[release/6.0] Clear reference to DbDataReader from RelationalDataReader #29005
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Fixes dotnet#28988 (cherry picked from commit 4bb67a7)
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ajcvickers
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Sep 16, 2022
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Fixes #28988
Description
In EF Core 6.0, we started recycling RelationalDataReader instances across RelationalCommand invocations, to optimize the query pipeline and cut down on needless allocations. However, the RelationalDataReader retains its reference to its DbDataReader until a new query is executed; if a BufferedDataReader is used, that can mean needlessly preventing garbage collection of lots of all query data. This is exarcebated by context pooling (where the context is kept around for much longer).
Customer impact
Significantly increased memory usage when a retrying execution is used, context pooling is activated and large results are queries from the database.
How found
Customer reported on 6.0
Regression
Yes, in 6.0.
Testing
Added a test.
Risk
Low.
This is port of #28989 which was already merged for 7.0.