GdaVconnectionDataModel

GdaVconnectionDataModel — Virtual connection based on a list of GdaDataModel

Synopsis

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);

Object Hierarchy

  GObject
   +----GdaConnection
         +----GdaVirtualConnection
               +----GdaVconnectionDataModel
                     +----GdaLdapConnection
                     +----GdaVconnectionHub

Implemented Interfaces

GdaVconnectionDataModel implements GdaLockable.

Signals

  "vtable-created"                                 : Run Last
  "vtable-dropped"                                 : Run Last

Description

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.

Details

struct GdaVconnectionDataModel

struct GdaVconnectionDataModel;


GdaVconnectionDataModelFunc ()

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.

Param1 :

a pointer to a GdaDataModel. [allow-none]

Param2 :

the name of the table represented by Param1

Param3 :

a data pointer, passed as last ergument to gda_vconnection_data_model_foreach()

struct GdaVconnectionDataModelSpec

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.


GdaVconnectionDataModelCreateColumnsFunc ()

GList *             (*GdaVconnectionDataModelCreateColumnsFunc)
                                                        (GdaVconnectionDataModelSpec *Param1,
                                                         GError **Param2);

Function called to create the virtual table's columns, as GdaColumn objects.

Param1 :

a pointer to a GdaVconnectionDataModelSpec structure

Param2 :

a place to store errors, or NULL

Returns :

a new list of GdaColumn objects. [element-type GdaColumn][transfer full]

GdaVconnectionDataModelCreateModelFunc ()

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.

Param1 :

a pointer to a GdaVconnectionDataModelSpec structure

Returns :

a new GdaDataModel. [transfer full]

gda_vconnection_data_model_add ()

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.

cnc :

a GdaVconnectionDataModel connection

spec :

a GdaVconnectionDataModelSpec structure, used AS IS (not copied) and can be modified

spec_free_func :

function to call when freeing spec, or NULL. [allow-none]

table_name :

the name of the table

error :

a place to store errors, or NULL

Returns :

TRUE if no error occurred

gda_vconnection_data_model_add_model ()

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.

cnc :

a GdaVconnectionDataModel connection

model :

a GdaDataModel

table_name :

the name of the table

error :

a place to store errors, or NULL

Returns :

TRUE if no error occurred

gda_vconnection_data_model_remove ()

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).

cnc :

a GdaVconnectionDataModel connection

table_name :

the name of the table to remove from cnc

error :

a place to store errors, or NULL

Returns :

TRUE if no error occurred

gda_vconnection_data_model_get_table_name ()

const gchar *       gda_vconnection_data_model_get_table_name
                                                        (GdaVconnectionDataModel *cnc,
                                                         GdaDataModel *model);

Find the name of the table associated to model in cnc

cnc :

a GdaVconnectionDataModel connection

model :

a GdaDataModel representing a table within cnc

Returns :

the table name, or NULL if not found. [transfer none][allow-none]

gda_vconnection_data_model_get_model ()

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().

cnc :

a GdaVconnectionDataModel connection

table_name :

a table name within cnc

Returns :

the GdaDataModel, or NULL. [transfer none][allow-none]

gda_vconnection_data_model_get ()

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.

cnc :

a GdaVconnectionDataModel connection

table_name :

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


gda_vconnection_data_model_foreach ()

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)

cnc :

a GdaVconnectionDataModel connection

func :

a GdaVconnectionDataModelFunc function pointer

data :

data to pass to func calls

Signal Details

The "vtable-created" signal

void                user_function                      (GdaVconnectionDataModel *cnc,
                                                        gchar                   *spec,
                                                        gpointer                 user_data)      : Run Last

Signal emitted when a new virtual table has been declared

cnc :

the GdaVconnectionDataModel connection

spec :

the GdaVconnectionDataModelSpec for the new virtual table

user_data :

user data set when the signal handler was connected.

The "vtable-dropped" signal

void                user_function                      (GdaVconnectionDataModel *cnc,
                                                        gchar                   *spec,
                                                        gpointer                 user_data)      : Run Last

Signal emitted when a new virtual table has been undeclared

cnc :

the GdaVconnectionDataModel connection

spec :

the GdaVconnectionDataModelSpec for the new virtual table

user_data :

user data set when the signal handler was connected.

See Also

The GdaVproviderDataModel provider to use to create such connection objects.



[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.