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Posted to commits@druid.apache.org by GitBox <gi...@apache.org> on 2019/08/01 22:41:31 UTC
[GitHub] [incubator-druid] vogievetsky commented on issue #8208: Druid SQL:
Fetch latest records from streaming ingestion
vogievetsky commented on issue #8208: Druid SQL: Fetch latest records from streaming ingestion
URL: https://github.com/apache/incubator-druid/issues/8208#issuecomment-517483429
This is funny we were just talking about a very similar thing in the [Slack channel](https://druid.apache.org/community/join-slack) the other week...
You can use
```sql
SELECT * FROM wikipedia ORDER BY __time DESC LIMIT 1
```
To get the latest ingested record this is the most efficient thing you can do.
Your query logically would return all the records for the latest time, if that is really what you want to do that could be accomplished like so:
```sql
SELECT *
FROM wikipedia
WHERE __time IN (
SELECT __time
FROM wikipedia
WHERE "__time" >= CURRENT_TIMESTAMP - INTERVAL '1' DAY
GROUP BY 1
ORDER BY 1 DESC
LIMIT 1
)
```
Your query does did not work because it can not plan the result of an aggregate (`MAX(__time)`) into a filter. The query above groups on time in the inner query.
Notice also that I apply a filter to the inner query to not have to scan across the entire data set - I am assuming that my latest time will always be within the last day.
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