feat: add support for query that have aggregation but missing group by #124
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kotharironak
requested review from
avinashkolluru,
skjindal93 and
suresh-prakash
as code owners
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| * this transformer removes all the non-aggregated expressions. So, the above query will be transformed | ||
| * to: | ||
| * | ||
| * SELECT COUNT(DISTINCT document->>'quantity' ) AS QTY |
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Not sure if we should go this route. We have never transformed the user-given query to a different non-equivalent query just because some database does not support it. In fact, this transformation alters the input selections and removes some of them. This might result in unexpected/undesired effects in the clients because they are asking for 2 selections, but, we only return 1 silently ignoring the other.
The query transformer in Mongo only builds equivalent queries by modifying the given expressions to other equivalent forms or adds some expressions to support the modification. But, the overall query is transformed to another equivalent query supported by the database. We neither remove anything nor transform to a non-equivalent query. Ideally, for such scenarios, we should fail (even in Mongo if that's not the case today). I suspect, the DB itself is not returning the rows in case of Mongo.
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For example, in Mongo we convert "DISTINCT_COUNT" into "$addToSet" in the "$group" stage and add "$size" in the "$project" stage. But, the query is still equivalent.
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Mongo internally does that and discards them. And, thought of the above path, but have to do this for backward compatibility as currently in the Query API layer, we are not discarding those queries.
e.g Mongo Query for the above sample query
[{"$match": {"$and": [{"price": {"$lte": 10}}, {"item": {"$in": ["Mirror", "Comb", "Shampoo", "Bottle"]}}]}},
{"$group": {"qty_count": {"$addToSet": "$quantity"}, "_id": null}},
{"$project": {"item": 1, "qty_count": {"$size": "$qty_count"}, "price": 1}}]
Response to the above query from mongo (selections are discarded):
[{"qty_count":3}]
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|
@suresh-prakash As discussed,
I am still testing this one with a custom build, if any issue, will fix it first. |
Description
As part of the issue - #123, This PR
Solution:
Mongo:
Postgres:
Testing
Checklist: