Function exec_run_select

src/pl/plpgsql/src/pl_exec.c:5698–5774

---------- * exec_run_select Execute a select query * ---------- */

 * ----------
 */
static int
exec_run_select(PLpgSQL_execstate *estate,
				PLpgSQL_expr *expr, long maxtuples, Portal *portalP)
{
	ParamListInfo paramLI;
	int			rc;

	/*
	 * On the first call for this expression generate the plan.
	 *
	 * If we don't need to return a portal, then we're just going to execute
	 * the query immediately, which means it's OK to use a parallel plan, even
	 * if the number of rows being fetched is limited.  If we do need to
	 * return a portal (i.e., this is for a FOR loop), the user's code might
	 * invoke additional operations inside the FOR loop, making parallel query
	 * unsafe.  In any case, we don't expect any cursor operations to be done,
	 * so specify NO_SCROLL for efficiency and semantic safety.
	 */
	if (expr->plan == NULL)
	{
		int			cursorOptions = CURSOR_OPT_NO_SCROLL;

		if (portalP == NULL)
			cursorOptions |= CURSOR_OPT_PARALLEL_OK;
		exec_prepare_plan(estate, expr, cursorOptions);
	}

	/*
	 * Set up ParamListInfo to pass to executor
	 */
	paramLI = setup_param_list(estate, expr);

	/*
	 * If a portal was requested, put the query and paramlist into the portal
	 */
	if (portalP != NULL)
	{
		*portalP = SPI_cursor_open_with_paramlist(NULL, expr->plan,
												  paramLI,
												  estate->readonly_func);
		if (*portalP == NULL)
			elog(ERROR, "could not open implicit cursor for query \"%s\": %s",
				 expr->query, SPI_result_code_string(SPI_result));
		exec_eval_cleanup(estate);
		return SPI_OK_CURSOR;
	}

	/*
	 * Execute the query
	 */
	rc = SPI_execute_plan_with_paramlist(expr->plan, paramLI,
										 estate->readonly_func, maxtuples);
	if (rc != SPI_OK_SELECT)
	{
		/*
		 * SELECT INTO deserves a special error message, because "query is not
		 * a SELECT" is not very helpful in that case.
		 */