Remove support for old translog checkpoint formats

server/src/main/java/org/elasticsearch/index/translog/Checkpoint.java

@@ -47,8 +47,6 @@ final class Checkpoint {
     final long minTranslogGeneration;
     final long trimmedAboveSeqNo;
 
-    private static final int INITIAL_VERSION = 1; // start with 1, just to recognize there was some magic serialization logic before
-    private static final int VERSION_6_0_0 = 2; // introduction of global checkpoints
     private static final int CURRENT_VERSION = 3; // introduction of trimmed above seq#
 
     private static final String CHECKPOINT_CODEC = "ckp";
@@ -66,24 +64,6 @@ final class Checkpoint {
         + Long.BYTES // maximum reachable (trimmed) sequence number, introduced in 6.4.0
         + CodecUtil.footerLength();
 
-    // size of 6.0.0 checkpoint
-    static final int V2_FILE_SIZE = CodecUtil.headerLength(CHECKPOINT_CODEC)
-        + Integer.BYTES  // ops
-        + Long.BYTES // offset
-        + Long.BYTES // generation
-        + Long.BYTES // minimum sequence number, introduced in 6.0.0
-        + Long.BYTES // maximum sequence number, introduced in 6.0.0
-        + Long.BYTES // global checkpoint, introduced in 6.0.0
-        + Long.BYTES // minimum translog generation in the translog - introduced in 6.0.0
-        + CodecUtil.footerLength();
-
-    // size of 5.0.0 checkpoint
-    static final int V1_FILE_SIZE = CodecUtil.headerLength(CHECKPOINT_CODEC)
-        + Integer.BYTES  // ops
-        + Long.BYTES // offset
-        + Long.BYTES // generation
-        + CodecUtil.footerLength();
-
     /**
      * Create a new translog checkpoint.
      *
@@ -144,31 +124,6 @@ static Checkpoint readCheckpointV6_4_0(final DataInput in) throws IOException {
         return new Checkpoint(offset, numOps, generation, minSeqNo, maxSeqNo, globalCheckpoint, minTranslogGeneration, trimmedAboveSeqNo);
     }
 
-    static Checkpoint readCheckpointV6_0_0(final DataInput in) throws IOException {
-        final long offset = in.readLong();
-        final int numOps = in.readInt();
-        final long generation = in.readLong();
-        final long minSeqNo = in.readLong();
-        final long maxSeqNo = in.readLong();
-        final long globalCheckpoint = in.readLong();
-        final long minTranslogGeneration = in.readLong();
-        final long trimmedAboveSeqNo = SequenceNumbers.UNASSIGNED_SEQ_NO;
-        return new Checkpoint(offset, numOps, generation, minSeqNo, maxSeqNo, globalCheckpoint, minTranslogGeneration, trimmedAboveSeqNo);
-    }
-
-    // reads a checksummed checkpoint introduced in ES 5.0.0
-    static Checkpoint readCheckpointV5_0_0(final DataInput in) throws IOException {
-        final long offset = in.readLong();
-        final int numOps = in.readInt();
-        final long generation = in.readLong();
-        final long minSeqNo = SequenceNumbers.NO_OPS_PERFORMED;
-        final long maxSeqNo = SequenceNumbers.NO_OPS_PERFORMED;
-        final long globalCheckpoint = SequenceNumbers.UNASSIGNED_SEQ_NO;
-        final long minTranslogGeneration = -1;
-        final long trimmedAboveSeqNo = SequenceNumbers.UNASSIGNED_SEQ_NO;
-        return new Checkpoint(offset, numOps, generation, minSeqNo, maxSeqNo, globalCheckpoint, minTranslogGeneration, trimmedAboveSeqNo);
-    }
-
     @Override
     public String toString() {
         return "Checkpoint{" +
@@ -188,18 +143,10 @@ public static Checkpoint read(Path path) throws IOException {
             try (IndexInput indexInput = dir.openInput(path.getFileName().toString(), IOContext.DEFAULT)) {
                 // We checksum the entire file before we even go and parse it. If it's corrupted we barf right here.
                 CodecUtil.checksumEntireFile(indexInput);
-                final int fileVersion = CodecUtil.checkHeader(indexInput, CHECKPOINT_CODEC, INITIAL_VERSION, CURRENT_VERSION);
-                if (fileVersion == INITIAL_VERSION) {
-                    assert indexInput.length() == V1_FILE_SIZE : indexInput.length();
-                    return Checkpoint.readCheckpointV5_0_0(indexInput);
-                } else if (fileVersion == VERSION_6_0_0) {
-                    assert indexInput.length() == V2_FILE_SIZE : indexInput.length();
-                    return Checkpoint.readCheckpointV6_0_0(indexInput);
-                } else {
-                    assert fileVersion == CURRENT_VERSION : fileVersion;
-                    assert indexInput.length() == V3_FILE_SIZE : indexInput.length();
-                    return Checkpoint.readCheckpointV6_4_0(indexInput);
-                }
+                final int fileVersion = CodecUtil.checkHeader(indexInput, CHECKPOINT_CODEC, CURRENT_VERSION, CURRENT_VERSION);
+                assert fileVersion == CURRENT_VERSION : fileVersion;
+                assert indexInput.length() == V3_FILE_SIZE : indexInput.length();
+                return Checkpoint.readCheckpointV6_4_0(indexInput);
             }
         }
     }