Query results

Query results — RDF query results.

Synopsis

typedef             librdf_query_results;
librdf_stream*      librdf_query_results_as_stream      (librdf_query_results *query_results);
int                 librdf_query_results_get_count      (librdf_query_results *query_results);
int                 librdf_query_results_next           (librdf_query_results *query_results);
int                 librdf_query_results_finished       (librdf_query_results *query_results);
int                 librdf_query_results_get_bindings   (librdf_query_results *query_results,
                                                         const char ***names,
                                                         librdf_node **values);
librdf_node*        librdf_query_results_get_binding_value
                                                        (librdf_query_results *query_results,
                                                         int offset);
const char*         librdf_query_results_get_binding_name
                                                        (librdf_query_results *query_results,
                                                         int offset);
librdf_node*        librdf_query_results_get_binding_value_by_name
                                                        (librdf_query_results *query_results,
                                                         const char *name);
int                 librdf_query_results_get_bindings_count
                                                        (librdf_query_results *query_results);
unsigned char*      librdf_query_results_to_counted_string
                                                        (librdf_query_results *query_results,
                                                         librdf_uri *format_uri,
                                                         librdf_uri *base_uri,
                                                         size_t *length_p);
unsigned char*      librdf_query_results_to_string      (librdf_query_results *query_results,
                                                         librdf_uri *format_uri,
                                                         librdf_uri *base_uri);
int                 librdf_query_results_to_file_handle (librdf_query_results *query_results,
                                                         FILE *handle,
                                                         librdf_uri *format_uri,
                                                         librdf_uri *base_uri);
int                 librdf_query_results_to_file        (librdf_query_results *query_results,
                                                         const char *name,
                                                         librdf_uri *format_uri,
                                                         librdf_uri *base_uri);
void                librdf_free_query_results           (librdf_query_results *query_results);
int                 librdf_query_results_is_bindings    (librdf_query_results *query_results);
int                 librdf_query_results_is_boolean     (librdf_query_results *query_results);
int                 librdf_query_results_is_graph       (librdf_query_results *query_results);
int                 librdf_query_results_is_syntax      (librdf_query_results *query_results);
int                 librdf_query_results_get_boolean    (librdf_query_results *query_results);
librdf_query_results_formatter* librdf_new_query_results_formatter
                                                        (librdf_query_results *query_results,
                                                         const char *name,
                                                         librdf_uri *uri);
librdf_query_results_formatter* librdf_new_query_results_formatter_by_mime_type
                                                        (librdf_query_results *query_results,
                                                         const char *mime_type);
void                librdf_free_query_results_formatter (librdf_query_results_formatter *formatter);
int                 librdf_query_results_formats_check  (librdf_world *world,
                                                         const char *name,
                                                         librdf_uri *uri,
                                                         const char *mime_type);
int                 librdf_query_results_formats_enumerate
                                                        (librdf_world *world,
                                                         unsigned int counter,
                                                         const char **name,
                                                         const char **label,
                                                         unsigned char **uri_string,
                                                         const char **mime_type);
typedef             librdf_query_results_formatter;
int                 librdf_query_results_formatter_write
                                                        (raptor_iostream *iostr,
                                                         librdf_query_results_formatter *formatter,
                                                         librdf_query_results *results,
                                                         librdf_uri *base_uri);

Description

The results of an librdf_query execution as a sequence of individual results, an RDF graph as a sequence of triples or a boolean. For variable binding results, the binding names and values can be read in multiple forms and the number of results returned as well as the current result moved to the next. For an RDF graph result, the stream of triples can be returned. For a boolean result, the value can be returned. All results can be turned into a string XML format based on the SPARQL XML results format which can also be written to a file.

Details

librdf_query_results

typedef struct librdf_query_results_s librdf_query_results;

Redland query results class.

librdf_query_results_as_stream ()

librdf_stream*      librdf_query_results_as_stream      (librdf_query_results *query_results);

Get a query result as an RDF graph in librdf_stream form

The return value is only meaningful if this is an RDF graph query result - see librdf_query_results_is_graph

query_results :

 librdf_query_results query_results

Returns :

 a new librdf_stream result or NULL on error

librdf_query_results_get_count ()

int                 librdf_query_results_get_count      (librdf_query_results *query_results);

Get number of bindings so far.

query_results :

 librdf_query_results query results

Returns :

 number of bindings found so far

librdf_query_results_next ()

int                 librdf_query_results_next           (librdf_query_results *query_results);

Move to the next result.

query_results :

 librdf_query_results query results

Returns :

 non-0 if failed or results exhausted

librdf_query_results_finished ()

int                 librdf_query_results_finished       (librdf_query_results *query_results);

Find out if binding results are exhausted.

query_results :

 librdf_query_results query results

Returns :

 non-0 if results are finished or query failed

librdf_query_results_get_bindings ()

int                 librdf_query_results_get_bindings   (librdf_query_results *query_results,
                                                         const char ***names,
                                                         librdf_node **values);

Get all binding names, values for current result.

If names is not NULL, it is set to the address of a shared array of names of the bindings (an output parameter). These names are shared and must not be freed by the caller

If values is not NULL, it is used as an array to store pointers to the librdf_node* of the results. These nodes must be freed by the caller. The size of the array is determined by the number of names of bindings, returned by librdf_query_get_bindings_count dynamically or will be known in advanced if hard-coded into the query string.

Example

const char **names=NULL; librdf_node* values[10];

if(librdf_query_results_get_bindings(results, &names, values)) ...

query_results :

 librdf_query_results query results

names :

 pointer to an array of binding names (or NULL)

values :

 pointer to an array of binding value librdf_node (or NULL)

Returns :

 non-0 if the assignment failed

librdf_query_results_get_binding_value ()

librdf_node*        librdf_query_results_get_binding_value
                                                        (librdf_query_results *query_results,
                                                         int offset);

Get one binding value for the current result.

query_results :

 librdf_query_results query results

offset :

 offset of binding name into array of known names

Returns :

 a new librdf_node binding value or NULL on failure

librdf_query_results_get_binding_name ()

const char*         librdf_query_results_get_binding_name
                                                        (librdf_query_results *query_results,
                                                         int offset);

Get binding name for the current result.

query_results :

 librdf_query_results query results

offset :

 offset of binding name into array of known names

Returns :

 a pointer to a shared copy of the binding name or NULL on failure

librdf_query_results_get_binding_value_by_name ()

librdf_node*        librdf_query_results_get_binding_value_by_name
                                                        (librdf_query_results *query_results,
                                                         const char *name);

Get one binding value for a given name in the current result.

query_results :

 librdf_query_results query results

name :

 variable name

Returns :

 a new librdf_node binding value or NULL on failure

librdf_query_results_get_bindings_count ()

int                 librdf_query_results_get_bindings_count
                                                        (librdf_query_results *query_results);

Get the number of bound variables in the result.

query_results :

 librdf_query_results query results

Returns :

 <0 if failed or results exhausted

librdf_query_results_to_counted_string ()

unsigned char*      librdf_query_results_to_counted_string
                                                        (librdf_query_results *query_results,
                                                         librdf_uri *format_uri,
                                                         librdf_uri *base_uri,
                                                         size_t *length_p);

Turn a query results into a string.

Values of format_uri currently supported (via Rasqal) are: http://www.w3.org/TR/2004/WD-rdf-sparql-XMLres-20041221/

The base URI may be used for the generated syntax, depending on the format.

The returned string must be freed by the caller

query_results :

 librdf_query_results object

format_uri :

 URI of syntax to format to

base_uri :

 Base URI of output formatted syntax or NULL

length_p :

 Pointer to where to store length of string or NULL

Returns :

 new string value or NULL on failure

librdf_query_results_to_string ()

unsigned char*      librdf_query_results_to_string      (librdf_query_results *query_results,
                                                         librdf_uri *format_uri,
                                                         librdf_uri *base_uri);

Turn a query results into a string.

See librdf_query_results_to_counted_string for information on the format_uri and base_uri parameters.

The returned string must be freed by the caller

query_results :

 librdf_query_results object

format_uri :

 URI of syntax to format to

base_uri :

 Base URI of output formatted syntax

Returns :

 new string value or NULL on failure

librdf_query_results_to_file_handle ()

int                 librdf_query_results_to_file_handle (librdf_query_results *query_results,
                                                         FILE *handle,
                                                         librdf_uri *format_uri,
                                                         librdf_uri *base_uri);

Write a query results to a FILE*.

See librdf_query_results_to_counted_string for information on the format_uri and base_uri parameters.

query_results :

 librdf_query_results object

handle :

 file handle to write to

format_uri :

 URI of syntax to format to

base_uri :

 Base URI of output formatted syntax

Returns :

 non 0 on failure

librdf_query_results_to_file ()

int                 librdf_query_results_to_file        (librdf_query_results *query_results,
                                                         const char *name,
                                                         librdf_uri *format_uri,
                                                         librdf_uri *base_uri);

Write a query results to a file.

See librdf_query_results_to_counted_string for information on the format_uri and base_uri parameters.

query_results :

 librdf_query_results object

name :

 filename to write to

format_uri :

 URI of syntax to format to

base_uri :

 Base URI of output formatted syntax

Returns :

 non 0 on failure

librdf_free_query_results ()

void                librdf_free_query_results           (librdf_query_results *query_results);

Destructor - destroy a librdf_query_results object.

query_results :

 librdf_query_results object

librdf_query_results_is_bindings ()

int                 librdf_query_results_is_bindings    (librdf_query_results *query_results);

Test if librdf_query_results is variable bindings format.

query_results :

 librdf_query_results object

Returns :

 non-0 if true

librdf_query_results_is_boolean ()

int                 librdf_query_results_is_boolean     (librdf_query_results *query_results);

Test if librdf_query_results is boolean format.

If this function returns true, the result can be retrieved by librdf_query_results_get_boolean().

query_results :

 librdf_query_results object

Returns :

 non-0 if true

librdf_query_results_is_graph ()

int                 librdf_query_results_is_graph       (librdf_query_results *query_results);

Test if librdf_query_results is RDF graph format.

query_results :

 librdf_query_results object

Returns :

 non-0 if true

librdf_query_results_is_syntax ()

int                 librdf_query_results_is_syntax      (librdf_query_results *query_results);

Test if librdf_query_results is a syntax.

If this function returns true, the ONLY result available from this query is a syntax that can be serialized using one of the query_result_formatter class methods or with librdf_query_results_to_counted_string(), librdf_query_results_to_string(), librdf_query_results_to_file_handle() or librdf_query_results_to_file()

query_results :

 librdf_query_results object

Returns :

 non-0 if true

librdf_query_results_get_boolean ()

int                 librdf_query_results_get_boolean    (librdf_query_results *query_results);

Get boolean query result.

The return value is only meaningful if this is a boolean query result - see librdf_query_results_is_boolean

query_results :

 librdf_query_results query_results

Returns :

 boolean query result - >0 is true, 0 is false, <0 on error or finished

librdf_new_query_results_formatter ()

librdf_query_results_formatter* librdf_new_query_results_formatter
                                                        (librdf_query_results *query_results,
                                                         const char *name,
                                                         librdf_uri *uri);

Constructor - create a new librdf_query_results_formatter object by identified format.

A query results format can be named or identified by a URI, both of which are optional. The default query results format will be used if both are NULL. librdf_query_results_formats_enumerate() returns information on the known query results names, labels and URIs.

query_results :

 librdf_query_results query_results

name :

 the query results format name (or NULL)

uri :

 librdf_uri query results format uri (or NULL)

Returns :

 a new librdf_query_results_formatter object or NULL on failure

librdf_new_query_results_formatter_by_mime_type ()

librdf_query_results_formatter* librdf_new_query_results_formatter_by_mime_type
                                                        (librdf_query_results *query_results,
                                                         const char *mime_type);

Constructor - create a new librdf_query_results_formatter object by mime type.

A query results format generates a syntax with a mime type which may be requested with this constructor.

Note that there may be several formatters that generate the same MIME Type (such as SPARQL XML results format drafts) and in thot case the librdf_new_query_results_formatter() constructor allows selecting of a specific one by name or URI.

query_results :

 librdf_query_results query_results

mime_type :

 mime type name

Returns :

 a new librdf_query_results_formatter object or NULL on failure

librdf_free_query_results_formatter ()

void                librdf_free_query_results_formatter (librdf_query_results_formatter *formatter);

Destructor - destroy a librdf_query_results_formatter object.

formatter :

 librdf_query_results_formatter object

librdf_query_results_formats_check ()

int                 librdf_query_results_formats_check  (librdf_world *world,
                                                         const char *name,
                                                         librdf_uri *uri,
                                                         const char *mime_type);

Check if a query results formatter exists for the requested format.

world :

 librdf_world

name :

 the query results format name (or NULL)

uri :

 librdf_uri query results format uri (or NULL)

mime_type :

 mime type name

Returns :

 non-0 if a formatter exists.

librdf_query_results_formats_enumerate ()

int                 librdf_query_results_formats_enumerate
                                                        (librdf_world *world,
                                                         unsigned int counter,
                                                         const char **name,
                                                         const char **label,
                                                         unsigned char **uri_string,
                                                         const char **mime_type);

Get information on query result syntaxes.

All returned strings are shared and must be copied if needed to be used dynamically.

world :

 librdf_world

counter :

 index into the list of query result syntaxes

name :

 pointer to store the name of the query result syntax (or NULL)

label :

 pointer to store query result syntax readable label (or NULL)

uri_string :

 pointer to store query result syntax URI string (or NULL)

mime_type :

 pointer to store query result syntax mime type string (or NULL)

Returns :

 non 0 on failure of if counter is out of range

librdf_query_results_formatter

typedef struct librdf_query_results_formatter_s librdf_query_results_formatter;

Redland query results formatter class.

librdf_query_results_formatter_write ()

int                 librdf_query_results_formatter_write
                                                        (raptor_iostream *iostr,
                                                         librdf_query_results_formatter *formatter,
                                                         librdf_query_results *results,
                                                         librdf_uri *base_uri);

Write the query results using the given formatter to an iostream

See librdf_query_results_formats_enumerate() to get the list of syntax URIs and their description.

iostr :

 raptor_iostream to write the query to

formatter :

 librdf_query_results_formatter object

results :

 librdf_query_results query results format

base_uri :

 librdf_uri base URI of the output format

Returns :

 non-0 on failure
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