Function sql_exec_error_callback

src/backend/executor/functions.c:1545–1620

* error context callback to let us supply a call-stack traceback */

 * error context callback to let us supply a call-stack traceback
 */
static void
sql_exec_error_callback(void *arg)
{
	FmgrInfo   *flinfo = (FmgrInfo *) arg;
	SQLFunctionCachePtr fcache = (SQLFunctionCachePtr) flinfo->fn_extra;
	int			syntaxerrposition;

	/*
	 * We can do nothing useful if init_sql_fcache() didn't get as far as
	 * saving the function name
	 */
	if (fcache == NULL || fcache->fname == NULL)
		return;

	/*
	 * If there is a syntax error position, convert to internal syntax error
	 */
	syntaxerrposition = geterrposition();
	if (syntaxerrposition > 0 && fcache->src != NULL)
	{
		errposition(0);
		internalerrposition(syntaxerrposition);
		internalerrquery(fcache->src);
	}

	/*
	 * Try to determine where in the function we failed.  If there is a query
	 * with non-null QueryDesc, finger it.  (We check this rather than looking
	 * for F_EXEC_RUN state, so that errors during ExecutorStart or
	 * ExecutorEnd are blamed on the appropriate query; see postquel_start and
	 * postquel_end.)
	 */
	if (fcache->func_state)
	{
		execution_state *es;
		int			query_num;
		ListCell   *lc;

		es = NULL;
		query_num = 1;
		foreach(lc, fcache->func_state)
		{
			es = (execution_state *) lfirst(lc);
			while (es)
			{
				if (es->qd)
				{
					errcontext("SQL function \"%s\" statement %d",
							   fcache->fname, query_num);
					break;
				}
				es = es->next;
			}
			if (es)
				break;
			query_num++;
		}
		if (es == NULL)