Prefetch a chunk of result for stream operation #2137
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jatcwang
reviewed
Nov 17, 2024
jatcwang
reviewed
Nov 17, 2024
modules/hikari/src/test/scala/doobie/postgres/PGConcurrentSuite.scala
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jatcwang
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Nov 17, 2024
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| // if buffer is less than result set, it will be still block new connection since the result set is not drained | ||
| // use sleep to test the result set can be drained | ||
| val streamSmallerBuffer = fr"select * from stream_cancel_test".query[Int].stream.transactBuffer(xa, 50) |
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Hm sorry I can't quite understand how this is testing that the connection is closed before the stream is completed 🤔
An alternative way I can think of to test this is to use some sort of atomic boolean and set it to true when the transactor finishes the transaction, and then you can assert that this was set to true before you process the last chunk of the stream.
import doobie.util.transactor.Strategy
import doobie.FC
import java.util.concurrent.atomic.AtomicBoolean
val hasClosed = new AtomicBoolean(false)
xa.copy(
strategy0 = Strategy.default.copy(
always = Strategy.default.always.flatMap(_ => FC.delay(hasClosed.set(true)))
)
)
It's probably possible to use Deferred instead of AtomicBoolean but there will be more ceremony to instantiates a Deferred inside ConnectionIO
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Fixed the test to assert if it's closed
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Resolves typelevel#2132. Use fs2 Stream's `prefetchN` to buffer query results so that slow downstream operations don't slow down transaction commit. The buffered result size is `chunkSize` (equals to `fetchSize`) by default. If want a different buffer size, can use `transactNoPrefetc` to get a stream without `prefetchN` and append any prefetch operations wanted.
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Hi @jatcwang just follow up on this PR. Please let me know if the updated code addressed your comments or not. |
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Resolves #2132.
Use fs2 Stream's
prefetchNto buffer query results so that slow downstream operations don't slow down transaction commit.The buffered result size is
chunkSize(equals tofetchSize) by default. If want a different buffer size, can usetransactNoPrefetcto get a stream withoutprefetchNand append any prefetch operations wanted.