Function exec_eval_simple_expr

src/pl/plpgsql/src/pl_exec.c:5964–6167

---------- * exec_eval_simple_expr - Evaluate a simple expression returning * a Datum by directly calling ExecEvalExpr(). * * If successful, store results into *result, *isNull, *rettype, *rettypmod * and return true. If the expression cannot be handled by simple evaluation, * return false. * * Because we only store one execution tree for a simple expression, we * can't handle re

 * ----------
 */
static bool
exec_eval_simple_expr(PLpgSQL_execstate *estate,
					  PLpgSQL_expr *expr,
					  Datum *result,
					  bool *isNull,
					  Oid *rettype,
					  int32 *rettypmod)
{
	ExprContext *econtext = estate->eval_econtext;
	LocalTransactionId curlxid = MyProc->lxid;
	ParamListInfo paramLI;
	void	   *save_setup_arg;
	bool		need_snapshot;
	MemoryContext oldcontext;

	/*
	 * Forget it if expression wasn't simple before.
	 */
	if (expr->expr_simple_expr == NULL)
		return false;

	/*
	 * If expression is in use in current xact, don't touch it.
	 */
	if (unlikely(expr->expr_simple_in_use) &&
		expr->expr_simple_lxid == curlxid)
		return false;

	/*
	 * Ensure that there's a portal-level snapshot, in case this simple
	 * expression is the first thing evaluated after a COMMIT or ROLLBACK.
	 * We'd have to do this anyway before executing the expression, so we
	 * might as well do it now to ensure that any possible replanning doesn't
	 * need to take a new snapshot.
	 */
	EnsurePortalSnapshotExists();

	/*
	 * Check to see if the cached plan has been invalidated.  If not, and this
	 * is the first use in the current transaction, save a plan refcount in
	 * the simple-expression resowner.
	 */
	if (likely(CachedPlanIsSimplyValid(expr->expr_simple_plansource,
									   expr->expr_simple_plan,
									   (expr->expr_simple_plan_lxid != curlxid ?
										estate->simple_eval_resowner : NULL))))
	{
		/*
		 * It's still good, so just remember that we have a refcount on the
		 * plan in the current transaction.  (If we already had one, this
		 * assignment is a no-op.)
		 */
		expr->expr_simple_plan_lxid = curlxid;
	}
	else
	{
		/* Need to replan */
		CachedPlan *cplan;