SPI_saveplan saves a passed plan
SPI_prepare) in memory
protected from freeing by
SPI_finish and by the transaction manager and
returns a pointer to the saved plan. This gives you the ability
to reuse prepared plans in the subsequent invocations of your
procedure in the current session.
Pointer to the saved plan; NULL if unsuccessful. On error, SPI_result is set thus:
if plan is NULL
if called from an unconnected procedure
If one of the objects (a table, function, etc.) referenced by
the prepared plan is dropped during the session then the results
SPI_execute_plan for this plan
will be unpredictable.