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 statement 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 statement 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
prepared statement (returned by SPI_prepare)
An array of actual parameter values. Must have same length as the statement's number of arguments.
An array describing which parameters are null. Must have same length as the statement's number of arguments.
If nulls is NULL then SPI_cursor_open assumes that no parameters are null. Otherwise, each entry of the nulls array should be ' ' if the corresponding parameter value is non-null, or 'n' if the corresponding parameter value is null. (In the latter case, the actual value in the corresponding values entry doesn't matter.) Note that nulls is not a text string, just an array: it does not need a '\0' terminator.
true for read-only execution