Add kernel structure

kernel/README.md

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+# Delta Kernel
+
+[TODO] - For now refer to [delta-io/delta#1783](https://github.com/delta-io/delta/issues/1783) for further information.

kernel/build.sbt

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+/*
+ * Copyright (2021) The Delta Lake Project Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+val scala212 = "2.12.15"
+scalaVersion := scala212
+
+lazy val commonSettings = Seq(
+  organization := "io.delta",
+  scalaVersion := scala212,
+  fork := true,
+  scalacOptions ++= Seq("-target:jvm-1.8", "-Ywarn-unused:imports"),
+  javacOptions ++= Seq("-source", "1.8"),
+  // -target cannot be passed as a parameter to javadoc. See https://github.com/sbt/sbt/issues/355
+  Compile / compile / javacOptions ++= Seq("-target", "1.8", "-Xlint:unchecked"),
+  // Configurations to speed up tests and reduce memory footprint
+  Test / javaOptions += "-Xmx1024m",
+)
+
+// TODO javastyle checkstyle tests
+// TODO unidoc/javadoc settings
+
+lazy val kernelApi = (project in file("kernel-api"))
+  .settings(
+    name := "delta-kernel-api",
+    commonSettings,
+    scalaStyleSettings,
+    releaseSettings,
+    libraryDependencies ++= Seq()
+  )
+
+val hadoopVersion = "3.3.1"
+val deltaStorageVersion = "2.2.0"
+val scalaTestVersion = "3.2.15"
+val deltaSparkVersion = deltaStorageVersion
+val sparkVersion = "3.3.2"
+
+lazy val kernelDefault = (project in file("kernel-default"))
+  .dependsOn(kernelApi)
+  .settings(
+    name := "delta-kernel-default",
+    commonSettings,
+    scalaStyleSettings,
+    releaseSettings,
+    libraryDependencies ++= Seq(
+      "org.apache.hadoop" % "hadoop-client-api" % hadoopVersion, // Configuration, Path
+      "io.delta" % "delta-storage" % deltaStorageVersion, // LogStore
+      "com.fasterxml.jackson.core" % "jackson-databind" % "2.13.5", // ObjectMapper
+      "org.apache.parquet" % "parquet-hadoop" % "1.12.3",
+
+      "org.scalatest" %% "scalatest" % scalaTestVersion % "test",
+      "io.delta" %% "delta-core" % deltaSparkVersion % "test",
+      "org.apache.spark" %% "spark-sql" % sparkVersion % "test", // SparkSession
+      "org.apache.spark" %% "spark-sql" % sparkVersion % "test" classifier "tests",
+      "org.apache.spark" %% "spark-core" % sparkVersion % "test" classifier "tests",
+      "org.apache.spark" %% "spark-catalyst" % sparkVersion % "test" classifier "tests",
+      "junit" % "junit" % "4.11" % "test",
+      "com.novocode" % "junit-interface" % "0.11" % "test"
+    )
+  )
+
+/*
+ ***********************
+ * ScalaStyle settings *
+ ***********************
+ */
+ThisBuild / scalastyleConfig := baseDirectory.value / "scalastyle-config.xml"
+
+// Not used since scala is test-only
+lazy val compileScalastyle = taskKey[Unit]("compileScalastyle")
+lazy val testScalastyle = taskKey[Unit]("testScalastyle")
+
+lazy val scalaStyleSettings = Seq(
+  compileScalastyle := (Compile / scalastyle).toTask("").value,
+  Compile / compile := ((Compile / compile) dependsOn compileScalastyle).value,
+  testScalastyle := (Test / scalastyle).toTask("").value,
+  Test / test := ((Test / test) dependsOn testScalastyle).value
+)
+
+/*
+ ********************
+ * Release settings *
+ ********************
+ */
+
+// Don't release the root project
+publishArtifact := false
+publish / skip := true
+
+lazy val releaseSettings = Seq(
+  // Java only release settings
+  crossPaths := false, // drop off Scala suffix from artifact names
+  autoScalaLibrary := false, // exclude scala-library from dependencies in generated pom.xml
+
+  // Other release settings
+  publishArtifact := true,
+  Test / publishArtifact := false
+)

kernel/build/sbt

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+#!/usr/bin/env bash
+
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+#
+# This file contains code from the Apache Spark project (original license above).
+# It contains modifications, which are licensed as follows:
+#
+
+#
+#  Copyright (2021) The Delta Lake Project Authors.
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#  http://www.apache.org/licenses/LICENSE-2.0
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+
+# When creating new tests for Spark SQL Hive, the HADOOP_CLASSPATH must contain the hive jars so
+# that we can run Hive to generate the golden answer.  This is not required for normal development
+# or testing.
+if [ -n "$HIVE_HOME" ]; then
+    for i in "$HIVE_HOME"/lib/*
+    do HADOOP_CLASSPATH="$HADOOP_CLASSPATH:$i"
+    done
+    export HADOOP_CLASSPATH
+fi
+
+realpath () {
+(
+  TARGET_FILE="$1"
+
+  cd "$(dirname "$TARGET_FILE")"
+  TARGET_FILE="$(basename "$TARGET_FILE")"
+
+  COUNT=0
+  while [ -L "$TARGET_FILE" -a $COUNT -lt 100 ]
+  do
+      TARGET_FILE="$(readlink "$TARGET_FILE")"
+      cd $(dirname "$TARGET_FILE")
+      TARGET_FILE="$(basename $TARGET_FILE)"
+      COUNT=$(($COUNT + 1))
+  done
+
+  echo "$(pwd -P)/"$TARGET_FILE""
+)
+}
+
+if [[ "$JENKINS_URL" != "" ]]; then
+  # Make Jenkins use Google Mirror first as Maven Central may ban us
+  SBT_REPOSITORIES_CONFIG="$(dirname "$(realpath "$0")")/sbt-config/repositories"
+  export SBT_OPTS="-Dsbt.override.build.repos=true -Dsbt.repository.config=$SBT_REPOSITORIES_CONFIG"
+fi
+
+. "$(dirname "$(realpath "$0")")"/sbt-launch-lib.bash
+
+
+declare -r noshare_opts="-Dsbt.global.base=project/.sbtboot -Dsbt.boot.directory=project/.boot -Dsbt.ivy.home=project/.ivy"
+declare -r sbt_opts_file=".sbtopts"
+declare -r etc_sbt_opts_file="/etc/sbt/sbtopts"
+
+usage() {
+ cat <<EOM
+Usage: $script_name [options]
+
+  -h | -help         print this message
+  -v | -verbose      this runner is chattier
+  -d | -debug        set sbt log level to debug
+  -no-colors         disable ANSI color codes
+  -sbt-create        start sbt even if current directory contains no sbt project
+  -sbt-dir   <path>  path to global settings/plugins directory (default: ~/.sbt)
+  -sbt-boot  <path>  path to shared boot directory (default: ~/.sbt/boot in 0.11 series)
+  -ivy       <path>  path to local Ivy repository (default: ~/.ivy2)
+  -mem    <integer>  set memory options (default: $sbt_mem, which is $(get_mem_opts $sbt_mem))
+  -no-share          use all local caches; no sharing
+  -no-global         uses global caches, but does not use global ~/.sbt directory.
+  -jvm-debug <port>  Turn on JVM debugging, open at the given port.
+  -batch             Disable interactive mode
+
+  # sbt version (default: from project/build.properties if present, else latest release)
+  -sbt-version  <version>   use the specified version of sbt
+  -sbt-jar      <path>      use the specified jar as the sbt launcher
+  -sbt-rc                   use an RC version of sbt
+  -sbt-snapshot             use a snapshot version of sbt
+
+  # java version (default: java from PATH, currently $(java -version 2>&1 | grep version))
+  -java-home <path>         alternate JAVA_HOME
+
+  # jvm options and output control
+  JAVA_OPTS          environment variable, if unset uses "$java_opts"
+  SBT_OPTS           environment variable, if unset uses "$default_sbt_opts"
+  .sbtopts           if this file exists in the current directory, it is
+                     prepended to the runner args
+  /etc/sbt/sbtopts   if this file exists, it is prepended to the runner args
+  -Dkey=val          pass -Dkey=val directly to the java runtime
+  -J-X               pass option -X directly to the java runtime
+                     (-J is stripped)
+  -S-X               add -X to sbt's scalacOptions (-S is stripped)
+  -PmavenProfiles    Enable a maven profile for the build.
+
+In the case of duplicated or conflicting options, the order above
+shows precedence: JAVA_OPTS lowest, command line options highest.
+EOM
+}
+
+process_my_args () {
+  while [[ $# -gt 0 ]]; do
+    case "$1" in
+     -no-colors) addJava "-Dsbt.log.noformat=true" && shift ;;
+      -no-share) addJava "$noshare_opts" && shift ;;
+     -no-global) addJava "-Dsbt.global.base=$(pwd)/project/.sbtboot" && shift ;;
+      -sbt-boot) require_arg path "$1" "$2" && addJava "-Dsbt.boot.directory=$2" && shift 2 ;;
+       -sbt-dir) require_arg path "$1" "$2" && addJava "-Dsbt.global.base=$2" && shift 2 ;;
+     -debug-inc) addJava "-Dxsbt.inc.debug=true" && shift ;;
+         -batch) exec </dev/null && shift ;;
+
+    -sbt-create) sbt_create=true && shift ;;
+
+              *) addResidual "$1" && shift ;;
+    esac
+  done
+
+  # Now, ensure sbt version is used.
+  [[ "${sbt_version}XXX" != "XXX" ]] && addJava "-Dsbt.version=$sbt_version"
+}
+
+loadConfigFile() {
+  cat "$1" | sed '/^\#/d'
+}
+
+# if sbtopts files exist, prepend their contents to $@ so it can be processed by this runner
+[[ -f "$etc_sbt_opts_file" ]] && set -- $(loadConfigFile "$etc_sbt_opts_file") "$@"
+[[ -f "$sbt_opts_file" ]] && set -- $(loadConfigFile "$sbt_opts_file") "$@"
+
+exit_status=127
+saved_stty=""
+
+restoreSttySettings() {
+  stty $saved_stty
+  saved_stty=""
+}
+
+onExit() {
+  if [[ "$saved_stty" != "" ]]; then
+    restoreSttySettings
+  fi
+  exit $exit_status
+}
+
+saveSttySettings() {
+  saved_stty=$(stty -g 2>/dev/null)
+  if [[ ! $? ]]; then
+    saved_stty=""
+  fi
+}
+
+saveSttySettings
+trap onExit INT
+
+run "$@"
+
+exit_status=$?
+onExit

kernel/build/sbt-config/repositories

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+[repositories]
+  local
+  local-preloaded-ivy: file:///${sbt.preloaded-${sbt.global.base-${user.home}/.sbt}/preloaded/}, [organization]/[module]/[revision]/[type]s/[artifact](-[classifier]).[ext]
+  local-preloaded: file:///${sbt.preloaded-${sbt.global.base-${user.home}/.sbt}/preloaded/}
+  gcs-maven-central-mirror: https://maven-central.storage-download.googleapis.com/repos/central/data/
+  maven-central
+  typesafe-ivy-releases: https://repo.typesafe.com/typesafe/ivy-releases/, [organization]/[module]/[revision]/[type]s/[artifact](-[classifier]).[ext], bootOnly
+  sbt-ivy-snapshots: https://repo.scala-sbt.org/scalasbt/ivy-snapshots/, [organization]/[module]/[revision]/[type]s/[artifact](-[classifier]).[ext], bootOnly
+  sbt-plugin-releases: https://repo.scala-sbt.org/scalasbt/sbt-plugin-releases/, [organization]/[module]/(scala_[scalaVersion]/)(sbt_[sbtVersion]/)[revision]/[type]s/[artifact](-[classifier]).[ext]
+  bintray-typesafe-sbt-plugin-releases: https://dl.bintray.com/typesafe/sbt-plugins/, [organization]/[module]/(scala_[scalaVersion]/)(sbt_[sbtVersion]/)[revision]/[type]s/[artifact](-[classifier]).[ext]
+  bintray-spark-packages: https://dl.bintray.com/spark-packages/maven/
+  typesafe-releases: https://repo.typesafe.com/typesafe/releases/