From 25342b191f2a16cc2fb9882d66090a89fb1d9a0e Mon Sep 17 00:00:00 2001
From: Andrew Kryczka <andrew.kryczka2@gmail.com>
Date: Thu, 26 Sep 2019 15:27:44 -0700
Subject: [PATCH] relax L0 seqno invariant for ingested files

This is necessary to revert
https://github.com/cockroachdb/cockroach/pull/39562 to support RocksDB
built without `-DNDEBUG`. Consecutive files ingested to L0 may be
assigned the same seqnum, and this PR updates the LSM validation to
allow that.

There is a longer-term fix in
https://github.com/facebook/rocksdb/pull/5539. We should take that
later, maybe after the 19.2 release.

Test Plan: ran some tests that previously failed with corruption error
like `ENABLE_ROCKSDB_ASSERTIONS=1 make
PKG=github.com/cockroachdb/cockroach/pkg/ccl/backupccl testrace`;
verified they succeed now.
---
 db/version_builder.cc | 38 +++++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/db/version_builder.cc b/db/version_builder.cc
index 598469a8e24..3fd4742efc1 100644
--- a/db/version_builder.cc
+++ b/db/version_builder.cc
@@ -170,21 +170,29 @@ class VersionBuilder::Rep {
           if (f2->fd.smallest_seqno == f2->fd.largest_seqno) {
             // This is an external file that we ingested
             SequenceNumber external_file_seqno = f2->fd.smallest_seqno;
-            if (!(external_file_seqno < f1->fd.largest_seqno ||
-                  external_file_seqno == 0)) {
-              fprintf(stderr,
-                      "L0 file with seqno %" PRIu64 " %" PRIu64
-                      " vs. file with global_seqno %" PRIu64 "\n",
-                      f1->fd.smallest_seqno, f1->fd.largest_seqno,
-                      external_file_seqno);
-              return Status::Corruption("L0 file with seqno " +
-                                        NumberToString(f1->fd.smallest_seqno) +
-                                        " " +
-                                        NumberToString(f1->fd.largest_seqno) +
-                                        " vs. file with global_seqno" +
-                                        NumberToString(external_file_seqno) +
-                                        " with fileNumber " +
-                                        NumberToString(f1->fd.GetNumber()));
+            bool is_f1_ingested = f1->fd.smallest_seqno == f1->fd.largest_seqno;
+            if (external_file_seqno != 0) {
+              // This file's seqnos were not zeroed so we can use its seqnos to
+              // determine it is ordered properly.
+              if (f1->fd.largest_seqno < external_file_seqno ||
+                  (!is_f1_ingested &&
+                   f1->fd.largest_seqno == external_file_seqno)) {
+                // Consecutive files having equal seqnos is allowed when both
+                // files were ingested.
+                fprintf(stderr,
+                        "L0 file with seqno %" PRIu64 " %" PRIu64
+                        " vs. file with global_seqno %" PRIu64 "\n",
+                        f1->fd.smallest_seqno, f1->fd.largest_seqno,
+                        external_file_seqno);
+                return Status::Corruption("L0 file with seqno " +
+                                          NumberToString(f1->fd.smallest_seqno) +
+                                          " " +
+                                          NumberToString(f1->fd.largest_seqno) +
+                                          " vs. file with global_seqno" +
+                                          NumberToString(external_file_seqno) +
+                                          " with fileNumber " +
+                                          NumberToString(f1->fd.GetNumber()));
+              }
             }
           } else if (f1->fd.smallest_seqno <= f2->fd.smallest_seqno) {
             fprintf(stderr,