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GNOME Data Access 4.0 manual | ![]() |
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GdaMetaStore; enum GdaMetaStoreError; GdaMetaStoreChange; enum GdaMetaStoreChangeType; GdaMetaContext; GdaMetaStore* gda_meta_store_new (const gchar *cnc_string); GdaMetaStore* gda_meta_store_new_with_file (const gchar *file_name); gint gda_meta_store_get_version (GdaMetaStore *store); GdaDataModel* gda_meta_store_extract (GdaMetaStore *store, const gchar *select_sql, GError **error, ...); gboolean gda_meta_store_modify (GdaMetaStore *store, const gchar *table_name, GdaDataModel *new_data, const gchar *condition, GError **error, ...); gboolean gda_meta_store_modify_with_context (GdaMetaStore *store, GdaMetaContext *context, GdaDataModel *new_data, GError **error); GdaMetaStruct* gda_meta_store_schema_get_structure (GdaMetaStore *store, GError **error); gboolean gda_meta_store_get_attribute_value (GdaMetaStore *store, const gchar *att_name, gchar **att_value, GError **error); gboolean gda_meta_store_set_attribute_value (GdaMetaStore *store, const gchar *att_name, const gchar *att_value, GError **error); gboolean gda_meta_store_schema_add_custom_object (GdaMetaStore *store, const gchar *xml_description, GError **error); GdaConnection* gda_meta_store_get_internal_connection (GdaMetaStore *store);
"catalog" gchararray : Write / Construct Only "cnc" GdaConnection : Read / Write / Construct Only "cnc-string" gchararray : Write / Construct Only "schema" gchararray : Write / Construct Only
Previous versions of libgda relied on an XML based file to store dictionary information, such as the database's schema (tables, views, etc) and various other information. The problems were that it was difficult for an application to integrate its own data into the dictionary and that there were some performances problems as the XML file needed to be parsed (and converted into its own in-memory structure) before any data could be read out of it.
The new dictionary now relies on a database structure to store its data. The actual database can be a single file (using an SQLite database), an entirely in memory database (also using an SQLite database), or a more conventional backend such as a PostgreSQL database for a shared dictionary on a server.
libgda imposes its own structure (based on objects such as tables and views which name starts with an underscore '_'), but a user can also add its own tables or other database objects. The following diagram shows the tables defined by libgda for its internal needs:
typedef enum { GDA_META_STORE_INCORRECT_SCHEMA, GDA_META_STORE_UNSUPPORTED_PROVIDER, GDA_META_STORE_INTERNAL_ERROR, GDA_META_STORE_META_CONTEXT_ERROR, GDA_META_STORE_MODIFY_CONTENTS_ERROR, GDA_META_STORE_EXTRACT_SQL_ERROR, GDA_META_STORE_ATTRIBUTE_NOT_FOUND_ERROR, GDA_META_STORE_ATTRIBUTE_ERROR, GDA_META_STORE_SCHEMA_OBJECT_NOT_FOUND_ERROR, GDA_META_STORE_SCHEMA_OBJECT_CONFLICT_ERROR, GDA_META_STORE_SCHEMA_OBJECT_DESCR_ERROR, GDA_META_STORE_TRANSACTION_ALREADY_STARTED_ERROR } GdaMetaStoreError;
typedef struct { /* change general information */ GdaMetaStoreChangeType c_type; gchar *table_name; GHashTable *keys; /* key = ('+' or '-') and a column position in @table (string) starting at 0, * value = a GValue pointer */ } GdaMetaStoreChange;
typedef enum { GDA_META_STORE_ADD, GDA_META_STORE_REMOVE, GDA_META_STORE_MODIFY, } GdaMetaStoreChangeType;
typedef struct { gchar *table_name; gint size; gchar **column_names; GValue **column_values; } GdaMetaContext;
GdaMetaStore* gda_meta_store_new (const gchar *cnc_string);
Create a new GdaMetaStore object.
cnc_string : |
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Returns : | the newly created object, or NULL if an error occurred
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GdaMetaStore* gda_meta_store_new_with_file (const gchar *file_name);
Create a new GdaMetaStore object using file_name
as its internal
database
file_name : |
a file name |
Returns : | the newly created object, or NULL if an error occurred
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gint gda_meta_store_get_version (GdaMetaStore *store);
Get store
's internal schema's version
Retunrs: the version (1 at the moment)
store : |
a GdaMetaStore object |
Returns : |
GdaDataModel* gda_meta_store_extract (GdaMetaStore *store, const gchar *select_sql, GError **error, ...);
Extracts some data stored in store
using a custom SELECT query.
store : |
a GdaMetaStore object |
select_sql : |
a SELECT statement |
error : |
a place to store errors, or NULL
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... : |
a list of (variable name (gchar *), GValue *value) terminated with NULL, representing values for all the
variables mentionned in select_sql . If there is no variable then this part can be omitted.
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Returns : | a new GdaDataModel, or NULL if an error occurred
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gboolean gda_meta_store_modify (GdaMetaStore *store, const gchar *table_name, GdaDataModel *new_data, const gchar *condition, GError **error, ...);
Propagates an update to store
, the update's contents is represented by new_data
, this function is
primarily reserved to database providers.
For example tell store
to update its list of tables, new_data
should contain the same columns as the "_tables"
table of store
, and contain one row per table in the store; there should not be any more argument after the error
argument.
Now, to update only one table, the new_data
data model should have one row for the table to update (or no row
at all if the table does not exist anymore), and have values for the promary key of the "_tables" table of
store
, namely "table_catalog", "table_schema" and "table_name".
store : |
a GdaMetaStore object |
table_name : |
the name of the table to modify within store
|
new_data : |
a GdaDataModel containing the new data to set in table_name , or NULL (treated as a data model
with no row at all)
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condition : |
SQL expression (which may contain variables) defining the rows which are being obsoleted by new_data , or NULL
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error : |
a place to store errors, or NULL
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... : |
a list of (variable name (gchar *), GValue *value) terminated with NULL, representing values for all the
variables mentionned in condition .
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Returns : | TRUE if no error occurred |
gboolean gda_meta_store_modify_with_context (GdaMetaStore *store, GdaMetaContext *context, GdaDataModel *new_data, GError **error);
Propagates an update to store
, the update's contents is represented by new_data
, this function is
primarily reserved to database providers.
store : |
a GdaMetaStore object |
context : |
a GdaMetaContext context describing what to modify in store
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new_data : |
a GdaDataModel containing the new data to set in table_name , or NULL (treated as a data model
with no row at all)
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error : |
a place to store errors, or NULL
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Returns : | TRUE if no error occurred |
GdaMetaStruct* gda_meta_store_schema_get_structure (GdaMetaStore *store, GError **error);
Creates a new GdaMetaStruct object representing store
's interal database structure.
store : |
a GdaMetaStore object |
error : |
a place to store errors, or NULL
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Returns : | a new GdaMetaStruct object, or NULL if an error occurred
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gboolean gda_meta_store_get_attribute_value (GdaMetaStore *store, const gchar *att_name, gchar **att_value, GError **error);
The GdaMetaStore object maintains a list of (name,value) attributes (attributes names starting with a '_'
character are for intarnal use only and cannot be altered). This method and the gda_meta_store_set_attribute_value()
method allows the user to add, set or remove attributes specific to their usage.
This method allows to get the value of a attribute stored in store
. The returned attribute value is
placed at att_value
, the caller is responsible to free that string.
If there is no attribute named att_name
then att_value
is set to NULL
and error
will contain the GDA_META_STORE_ATTRIBUTE_NOT_FOUND_ERROR error code, and FALSE is returned.
store : |
a GdaMetaStore object |
att_name : |
name of the attribute to get |
att_value : |
the place to store the attribute value |
error : |
a place to store errors, or NULL
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Returns : | TRUE if no error occurred |
gboolean gda_meta_store_set_attribute_value (GdaMetaStore *store, const gchar *att_name, const gchar *att_value, GError **error);
Set the value of the attribute named att_name
to att_value
; see gda_meta_store_get_attribute_value()
for
more information.
store : |
a GdaMetaStore object |
att_name : |
name of the attribute to set |
att_value : |
value of the attribute to set, or NULL to unset the attribute
|
error : |
a place to store errors, or NULL
|
Returns : | TRUE if no error occurred |
gboolean gda_meta_store_schema_add_custom_object (GdaMetaStore *store, const gchar *xml_description, GError **error);
The internal database used by store
can be 'augmented' with some user-defined database objects
(such as tables or views). This method allows one to add a new database object.
If the internal database already contains the object, then:
if the object is equal to the provided description then TRUE is returned
if the object exists but differs from the provided description, then FALSE is returned, with the GDA_META_STORE_SCHEMA_OBJECT_CONFLICT_ERROR error code
store : |
a GdaMetaStore object |
xml_description : |
an XML description of the table or view to add to store
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error : |
a place to store errors, or NULL
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Returns : | TRUE if the new object has sucessfully been added |
GdaConnection* gda_meta_store_get_internal_connection (GdaMetaStore *store);
Get a pointer to the GdaConnection object internally used by store
to store
its contents.
The returned connection can be used to access some other data than the one managed by store
itself. Don not close the connection.
store : |
a GdaMetaStore object |
Returns : | a GdaConnection, or NULL
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void user_function (GdaMetaStore *gdametastore, gpointer arg1, gpointer user_data) : Run First
gdametastore : |
the object which received the signal. |
arg1 : |
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user_data : |
user data set when the signal handler was connected. |
void user_function (GdaMetaStore *gdametastore, gpointer user_data) : Run First
gdametastore : |
the object which received the signal. |
user_data : |
user data set when the signal handler was connected. |
gpointer user_function (GdaMetaStore *store, gpointer suggest, gpointer user_data) : Run Last
This signal is emitted when the contents of a table should be updated (data updated or inserted; deleting data is done automatically).
store : |
the GdaMetaStore instance that emitted the signal |
suggest : |
the suggested update, as a GdaMetaContext structure |
user_data : |
user data set when the signal handler was connected. |
Returns : | a new GError error structure if there was an error when processing the
signal, or NULL if signal propagation should continue
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