Function isAssignmentIndirectionExpr

src/backend/executor/execExpr.c:3182–3214

* Helper for preparing SubscriptingRef expressions for evaluation: is expr * a nested FieldStore or SubscriptingRef that needs the old element value * passed down? * * (We could use this in FieldStore too, but in that case passing the old * value is so cheap there's no need.) * * Note: it might seem that this needs to recurse, but in most cases it does * not; the CaseTestExpr, if any, will

 * be able to look through that.
 */
static bool
isAssignmentIndirectionExpr(Expr *expr)
{
	if (expr == NULL)
		return false;			/* just paranoia */
	if (IsA(expr, FieldStore))
	{
		FieldStore *fstore = (FieldStore *) expr;

		if (fstore->arg && IsA(fstore->arg, CaseTestExpr))
			return true;
	}
	else if (IsA(expr, SubscriptingRef))
	{
		SubscriptingRef *sbsRef = (SubscriptingRef *) expr;

		if (sbsRef->refexpr && IsA(sbsRef->refexpr, CaseTestExpr))
			return true;
	}
	else if (IsA(expr, CoerceToDomain))
	{
		CoerceToDomain *cd = (CoerceToDomain *) expr;

		return isAssignmentIndirectionExpr(cd->arg);
	}
	else if (IsA(expr, RelabelType))
	{
		RelabelType *r = (RelabelType *) expr;

		return isAssignmentIndirectionExpr(r->arg);
	}
	return false;
}

/*
 * Prepare evaluation of a CoerceToDomain expression.