SPI_cursor

SPI_cursor_open
Prev	Up	46.1. Interface Functions	Home	Next

SPI_cursor_open

SPI_cursor_open — set up a cursor using a statement 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 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 C function (it can, in fact, live + to the end of the current transaction). Returning the portal name + to the C function'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

+ 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. +

+ 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. +

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. +