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13.1.17 SPI_cursor_open

Name

SPI_cursor_open -- set up a cursor using a plan created with SPI_prepare

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 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, 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_open assumes that no parameters are null.

bool read_only

true for read-only execution

Return Value

Pointer to portal containing the cursor. Note there is no error return convention; any error will be reported via elog.