stores a plan prepared by SPI_prepare in safe memory
protected from freeing by SPI_finish or the transaction manager.
In the current version of PostgreSQL there is no ability to
store prepared plans in the system
catalog and fetch them from there for execution. This will be implemented
in future versions.
As an alternative, there is the ability to reuse prepared plans in the
subsequent invocations of your procedure in the current session.
Use SPI_execp to execute this saved plan.
SPI_saveplan saves a passed plan (prepared by SPI_prepare) in memory
protected from freeing by SPI_finish and by the transaction manager and
returns a pointer to the saved plan. You may save the pointer returned in
a local variable. Always check if this pointer is NULL or not either when
preparing a plan or using an already prepared plan in SPI_execp (see below).
Note: If one of the objects (a relation, function, etc.) referenced by the prepared
plan is dropped during your session (by your backend or another process) then the
results of SPI_execp for this plan will be unpredictable.