Query related functions

Data Structures
struct	qdb_point_result_t
	A variadic structure holding the result type as well as the result value. More...
struct	qdb_query_result_t
	Holds the result of a query. More...
struct	qdb_query_arrow_result_t
	Holds the result of a query in Arrow format. More...

Typedefs
typedef enum qdb_query_result_value_type_t	qdb_query_result_value_type_t
	The type of a result.
typedef enum qdb_query_continuous_mode_type_t	qdb_query_continuous_mode_type_t
	The continuous query mode.
typedef struct qdb_dedup_handle_internal *	qdb_dedup_handle_t
	An opaque handle to internal API-allocated structures needed for deduplicating query results.
typedef struct qdb_query_cont_internal *	qdb_query_cont_handle_t
	An opaque handle to internal API-allocated structures needed for managing a continuous query.
typedef int	qdb_query_cont_callback_t (void *, qdb_error_t, const qdb_query_result_t *)
	A callback used by qdb_query_continuous. The first parameter of the callback will receive the context given when calling qdb_query_continuous The second parameter is the error result of the operation The third parameter are the new results for the query since the callback has been last called The callback MUST NOT throw exceptions. Throwing exceptions will terminate the program as exceptions cannot cross the C/C++ boundary. More...

Enumerations
enum	qdb_query_result_value_type_t
	The type of a result.
enum	qdb_query_continuous_mode_type_t
	The continuous query mode.

Functions
QDB_API_LINKAGE qdb_error_t	qdb_query_find (qdb_handle_t handle, const char *query, const char ***aliases, size_t *alias_count)
	Retrieves all entries' aliases that match the specified find query. More...
QDB_API_LINKAGE qdb_error_t	qdb_query (qdb_handle_t handle, const char *query, qdb_query_result_t **result)
	Run the provided query and creates a table directory with the results. More...
QDB_API_LINKAGE qdb_error_t	qdb_query_to_arrow (qdb_handle_t handle, const qdb_query_result_t *result, qdb_query_arrow_result_t **result_copy)
	Copies a query result to the Arrow format. More...
QDB_API_LINKAGE qdb_error_t	qdb_init_query_dedup (qdb_handle_t handle, qdb_dedup_handle_t *dedup_handle)
	Creates a qdb_dedup_handle_t. More...
QDB_API_LINKAGE qdb_error_t	qdb_query_dedup (qdb_dedup_handle_t dedup_handle, const qdb_query_result_t *result, qdb_query_result_t **dedup_result)
	Deduplicates query results. More...
QDB_API_LINKAGE qdb_error_t	qdb_query_dedup_prune (qdb_dedup_handle_t dedup_handle, const qdb_ts_range_t *range)
	Removes previously seen rows from the given deduplication handler. More...
QDB_API_LINKAGE qdb_error_t	qdb_query_continuous (qdb_handle_t handle, const char *query, qdb_query_continuous_mode_type_t mode, unsigned int refresh_rate_ms, qdb_query_cont_callback_t cb, void *cb_context, qdb_query_cont_handle_t *cont_handle)
	Continuously and efficiently query the server with the given query. More...

Detailed Description

Typedef Documentation

qdb_query_cont_callback_t

A callback used by qdb_query_continuous. The first parameter of the callback will receive the context given when calling qdb_query_continuous The second parameter is the error result of the operation The third parameter are the new results for the query since the callback has been last called The callback MUST NOT throw exceptions. Throwing exceptions will terminate the program as exceptions cannot cross the C/C++ boundary.

See Also

qdb_query_continuous

Function Documentation

QDB_API_LINKAGE qdb_error_t qdb_init_query_dedup	(	qdb_handle_t	handle,
		qdb_dedup_handle_t *	dedup_handle
	)

Creates a qdb_dedup_handle_t.

Parameters

	handle	A valid handle previously initialized by qdb_open or qdb_open_tcp.
[out]	dedup_handle	A pointer to a qdb_dedup_handle_t that will be ready for deduplicating query results. It must be released later with qdb_release.

Returns

A qdb_error_t code indicating success or failure.

See Also

qdb_release

QDB_API_LINKAGE qdb_error_t qdb_query	(	qdb_handle_t	handle,
		const char *	query,
		qdb_query_result_t **	result
	)

Run the provided query and creates a table directory with the results.

For the complete grammar, please refer to the documentation.

Queries are transactional.

The complexity of this function is dependent on the complexity of the query.

Parameters

	handle	A valid handle previously initialized by qdb_open or qdb_open_tcp.
	query	A pointer to a null-terminated UTF-8 string representing the query to perform.
[out]	result	A pointer to a pointer of qdb_query_result_t that will receive the results. It must be released later with qdb_release.

Returns

A qdb_error_t code indicating success or failure.

See Also

qdb_release, qdb_option_set_client_max_parallelism

QDB_API_LINKAGE qdb_error_t qdb_query_continuous	(	qdb_handle_t	handle,
		const char *	query,
		qdb_query_continuous_mode_type_t	mode,
		unsigned int	refresh_rate_ms,
		qdb_query_cont_callback_t	cb,
		void *	cb_context,
		qdb_query_cont_handle_t *	cont_handle
	)

Continuously and efficiently query the server with the given query.

A continuous query receives results in a callback asynchronously as they are available on the server. This API uses push notifications from the server to minimize data exchange and resource usage.

Parameters

	handle	A valid handle previously initialized by qdb_open or qdb_open_tcp.
	query	A pointer to a null-terminated UTF-8 string representing the query to perform. Any valid QuasarDB query is supported.
	mode	The mode of the query. Full will return all values at every call whereas new values will only deliver updates values.
	refresh_rate_ms	The refresh rate (in ms) at which the query will return results.
	cb	A pointer to a function that will be called when new data is available. The function MUST NOT throw exceptions.
	cb_context	An opaque pointer to any client managed structure to pass to the callback. May be null if no context is needed.
[out]	cont_handle	A handle to the continuous query handle. Updates to the query will be received until qdb_release is called on this handle.

Returns

A qdb_error_t code indicating success or failure.

See Also

qdb_release

QDB_API_LINKAGE qdb_error_t qdb_query_dedup	(	qdb_dedup_handle_t	dedup_handle,
		const qdb_query_result_t *	result,
		qdb_query_result_t **	dedup_result
	)

Deduplicates query results.

Rows already seen by previous calls to qdb_query_dedup for the given deduplication handler will not be included in the deduplicated results.

Parameters

	dedup_handle	A valid deduplication handle previously initialized by qdb_init_query_dedup.
	result	A pointer to a qdb_query_result_t that holds the results from a previous call to qdb_query. Results given to a deduplication filter must all come from the same query, but different ranges or where clauses are allowed.
[out]	dedup_result	A pointer to a pointer of qdb_query_result_t that will receive the deduplicated results. It must be released later with qdb_release.

Returns

A qdb_error_t code indicating success or failure.

See Also

qdb_release

QDB_API_LINKAGE qdb_error_t qdb_query_dedup_prune	(	qdb_dedup_handle_t	dedup_handle,
		const qdb_ts_range_t *	range
	)

Removes previously seen rows from the given deduplication handler.

Parameters

dedup_handle	A valid deduplication handle previously initialized by qdb_init_query_dedup. If the $timestamp special column hasn't been selected all rows are removed.
range	A pointer to a qdb_ts_range_t (interval) for which rows should be removed.

Returns

A qdb_error_t code indicating success or failure.

QDB_API_LINKAGE qdb_error_t qdb_query_find	(	qdb_handle_t	handle,
		const char *	query,
		const char ***	aliases,
		size_t *	alias_count
	)

Retrieves all entries' aliases that match the specified find query.

For the complete grammar, please refer to the documentation.

Queries are transactional.

The complexity of this function is dependent on the complexity of the query.

Parameters

	handle	A valid handle previously initialized by qdb_open or qdb_open_tcp.
	query	A pointer to a null-terminated UTF-8 string representing the query to perform.
[out]	aliases	A pointer to an array of null-terminated UTF-8 string that will list the aliases of the entries matching the query.
[out]	alias_count	A pointer to an integer that will receive the number of returned aliases.

Returns

A qdb_error_t code indicating success or failure.

See Also

qdb_release

QDB_API_LINKAGE qdb_error_t qdb_query_to_arrow	(	qdb_handle_t	handle,
		const qdb_query_result_t *	result,
		qdb_query_arrow_result_t **	result_copy
	)

Copies a query result to the Arrow format.

The allocated results have to be released later with qdb_release.

Parameters

	handle	A valid handle previously initialized by qdb_open or qdb_open_tcp.
	result	A pointer to a query result to clone
[out]	result_copy	A pointer to a a pointer that will receive API-allocated results whose content will be a copy of the source results

Returns

A qdb_error_t code indicating success or failure.

See Also

qdb_release