 56 KDbPreparedStatement statement = conn->prepareStatement( 57 KDbPreparedStatement::Insert, tableSchema); 58 for (i=0; i<10000; i++) { 59 KDbPreparedStatementParameters parameters; 60 parameters << qrand() << getText(i); 61 if (!statement.execute(parameters)) 62 return false; 63 } 64 return true; 65 } 66 @endcode 67 68 If you do not call clearParameters() after every insert, you can insert 69 the same value multiple times using execute() what increases efficiency even more. 70 71 Another use case is inserting large objects (BLOBs or CLOBs). 72 Depending on database backend, you can avoid escaping BLOBs. 73 See KexiFormView::storeData() for example use. 74 */ 75 class KDB_EXPORT KDbPreparedStatement : public KDbResultable 76 { 77 public: 78 79 //! Defines type of the prepared statement. 80 enum Type { 81 InvalidStatement, //!< Used only in invalid statements 82 SelectStatement, //!< SELECT statement will be prepared end executed 83 InsertStatement //!< INSERT statement will be prepared end executed 84 }; 85 86 //! @internal 87 class KDB_EXPORT Data : public QSharedData { 88 public: 89 Data(); 90 Data(Type _type, KDbPreparedStatementInterface* _iface, KDbFieldList* _fields, 91 const QStringList& _whereFieldNames); 92 ~Data(); 93 Type type; 94 KDbFieldList *fields; 95 QStringList whereFieldNames; 96 const KDbField::List* fieldsForParameters; //!< fields where we'll put the inserted parameters 97 KDbField::List* whereFields; //!< temporary, used for select statements, based on whereFieldNames 98 bool dirty; //!< true if the statement has to be internally 99 //!< prepared (possible again) before calling executeInternal() 100 KDbPreparedStatementInterface *iface; 101 quint64 lastInsertRecordId; 102 }; 103 104 //! Creates an invalid prepared statement. 105 KDbPreparedStatement(); 106 107 ~KDbPreparedStatement() override; 108 109 bool isValid() const; 110 111 KDbPreparedStatement::Type type() const; 112 113 void setType(KDbPreparedStatement::Type type); 114 115 const KDbFieldList* fields() const; 116 117 //! Sets fields for the statement. Does nothing if @a fields is @c nullptr. 118 void setFields(KDbFieldList* fields); 119 120 QStringList whereFieldNames() const; 121 122 void setWhereFieldNames(const QStringList& whereFieldNames); 123 124 /*! Executes the prepared statement using @a parameters parameters. 125 A number parameters set up for the statement must be the same as a number of fields 126 defined in the underlying database table. 127 @return false on failure. Detailed error status can be obtained 128 from KDbConnection object that was used to create this statement object. */ 129 bool execute(const KDbPreparedStatementParameters& parameters); 130 131 /*! @return unique identifier of the most recently inserted record. 132 Typically this is just primary key value. This identifier could be reused when we want 133 to reference just inserted record. If there was no insertion recently performed, 134 std::numeric_limits<quint64>::max() is returned. */ 135 quint64 lastInsertRecordId() const; 136 137 protected: 138 //! Creates a new prepared statement. In your code use 139 //! Users call KDbConnection:prepareStatement() instead. 140 KDbPreparedStatement(KDbPreparedStatementInterface* iface, Type type, 141 KDbFieldList* fields, 142 const QStringList& whereFieldNames = QStringList()); 143 144 friend class KDbConnection; 145 146 private: 147 //! @todo is this portable across backends? 148 bool generateStatementString(KDbEscapedString* s); 149 bool generateSelectStatementString(KDbEscapedString * s); 150 bool generateInsertStatementString(KDbEscapedString * s); 151 152 QSharedDataPointer<Data> d; 153 }; 154 155 #endif 156