⚡️ Improve getLastUse performance

Previously, the getLastUse flow would simply grab all uses and programmatically calculate the latest. This commit moves this behavior to the database in order to enhance performance. Performance was demonstrated in a test ensuring the execution takes less than the original implementation. Closes #108 Signed-off-by: Leonardo Colman Lopes <[email protected]>
LeoColman · Oct 10, 2022 · 2952062 · 2952062
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commit 2952062
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diff --git a/app/src/main/kotlin/br/com/colman/petals/use/repository/UseRepository.kt b/app/src/main/kotlin/br/com/colman/petals/use/repository/UseRepository.kt
@@ -3,6 +3,7 @@ package br.com.colman.petals.use.repository
 import br.com.colman.petals.UseQueries
 import com.squareup.sqldelight.runtime.coroutines.asFlow
 import com.squareup.sqldelight.runtime.coroutines.mapToList
+import com.squareup.sqldelight.runtime.coroutines.mapToOneOrNull
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.map
 import timber.log.Timber
@@ -23,7 +24,7 @@ class UseRepository(
     useQueries.insert(use.toEntity())
   }
 
-  fun getLastUse() = all().map { it.maxByOrNull { it.date } }
+  fun getLastUse() = useQueries.selectLast().asFlow().mapToOneOrNull().map { it?.toUse() }
 
   fun getLastUseDate() = getLastUse().map { it?.date }
 

diff --git a/app/src/main/sqldelight/br/com/colman/petals/Use.sq b/app/src/main/sqldelight/br/com/colman/petals/Use.sq
@@ -8,6 +8,9 @@ CREATE TABLE Use(
 insert:
 INSERT INTO Use(date, amount_grams, cost_per_gram, id) VALUES ?;
 
+selectLast:
+SELECT * FROM Use ORDER BY date DESC LIMIT 1;
+
 selectAll:
 SELECT * FROM Use;
 

diff --git a/app/src/test/kotlin/br/com/colman/petals/use/repository/UseRepositoryTest.kt b/app/src/test/kotlin/br/com/colman/petals/use/repository/UseRepositoryTest.kt
@@ -19,14 +19,18 @@
 package br.com.colman.petals.use.repository
 
 import br.com.colman.petals.Database
+import br.com.colman.petals.use.io.useArb
 import com.squareup.sqldelight.sqlite.driver.JdbcSqliteDriver
 import com.squareup.sqldelight.sqlite.driver.JdbcSqliteDriver.Companion.IN_MEMORY
 import io.kotest.core.spec.IsolationMode
 import io.kotest.core.spec.style.FunSpec
 import io.kotest.matchers.collections.shouldBeEmpty
+import io.kotest.matchers.longs.shouldBeLessThan
 import io.kotest.matchers.shouldBe
+import io.kotest.property.arbitrary.take
 import kotlinx.coroutines.flow.first
 import java.math.BigDecimal
+import kotlin.system.measureTimeMillis
 
 class UseRepositoryTest : FunSpec({
 
@@ -72,5 +76,15 @@ class UseRepositoryTest : FunSpec({
     target.getLastUseDate().first() shouldBe use.date
   }
 
+  test("Last use performance") {
+    useArb.take(100_000).map(Use::toEntity).forEach(database.useQueries::insert)
+
+    measureTimeMillis {
+      target.getLastUseDate().first()
+    } shouldBeLessThan measureTimeMillis {
+      target.all().first().maxByOrNull { it.date }
+    }
+  }
+
   isolationMode = IsolationMode.InstancePerTest
 })