Use the a_v4_extfn_proc_context structure to retain context information from the server and from the UDF.
typedef struct a_v4_extfn_proc_context {
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} a_v4_extfn_proc_context;
| Return Type | Method | Description |
|---|---|---|
| short | get_value | Gets input arguments to the UDF. |
| short | get_value_is_constant | Allows the UDF to ask whether a given argument is a constant. |
| short | set_value | Used by the UDF in either the _evaluate_extfn or _describe_extfn functions to describe to the server what its output will look like and to inform the server how to fetch results from the UDF. |
| a_sql_uint32 | get_is_cancelled | Call the get_is_cancelled callback every second or two to see if the user has interrupted the current statement. |
| short | set_error | Rolls back the current statement and generates an error. |
| void | log_message | Writes a message to the message log. |
| short | convert_value | Converts one data type to another. |
| short | get_option | Gets the value of a settable option. |
| void | alloc | Allocates a block of memory of length at least "len". |
| void | free | Free the memory allocated by alloc() for the specified lifetime. |
| a_sql_uint32 | describe_column_get | See *describe_column_get. |
| a_sql_uint32 | describe_column_set | See *describe_column_set. |
| a_sql_uint32 | describe_parameter_get | See *describe_parameter_get. |
| a_sql_uint32 | describe_parameter_set | See *describe_parameter_set. |
| a_sql_uint32 | describe_udf_get | See *describe_udf_get. |
| a_sql_uint32 | describe_udf_set | See *describe_udf_set. |
| short | open_result_set | Opens a result set for a table value. |
| short | close_result_set | Closes an open result set. |
| short | get_blob | Retrieves an input parameter that is a blob. |
| short | set_cannot_be_distributed | Disables distribution at the UDF level even if the library is distributable. |
| Data Member | Data Type | Description |
|---|---|---|
| _user_data | void * | This data pointer can be filled in by any usage with whatever context data the external routine requires. |
| _executionMode | a_sql_uint32 | Indicates the debug/trace level requested via the External_UDF_Execution_Mode option. This is a read-only field. |
| current_state | a_sql_uint32 | The current_state attribute reflects the current execution mode of the context. This can be queried from functions such as _describe_extfn to determine what course of action to take. |
In addition to retaining context information from the server and the UDF, the structure a_v4_extfn_proc_context allows the UDF to call back into the server to perform certain actions. The UDF can store private data in this structure in the _user_data member. An instance of this structure gets passed to the functions in the a_v4_extfn_proc method by the server. User data is not maintained until after the server reaches the Annotation state.