Info messages for exorciseIndex() take into account segments with mis…

…sing segment info

lucene/core/src/java/org/apache/lucene/index/CheckIndex.java

@@ -152,6 +152,9 @@ public static class Status {
     /** How many bad segments were found. */
     public int numBadSegments;
 
+    /** How many segments with missing segment info. */
+    public int numBadSegmentsWithoutSegmentInfo;
+
     /**
      * True if we checked only specific segments ({@link #checkIndex(List)}) was called with
      * non-null argument).
@@ -664,7 +667,7 @@ public int compare(String a, String b) {
     // failure (fastFail == false).  so if we get here, we should // always have a valid lastCommit:
     assert lastCommit != null;
 
-    if (lastCommit == null) {
+    if (lastCommit == null) { // TODO: Remove/move unreachable if statement?
       msg(infoStream, "ERROR: could not read any segments file in directory");
       result.missingSegments = true;
       return result;
@@ -873,13 +876,26 @@ public int compare(String a, String b) {
     if (0 == result.numBadSegments) {
       result.clean = true;
     } else {
-      msg(
-          infoStream,
-          "WARNING: "
-              + result.numBadSegments
-              + " broken segments (containing "
-              + result.totLoseDocCount
-              + " documents) detected");
+      if (result.numBadSegmentsWithoutSegmentInfo > 0) {
+        msg(
+            infoStream,
+            "WARNING: "
+                + result.numBadSegments
+                + " broken segments (containing "
+                + result.totLoseDocCount
+                + " or more documents) detected;"
+                + " cannot precisely estimate number of documents lost because "
+                + result.numBadSegmentsWithoutSegmentInfo
+                + " segments had missing info");
+      } else {
+        msg(
+            infoStream,
+            "WARNING: "
+                + result.numBadSegments
+                + " broken segments (containing "
+                + result.totLoseDocCount
+                + " documents) detected");
+      }
     }
 
     result.validCounter = result.maxSegmentName < lastCommit.counter;
@@ -918,6 +934,7 @@ private void processSegmentInfoStatusResult(
     if (segmentInfoStatus.error != null) {
       result.totLoseDocCount += segmentInfoStatus.toLoseDocCount;
       result.numBadSegments++;
+      result.numBadSegmentsWithoutSegmentInfo++;
     } else {
       // Keeper
       result.newSegments.add(info.clone());
@@ -948,7 +965,7 @@ private Status.SegmentInfoStatus testSegment(
     segInfoStat.maxDoc = info.info.maxDoc();
 
     final Version version = info.info.getVersion();
-    if (info.info.maxDoc() <= 0) {
+    if (info.info.maxDoc() < 0) {
       throw new CheckIndexException(" illegal number of documents: maxDoc=" + info.info.maxDoc());
     }
 
@@ -957,6 +974,9 @@ private Status.SegmentInfoStatus testSegment(
     SegmentReader reader = null;
 
     try {
+      if (info.info.maxDoc() == 0) {
+        throw new CheckIndexException(" this segment has missing or corrupt segment info");
+      }
       msg(infoStream, "    version=" + (version == null ? "3.0" : version));
       msg(infoStream, "    id=" + StringHelper.idToString(info.info.getId()));
       final Codec codec = info.info.getCodec();
@@ -4270,11 +4290,21 @@ public int doCheck(Options opts) throws IOException, InterruptedException {
                 + result.totLoseDocCount
                 + " documents would be lost, if -exorcise were specified\n");
       } else {
-        opts.out.println("WARNING: " + result.totLoseDocCount + " documents will be lost\n");
-        opts.out.println(
-            "NOTE: will write new segments file in 5 seconds; this will remove "
-                + result.totLoseDocCount
-                + " docs from the index. YOU WILL LOSE DATA. THIS IS YOUR LAST CHANCE TO CTRL+C!");
+        if (result.numBadSegmentsWithoutSegmentInfo > 0) {
+          opts.out.println(
+              "WARNING: " + result.totLoseDocCount + " or more documents will be lost\n");
+          opts.out.println(
+              "NOTE: will write new segments file in 5 seconds; this will remove "
+                  + result.totLoseDocCount
+                  + " or more docs from the index. YOU WILL LOSE DATA. THIS IS YOUR LAST CHANCE TO CTRL+C!");
+        } else {
+          opts.out.println("WARNING: " + result.totLoseDocCount + " documents will be lost\n");
+          opts.out.println(
+              "NOTE: will write new segments file in 5 seconds; this will remove "
+                  + result.totLoseDocCount
+                  + " docs from the index. YOU WILL LOSE DATA. THIS IS YOUR LAST CHANCE TO CTRL+C!");
+        }
+
         for (int s = 0; s < 5; s++) {
           Thread.sleep(1000);
           opts.out.println("  " + (5 - s) + "...");