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GNOME Data Access 4 manual | ![]() |
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Top | Description | Object Hierarchy | Implemented Interfaces | Signals |
GdaVconnectionDataModelGdaVconnectionDataModel — Virtual connection based on a list of GdaDataModel |
struct GdaVconnectionDataModel; void (*GdaVconnectionDataModelFunc) (GdaDataModel *Param1
,const gchar *Param2
,gpointer Param3
); struct GdaVconnectionDataModelSpec; GList * (*GdaVconnectionDataModelCreateColumnsFunc) (GdaVconnectionDataModelSpec *Param1
,GError **Param2
); GdaDataModel * (*GdaVconnectionDataModelCreateModelFunc) (GdaVconnectionDataModelSpec *Param1
); gboolean gda_vconnection_data_model_add (GdaVconnectionDataModel *cnc
,GdaVconnectionDataModelSpec *spec
,GDestroyNotify spec_free_func
,const gchar *table_name
,GError **error
); gboolean gda_vconnection_data_model_add_model (GdaVconnectionDataModel *cnc
,GdaDataModel *model
,const gchar *table_name
,GError **error
); gboolean gda_vconnection_data_model_remove (GdaVconnectionDataModel *cnc
,const gchar *table_name
,GError **error
); const gchar * gda_vconnection_data_model_get_table_name (GdaVconnectionDataModel *cnc
,GdaDataModel *model
); GdaDataModel * gda_vconnection_data_model_get_model (GdaVconnectionDataModel *cnc
,const gchar *table_name
); GdaVconnectionDataModelSpec * gda_vconnection_data_model_get (GdaVconnectionDataModel *cnc
,const gchar *table_name
); void gda_vconnection_data_model_foreach (GdaVconnectionDataModel *cnc
,GdaVconnectionDataModelFunc func
,gpointer data
);
GObject +----GdaConnection +----GdaVirtualConnection +----GdaVconnectionDataModel +----GdaLdapConnection +----GdaVconnectionHub
the GdaVconnectionDataModel is a virtual connection in which GdaDataModel data models can bas added or removed, each representing a table in the connection.
Note that virtual connections have some inherent limitations [2]due to the implementation.
void (*GdaVconnectionDataModelFunc) (GdaDataModel *Param1
,const gchar *Param2
,gpointer Param3
);
This function is called for every GdaDataModel representing a table in a GdaVconnectionDataModel
connection, when using the gda_vconnection_data_model_foreach()
method.
|
a pointer to a GdaDataModel. [allow-none] |
|
the name of the table represented by Param1
|
|
a data pointer, passed as last ergument to gda_vconnection_data_model_foreach()
|
struct GdaVconnectionDataModelSpec { GdaDataModel *data_model; GdaVconnectionDataModelCreateColumnsFunc create_columns_func; GdaVconnectionDataModelCreateModelFunc create_model_func; GdaVconnectionDataModelParseFilterFunc create_filter_func; GdaVconnectionDataModelCreateFModelFunc create_filtered_model_func; };
This structure holds all the information supplied to declare a virtual table using
gda_vconnection_data_model_add()
. You don't need to provider pointers for all the functions and
for data_model
, but the following rules have to be respected:
data_model
is not NULL
and all the function pointers are NULL
: this is the situation
when the virtual table's contents is defined once by data_model
data_model
is NULL
and create_columns_func
is not NULL
:
create_filtered_model_func
is not NULL
: this is the situation where the
virtual table's associated data model handles filter optimizations.
create_model_func
is ignored in this case.
create_model_func
is not NULL
: this is the situation where the
virtual table's associated data model does not handle filter optimizations
Note that if specifying a create_filtered_model_func
, you should also specifiy a create_filter_func
function which is actually responsible for analysing the optimization.
GdaDataModel * |
a GdaDataModel, or NULL . [allow-none]
|
GdaVconnectionDataModelCreateColumnsFunc |
a pointer to a GdaVconnectionDataModelCreateColumnsFunc function, or NULL . [allow-none]
|
GdaVconnectionDataModelCreateModelFunc |
a pointer to a GdaVconnectionDataModelCreateModelFunc function, or NULL . [allow-none]
|
GdaVconnectionDataModelParseFilterFunc |
a pointer to a GdaVconnectionDataModelParseFilterFunc function, or NULL . [allow-none]
|
GdaVconnectionDataModelCreateFModelFunc |
a pointer to a GdaVconnectionDataModelCreateFModelFunc function, or NULL . [allow-none]
|
GList * (*GdaVconnectionDataModelCreateColumnsFunc) (GdaVconnectionDataModelSpec *Param1
,GError **Param2
);
Function called to create the virtual table's columns, as GdaColumn objects.
|
a pointer to a GdaVconnectionDataModelSpec structure |
|
a place to store errors, or NULL
|
Returns : |
a new list of GdaColumn objects. [element-type GdaColumn][transfer full] |
GdaDataModel * (*GdaVconnectionDataModelCreateModelFunc)
(GdaVconnectionDataModelSpec *Param1
);
Function called to create a GdaDataModel object, called when a virtual table's data need to be accessed, and when optimization is not handled.
|
a pointer to a GdaVconnectionDataModelSpec structure |
Returns : |
a new GdaDataModel. [transfer full] |
gboolean gda_vconnection_data_model_add (GdaVconnectionDataModel *cnc
,GdaVconnectionDataModelSpec *spec
,GDestroyNotify spec_free_func
,const gchar *table_name
,GError **error
);
Create a new virtual table named table_name
in cnc
. The contents of that new table
is dictated by what's in spec
.
If there is just one GdaDataModel to make appear as a table
then the gda_vconnection_data_model_add_model()
method is easier to use.
The spec_free_func
can (depending on your code) be used to clean memory allocated for spec
or
spec->data_model
.
If an error occurs, then the spec_free_func
function is called using spec
as argument.
|
a GdaVconnectionDataModel connection |
|
a GdaVconnectionDataModelSpec structure, used AS IS (not copied) and can be modified |
|
function to call when freeing spec , or NULL . [allow-none]
|
|
the name of the table |
|
a place to store errors, or NULL
|
Returns : |
TRUE if no error occurred |
gboolean gda_vconnection_data_model_add_model (GdaVconnectionDataModel *cnc
,GdaDataModel *model
,const gchar *table_name
,GError **error
);
Make model
appear as a table named table_name
in the cnc
connection (as if a
"CREATE TABLE..." statement was executed, except that the data contained within model
is actually used when table_name
's contents is read or written).
For a more general approach, see the gda_vconnection_data_model_add()
method.
|
a GdaVconnectionDataModel connection |
|
a GdaDataModel |
|
the name of the table |
|
a place to store errors, or NULL
|
Returns : |
TRUE if no error occurred |
gboolean gda_vconnection_data_model_remove (GdaVconnectionDataModel *cnc
,const gchar *table_name
,GError **error
);
Remove the table named table_name
in the cnc
connection (as if a "DROP TABLE..."
statement was executed, except that no data gets destroyed as the associated data model remains the same).
|
a GdaVconnectionDataModel connection |
|
the name of the table to remove from cnc
|
|
a place to store errors, or NULL
|
Returns : |
TRUE if no error occurred |
const gchar * gda_vconnection_data_model_get_table_name (GdaVconnectionDataModel *cnc
,GdaDataModel *model
);
Find the name of the table associated to model
in cnc
|
a GdaVconnectionDataModel connection |
|
a GdaDataModel representing a table within cnc
|
Returns : |
the table name, or NULL if not found. [transfer none][allow-none]
|
GdaDataModel * gda_vconnection_data_model_get_model (GdaVconnectionDataModel *cnc
,const gchar *table_name
);
Find the GdaDataModel object representing the table_name
table in cnc
. it can return NULL
either if no table named table_name
exists, or if that table actually exists but no GdaDataModel
has yet been created. For a more general approach, use the gda_vconnection_data_model_get()
.
|
a GdaVconnectionDataModel connection |
|
a table name within cnc
|
Returns : |
the GdaDataModel, or NULL . [transfer none][allow-none]
|
GdaVconnectionDataModelSpec * gda_vconnection_data_model_get (GdaVconnectionDataModel *cnc
,const gchar *table_name
);
Find the GdaVconnectionDataModelSpec specifying how the table named table_name
is represented
in cnc
.
|
a GdaVconnectionDataModel connection |
|
a table name within cnc
|
Returns : |
a GdaVconnectionDataModelSpec pointer, of NULL if there is no table named table_name . [transfer none][allow-none]
|
Since 4.2.6
void gda_vconnection_data_model_foreach (GdaVconnectionDataModel *cnc
,GdaVconnectionDataModelFunc func
,gpointer data
);
Call func
for each table in cnc
.
Warning: func
will be called for any table present in cnc
even if no data
model represents the contents of the table (which means the 1st argument of func
may be NULL
)
|
a GdaVconnectionDataModel connection |
|
a GdaVconnectionDataModelFunc function pointer |
|
data to pass to func calls |
"vtable-created"
signalvoid user_function (GdaVconnectionDataModel *cnc,
gchar *spec,
gpointer user_data) : Run Last
Signal emitted when a new virtual table has been declared
|
the GdaVconnectionDataModel connection |
|
the GdaVconnectionDataModelSpec for the new virtual table |
|
user data set when the signal handler was connected. |
"vtable-dropped"
signalvoid user_function (GdaVconnectionDataModel *cnc,
gchar *spec,
gpointer user_data) : Run Last
Signal emitted when a new virtual table has been undeclared
|
the GdaVconnectionDataModel connection |
|
the GdaVconnectionDataModelSpec for the new virtual table |
|
user data set when the signal handler was connected. |
[2] As virtual connections are implemented using SQLite's virtual table features, the SQL dialect which can be used is the SQLite one (see the SQL as Understood By SQLite page), and there are a few limitations inherent to this implementation (see link for more information).
Also note that it is possible to create temporary tables in virtual connections using "CREATE TEMP TABLE..." statements, but the contents of such tables will be lost once the connection is closed.