KDb

KDbPreparedStatement.h
1 /* This file is part of the KDE project
2  Copyright (C) 2005-2016 JarosÅ‚aw Staniek <[email protected]>
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;
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 */
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()
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 
137 protected:
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 
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 
153 };
154 
155 #endif
@ SelectStatement
SELECT statement will be prepared end executed.
bool dirty
true if the statement has to be internally prepared (possible again) before calling executeInternal()
Specialized string for escaping.
@ InvalidStatement
Used only in invalid statements.
Interface for classes providing a result.
Type
Defines type of the prepared statement.
Prepared statement interface for backend-dependent implementations.
Prepared database command for optimizing sequences of multiple database actions.
Provides database connection, allowing queries and data modification.
Definition: KDbConnection.h:51
const KDbField::List * fieldsForParameters
fields where we'll put the inserted parameters
KDbField::List * whereFields
temporary, used for select statements, based on whereFieldNames
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