Realtime SQL query for MySQL

Hi,
I looked at the implementation of the [realtime chart](https://github.com/cube-js/cube.js/blob/master/examples/real-time-dashboard/schema/Events.js) for MongoDB, but I can't figure out how to query MySQL database the same way.

Here is how I tried to recreate the schema for my page views

```javascript
cube(`Pageview`, {
sql: `SELECT * FROM mydb.pageview`,

joins: {
Session: {
sql: `${CUBE}.session_id = ${Session}.session_id`,
relationship: `belongsTo`
},

Website: {
sql: `${CUBE}.website_id = ${Website}.website_id`,
relationship: `belongsTo`
}
},

measures: {
count: {
type: `count`,
drillMembers: [createdAt]
}
},

dimensions: {
viewId: {
sql: `view_id`,
type: `number`,
primaryKey: true
},

referrer: {
sql: `referrer`,
type: `string`
},

url: {
sql: `url`,
type: `string`
},

createdAt: {
sql: `created_at`,
type: `time`
}
},

dataSource: `default`
});

const derivedTables = (where) => (
`
with generator as (
select 0 as d union all
select 1 union all select 2 union all select 3 union all
select 4 union all select 5 union all select 6 union all
select 7 union all select 8 union all select 9
),
seq as (
SELECT ( hii.d * 100 + hi.d * 10 + lo.d ) AS num
FROM generator lo
, generator hi,
generator hii
order by num
limit 250
),
series as (
SELECT
DATE_SUB(now(), INTERVAL seq.num SECOND) AS created_at
from seq
),
unioned as (
select
1 as pageview,
pageview.created_at
from mydb.pageview
WHERE ${where}
union all
select
0,
series.created_at
from series
)
`
)

const filterSuffix = (from, to) => `mydb.pageview.created_at >= TIMESTAMP(${from}) AND mydb.pageview.created_at <= TIMESTAMP(${to})`

cube(`ViewsBucketed`, {
sql:
`
${derivedTables(FILTER_PARAMS.ViewsBucketed.time.filter(filterSuffix))}
select * from unioned
`,

refreshKey: {
sql: `select (FLOOR(UNIX_TIMESTAMP(now())/15))*15`
},

measures: {
pageview: {
type: `sum`,
sql: `pageview`
}
},

dimensions: {
time: {
sql: `created_at`,
type: `time`
},

quarter: {
sql:`
STR_TO_DATE(CONCAT(
DATE_FORMAT(created_at, "%H:%i"), ":",
LPAD(CAST((FLOOR(SECOND(created_at)/15))*15 as CHAR), 2, 0)
), "%H:%i:%s")`,
type: `time`
}
}
})
```

So the query looks like this:

```
SELECT

STR_TO_DATE(CONCAT(
DATE_FORMAT(created_at, "%H:%i"), ":",
LPAD(CAST((FLOOR(SECOND(created_at)/15))*15 as CHAR), 2, 0)
), "%H:%i:%s") `views_bucketed__quarter`, sum(`views_bucketed`.pageview) `views_bucketed__pageview`
FROM
(

with generator as (
select 0 as d union all
select 1 union all select 2 union all select 3 union all
select 4 union all select 5 union all select 6 union all
select 7 union all select 8 union all select 9
),
seq as (
SELECT ( hii.d * 100 + hi.d * 10 + lo.d ) AS num
FROM generator lo
, generator hi,
generator hii
order by num
limit 250
),
series as (
SELECT
DATE_SUB(now(), INTERVAL seq.num SECOND) AS created_at
from seq
),
unioned as (
select
1 as pageview,
pageview.created_at
from mydb.pageview
WHERE mydb.pageview.created_at >= TIMESTAMP('2021-04-21T09:47:06.000') AND mydb.pageview.created_at <= TIMESTAMP('2021-04-21T09:49:35.999')
union all
select
0,
series.created_at
from series
)

select * from unioned
) AS `views_bucketed` WHERE (`views_bucketed`.created_at >= TIMESTAMP(convert_tz('2021-04-21T09:47:06.000', '+00:00', @@session.time_zone)) AND `views_bucketed`.created_at <= TIMESTAMP(convert_tz('2021-04-21T09:49:35.999', '+00:00', @@session.time_zone))) GROUP BY 1 ORDER BY 1 ASC LIMIT 10000
```

And here is what it returns


And this is how my pageview table looks like


Could you please suggest what I'm doing wrong? Thanks.