gortiz opened a new issue, #13617:
URL: https://github.com/apache/pinot/issues/13617
Since we updated Calcite dependency from 1.31 to 1.37, multi stage engine
has issues executing queries that use IN expressions with a lot (lets say >50)
elements. Specifically, we spend a lot (in the order of seconds) time
optimizing the query.
It can be easily tested by running `MultistageEngineQuickStart` and
executing a query like:
```sql
explain plan for
SELECT DestCityName
FROM (
SELECT DestCityName
FROM airlineStats
WHERE DestCityName IN (
'a0',
'a1','a2','a3','a4','a5','a6','a7','a8','a9',
'a10', 'a11', 'a12', 'a13', 'a14', 'a15', 'a16',
'a17', 'a18', 'a19',
'a20', 'a21', 'a22', 'a23', 'a24', 'a25', 'a26',
'a27', 'a28', 'a29',
'a30', 'a31', 'a32', 'a33', 'a34', 'a35', 'a36',
'a37', 'a38', 'a39',
'a40', 'a41', 'a42', 'a43', 'a44', 'a45', 'a46',
'a47', 'a48', 'a49'
)
GROUP BY DestCityName
LIMIT 2147483647
) as a
```
After studying the issue for a while, it looks like the issue comes from a
newly introduced Calcite optimization when dealing with ORs. In order to
calculate that optimization, Calcite applies an algorithm whose cost is at
least quadratic in terms of sub-predicates in the OR.
These OR expressions are generated either by Calcite or by Pinot in
different parts of the code. Right now I found that:
- IN can be transformed into OR while SqlNodes are converted into RelNodes.
Calcite knows it may be a problem and by default does not convert INs that have
more than 20 elements. But we explicitly set that limit to `Integer.MAX_VALUE`
in
[PinotRuleUtils.PINOT_SQL_TO_REL_CONFIG](https://github.com/apache/pinot/blob/3db93ccc210991ad91b6a5306b3b610d8f5e0507/pinot-query-planner/src/main/java/org/apache/pinot/calcite/rel/rules/PinotRuleUtils.java#L50).
- `PinotFilterExpandSearchRule`, where we transform any remanent SEARCH node
into ORS.
We have explored a couple of alternatives to fix the problem in
https://github.com/apache/pinot/pull/13605 and
https://github.com/apache/pinot/pull/13614
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