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The Aerospike Query Operations provide the ability to query data in the Aerospike database. The queries can only be performed on secondary indexes, which have been created in the database. To scan all the records in the database, then you must use the Scan Operations.
Before you can execute a query, you first need to build a query using as_query. See as_query for details on building queries.
Once you have a query defined, then you can execute the query :
When aerospike_query_foreach() is executed, it will process the results and create records on the stack. Because the records are on the stack, they will only be available within the context of the callback function.
First, we define a query using as_query. The query will be for the "test" namespace and "demo" set. We will add a where predicate on "bin2", on which we have already created a secondary index.
Now that we have a query defined, we want to execute it using aerospike_query_foreach().
The callback provided to the function above is implemented as:
An as_query is simply a query definition, so it does not contain any state, allowing it to be reused for multiple query operations.
When you are finished with the query, you should destroy the resources allocated to it:
Typedefs | |
typedef bool(* | aerospike_query_foreach_callback) (const as_val *val, void *udata) |
Functions | |
as_status | aerospike_query_foreach (aerospike *as, as_error *err, const as_policy_query *policy, const as_query *query, aerospike_query_foreach_callback callback, void *udata) |
bool(* |
This callback will be called for each value or record returned from a query.
The aerospike_query_foreach() function accepts this callback.
val | The value received from the query. |
udata | User-data provided to the calling function. |
true
to continue to the next value. Otherwise, iteration will end. Definition at line 119 of file aerospike_query.h.
as_status aerospike_query_foreach | ( | aerospike * | as, |
as_error * | err, | ||
const as_policy_query * | policy, | ||
const as_query * | query, | ||
aerospike_query_foreach_callback | callback, | ||
void * | udata | ||
) |
Execute a query and call the callback function for each result item.
as | The aerospike instance to use for this operation. |
err | The as_error to be populated if an error occurs. |
policy | The policy to use for this operation. If NULL, then the default policy will be used. |
query | The query to execute against the cluster. |
callback | The callback function to call for each result value. |
udata | User-data to be passed to the callback. |