SPI_cursor_open — set up a cursor using a plan created with SPI_prepare
Portal SPI_cursor_open(const char *name
, void *plan
, Datum *values
, const char *nulls
, boolread_only
)
SPI_cursor_open
sets up a cursor (internally,
a portal) that will execute a plan prepared by
SPI_prepare
. The parameters have the same
meanings as the corresponding parameters to
SPI_execute_plan
.
Using a cursor instead of executing the plan directly has two benefits. First, the result rows can be retrieved a few at a time, avoiding memory overrun for queries that return many rows. Second, a portal can outlive the current procedure (it can, in fact, live to the end of the current transaction). Returning the portal name to the procedure's caller provides a way of returning a row set as result.
const char * name
name for portal, or NULL
to let the system
select a name
void * plan
execution plan (returned by SPI_prepare
)
Datum * values
An array of actual parameter values. Must have same length as the plan's number of arguments.
const char * nulls
An array describing which parameters are null. Must have same length as
the plan's number of arguments.
n
indicates a null value (entry in
values
will be ignored); a space indicates a
nonnull value (entry in values
is valid).
If nulls
is NULL
then
SPI_cursor_open
assumes that no parameters are
null.
bool read_only
true
for read-only execution