Use orphaned docs as part of GC calculation (#80)

* Use orphaned documents in sequence number calculation

Author: Greg Soltis

firebase-firestore/src/main/java/com/google/firebase/firestore/local/LruDelegate.java

@@ -26,7 +26,7 @@ public interface LruDelegate {
   /** Enumerates all the targets in the QueryCache. */
   void forEachTarget(Consumer<QueryData> consumer);
 
-  long getTargetCount();
+  long getSequenceNumberCount();
 
   /** Enumerates sequence numbers for documents not associated with a target. */
   void forEachOrphanedDocumentSequenceNumber(Consumer<Long> consumer);

firebase-firestore/src/main/java/com/google/firebase/firestore/local/LruGarbageCollector.java

@@ -109,7 +109,7 @@ public int getDocumentsRemoved() {
 
   /** Given a percentile of target to collect, returns the number of targets to collect. */
   int calculateQueryCount(int percentile) {
-    long targetCount = delegate.getTargetCount();
+    long targetCount = delegate.getSequenceNumberCount();
     return (int) ((percentile / 100.0f) * targetCount);
   }
 
@@ -216,15 +216,13 @@ private Results runGarbageCollection(SparseArray<?> liveTargetIds) {
     int numDocumentsRemoved = removeOrphanedDocuments(upperBound);
     long removedDocumentsTs = System.currentTimeMillis();
 
-    // TODO(gsoltis): post-compaction?
-
     if (Logger.isDebugEnabled()) {
       String desc = "LRU Garbage Collection:\n";
       desc += "\tCounted targets in " + (countedTargetsTs - startTs) + "ms\n";
       desc +=
           String.format(
               Locale.ROOT,
-              "\tDetermined least recently used %d sequence numbers in %dms",
+              "\tDetermined least recently used %d sequence numbers in %dms\n",
               sequenceNumbers,
               (foundUpperBoundTs - countedTargetsTs));
       desc +=

firebase-firestore/src/main/java/com/google/firebase/firestore/local/MemoryLruReferenceDelegate.java

@@ -82,8 +82,14 @@ public void forEachTarget(Consumer<QueryData> consumer) {
   }
 
   @Override
-  public long getTargetCount() {
-    return persistence.getQueryCache().getTargetCount();
+  public long getSequenceNumberCount() {
+    long targetCount = persistence.getQueryCache().getTargetCount();
+    long orphanedCount[] = new long[1];
+    forEachOrphanedDocumentSequenceNumber(
+        sequenceNumber -> {
+          orphanedCount[0]++;
+        });
+    return targetCount + orphanedCount[0];
   }
 
   @Override

firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLiteLruReferenceDelegate.java

@@ -70,8 +70,14 @@ public LruGarbageCollector getGarbageCollector() {
   }
 
   @Override
-  public long getTargetCount() {
-    return persistence.getQueryCache().getTargetCount();
+  public long getSequenceNumberCount() {
+    long targetCount = persistence.getQueryCache().getTargetCount();
+    long orphanedDocumentCount =
+        persistence
+            .query(
+                "SELECT COUNT(*) FROM (SELECT sequence_number FROM target_documents GROUP BY path HAVING COUNT(*) = 1 AND target_id = 0)")
+            .firstValue(row -> row.getLong(0));
+    return targetCount + orphanedDocumentCount;
   }
 
   @Override