Function SPI_cursor_open_internal

src/backend/executor/spi.c:1604–1828

* SPI_cursor_open_internal() * * Common code for SPI_cursor_open variants */

 *	Common code for SPI_cursor_open variants
 */
static Portal
SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
						 ParamListInfo paramLI, bool read_only)
{
	CachedPlanSource *plansource;
	CachedPlan *cplan;
	List	   *stmt_list;
	char	   *query_string;
	ListCell   *lc;
	Snapshot	snapshot;
	MemoryContext oldcontext;
	Portal		portal;
	SPICallbackArg spicallbackarg;
	ErrorContextCallback spierrcontext;

	/*
	 * Check that the plan is something the Portal code will special-case as
	 * returning one tupleset.
	 */
	if (!SPI_is_cursor_plan(plan))
	{
		/* try to give a good error message */
		const char *cmdtag;

		if (list_length(plan->plancache_list) != 1)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_CURSOR_DEFINITION),
					 errmsg("cannot open multi-query plan as cursor")));
		plansource = (CachedPlanSource *) linitial(plan->plancache_list);
		/* A SELECT that fails SPI_is_cursor_plan() must be SELECT INTO */
		if (plansource->commandTag == CMDTAG_SELECT)
			cmdtag = "SELECT INTO";
		else
			cmdtag = GetCommandTagName(plansource->commandTag);
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_CURSOR_DEFINITION),
		/* translator: %s is name of a SQL command, eg INSERT */
				 errmsg("cannot open %s query as cursor", cmdtag)));
	}

	Assert(list_length(plan->plancache_list) == 1);
	plansource = (CachedPlanSource *) linitial(plan->plancache_list);

	/* Push the SPI stack */
	if (_SPI_begin_call(true) < 0)
		elog(ERROR, "SPI_cursor_open called while not connected");

	/* Reset SPI result (note we deliberately don't touch lastoid) */
	SPI_processed = 0;
	SPI_tuptable = NULL;
	_SPI_current->processed = 0;
	_SPI_current->tuptable = NULL;

	/* Create the portal */
	if (name == NULL || name[0] == '\0')
	{
		/* Use a random nonconflicting name */
		portal = CreateNewPortal();