make some progress

Signed-off-by: Kengo TODA <skypencil@gmail.com>

README.md

@@ -0,0 +1,44 @@
+# Kosmo
+
+[![Continuous Integration](https://github.com/KengoTODA/kosmo/actions/workflows/ci.yaml/badge.svg)](https://github.com/KengoTODA/kosmo/actions/workflows/ci.yaml)
+
+Kosmo is a simple Relational Database implemented in Kotlin.
+This product is not developed for production use, just for personal learning.
+
+## Architecture
+
+```mermaid
+graph TD
+  subgraph frontend
+    main-process --> cpf[connection pool]
+    subgraph worker
+        worker-process -->
+        optimizer -->
+        rewriter -->
+        planner --> worker-process
+    end
+    main-process --> worker-process
+    worker-process --> al[(audit-log)]
+  end
+  subgraph backend
+    coordinator-process --> cpb[connection pool]
+    subgraph database
+        database-process
+        wal[(write ahead log)]
+        subgraph storage-engine
+            table --> df[(data file)]
+            index --> df
+            vacuumer --> df
+        end
+        database-process --> wal
+        database-process --> table
+        database-process --> index
+        database-process --> vacuumer
+    end
+  end
+  subgraph replica
+    wal --> replica-process
+  end
+  client --> main-process
+  worker-process --> coordinator-process --> database-process
+```

backend/build.gradle.kts

@@ -3,5 +3,11 @@ plugins {
 }
 
 application {
-    mainClass.set("jp.skypencil.kosmo.backend.AppKt")
+    mainClass = "jp.skypencil.kosmo.backend.Coordinator"
+}
+
+dependencies {
+    implementation(libs.slf4j.api)
+    implementation(libs.uuid.creator)
+    runtimeOnly(libs.log4j.slf4j2.impl)
 }

backend/src/main/kotlin/jp/skypencil/kosmo/backend/Coordinator.kt

@@ -1,4 +1,12 @@
 package jp.skypencil.kosmo.backend
 
+import jp.skypencil.kosmo.backend.storage.onmemory.OnMemoryDatabase
+import jp.skypencil.kosmo.backend.wal.LogWriter
+
+/**
+ * フロントエンドからの要求を受け取り、それぞれのクラスを組み合わせて実現する。
+ */
 class Coordinator {
-}
+    private val database = OnMemoryDatabase()
+    private val logWriter = LogWriter()
+}

backend/src/main/kotlin/jp/skypencil/kosmo/backend/storage/onmemory/OnMemoryDatabase.kt

@@ -0,0 +1,17 @@
+package jp.skypencil.kosmo.backend.storage.onmemory
+
+import jp.skypencil.kosmo.backend.storage.shared.Table
+import jp.skypencil.kosmo.backend.storage.shared.Database
+
+class OnMemoryDatabase : Database {
+    private val tables = mutableMapOf<String, OnMemoryTable>()
+    override suspend fun findTable(name: String): Table =
+        checkNotNull(tables[name])
+
+    override suspend fun createTable(name: String): Table {
+        require(!tables.containsKey(name))
+        return OnMemoryTable(name).also {
+            tables[name] = it
+        }
+    }
+}

backend/src/main/kotlin/jp/skypencil/kosmo/backend/storage/onmemory/OnMemoryTable.kt

@@ -0,0 +1,31 @@
+package jp.skypencil.kosmo.backend.storage.onmemory
+
+import jp.skypencil.kosmo.backend.storage.shared.Table
+import jp.skypencil.kosmo.backend.value.Row
+import jp.skypencil.kosmo.backend.value.RowId
+import jp.skypencil.kosmo.backend.value.TransactionId
+import kotlin.streams.asSequence
+
+// TODO トランザクション
+// TODO スレッドセーフティ
+class OnMemoryTable(private val name: String) : Table {
+    private val map = mutableMapOf<RowId, Row>()
+
+    override fun getName(): String = name
+
+    override suspend fun find(transactionId: TransactionId, id: RowId): Row = checkNotNull(map[id])
+
+    override suspend fun tableScan(transactionId: TransactionId): Sequence<Row> = map.values.stream().asSequence()
+
+    override suspend fun insert(transactionId: TransactionId, row: Row) {
+        check(map[row.id] == null)
+        map[row.id] = row
+    }
+
+    override suspend fun delete(transactionId: TransactionId, id: RowId): Boolean = map.remove(id) != null
+
+    override suspend fun update(transactionId: TransactionId, row: Row) {
+        checkNotNull(map[row.id])
+        map[row.id] = row
+    }
+}

backend/src/main/kotlin/jp/skypencil/kosmo/backend/storage/shared/Database.kt

@@ -0,0 +1,6 @@
+package jp.skypencil.kosmo.backend.storage.shared
+
+interface Database {
+    suspend fun findTable(name: String): Table
+    suspend fun createTable(name: String): Table
+}

backend/src/main/kotlin/jp/skypencil/kosmo/backend/storage/shared/StorageEngine.kt

@@ -0,0 +1,13 @@
+package jp.skypencil.kosmo.backend.storage.shared
+
+import jp.skypencil.kosmo.backend.value.Row
+import jp.skypencil.kosmo.backend.value.RowId
+
+/**
+ * データや索引の管理を抽象化する。
+ */
+interface StorageEngine {
+    suspend fun find(id: RowId): Row
+    suspend fun tableScan(): Sequence<Row>
+    suspend fun indexScan(): Sequence<Row>
+}

backend/src/main/kotlin/jp/skypencil/kosmo/backend/storage/shared/Table.kt

@@ -0,0 +1,15 @@
+package jp.skypencil.kosmo.backend.storage.shared
+
+import jp.skypencil.kosmo.backend.value.Row
+import jp.skypencil.kosmo.backend.value.RowId
+import jp.skypencil.kosmo.backend.value.TransactionId
+
+interface Table {
+    fun getName(): String
+
+    suspend fun find(tx: TransactionId, id: RowId): Row
+    suspend fun tableScan(tx: TransactionId): Sequence<Row>
+    suspend fun insert(tx: TransactionId, row: Row)
+    suspend fun delete(tx: TransactionId, id: RowId): Boolean
+    suspend fun update(tx: TransactionId, row: Row)
+}

backend/src/main/kotlin/jp/skypencil/kosmo/backend/value/LogEntry.kt

@@ -0,0 +1,7 @@
+package jp.skypencil.kosmo.backend.value
+
+/**
+ * データベースの変更を表す。
+ */
+interface LogEntry {
+}

backend/src/main/kotlin/jp/skypencil/kosmo/backend/value/Row.kt

@@ -0,0 +1,4 @@
+package jp.skypencil.kosmo.backend.value
+
+data class Row(val id: RowId) {
+}

backend/src/main/kotlin/jp/skypencil/kosmo/backend/value/RowId.kt

@@ -0,0 +1,15 @@
+package jp.skypencil.kosmo.backend.value
+
+import java.util.UUID
+
+data class RowId(private val uuid: UUID): Comparable<RowId> {
+    init {
+        check(uuid.version() == 6) {
+            "RowIdはTime-basedなUUIDである必要があります"
+        }
+    }
+
+    override fun compareTo(other: RowId): Int =
+        this.uuid.compareTo(other.uuid)
+
+}

backend/src/main/kotlin/jp/skypencil/kosmo/backend/value/TransactionId.kt

@@ -1,4 +1,12 @@
 package jp.skypencil.kosmo.backend.value
 
-class TransactionId {
-}
+import com.github.f4b6a3.uuid.UuidCreator
+import java.util.UUID
+
+class TransactionId(private val uuid: UUID): Comparable<TransactionId> {
+    companion object {
+        fun create() = TransactionId(UuidCreator.getTimeOrdered())
+    }
+
+    override fun compareTo(other: TransactionId): Int = uuid.compareTo(other.uuid)
+}

backend/src/main/kotlin/jp/skypencil/kosmo/backend/wal/LogWriter.kt

@@ -0,0 +1,12 @@
+package jp.skypencil.kosmo.backend.wal
+
+import jp.skypencil.kosmo.backend.value.LogEntry
+
+/**
+ * Write Ahead Log（WAL）を記録する責務を負う。
+ */
+class LogWriter {
+    suspend fun write(logEntry: LogEntry) {
+
+    }
+}

buildSrc/build.gradle.kts

@@ -3,9 +3,11 @@ plugins {
 }
 
 repositories {
+    mavenCentral()
     gradlePluginPortal()
 }
 
 dependencies {
+    implementation("com.diffplug.spotless:spotless-plugin-gradle:6.22.0")
     implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:1.9.10")
 }

buildSrc/settings.gradle.kts

@@ -1,7 +1,9 @@
-/*
- * This file was generated by the Gradle 'init' task.
- *
- * This settings file is used to specify which projects to include in your build-logic build.
- */
-
 rootProject.name = "buildSrc"
+
+dependencyResolutionManagement {
+    versionCatalogs {
+        create("libs") {
+            from(files("../gradle/libs.versions.toml"))
+        }
+    }
+}

buildSrc/src/main/kotlin/jp.skypencil.kosmo.kotlin-common-conventions.gradle.kts

@@ -1,5 +1,6 @@
 plugins {
     id("org.jetbrains.kotlin.jvm")
+    id("com.diffplug.spotless")
 }
 
 repositories {
@@ -12,6 +13,17 @@ java {
     }
 }
 
+val kotest = "5.8.0"
+dependencies {
+    testImplementation("io.kotest:kotest-assertions-core:$kotest")
+    testImplementation("io.kotest:kotest-property:$kotest")
+    testRuntimeOnly("io.kotest:kotest-runner-junit5:$kotest")
+}
+
 tasks.named<Test>("test") {
     useJUnitPlatform()
 }
+
+tasks.withType<Test>().configureEach {
+    useJUnitPlatform()
+}

gradle.properties

@@ -0,0 +1,2 @@
+org.gradle.parallel=true
+org.gradle.caching=true

gradle/libs.versions.toml

@@ -0,0 +1,10 @@
+[versions]
+kotest = "5.8.0"
+log4j = "2.20.0"
+slf4j = "2.0.9"
+
+[libraries]
+kotest-runner-juni5 = { module = "io.kotest:kotest-runner-junit5", version.ref = "kotest" }
+log4j-slf4j2-impl = { module = "org.apache.logging.log4j:log4j-slf4j2-impl", version.ref = "log4j" }
+slf4j-api = { module = "org.slf4j:slf4j-api", version.ref = "slf4j" }
+uuid-creator = { module = "com.github.f4b6a3:uuid-creator", version = "5.3.3" }

settings.gradle.kts

@@ -3,4 +3,4 @@ plugins {
 }
 
 rootProject.name = "kosmo"
-include("backend", "frontend", "jdbc-driver")
+include("backend", "frontend")