KDbCursor

Search for usage in LXR

#include <KDbCursor.h>

Inheritance diagram for KDbCursor:

Public Types

enum  Option { None = 0, Buffered = 1 }
 
typedef QFlags< OptionOptions
 

Public Member Functions

qint64 at () const
 
bool bof () const
 
virtual bool close ()
 
KDbConnectionconnection ()
 
const KDbConnectionconnection () const
 
bool containsRecordIdInfo () const
 
bool deleteAllRecords ()
 
bool deleteRecord (KDbRecordData *data, bool useRecordId=false)
 
bool eof () const
 
int fieldCount () const
 
bool insertRecord (KDbRecordData *data, KDbRecordEditBuffer *buf, bool getRecrordId=false)
 
bool isBuffered () const
 
bool isOpened () const
 
bool moveFirst ()
 
virtual bool moveLast ()
 
virtual bool moveNext ()
 
virtual bool movePrev ()
 
bool open ()
 
Options options () const
 
KDbQueryColumnInfo::Vector orderByColumnList () const
 
KDbQuerySchemaquery () const
 
QList< QVariantqueryParameters () const
 
KDbEscapedString rawSql () const
 
virtual const char ** recordData () const =0
 
bool reopen ()
 
void setBuffered (bool buffered)
 
void setOrderByColumnList (const QString &column1, const QString &column2=QString(), const QString &column3=QString(), const QString &column4=QString(), const QString &column5=QString())
 
void setOrderByColumnList (const QStringList &columnNames)
 
void setQueryParameters (const QList< QVariant > &params)
 
KDbRecordDatastoreCurrentRecord () const
 
bool storeCurrentRecord (KDbRecordData *data) const
 
bool updateRecord (KDbRecordData *data, KDbRecordEditBuffer *buf, bool useRecordId=false)
 
virtual QVariant value (int i)=0
 
- Public Member Functions inherited from KDbResultable
 KDbResultable (const KDbResultable &other)
 
void clearResult ()
 
KDbMessageHandlermessageHandler () const
 
KDbResultableoperator= (const KDbResultable &other)
 
KDbResult result () const
 
virtual QString serverResultName () const
 
void setMessageHandler (KDbMessageHandler *handler)
 
void showMessage ()
 

Protected Types

enum  FetchResult { FetchResult::Invalid, FetchResult::Error, FetchResult::Ok, FetchResult::End }
 

Protected Member Functions

 KDbCursor (KDbConnection *conn, const KDbEscapedString &sql, Options options=KDbCursor::Option::None)
 
 KDbCursor (KDbConnection *conn, KDbQuerySchema *query, Options options=KDbCursor::Option::None)
 
void clearBuffer ()
 
virtual void drv_appendCurrentRecordToBuffer ()=0
 
virtual void drv_bufferMovePointerNext ()=0
 
virtual void drv_bufferMovePointerPrev ()=0
 
virtual void drv_bufferMovePointerTo (qint64 at)=0
 
virtual void drv_clearBuffer ()
 
virtual bool drv_close ()=0
 
virtual void drv_getNextRecord ()=0
 
virtual bool drv_open (const KDbEscapedString &sql)=0
 
virtual bool drv_storeCurrentRecord (KDbRecordData *data) const =0
 
bool getNextRecord ()
 
void init (KDbConnection *conn)
 

Protected Attributes

bool m_afterLast
 
qint64 m_at
 
bool m_buffering_completed
 
FetchResult m_fetchResult
 
int m_fieldCount
 
int m_fieldsToStoreInRecord
 
int m_logicalFieldCount
 
KDbCursor::Options m_options
 
KDbQuerySchemam_query
 
int m_records_in_buf
 
KDbQueryColumnInfo::Vectorm_visibleFieldsExpanded
 
- Protected Attributes inherited from KDbResultable
Private *const d
 
KDbResult m_result
 

Detailed Description

Provides database cursor functionality.

Cursor can be defined in two ways:

  1. by passing KDbQuerySchema object to KDbConnection::executeQuery() or KDbConnection::prepareQuery(); then query is defined for in engine-independent way – this is recommended usage
  2. by passing raw query statement string to KDbConnection::executeQuery() or KDbConnection::prepareQuery(); then query may be defined for in engine-dependent way – this is not recommended usage, but convenient when we can't or do not want to allocate KDbQuerySchema object, while we know that the query statement is syntactically and logically ok in our context.

You can move cursor to next record with moveNext() and move back with movePrev(). The cursor is always positioned on record, not between records, with exception that after open() it is positioned before the first record (if any) – then bof() equals true. The cursor can also be positioned after the last record (if any) with moveNext() – then eof() equals true. For example, if you have four records, 1, 2, 3, 4, then after calling open(), moveNext(), moveNext(), moveNext(), movePrev() you are going through records: 1, 2, 3, 2.

Cursor can be buffered or unbuferred.

Warning
Buffered cursors are not implemented!

Buffering in this class is not related to any SQL engine capatibilities for server-side cursors (eg. like 'DECLARE CURSOR' statement) - buffered data is at client (application) side. Any record retrieved in buffered cursor will be stored inside an internal buffer and reused when needed. Unbuffered cursor always requires one record fetching from db connection at every step done with moveNext(), movePrev(), etc.

Notes:

Definition at line 68 of file KDbCursor.h.

Member Enumeration Documentation

◆ FetchResult

enum KDbCursor::FetchResult
strongprotected

Possible results of record fetching, used for m_fetchResult.

Enumerator
Invalid 

used before starting the fetching, result is not known yet

Error 

error of fetching

Ok 

the data is fetched

End 

at the end of data

Definition at line 309 of file KDbCursor.h.

◆ Option

enum KDbCursor::Option
strong

Options that describe behavior of database cursor.

Definition at line 73 of file KDbCursor.h.

Constructor & Destructor Documentation

◆ KDbCursor() [1/2]

KDbCursor::KDbCursor ( KDbConnection conn,
const KDbEscapedString sql,
Options  options = KDbCursor::Option::None 
)
protected

Cursor will operate on conn, raw SQL statement sql will be used to execute query.

Definition at line 66 of file KDbCursor.cpp.

◆ KDbCursor() [2/2]

KDbCursor::KDbCursor ( KDbConnection conn,
KDbQuerySchema query,
Options  options = KDbCursor::Option::None 
)
protected

Cursor will operate on conn, query schema will be used to execute query.

Definition at line 78 of file KDbCursor.cpp.

Member Function Documentation

◆ at()

qint64 KDbCursor::at ( ) const
inline
Returns
current internal position of the cursor's query. We are counting records from 0. Value -1 means that cursor does not point to any valid record (this happens eg. after open(), close(), and after moving after last record or before first one.

Definition at line 161 of file KDbCursor.h.

◆ bof()

bool KDbCursor::bof ( ) const
inline
Returns
true if current position is before first record.

Definition at line 152 of file KDbCursor.h.

◆ clearBuffer()

void KDbCursor::clearBuffer ( )
protected

clears buffer with reimplemented drv_clearBuffer(). *‍/

Definition at line 413 of file KDbCursor.cpp.

◆ close()

bool KDbCursor::close ( )
virtual

Closes previously opened cursor. If the cursor is closed, nothing happens.

Definition at line 256 of file KDbCursor.cpp.

◆ connection() [1/2]

const KDbConnection * KDbCursor::connection ( )
Returns
connection used for the cursor

Definition at line 148 of file KDbCursor.cpp.

◆ connection() [2/2]

const KDbConnection* KDbCursor::connection ( ) const

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Since
3.1

◆ containsRecordIdInfo()

bool KDbCursor::containsRecordIdInfo ( ) const
Returns
true if ROWID information is available for each record. ROWID information is available if KDbDriverBehavior::ROW_ID_FIELD_RETURNS_LAST_AUTOINCREMENTED_VALUE == false for a KDb database driver and the master table has no primary key defined. Phisically, ROWID value is returned after last returned field, so data vector's length is expanded by one.

Definition at line 178 of file KDbCursor.cpp.

◆ deleteAllRecords()

bool KDbCursor::deleteAllRecords ( )
Todo:
doesn't update cursor's buffer YET!

Definition at line 526 of file KDbCursor.cpp.

◆ deleteRecord()

bool KDbCursor::deleteRecord ( KDbRecordData data,
bool  useRecordId = false 
)
Todo:
doesn't update cursor's buffer YET!

Definition at line 517 of file KDbCursor.cpp.

◆ drv_appendCurrentRecordToBuffer()

virtual void KDbCursor::drv_appendCurrentRecordToBuffer ( )
protectedpure virtual

Stores currently fetched record's values in appropriate place of the buffer. Note for driver developers: This place can be computed using m_at. Do not change value of m_at or any other KDbCursor members, only change your internal structures like pointer to current record, etc. If your database engine's API function (for record fetching) do not allocates such a space, you want to allocate a space for current record. Otherwise, reuse existing structure, what could be more efficient. All functions like drv_appendCurrentRecordToBuffer() operates on the buffer, i.e. array of stored records. You are not forced to have any particular fixed structure for buffer item or buffer itself - the structure is internal and only methods like storeCurrentRecord() visible to public.

◆ drv_bufferMovePointerNext()

virtual void KDbCursor::drv_bufferMovePointerNext ( )
protectedpure virtual

Moves pointer (that points to the buffer) – to next item in this buffer. Note for driver developers: probably just execute "your_pointer++" is enough.

◆ drv_bufferMovePointerPrev()

virtual void KDbCursor::drv_bufferMovePointerPrev ( )
protectedpure virtual

Like drv_bufferMovePointerNext() but execute "your_pointer--".

◆ drv_bufferMovePointerTo()

virtual void KDbCursor::drv_bufferMovePointerTo ( qint64  at)
protectedpure virtual

Moves pointer (that points to the buffer) to a new place: at.

◆ drv_clearBuffer()

virtual void KDbCursor::drv_clearBuffer ( )
inlineprotectedvirtual

Clears cursor's buffer if this was allocated (only for buffered cursor type). Otherwise do nothing. For reimplementing. Default implementation does nothing.

Definition at line 285 of file KDbCursor.h.

◆ drv_open()

virtual bool KDbCursor::drv_open ( const KDbEscapedString sql)
protectedpure virtual

Note for driver developers: this method should initialize engine-specific cursor's resources using an SQL statement sql. It is not required to store sql statement somewhere in your KDbCursor subclass (it is already stored in m_query or m_rawStatement, depending query type) - only pass it to proper engine's function.

◆ drv_storeCurrentRecord()

virtual bool KDbCursor::drv_storeCurrentRecord ( KDbRecordData data) const
protectedpure virtual

Puts current record's data into data (makes a deep copy of each field). This method has unspecified behavior if the cursor is not at valid record.

Returns
true on success. Note: For reimplementation in driver's code. Shortly, this method translates a record data from internal representation (probably also used in buffer) to simple public KDbRecordData representation.

◆ eof()

bool KDbCursor::eof ( ) const
inline
Returns
true if current position is after last record.

Definition at line 147 of file KDbCursor.h.

◆ fieldCount()

int KDbCursor::fieldCount ( ) const
inline
Returns
number of fields available for this cursor. This never includes ROWID column or other internal columns (e.g. lookup).

Definition at line 167 of file KDbCursor.h.

◆ getNextRecord()

bool KDbCursor::getNextRecord ( )
protected

Internal: cares about proper flag setting depending on result of drv_getNextRecord() and depending on wherher a cursor is buffered.

Definition at line 424 of file KDbCursor.cpp.

◆ insertRecord()

bool KDbCursor::insertRecord ( KDbRecordData data,
KDbRecordEditBuffer buf,
bool  getRecrordId = false 
)
Todo:
doesn't update cursor's buffer YET!

Definition at line 507 of file KDbCursor.cpp.

◆ isBuffered()

bool KDbCursor::isBuffered ( ) const
Returns
true if the cursor is buffered.

Definition at line 398 of file KDbCursor.cpp.

◆ isOpened()

bool KDbCursor::isOpened ( ) const
Returns
true if the cursor is opened.

Definition at line 173 of file KDbCursor.cpp.

◆ moveFirst()

bool KDbCursor::moveFirst ( )

Moves current position to the first record and retrieves it.

Returns
true if the first record was retrieved. False could mean that there was an error or there is no record available.

Definition at line 285 of file KDbCursor.cpp.

◆ moveLast()

bool KDbCursor::moveLast ( )
virtual

Moves current position to the last record and retrieves it.

Returns
true if the last record was retrieved. False could mean that there was an error or there is no record available.

Definition at line 329 of file KDbCursor.cpp.

◆ moveNext()

bool KDbCursor::moveNext ( )
virtual

Moves current position to the next record and retrieves it.

Definition at line 351 of file KDbCursor.cpp.

◆ movePrev()

bool KDbCursor::movePrev ( )
virtual

Moves current position to the next record and retrieves it. Currently it's only supported for buffered cursors.

Definition at line 362 of file KDbCursor.cpp.

◆ open()

bool KDbCursor::open ( )

Opens the cursor using data provided on creation. The data might be either KDbQuerySchema or a raw SQL statement.

Definition at line 202 of file KDbCursor.cpp.

◆ options()

KDbCursor::Options KDbCursor::options ( ) const
Returns
cursor options

Definition at line 168 of file KDbCursor.cpp.

◆ orderByColumnList()

KDbQueryColumnInfo::Vector KDbCursor::orderByColumnList ( ) const
Returns
a list of fields contained in ORDER BY section of the query.
See also
setOrderBy(const QStringList&)

Definition at line 602 of file KDbCursor.cpp.

◆ query()

KDbQuerySchema * KDbCursor::query ( ) const
Returns
query schema used to define this cursor or 0 if the cursor is not defined by a query schema but by a raw SQL statement.

Definition at line 158 of file KDbCursor.cpp.

◆ queryParameters()

QList< QVariant > KDbCursor::queryParameters ( ) const
Returns
query parameters assigned to this cursor

Definition at line 607 of file KDbCursor.cpp.

◆ rawSql()

KDbEscapedString KDbCursor::rawSql ( ) const
Returns
raw query statement used to define this cursor or null string if raw statement instead (but KDbQuerySchema is defined instead).

Definition at line 163 of file KDbCursor.cpp.

◆ recordData()

virtual const char** KDbCursor::recordData ( ) const
pure virtual

[PROTOTYPE]

Returns
current record data or nullptr if there is no current records.

◆ reopen()

bool KDbCursor::reopen ( )

Closes and then opens again the same cursor. If the cursor is not opened it is just opened and result of this open is returned. Otherwise, true is returned if cursor is successfully closed and then opened.

Definition at line 277 of file KDbCursor.cpp.

◆ setBuffered()

void KDbCursor::setBuffered ( bool  buffered)

Sets this cursor to buffered type or not. See description of buffered and nonbuffered cursors in class description. This method only works if cursor is not opened (isOpened()==false). You can close already opened cursor and then switch this option on/off.

Definition at line 403 of file KDbCursor.cpp.

◆ setOrderByColumnList() [1/2]

void KDbCursor::setOrderByColumnList ( const QString column1,
const QString column2 = QString(),
const QString column3 = QString(),
const QString column4 = QString(),
const QString column5 = QString() 
)

Convenience method, similar to setOrderByColumnList(const QStringList&).

Todo:
implement this

Convenience method, similar to setOrderBy(const QStringList&).

Todo:
implement this, like above
Todo:
add ORDER BY info to debugString()

Definition at line 590 of file KDbCursor.cpp.

◆ setOrderByColumnList() [2/2]

void KDbCursor::setOrderByColumnList ( const QStringList columnNames)

Sets a list of columns for ORDER BY section of the query. Only works when the cursor has been created using KDbQuerySchema object (i.e. when query()!=0; does not work with raw statements). Each name on the list must be a field or alias present within the query and must not be covered by aliases. If one or more names cannot be found within the query, the method will have no effect. Any previous ORDER BY settings will be removed.

The order list provided here has priority over a list defined in the KDbQuerySchema object itseld (using KDbQuerySchema::setOrderByColumnList()). The KDbQuerySchema object itself is not modifed by this method: only order of records retrieved by this cursor is affected.

Use this method before calling open(). You can also call reopen() after calling this method to see effects of applying records order.

Todo:
implement this
Todo:
implement this: all field names should be found, exit otherwise
Todo:
if (!d->orderByColumnList)

Definition at line 580 of file KDbCursor.cpp.

◆ setQueryParameters()

void KDbCursor::setQueryParameters ( const QList< QVariant > &  params)

Sets query parameters params for this cursor.

Definition at line 612 of file KDbCursor.cpp.

◆ storeCurrentRecord() [1/2]

KDbRecordData * KDbCursor::storeCurrentRecord ( ) const

Allocates a new KDbRecordData and stores data in it (makes a deep copy of each field). If the cursor is not at valid record, the result is undefined.

Returns
newly created record data object or 0 on error.

Definition at line 183 of file KDbCursor.cpp.

◆ storeCurrentRecord() [2/2]

bool KDbCursor::storeCurrentRecord ( KDbRecordData data) const

Puts current record's data into data (makes a deep copy of each field). If the cursor is not at valid record, the result is undefined.

Returns
true on success. false is returned if data is nullptr.

Definition at line 193 of file KDbCursor.cpp.

◆ updateRecord()

bool KDbCursor::updateRecord ( KDbRecordData data,
KDbRecordEditBuffer buf,
bool  useRecordId = false 
)
Todo:
doesn't update cursor's buffer YET!

Definition at line 498 of file KDbCursor.cpp.

◆ value()

virtual QVariant KDbCursor::value ( int  i)
pure virtual
Returns
a value stored in column number i (counting from 0). It has unspecified behavior if the cursor is not at valid record. Note for driver developers: If i is >= than m_fieldCount, null QVariant value should be returned. To return a value typically you can use a pointer to internal structure that contain current record data (buffered or unbuffered).

Member Data Documentation

◆ m_buffering_completed

bool KDbCursor::m_buffering_completed
protected

true if we already have all records stored in the buffer

Definition at line 320 of file KDbCursor.h.

◆ m_fetchResult

FetchResult KDbCursor::m_fetchResult
protected

result of a record fetching

Definition at line 316 of file KDbCursor.h.

◆ m_fieldCount

int KDbCursor::m_fieldCount
protected

cached field count information

Definition at line 301 of file KDbCursor.h.

◆ m_fieldsToStoreInRecord

int KDbCursor::m_fieldsToStoreInRecord
protected

Used by storeCurrentRecord(), reimplement if needed.

(e.g. PostgreSQL driver, when m_containsRecordIdInfo is true sets m_fieldCount+1 here)

Definition at line 302 of file KDbCursor.h.

◆ m_logicalFieldCount

int KDbCursor::m_logicalFieldCount
protected

logical field count, i.e. without internal values like Record Id or lookup

Definition at line 305 of file KDbCursor.h.

◆ m_options

KDbCursor::Options KDbCursor::m_options
protected

cursor options that describes its behavior

Definition at line 306 of file KDbCursor.h.

◆ m_records_in_buf

int KDbCursor::m_records_in_buf
protected

number of records currently stored in the buffer

Definition at line 319 of file KDbCursor.h.

◆ m_visibleFieldsExpanded

KDbQueryColumnInfo::Vector* KDbCursor::m_visibleFieldsExpanded
protected

Useful e.g. for value(int) method to obtain access to schema definition.

Definition at line 324 of file KDbCursor.h.


The documentation for this class was generated from the following files:
This file is part of the KDE documentation.
Documentation copyright © 1996-2022 The KDE developers.
Generated on Tue Aug 9 2022 04:12:08 by doxygen 1.8.17 written by Dimitri van Heesch, © 1997-2006

KDE's Doxygen guidelines are available online.