SPI_cursor_open
Synopsis
Portal SPI_cursor_open(const char * name, SPIPlanPtr plan,
Datum * values, const char * nulls,
bool read_only)Description
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 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, or NULL to let the system select a name
- SPIPlanPtr 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_openassumes that no parameters are null.- bool read_only
true for read-only execution
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