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Digikam::BdEngineBackend Class Reference
+ Inheritance diagram for Digikam::BdEngineBackend:

Classes

class  QueryState
 

Public Types

enum  DbType { SQLite , MySQL }
 
enum  QueryOperationStatus { ExecuteNormal , Wait , AbortQueries }
 
enum  QueryStateEnum { NoErrors , SQLError , ConnectionError }
 
enum  Status { Unavailable , Open , OpenSchemaChecked }
 

Public Member Functions

 BdEngineBackend (const QString &backendName, DbEngineLocking *const locking)
 Creates a database backend.
 
 BdEngineBackend (const QString &backendName, DbEngineLocking *const locking, BdEngineBackendPrivate &dd)
 
QDateTime asDBDateTime (const QDateTime &dateTime) const
 Depending on the database backend return a local or UTC date format.
 
BdEngineBackend::QueryState beginTransaction ()
 Begin a database transaction.
 
bool checkOrSetWALMode ()
 Check or set WAL mode for SQLite database if enabled in settings.
 
void close ()
 Close the database connection.
 
BdEngineBackend::QueryState commitTransaction ()
 Commit the current database transaction.
 
DbEngineConfigSettings configElement () const
 Return config read from XML, corresponding to this backend's database type.
 
bool connectionErrorHandling (int retries)
 Called when an attempted connection to the database failed.
 
DbEngineSqlQuery copyQuery (const DbEngineSqlQuery &old)
 Creates a faithful copy of the passed query, with the current db connection.
 
DbType databaseType () const
 Return the database type.
 
bool exec (DbEngineSqlQuery &query)
 Calls exec/execBatch on the query, and handles debug output if something went wrong.
 
bool execBatch (DbEngineSqlQuery &query)
 
QueryState execDBAction (const DbEngineAction &action, const QMap< QString, QVariant > &bindingMap, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 Performs the database action on the current database.
 
QueryState execDBAction (const DbEngineAction &action, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 Performs the database action on the current database.
 
QueryState execDBAction (const QString &action, const QMap< QString, QVariant > &bindingMap, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execDBAction (const QString &action, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QSqlQuery execDBActionQuery (const DbEngineAction &action, const QMap< QString, QVariant > &bindingMap)
 Performs the database action on the current database.
 
QSqlQuery execDBActionQuery (const QString &action, const QMap< QString, QVariant > &bindingMap)
 
QueryState execDirectSql (const QString &query)
 Calls exec on the query, and handles debug output if something went wrong.
 
QueryState execDirectSqlWithResult (const QString &query, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 Calls exec on the query, and handles debug output if something went wrong.
 
DbEngineSqlQuery execQuery (const QString &sql)
 Executes the statement and returns the query object.
 
DbEngineSqlQuery execQuery (const QString &sql, const QList< QVariant > &boundValues)
 
DbEngineSqlQuery execQuery (const QString &sql, const QMap< QString, QVariant > &bindingMap)
 Method which accept a hashmap with key, values which are used for named binding.
 
DbEngineSqlQuery execQuery (const QString &sql, const QVariant &boundValue1)
 
DbEngineSqlQuery execQuery (const QString &sql, const QVariant &boundValue1, const QVariant &boundValue2)
 
DbEngineSqlQuery execQuery (const QString &sql, const QVariant &boundValue1, const QVariant &boundValue2, const QVariant &boundValue3)
 
DbEngineSqlQuery execQuery (const QString &sql, const QVariant &boundValue1, const QVariant &boundValue2, const QVariant &boundValue3, const QVariant &boundValue4)
 
void execQuery (DbEngineSqlQuery &preparedQuery, const QList< QVariant > &boundValues)
 
void execQuery (DbEngineSqlQuery &preparedQuery, const QVariant &boundValue1)
 Binds the values and executes the prepared query.
 
void execQuery (DbEngineSqlQuery &preparedQuery, const QVariant &boundValue1, const QVariant &boundValue2)
 
void execQuery (DbEngineSqlQuery &preparedQuery, const QVariant &boundValue1, const QVariant &boundValue2, const QVariant &boundValue3)
 
void execQuery (DbEngineSqlQuery &preparedQuery, const QVariant &boundValue1, const QVariant &boundValue2, const QVariant &boundValue3, const QVariant &boundValue4)
 
QueryState execSql (const QString &sql, const QList< QVariant > &boundValues, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execSql (const QString &sql, const QMap< QString, QVariant > &bindingMap, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 Method which accepts a map for named binding.
 
QueryState execSql (const QString &sql, const QVariant &boundValue1, const QVariant &boundValue2, const QVariant &boundValue3, const QVariant &boundValue4, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execSql (const QString &sql, const QVariant &boundValue1, const QVariant &boundValue2, const QVariant &boundValue3, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execSql (const QString &sql, const QVariant &boundValue1, const QVariant &boundValue2, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execSql (const QString &sql, const QVariant &boundValue1, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execSql (const QString &sql, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 Executes the SQL statement, and write the returned data into the values list.
 
QueryState execSql (DbEngineSqlQuery &preparedQuery, const QList< QVariant > &boundValues, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execSql (DbEngineSqlQuery &preparedQuery, const QVariant &boundValue1, const QVariant &boundValue2, const QVariant &boundValue3, const QVariant &boundValue4, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execSql (DbEngineSqlQuery &preparedQuery, const QVariant &boundValue1, const QVariant &boundValue2, const QVariant &boundValue3, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execSql (DbEngineSqlQuery &preparedQuery, const QVariant &boundValue1, const QVariant &boundValue2, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execSql (DbEngineSqlQuery &preparedQuery, const QVariant &boundValue1, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execSql (DbEngineSqlQuery &preparedQuery, QList< QVariant > *const values=nullptr, QVariant *const lastInsertId=nullptr)
 
QueryState execUpsertDBAction (const DbEngineAction &action, const QVariant &id, const QStringList &fieldNames, const QList< QVariant > &values)
 Performs a special DBAction that is usually needed to "INSERT or UPDATE" entries in a table.
 
QueryState execUpsertDBAction (const QString &action, const QVariant &id, const QStringList &fieldNames, const QList< QVariant > &values)
 
DbEngineAction getDBAction (const QString &actionName) const
 Returns a database action with name, specified in actionName, for the current database.
 
DbEngineSqlQuery getQuery ()
 Creates an empty query object waiting for the statement.
 
QueryState handleQueryResult (DbEngineSqlQuery &query, QList< QVariant > *const values, QVariant *const lastInsertId)
 Checks if there was a connection error.
 
bool isCompatible (const DbEngineParameters &parameters)
 Checks if the parameters can be used for this database backend.
 
bool isInTransaction () const
 Returns if the database is in a different thread in a transaction.
 
bool isOpen () const
 
bool isReady () const
 
QString lastError ()
 Returns a description of the last error that occurred on this database.
 
QSqlError lastSQLError ()
 Returns the last error that occurred on this database.
 
int maximumBoundValues () const
 Returns the maximum number of bound parameters allowed per query.
 
bool open (const DbEngineParameters &parameters)
 Open the database connection.
 
DbEngineSqlQuery prepareQuery (const QString &sql)
 Creates a query object prepared with the statement, waiting for bound values.
 
bool queryErrorHandling (DbEngineSqlQuery &query, int retries)
 Called with a failed query.
 
QList< QVariant > readToList (DbEngineSqlQuery &query)
 Reads data of returned result set into a list which is returned.
 
void rollbackTransaction ()
 Rollback the current database transaction.
 
void setDbEngineErrorHandler (DbEngineErrorHandler *const handler)
 Add a DbEngineErrorHandler.
 
void setForeignKeyChecks (bool check)
 Enables or disables FOREIGN_KEY_CHECKS for the database.
 
Status status () const
 Returns the current status of the database backend.
 
QStringList tables ()
 Returns a list with the names of tables in the database.
 
bool transactionErrorHandling (const QSqlError &lastError, int retries)
 

Protected Attributes

BdEngineBackendPrivate *const d_ptr = nullptr
 

Member Enumeration Documentation

◆ QueryStateEnum

Enumerator
NoErrors 

No errors occurred while executing the query.

SQLError 

An SQLError has occurred while executing the query.

ConnectionError 

An connection error has occurred while executing the query.

◆ Status

Enumerator
Unavailable 

The database is not available, because it has not been opened yet or because of an error condition.

Open 

The database is open.

It has not been verified that the schema is up to date. This status is sufficient for use in a context where it can be assumed that the necessary schema check has been carried out by a master process.

OpenSchemaChecked 

The database is open, and it has been verified that the schema is up to date, or the schema has been updated.

Constructor & Destructor Documentation

◆ BdEngineBackend()

Digikam::BdEngineBackend::BdEngineBackend ( const QString &  backendName,
DbEngineLocking *const  locking 
)
explicit

The backend name is an arbitrary string that shall be unique for this backend object. It will be used to create unique connection names per backend and thread.

Member Function Documentation

◆ asDBDateTime()

QDateTime Digikam::BdEngineBackend::asDBDateTime ( const QDateTime &  dateTime) const

SQLite: local date format MySQL: UTC date format

◆ checkOrSetWALMode()

bool Digikam::BdEngineBackend::checkOrSetWALMode ( )
Returns
true the WAL mode is confirmed enabled.

◆ close()

void Digikam::BdEngineBackend::close ( )

Shall only be called from the thread that called open().

◆ connectionErrorHandling()

bool Digikam::BdEngineBackend::connectionErrorHandling ( int  retries)

If it returns true, retry; if it returns false, bail out. Pass the number of connection retries to help with some decisions.

◆ execDBAction() [1/2]

BdEngineBackend::QueryState Digikam::BdEngineBackend::execDBAction ( const DbEngineAction action,
const QMap< QString, QVariant > &  bindingMap,
QList< QVariant > *const  values = nullptr,
QVariant *const  lastInsertId = nullptr 
)

Queries by the specified parameters can have named parameters which are substituted with values from the bindingMap parameter. The result values (if any) are stored within the values list.

◆ execDBAction() [2/2]

BdEngineBackend::QueryState Digikam::BdEngineBackend::execDBAction ( const DbEngineAction action,
QList< QVariant > *const  values = nullptr,
QVariant *const  lastInsertId = nullptr 
)

Queries by the specified parameters mustn't have named parameters. The result values (if any) are stored within the values list.

◆ execDBActionQuery()

QSqlQuery Digikam::BdEngineBackend::execDBActionQuery ( const DbEngineAction action,
const QMap< QString, QVariant > &  bindingMap 
)

Queries by the specified parameters can have named parameters which are substituted with values from the bindingMap parameter. The result values (if any) are stored within the values list. This method returns the last query, which is used to handle special cases.

◆ execDirectSql()

BdEngineBackend::QueryState Digikam::BdEngineBackend::execDirectSql ( const QString &  query)

The query is not prepared, which can be fail in certain situations (e.g. trigger statements on QMYSQL).

◆ execDirectSqlWithResult()

BdEngineBackend::QueryState Digikam::BdEngineBackend::execDirectSqlWithResult ( const QString &  query,
QList< QVariant > *const  values = nullptr,
QVariant *const  lastInsertId = nullptr 
)

The query is not prepared, which can be fail in certain situations (e.g. trigger statements on QMYSQL).

◆ execQuery()

DbEngineSqlQuery Digikam::BdEngineBackend::execQuery ( const QString &  sql)

Methods are provided for up to four bound values (positional binding), or for a list of bound values.

◆ execSql() [1/2]

BdEngineBackend::QueryState Digikam::BdEngineBackend::execSql ( const QString &  sql,
const QMap< QString, QVariant > &  bindingMap,
QList< QVariant > *const  values = nullptr,
QVariant *const  lastInsertId = nullptr 
)

For special cases it's also possible to add a DbEngineActionType which wraps another data object (also lists or maps) which can be used as field entry or as value (where it's prepared with positional binding). See more on DbEngineActionType class. If the wrapped data object is an instance of list, then the elements are separated by comma. If the wrapped data object is an instance of map, then the elements are inserted in the following way: key1=value1, key2=value2,...,keyN=valueN.

◆ execSql() [2/2]

BdEngineBackend::QueryState Digikam::BdEngineBackend::execSql ( const QString &  sql,
QList< QVariant > *const  values = nullptr,
QVariant *const  lastInsertId = nullptr 
)

If you are not interested in the returned data, set values to 0. Methods are provided for up to four bound values (positional binding), or for a list of bound values. If you want the last inserted id (and your query is suitable), set lastInsertId to the address of a QVariant. Additionally, methods are provided for prepared statements.

◆ execUpsertDBAction()

BdEngineBackend::QueryState Digikam::BdEngineBackend::execUpsertDBAction ( const DbEngineAction action,
const QVariant &  id,
const QStringList &  fieldNames,
const QList< QVariant > &  values 
)

The corresponding DBAction must contain exactly the named parameters :id, :fieldValueList, :fieldList and :valueList. You pass the value to be bound to the ":id" field, then two lists of the same size: The first containing the field names, the second one containing the values as QVariants ready for binding.

◆ handleQueryResult()

BdEngineBackend::QueryState Digikam::BdEngineBackend::handleQueryResult ( DbEngineSqlQuery query,
QList< QVariant > *const  values,
QVariant *const  lastInsertId 
)

If so BdEngineBackend::ConnectionError is returned. If not, the values are extracted from the query and inserted in the values list, the last insertion id is taken from the query and BdEngineBackend::NoErrors is returned.

◆ isInTransaction()

bool Digikam::BdEngineBackend::isInTransaction ( ) const

Note that a transaction does not require holding CoreDbAccess. Note that this does not give information about other processes locking the database.

◆ lastError()

QString Digikam::BdEngineBackend::lastError ( )

Use CoreDbAccess::lastError for errors presented to the user. This error will be included in that message. It may be empty.

◆ lastSQLError()

QSqlError Digikam::BdEngineBackend::lastSQLError ( )

Use CoreDbAccess::lastError for errors presented to the user. It may be empty.

◆ maximumBoundValues()

int Digikam::BdEngineBackend::maximumBoundValues ( ) const

This value depends on the database engine.

◆ open()

bool Digikam::BdEngineBackend::open ( const DbEngineParameters parameters)
Returns
true on success

◆ queryErrorHandling()

bool Digikam::BdEngineBackend::queryErrorHandling ( DbEngineSqlQuery query,
int  retries 
)

Handles certain known errors and debug output. If it returns true, reexecute the query; if it returns false, return it as failed. Pass the number of retries already done for this query to help with some decisions.

◆ readToList()

QList< QVariant > Digikam::BdEngineBackend::readToList ( DbEngineSqlQuery query)

The read process is column wise, which means all data elements of a row is read, then the resultset is switched to the next row.

◆ setDbEngineErrorHandler()

void Digikam::BdEngineBackend::setDbEngineErrorHandler ( DbEngineErrorHandler *const  handler)

This object must be created in the main thread. If a database error occurs, this object can handle problem solving and user interaction.

◆ setForeignKeyChecks()

void Digikam::BdEngineBackend::setForeignKeyChecks ( bool  check)

This function depends on the database engine.