LakshSingla opened a new pull request #12139:
URL: https://github.com/apache/druid/pull/12139
### Description
Currently, in the ClientQuerySegmentWalker, when the data sources get
inlined, they can be limited by the number of rows to prevent a query
(subquery) from hogging up the broker's memory. This however doesn't have a
proper correspondence with the memory used, since a row can have multiple
columns with varying amounts of data in them. Therefore it would be better if
there is a memory limit also available, which prevents the subquery's results
from exploding beyond a certain memory limit.
This PR aims to add the initial structure for limiting the subqueries by the
memory limit, and an initial implementation of estimating the memory of the
inlined results.
Another alternative, apart from estimating the final memory result
consumption was to calculate the gathered bytes from historicals, and then
limit based on that, however that seems far off the mark, considering that the
subqueries can increase or decrease in size in the broker before getting
materialized.
Estimating the size of the result in the memory is derived similarly to the
implementations of `DimensionIndexers`.
In case that the memory limit does get exceeded, it raises a
`ResourceException`.
<hr>
##### Key changed/added classes in this PR
* `ClientQuerySegmentWalker`
<hr>
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- [ ] added integration tests.
- [ ] been tested in a test Druid cluster.
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