> inner_join(memdb_frame(a=1), memdb_frame(a=1), by = "b")
Source:   query [?? x 2]
Database: sqlite 3.11.1 [:memory:]
Error in if (using) { : missing value where TRUE/FALSE needed

22: traceback(1)
21: sql_join.default(con, from_x, from_y, type = query$type, by = query$by) at sql-generic.R#91
20: sql_join(con, from_x, from_y, type = query$type, by = query$by) at sql-render.R#53
19: sql_render.join_query(query$from, con, ..., root = root) at sql-render.R#4
18: sql_render(query$from, con, ..., root = root)
17: inherits(x, "ident") at sql-escape.r#82
16: is.ident(from) at src-sqlite.r#177
15: sql_subquery.SQLiteConnection(con, sql_render(query$from, con,
        ..., root = root), name = NULL) at sql-generic.R#77
14: sql_subquery(con, sql_render(query$from, con, ..., root = root),
        name = NULL) at sql-render.R#24
13: sql_render.select_query(sql_build(query$ops, query$src$con, ...),
        con = query$src$con, ...) at sql-render.R#4
12: sql_render(sql_build(query$ops, query$src$con, ...), con = query$src$con,
        ...) at sql-render.R#14
11: sql_render.tbl_sql(x) at sql-render.R#4
10: sql_render(x) at tbl-sql.r#392
9: collect.tbl_sql(x, n = n) at compute-collect.r#38
8: collect(x, n = n)
7: as.data.frame(collect(x, n = n)) at tbl-sql.r#56
6: as.data.frame.tbl_sql(head(x, n))
5: as.data.frame(head(x, n)) at utils-format.r#40
4: trunc_mat(x, n = n, width = width)
3: print(trunc_mat(x, n = n, width = width)) at tbl-sql.r#71
2: print.tbl_sql(x)
1: function (x, ...)
   UseMethod("print")(x)