SPI_prepare(query, nargs, argtypes)
Number of input parameters ($1 ... $nargs - as in SQL-functions)
Pointer list of type OIDs to input arguments
SPI_prepare creates and returns an execution plan (parser+planner+optimizer) but doesn't execute the query. Should only be called from a connected procedure.
nargs is number of parameters ($1 ... $nargs - as in SQL-functions), and nargs may be 0 only if there is not any $1 in query.
Execution of prepared execution plans is sometimes much faster so this feature may be useful if the same query will be executed many times.
The plan returned by SPI_prepare may be used only in current invocation of the procedure since SPI_finish frees memory allocated for a plan. See SPI_saveplan.
If successful, a non-null pointer will be returned. Otherwise, you'll get a NULL plan. In both cases SPI_result will be set like the value returned by SPI_exec, except that it is set to SPI_ERROR_ARGUMENT if query is NULL or nargs < 0 or nargs > 0 && argtypes is NULL.
If you see anything in the documentation that is not correct, does not match your experience with the particular feature or requires further clarification, please use this form to report a documentation issue.