Remove snapshotAnalysis from TahoeLogFileIndex (delta-io#3722)

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#### Which Delta project/connector is this regarding?
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- [x] Spark
- [ ] Standalone
- [ ] Flink
- [ ] Kernel
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## Description
This PR fixes the OOM caused by SparkSession.cloneSession and
TemporaryView. It replaces the reference of `Snapshot` in
`TahoeLogFileIndex` using `SnapshotDescriptor`, thus remove the
reference to `SparkSession` from `TahoeLogFileIndex`.
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## How was this patch tested?
UT
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## Does this PR introduce _any_ user-facing changes?
No
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spark/src/main/scala/org/apache/spark/sql/delta/GeneratedColumn.scala

@@ -107,7 +107,7 @@ object GeneratedColumn extends DeltaLogging with AnalysisHelper {
    * - The table writer protocol >= GeneratedColumn.MIN_WRITER_VERSION;
    * - It has a generation expression in the column metadata.
    */
-  def getGeneratedColumns(snapshot: Snapshot): Seq[StructField] = {
+  def getGeneratedColumns(snapshot: SnapshotDescriptor): Seq[StructField] = {
     if (satisfyGeneratedColumnProtocol(snapshot.protocol)) {
       snapshot.metadata.schema.partition(isGeneratedColumn)._1
     } else {

spark/src/main/scala/org/apache/spark/sql/delta/PreprocessTableUpdate.scala

@@ -57,7 +57,7 @@ case class PreprocessTableUpdate(sqlConf: SQLConf)
         throw DeltaErrors.notADeltaSourceException("UPDATE", Some(o))
     }
 
-    val generatedColumns = GeneratedColumn.getGeneratedColumns(index.snapshotAtAnalysis)
+    val generatedColumns = GeneratedColumn.getGeneratedColumns(index)
     if (generatedColumns.nonEmpty && !deltaLogicalNode.isInstanceOf[LogicalRelation]) {
       // Disallow temp views referring to a Delta table that contains generated columns. When the
       // user doesn't provide expressions for generated columns, we need to create update

spark/src/main/scala/org/apache/spark/sql/delta/files/TahoeFileIndex.scala

@@ -216,6 +216,19 @@ abstract class TahoeFileIndexWithSnapshotDescriptor(
   protected[delta] def sizeInBytesIfKnown: Option[Long] = snapshot.sizeInBytesIfKnown
 }
 
+/**
+ * A lightweight [[SnapshotDescriptor]] implementation that points to an actual [[Snapshot]].
+ *
+ * @param snapshot the [[Snapshot]] this pointer points to
+ */
+class ShallowSnapshotDescriptor(snapshot: Snapshot) extends SnapshotDescriptor {
+  override val deltaLog: DeltaLog = snapshot.deltaLog
+  override val version: Long = snapshot.version
+  override val metadata: Metadata = snapshot.metadata
+  override val protocol: Protocol = snapshot.protocol
+  override protected[delta] val numOfFilesIfKnown: Option[Long] = snapshot.numOfFilesIfKnown
+  override protected[delta] val sizeInBytesIfKnown: Option[Long] = snapshot.sizeInBytesIfKnown
+}
 
 /**
  * A [[TahoeFileIndex]] that generates the list of files from DeltaLog with given partition filters.
@@ -227,10 +240,28 @@ case class TahoeLogFileIndex(
     override val spark: SparkSession,
     override val deltaLog: DeltaLog,
     override val path: Path,
+    snapshotAtAnalysis: SnapshotDescriptor,
+    partitionFilters: Seq[Expression],
+    isTimeTravelQuery: Boolean)
+  extends TahoeFileIndex(spark, deltaLog, path) {
+
+  def this(
+    spark: SparkSession,
+    deltaLog: DeltaLog,
+    path: Path,
     snapshotAtAnalysis: Snapshot,
     partitionFilters: Seq[Expression] = Nil,
-    isTimeTravelQuery: Boolean = false)
-  extends TahoeFileIndex(spark, deltaLog, path) {
+    isTimeTravelQuery: Boolean = false
+  ) = this (
+    spark,
+    deltaLog,
+    path,
+    if (isTimeTravelQuery) snapshotAtAnalysis
+    else new ShallowSnapshotDescriptor(snapshotAtAnalysis),
+    partitionFilters,
+    isTimeTravelQuery)
+
+  require(!isTimeTravelQuery || snapshotAtAnalysis.isInstanceOf[Snapshot])
 
 
   // WARNING: Stability of this method is _NOT_ guaranteed!
@@ -252,7 +283,7 @@ case class TahoeLogFileIndex(
 
   protected def getSnapshotToScan: Snapshot = {
     if (isTimeTravelQuery) {
-      snapshotAtAnalysis
+      snapshotAtAnalysis.asInstanceOf[Snapshot]
     } else {
       deltaLog.update(stalenessAcceptable = true)
     }
@@ -333,7 +364,18 @@ case class TahoeLogFileIndex(
 
 object TahoeLogFileIndex {
   def apply(spark: SparkSession, deltaLog: DeltaLog): TahoeLogFileIndex =
-    TahoeLogFileIndex(spark, deltaLog, deltaLog.dataPath, deltaLog.unsafeVolatileSnapshot)
+    new TahoeLogFileIndex(spark, deltaLog, deltaLog.dataPath, deltaLog.unsafeVolatileSnapshot)
+
+  def apply(
+    spark: SparkSession,
+    deltaLog: DeltaLog,
+    path: Path,
+    snapshotAtAnalysis: Snapshot,
+    partitionFilters: Seq[Expression] = Nil,
+    isTimeTravelQuery: Boolean = false): TahoeLogFileIndex
+  = new TahoeLogFileIndex(
+    spark, deltaLog, path, snapshotAtAnalysis, partitionFilters, isTimeTravelQuery
+  )
 }
 
 /**