]> Query 3 RASQAL Library Query Query object API, parsing and execution enum rasqal_query_verb; typedef rasqal_query; rasqal_query* rasqal_new_query (rasqal_world *world, const char *name, unsigned char *uri); void rasqal_free_query (rasqal_query *query); int rasqal_query_add_data_graph (rasqal_query *query, raptor_uri *uri, raptor_uri *name_uri, int flags); int rasqal_query_add_prefix (rasqal_query *query, rasqal_prefix *prefix); int rasqal_query_add_variable (rasqal_query *query, rasqal_variable *var); rasqal_query_results* rasqal_query_execute (rasqal_query *query); raptor_sequence* rasqal_query_get_all_variable_sequence (rasqal_query *query); raptor_sequence* rasqal_query_get_anonymous_variable_sequence (rasqal_query *query); raptor_sequence* rasqal_query_get_bound_variable_sequence (rasqal_query *query); rasqal_triple* rasqal_query_get_construct_triple (rasqal_query *query, int idx); raptor_sequence* rasqal_query_get_construct_triples_sequence (rasqal_query *query); rasqal_data_graph* rasqal_query_get_data_graph (rasqal_query *query, int idx); raptor_sequence* rasqal_query_get_data_graph_sequence (rasqal_query *query); int rasqal_query_get_distinct (rasqal_query *query); int rasqal_query_get_explain (rasqal_query *query); rasqal_expression* rasqal_query_get_group_condition (rasqal_query *query, int idx); raptor_sequence* rasqal_query_get_group_conditions_sequence (rasqal_query *query); rasqal_graph_pattern* rasqal_query_get_graph_pattern (rasqal_query *query, int idx); raptor_sequence* rasqal_query_get_graph_pattern_sequence (rasqal_query *query); const char* rasqal_query_get_label (rasqal_query *query); int rasqal_query_get_limit (rasqal_query *query); const char* rasqal_query_get_name (rasqal_query *query); int rasqal_query_get_offset (rasqal_query *query); rasqal_expression* rasqal_query_get_order_condition (rasqal_query *query, int idx); raptor_sequence* rasqal_query_get_order_conditions_sequence (rasqal_query *query); rasqal_prefix* rasqal_query_get_prefix (rasqal_query *query, int idx); raptor_sequence* rasqal_query_get_prefix_sequence (rasqal_query *query); rasqal_graph_pattern* rasqal_query_get_query_graph_pattern (rasqal_query *query); rasqal_triple* rasqal_query_get_triple (rasqal_query *query, int idx); raptor_sequence* rasqal_query_get_triple_sequence (rasqal_query *query); void* rasqal_query_get_user_data (rasqal_query *query); rasqal_variable* rasqal_query_get_variable (rasqal_query *query, int idx); rasqal_query_verb rasqal_query_get_verb (rasqal_query *query); int rasqal_query_get_wildcard (rasqal_query *query); int rasqal_query_has_variable (rasqal_query *query, unsigned char *name); int rasqal_query_prepare (rasqal_query *query, unsigned char *query_string, raptor_uri *base_uri); void rasqal_query_print (rasqal_query *query, FILE *fh); void rasqal_query_graph_pattern_visit (rasqal_query *query, rasqal_graph_pattern_visit_fn visit_fn, void *data); void rasqal_query_set_default_generate_bnodeid_parameters (rasqal_query *rdf_query, char *prefix, int base); void rasqal_query_set_distinct (rasqal_query *query, int distinct_mode); void rasqal_query_set_explain (rasqal_query *query, int is_explain); void rasqal_query_set_error_handler (rasqal_query *query, void *user_data, raptor_message_handler handler); void rasqal_query_set_fatal_error_handler (rasqal_query *query, void *user_data, raptor_message_handler handler); void rasqal_query_set_generate_bnodeid_handler (rasqal_query *query, void *user_data, rasqal_generate_bnodeid_handler handler); void rasqal_query_set_limit (rasqal_query *query, int limit); void rasqal_query_set_offset (rasqal_query *query, int offset); void rasqal_query_set_user_data (rasqal_query *query, void *user_data); int rasqal_query_set_variable (rasqal_query *query, unsigned char *name, rasqal_literal *value); void rasqal_query_set_warning_handler (rasqal_query *query, void *user_data, raptor_message_handler handler); const char* rasqal_query_verb_as_string (rasqal_query_verb verb); int rasqal_query_write (raptor_iostream *iostr, rasqal_query *query, raptor_uri *format_uri, raptor_uri *base_uri); int rasqal_query_iostream_write_escaped_counted_string (rasqal_query *query, raptor_iostream *iostr, unsigned char *string, size_t len); unsigned char* rasqal_query_escape_counted_string (rasqal_query *query, unsigned char *string, size_t len, size_t *output_len_p); int rasqal_query_set_feature (rasqal_query *query, rasqal_feature feature, int value); int rasqal_query_set_feature_string (rasqal_query *query, rasqal_feature feature, unsigned char *value); int rasqal_query_get_feature (rasqal_query *query, rasqal_feature feature); const unsigned char* rasqal_query_get_feature_string (rasqal_query *query, rasqal_feature feature); This class provides the main interface to the library. A query can be constructed by parsing a string, retrieving it from a URI and/or constructing it via API methods to build the query expression. The query structures can be read via methods to return the query verb rasqal_query_get_verb(), the rasqal_data_graph RDF data sources with rasqal_query_get_data_graph() etc., the rasqal_graph_pattern tree with rasqal_query_get_query_graph_pattern(), the sequence of order conditions with rasqal_query_get_order_condition() etc., the rasqal_variable selected to return with rasqal_query_get_bound_variable_sequence() or rasqal_query_get_all_variable_sequence(), and so on. To process a query string, the rasqal_query_prepare() method parses the query string in some query language and initialises the rasqal_query structures. The query can be evaluated with the internal query engine against some source of matches using rasqal_query_execute() to give an rasqal_query_results. There are multiple forms of results that can include variable bindings, a boolean or an RDF graph that can be tested for with methods on rasqal_query_results and then retrieved. rasqal_query_verbtypedef enum { /* internal */ RASQAL_QUERY_VERB_UNKNOWN = 0, RASQAL_QUERY_VERB_SELECT = 1, RASQAL_QUERY_VERB_CONSTRUCT = 2, RASQAL_QUERY_VERB_DESCRIBE = 3, RASQAL_QUERY_VERB_ASK = 4, RASQAL_QUERY_VERB_DELETE = 5, RASQAL_QUERY_VERB_INSERT = 6, /* internal */ RASQAL_QUERY_VERB_LAST=RASQAL_QUERY_VERB_INSERT } rasqal_query_verb; Query main operation verbs describing the major type of query being performed. RASQAL_QUERY_VERB_UNKNOWN Internal RASQAL_QUERY_VERB_SELECT RDQL/SPARQL query select verb. RASQAL_QUERY_VERB_CONSTRUCT SPARQL query construct verb. RASQAL_QUERY_VERB_DESCRIBE SPARQL query describe verb. RASQAL_QUERY_VERB_ASK SPARQL query ask verb. RASQAL_QUERY_VERB_DELETE LAQRS query delete verb. RASQAL_QUERY_VERB_INSERT LAQRS query insert verb. RASQAL_QUERY_VERB_LAST Internal rasqal_queryrasqal_graph_query* query; Rasqal query class. rasqal_new_queryrasqal_query* rasqal_new_query (rasqal_world *world, const char *name, unsigned char *uri); Constructor - create a new rasqal_query object. A query language can be named or identified by a URI, either of which is optional. The default query language will be used if both are NULL. rasqal_languages_enumerate returns information on the known names, labels and URIs. world : rasqal_world object name : the query language name (or NULL) uri : raptor_uri language uri (or NULL) Returns : a new rasqal_query object or NULL on failure rasqal_free_queryvoid rasqal_free_query (rasqal_query *query); Destructor - destroy a rasqal_query object. query : rasqal_query object rasqal_query_add_data_graphint rasqal_query_add_data_graph (rasqal_query *query, raptor_uri *uri, raptor_uri *name_uri, int flags); Add a data graph to the query. named_uri must be given if flags RASQAL_DATA_GRAPH_NAMED is set. It is the name of the graph and also used as the base URI when resolving any relative URIs for the graph in uri. query : rasqal_query query object uri : raptor_uri source uri for retrieval name_uri : raptor_uri name uri (or NULL) flags : RASQAL_DATA_GRAPH_NAMED or RASQAL_DATA_GRAPH_BACKGROUND Returns : non-0 on failure rasqal_query_add_prefixint rasqal_query_add_prefix (rasqal_query *query, rasqal_prefix *prefix); Add a namespace prefix to the query. If the prefix has already been used, the old URI will be overridden. query : rasqal_query query object prefix : rasqal_prefix namespace prefix, URI Returns : non-0 on failure rasqal_query_add_variableint rasqal_query_add_variable (rasqal_query *query, rasqal_variable *var); Add a binding variable to the query. See also rasqal_query_set_variable which assigns or removes a value to a previously added variable in the query. query : rasqal_query query object var : rasqal_variable variable Returns : non-0 on failure rasqal_query_executerasqal_query_results* rasqal_query_execute (rasqal_query *query); Excute a query - run and return results. query : the rasqal_query object Returns : a rasqal_query_results structure or NULL on failure. rasqal_query_get_all_variable_sequenceraptor_sequence* rasqal_query_get_all_variable_sequence (rasqal_query *query); Get the sequence of all variables mentioned in the query. query : rasqal_query query object Returns : a raptor_sequence of rasqal_variable pointers. rasqal_query_get_anonymous_variable_sequenceraptor_sequence* rasqal_query_get_anonymous_variable_sequence (rasqal_query *query); Get the sequence of anonymous variables mentioned in the query. query : rasqal_query query object Returns : a raptor_sequence of rasqal_variable pointers. rasqal_query_get_bound_variable_sequenceraptor_sequence* rasqal_query_get_bound_variable_sequence (rasqal_query *query); Get the sequence of variables to bind in the query. This returns the sequence of variables that are explicitly chosen via SELECT in RDQL, SPARQL. Or all variables mentioned with SELECT * query : rasqal_query query object Returns : a raptor_sequence of rasqal_variable pointers. rasqal_query_get_construct_triplerasqal_triple* rasqal_query_get_construct_triple (rasqal_query *query, int idx); Get a triple in the sequence of construct triples. query : rasqal_query query object idx : index into the sequence (0 or larger) Returns : a rasqal_triple pointer or NULL if out of the sequence range rasqal_query_get_construct_triples_sequenceraptor_sequence* rasqal_query_get_construct_triples_sequence (rasqal_query *query); Get the sequence of triples for a construct. query : rasqal_query query object Returns : a raptor_sequence of rasqal_triple pointers. rasqal_query_get_data_graphrasqal_data_graph* rasqal_query_get_data_graph (rasqal_query *query, int idx); Get a rasqal_data_graph* in the sequence of data_graphs. query : rasqal_query query object idx : index into the sequence (0 or larger) Returns : a rasqal_data_graph pointer or NULL if out of the sequence range rasqal_query_get_data_graph_sequenceraptor_sequence* rasqal_query_get_data_graph_sequence (rasqal_query *query); Get the sequence of data_graph URIs. query : rasqal_query query object Returns : a raptor_sequence of raptor_uri pointers. rasqal_query_get_distinctint rasqal_query_get_distinct (rasqal_query *query); Get the query distinct mode See rasqal_query_set_distinct() for the distinct modes. query : rasqal_query query object Returns : non-0 if the results should be distinct rasqal_query_get_explainint rasqal_query_get_explain (rasqal_query *query); Get the query explain results flag. query : rasqal_query query object Returns : non-0 if the results should be explain rasqal_query_get_group_conditionrasqal_expression* rasqal_query_get_group_condition (rasqal_query *query, int idx); Get a query grouping expression in the sequence of query grouping conditions. query : rasqal_query query object idx : index into the sequence (0 or larger) Returns : a rasqal_expression pointer or NULL if out of the sequence range rasqal_query_get_group_conditions_sequenceraptor_sequence* rasqal_query_get_group_conditions_sequence (rasqal_query *query); Get the sequence of query grouping conditions. query : rasqal_query query object Returns : a raptor_sequence of rasqal_expression pointers. rasqal_query_get_graph_patternrasqal_graph_pattern* rasqal_query_get_graph_pattern (rasqal_query *query, int idx); Get a graph_pattern in the sequence of graph_pattern expressions in the top query graph pattern. query : rasqal_query query object idx : index into the sequence (0 or larger) Returns : a rasqal_graph_pattern pointer or NULL if out of the sequence range rasqal_query_get_graph_pattern_sequenceraptor_sequence* rasqal_query_get_graph_pattern_sequence (rasqal_query *query); Get the sequence of graph_patterns expressions inside the top query graph pattern. query : rasqal_query query object Returns : a raptor_sequence of rasqal_graph_pattern pointers. rasqal_query_get_labelconst char* rasqal_query_get_label (rasqal_query *query); Get a readable label for the query language. query : rasqal_query query object Returns : shared string label value rasqal_query_get_limitint rasqal_query_get_limit (rasqal_query *query); Get the query-specified limit on results. This is the limit given in the query on the number of results allowed. query : rasqal_query query object Returns : integer >=0 if a limit is given, otherwise <0 rasqal_query_get_nameconst char* rasqal_query_get_name (rasqal_query *query); Get a short name for the query language. query : rasqal_query query object Returns : shared string label value rasqal_query_get_offsetint rasqal_query_get_offset (rasqal_query *query); Get the query-specified offset on results. This is the offset given in the query on the number of results allowed. query : rasqal_query query object Returns : integer >=0 if a offset is given, otherwise <0 rasqal_query_get_order_conditionrasqal_expression* rasqal_query_get_order_condition (rasqal_query *query, int idx); Get a query ordering expression in the sequence of query ordering conditions. query : rasqal_query query object idx : index into the sequence (0 or larger) Returns : a rasqal_expression pointer or NULL if out of the sequence range rasqal_query_get_order_conditions_sequenceraptor_sequence* rasqal_query_get_order_conditions_sequence (rasqal_query *query); Get the sequence of query ordering conditions. query : rasqal_query query object Returns : a raptor_sequence of rasqal_expression pointers. rasqal_query_get_prefixrasqal_prefix* rasqal_query_get_prefix (rasqal_query *query, int idx); Get a prefix in the sequence of namespsace prefixes in the query. query : rasqal_query query object idx : index into the sequence (0 or larger) Returns : a rasqal_prefix pointer or NULL if out of the sequence range rasqal_query_get_prefix_sequenceraptor_sequence* rasqal_query_get_prefix_sequence (rasqal_query *query); Get the sequence of namespace prefixes in the query. query : rasqal_query query object Returns : a raptor_sequence of rasqal_prefix pointers. rasqal_query_get_query_graph_patternrasqal_graph_pattern* rasqal_query_get_query_graph_pattern (rasqal_query *query); Get the top query graph pattern. query : rasqal_query query object Returns : a rasqal_graph_pattern of the top query graph pattern rasqal_query_get_triplerasqal_triple* rasqal_query_get_triple (rasqal_query *query, int idx); Get a triple in the sequence of matching triples in the query. query : rasqal_query query object idx : index into the sequence (0 or larger) Returns : a rasqal_triple pointer or NULL if out of the sequence range rasqal_query_get_triple_sequenceraptor_sequence* rasqal_query_get_triple_sequence (rasqal_query *query); Get the sequence of matching triples in the query. query : rasqal_query query object Returns : a raptor_sequence of rasqal_triple pointers. rasqal_query_get_user_datavoid* rasqal_query_get_user_data (rasqal_query *query); Get query user data. query : rasqal_query Returns : user data as set by rasqal_query_set_user_data rasqal_query_get_variablerasqal_variable* rasqal_query_get_variable (rasqal_query *query, int idx); Get a variable in the sequence of variables to bind. query : rasqal_query query object idx : index into the sequence (0 or larger) Returns : a rasqal_variable pointer or NULL if out of the sequence range rasqal_query_get_verbrasqal_query_verb rasqal_query_get_verb (rasqal_query *query); Get the query verb. query : rasqal_query Returns : the operating verb of the query of type rasqal_query_verb rasqal_query_get_wildcardint rasqal_query_get_wildcard (rasqal_query *query); Get the query verb is wildcard flag. query : rasqal_query Returns : non-0 if the query verb was a wildcard (such as SELECT *) rasqal_query_has_variableint rasqal_query_has_variable (rasqal_query *query, unsigned char *name); Find if the named variable is in the sequence of variables to bind. query : rasqal_query query object name : variable name Returns : non-0 if the variable name was found. rasqal_query_prepareint rasqal_query_prepare (rasqal_query *query, unsigned char *query_string, raptor_uri *base_uri); Prepare a query - typically parse it. Some query languages may require a base URI to resolve any relative URIs in the query string. If this is not given, the current directory in the filesystem is used as the base URI. The query string may be NULL in which case it is not parsed and the query parts may be created by API calls such as rasqal_query_add_source etc. query : the rasqal_query object query_string : the query string (or NULL) base_uri : base URI of query string (optional) Returns : non-0 on failure. rasqal_query_printvoid rasqal_query_print (rasqal_query *query, FILE *fh); Print a query in a debug format. query : the rasqal_query object fh : the FILE* handle to print to. rasqal_query_graph_pattern_visitvoid rasqal_query_graph_pattern_visit (rasqal_query *query, rasqal_graph_pattern_visit_fn visit_fn, void *data); Visit all graph patterns in a query with a user function visit_fn. See also rasqal_graph_pattern_visit(). query : query visit_fn : user function to operate on data : user data to pass to function rasqal_query_set_default_generate_bnodeid_parametersvoid rasqal_query_set_default_generate_bnodeid_parameters (rasqal_query *rdf_query, char *prefix, int base); Sets the parameters for the default algorithm used to generate blank node IDs. The default algorithm uses both prefix and base to generate a new identifier. The exact identifier generated is not guaranteed to be a strict concatenation of prefix and base but will use both parts. For finer control of the generated identifiers, use rasqal_set_default_generate_bnodeid_handler() If prefix is NULL, the default prefix is used (currently "bnodeid") If base is less than 1, it is initialised to 1. rdf_query : rasqal_query object prefix : prefix string base : integer base identifier rasqal_query_set_distinctvoid rasqal_query_set_distinct (rasqal_query *query, int distinct_mode); Set the query distinct results mode. The allowed distinct_mode values are: 0 if not given 1 if DISTINCT: ensure solutions are unique 2 if SPARQL REDUCED: permit elimination of some non-unique solutions query : rasqal_query query object distinct_mode : distinct mode rasqal_query_set_explainvoid rasqal_query_set_explain (rasqal_query *query, int is_explain); Set the query explain results flag. query : rasqal_query query object is_explain : non-0 if explain rasqal_query_set_error_handlervoid rasqal_query_set_error_handler (rasqal_query *query, void *user_data, raptor_message_handler handler); Set the query error handling function. The function will receive callbacks when the query fails. query : the query user_data : user data to pass to function handler : pointer to the function rasqal_query_set_fatal_error_handlervoid rasqal_query_set_fatal_error_handler (rasqal_query *query, void *user_data, raptor_message_handler handler); Set the query error handling function. The function will receive callbacks when the query fails. query : the query user_data : user data to pass to function handler : pointer to the function rasqal_query_set_generate_bnodeid_handlervoid rasqal_query_set_generate_bnodeid_handler (rasqal_query *query, void *user_data, rasqal_generate_bnodeid_handler handler); Set the generate blank node ID handler function for the query. Sets the function to generate blank node IDs for the query. The handler is called with a pointer to the rasqal_query, the user_data pointer and a user_bnodeid which is the value of a user-provided blank node identifier (may be NULL). It can either be returned directly as the generated value when present or modified. The passed in value must be free()d if it is not used. If handler is NULL, the default method is used query : rasqal_query query object user_data : user data pointer for callback handler : generate blank ID callback function rasqal_query_set_limitvoid rasqal_query_set_limit (rasqal_query *query, int limit); Set the query-specified limit on results. This is the limit given in the query on the number of results allowed. query : rasqal_query query object limit : the limit on results, >=0 to set a limit, <0 to have no limit rasqal_query_set_offsetvoid rasqal_query_set_offset (rasqal_query *query, int offset); Set the query-specified offset on results. This is the offset given in the query on the number of results allowed. query : rasqal_query query object offset : offset for results, >=0 to set an offset, <0 to have no offset rasqal_query_set_user_datavoid rasqal_query_set_user_data (rasqal_query *query, void *user_data); Set the query user data. query : rasqal_query user_data : some user data to associate with the query rasqal_query_set_variableint rasqal_query_set_variable (rasqal_query *query, unsigned char *name, rasqal_literal *value); Add a binding variable to the query. See also rasqal_query_add_variable which adds a new binding variable and must be called before this method is invoked. query : rasqal_query query object name : rasqal_variable variable value : rasqal_literal value to set or NULL Returns : non-0 on failure rasqal_query_set_warning_handlervoid rasqal_query_set_warning_handler (rasqal_query *query, void *user_data, raptor_message_handler handler); Set the query warning handling function. The function will receive callbacks when the query gives a warning. query : the query user_data : user data to pass to function handler : pointer to the function rasqal_query_verb_as_stringconst char* rasqal_query_verb_as_string (rasqal_query_verb verb); Get a string for the query verb. verb : the rasqal_query_verb verb of the query Returns : pointer to a shared string label for the query verb rasqal_query_writeint rasqal_query_write (raptor_iostream *iostr, rasqal_query *query, raptor_uri *format_uri, raptor_uri *base_uri); Write a query to an iostream in a specified format. The supported URIs for the format_uri are: Default: SPARQL Query Language 2006-04-06 http://www.w3.org/TR/2006/CR-rdf-sparql-query-20060406/ iostr : raptor_iostream to write the query to query : rasqal_query pointer. format_uri : raptor_uri describing the format to write (or NULL for default) base_uri : raptor_uri base URI of the output format Returns : non-0 on failure rasqal_query_iostream_write_escaped_counted_stringint rasqal_query_iostream_write_escaped_counted_string (rasqal_query *query, raptor_iostream *iostr, unsigned char *string, size_t len); Write a string to an iostream in escaped form suitable for the query string. query : rasqal_query object iostr : raptor_iostream to write the escaped string to string : string to escape len : Length of string to escape Returns : non-0 on failure rasqal_query_escape_counted_stringunsigned char* rasqal_query_escape_counted_string (rasqal_query *query, unsigned char *string, size_t len, size_t *output_len_p); Convert a string into an escaped form suitable for the query string. The returned string must be freed by the caller with rasqal_free_memory() query : rasqal_query object string : string to escape len : Length of string to escape output_len_p : Pointer to store length of output string (or NULL) Returns : the escaped string or NULL on failure. rasqal_query_set_featureint rasqal_query_set_feature (rasqal_query *query, rasqal_feature feature, int value); Set various query features. The allowed features are available via rasqal_features_enumerate(). query : rasqal_query query object feature : feature to set from enumerated rasqal_feature values value : integer feature value Returns : non 0 on failure or if the feature is unknown rasqal_query_set_feature_stringint rasqal_query_set_feature_string (rasqal_query *query, rasqal_feature feature, unsigned char *value); Set query features with string values. The allowed features are available via rasqal_features_enumerate(). If the feature type is integer, the value is interpreted as an integer. query : rasqal_query query object feature : feature to set from enumerated rasqal_feature values value : feature value Returns : non 0 on failure or if the feature is unknown rasqal_query_get_featureint rasqal_query_get_feature (rasqal_query *query, rasqal_feature feature); Get various query features. The allowed features are available via rasqal_features_enumerate(). Note: no feature value is negative query : rasqal_query query object feature : feature to get value Returns : feature value or < 0 for an illegal feature rasqal_query_get_feature_stringconst unsigned char* rasqal_query_get_feature_string (rasqal_query *query, rasqal_feature feature); Get query features with string values. The allowed features are available via rasqal_features_enumerate(). If a string is returned, it must be freed by the caller. query : rasqal_query query object feature : feature to get value Returns : feature value or NULL for an illegal feature or no value