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SPI_prepare
Portal SPI_cursor_open(const char * name, SPIPlanPtr plan,
Datum * values, const char * nulls,
bool read_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.
The passed-in parameter data will be copied into the cursor's portal, so it can be freed while the cursor still exists.
name for portal, or NULL to let the system select a name
execution plan (returned by SPI_prepare)
An array of actual parameter values. Must have same length as the plan's number of arguments.
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.
true for read-only execution
Pointer to portal containing the cursor. Note there is no error
return convention; any error will be reported via elog.