KDb

KDbPreparedStatement.h
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
30class KDbFieldList;
32
33//! Prepared statement paraneters used in KDbPreparedStatement::execute()
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*/
75class KDB_EXPORT KDbPreparedStatement : public KDbResultable
76{
77public:
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()
101 quint64 lastInsertRecordId;
102 };
103
104 //! Creates an invalid prepared statement.
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
137protected:
138 //! Creates a new prepared statement. In your code use
139 //! Users call KDbConnection:prepareStatement() instead.
141 KDbFieldList* fields,
142 const QStringList& whereFieldNames = QStringList());
143
144 friend class KDbConnection;
145
146private:
147//! @todo is this portable across backends?
148 bool generateStatementString(KDbEscapedString* s);
149 bool generateSelectStatementString(KDbEscapedString * s);
150 bool generateInsertStatementString(KDbEscapedString * s);
151
153};
154
155#endif
Provides database connection, allowing queries and data modification.
Specialized string for escaping.
Prepared statement interface for backend-dependent implementations.
KDbField::List * whereFields
temporary, used for select statements, based on whereFieldNames
const KDbField::List * fieldsForParameters
fields where we'll put the inserted parameters
bool dirty
true if the statement has to be internally prepared (possible again) before calling executeInternal()
Prepared database command for optimizing sequences of multiple database actions.
Type
Defines type of the prepared statement.
@ InvalidStatement
Used only in invalid statements.
@ SelectStatement
SELECT statement will be prepared end executed.
Interface for classes providing a result.
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