Relations and Tuples tables of data which can be indexed on any number of fields. A #GRelation is a table of data which can be indexed on any number of fields, rather like simple database tables. A #GRelation contains a number of records, called tuples. Each record contains a number of fields. Records are not ordered, so it is not possible to find the record at a particular index. Note that #GRelation tables are currently limited to 2 fields. To create a GRelation, use g_relation_new(). To specify which fields should be indexed, use g_relation_index(). Note that this must be called before any tuples are added to the #GRelation. To add records to a #GRelation use g_relation_insert(). To determine if a given record appears in a #GRelation, use g_relation_exists(). Note that fields are compared directly, so pointers must point to the exact same position (i.e. different copies of the same string will not match.) To count the number of records which have a particular value in a given field, use g_relation_count(). To get all the records which have a particular value in a given field, use g_relation_select(). To access fields of the resulting records, use g_tuples_index(). To free the resulting records use g_tuples_destroy(). To delete all records which have a particular value in a given field, use g_relation_delete(). To destroy the #GRelation, use g_relation_destroy(). To help debug #GRelation objects, use g_relation_print(). The #GRelation struct is an opaque data structure to represent a Relation. It should only be accessed via the following functions. Creates a new #GRelation with the given number of fields. Note that currently the number of fields must be 2. @fields: the number of fields. @Returns: a new #GRelation. Creates an index on the given field. Note that this must be called before any records are added to the #GRelation. @relation: a #GRelation. @field: the field to index, counting from 0. @hash_func: a function to produce a hash value from the field data. @key_equal_func: a function to compare two values of the given field. Inserts a record into a #GRelation. @relation: a #GRelation. @Varargs: the fields of the record to add. This must match the number of fields in the #GRelation. Returns %TRUE if a record with the given values exists in a #GRelation. Note that the values are compared directly, so that, for example, two copies of the same string will not match. @relation: a #GRelation. @Varargs: the fields of the record to compare. The number must match the number of fields in the #GRelation. @Returns: %TRUE if a record matches. Returns the number of tuples in a #GRelation that have the given value in the given field. @relation: a #GRelation. @key: the value to compare with. @field: the field of each record to match. @Returns: the number of matches. Returns all of the tuples which have the given key in the given field. Use g_tuples_index() to access the returned records. The returned records should be freed with g_tuples_destroy(). @relation: a #GRelation. @key: the value to compare with. @field: the field of each record to match. @Returns: the records (tuples) that matched. Deletes any records from a #GRelation that have the given key value in the given field. @relation: a #GRelation. @key: the value to compare with. @field: the field of each record to match. @Returns: the number of records deleted. Destroys the #GRelation, freeing all memory allocated. However, it does not free memory allocated for the tuple data, so you should free that first if appropriate. @relation: a #GRelation. Outputs information about all records in a #GRelation, as well as the indexes. It is for debugging. @relation: a #GRelation. The #GTuples struct is used to return records (or tuples) from the #GRelation by g_relation_select(). It only contains one public member - the number of records that matched. To access the matched records, you must use g_tuples_index(). @len: the number of records that matched. Frees the records which were returned by g_relation_select(). This should always be called after g_relation_select() when you are finished with the records. The records are not removed from the #GRelation. @tuples: the tuple data to free. Gets a field from the records returned by g_relation_select(). It returns the given field of the record at the given index. The returned value should not be changed. @tuples: the tuple data, returned by g_relation_select(). @index_: the index of the record. @field: the field to return. @Returns: the field of the record.