SPI_saveplan copies a passed
statement (prepared by SPI_prepare)
into memory that will not be freed by SPI_finish nor by the transaction manager, and
returns a pointer to the copied statement. This gives you the
ability to reuse prepared statements in the subsequent
invocations of your procedure in the current session.
Pointer to the copied statement; or NULL if unsuccessful. On error, SPI_result is set thus:
if plan is NULL or invalid
if called from an unconnected procedure
The originally passed-in statement is not freed, so you might
wish to do SPI_freeplan on it to
avoid leaking memory until SPI_finish.
In most cases, SPI_keepplan is
preferred to this function, since it accomplishes largely the
same result without needing to physically copy the prepared
statement's data structures.