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selectStream performance #189

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merged 2 commits into from
Dec 28, 2023
Merged

selectStream performance #189

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319a8ad
made selectStream more efficient by batching multiple rows is a singl…
oridag Dec 24, 2023
a3179b0
drop scala 2.13 api use
oridag Dec 24, 2023
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26 changes: 17 additions & 9 deletions core/src/main/scala/zio/jdbc/Query.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -54,19 +54,27 @@ final case class Query[+A](sql: SqlFragment, decode: ZResultSet => A) {
/**
* Performs a SQL select query, returning a stream of results.
*/
def selectStream: ZStream[ZConnection, Throwable, A] =
def selectStream(chunkSize: => Int = ZStream.DefaultChunkSize): ZStream[ZConnection, Throwable, A] =
ZStream.unwrapScoped {
for {
zrs <- executeQuery(sql)
stream = ZStream.repeatZIOOption {
ZIO
.suspend(if (zrs.next()) ZIO.attempt(Some(decode(zrs))) else ZIO.none)
.mapError(Option(_))
.flatMap {
case None => ZIO.fail(None)
case Some(v) => ZIO.succeed(v)
stream = ZStream.paginateChunkZIO(())(_ =>
ZIO.attemptBlocking {
val builder = ChunkBuilder.make[A](chunkSize)
var hasNext = false
var i = 0
while (
i < chunkSize && {
hasNext = zrs.next()
hasNext
}
) {
builder.addOne(decode(zrs))
i += 1
}
}
(builder.result(), if (hasNext) Some(()) else None)
}
)
} yield stream
}

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6 changes: 3 additions & 3 deletions core/src/test/scala/zio/jdbc/ZConnectionPoolSpec.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -303,11 +303,11 @@ object ZConnectionPoolSpec extends ZIOSpecDefault {
} +
test("select stream") {
for {
_ <- createUsers *> insertSherlock *> insertWatson
_ <- createUsersNoId *> insertFive
value <- transaction {
sql"select name, age from users".query[User].selectStream.runCollect
sql"select name, age from users_no_id".query[UserNoId].selectStream(2).chunks.runCollect
}
} yield assertTrue(value == Chunk(sherlockHolmes, johnWatson))
} yield assertTrue(value == Chunk(Chunk(user1, user2), Chunk(user3, user4), Chunk(user5)))
} +
test("delete") {
for {
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