SPI_cursor_open
Synopsis
Portal SPI_cursor_open(const char *name, SPIPlanPtrplan, Datum *values, const char *nulls, boolread_only)
Description
SPI_cursor_open sets up a cursor (internally, a portal) that will execute a statement prepared bySPI_prepare. The parameters have the same meanings as the corresponding parameters toSPI_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.
Arguments
- const char *name
name for portal, orNULL to let the system select a name
- SPIPlanPtrplan
prepared statement (returned by
SPI_prepare)- Datum *values
An array of actual parameter values. Must have same length as the statement's number of arguments.
- const char *nulls
An array describing which parameters are null. Must have same length as the statement's number of arguments.
Ifnulls isNULL then
SPI_cursor_openassumes that no parameters are null. Otherwise, each entry of thenulls 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 correspondingvalues entry doesn't matter.) Note thatnulls is not a text string, just an array: it does not need a'\0' terminator.- boolread_only
true for read-only execution