SPI_cursor_open sets up a cursor (internally, a portal) that will execute a plan prepared by SPI_prepare.
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.
Arguments
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
actual parameter values
const char *nulls
An array describing which parameters are null values. 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.
Return Value
pointer to portal containing the cursor, or NULL on error
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