[sql] Track SQLite error codes from sql::Recovery ATTACH.

The major reason for sql::Recover::Begin() to fail is in the statement
attaching the original database to the recovery database.  I believe
this is because of SQLITE_NOTADB.  This is to verify that hypothesis.
If the hypothesis is true, then the best course of action is to Raze()
the database, as SQLITE_NOTADB means that some or all of the SQLite
header data appears to be garbage.

BUG=597785
R=michaeln@chromium.org

Review-Url: https://codereview.chromium.org/2274883003
Cr-Commit-Position: refs/heads/master@{#414885}

sql/recovery.cc

@@ -240,6 +240,8 @@ bool Recovery::Init(const base::FilePath& db_path) {
 
   if (!recover_db_.AttachDatabase(db_path, "corrupt")) {
     RecordRecoveryEvent(RECOVERY_FAILED_ATTACH);
+    UMA_HISTOGRAM_SPARSE_SLOWLY("Sqlite.RecoveryAttachError",
+                                recover_db_.GetErrorCode());
     return false;
   }
 

sql/recovery_unittest.cc

@@ -16,6 +16,7 @@
 #include "base/files/scoped_temp_dir.h"
 #include "base/path_service.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/test/histogram_tester.h"
 #include "sql/connection.h"
 #include "sql/meta_table.h"
 #include "sql/statement.h"
@@ -832,4 +833,38 @@ TEST_F(SQLRecoveryTest, RecoverDatabase) {
   EXPECT_EQ("trailer", ExecuteWithResults(&db(), kVSql, "|", "\n"));
 }
 
+// Test histograms recorded when the invalid database cannot be attached.
+TEST_F(SQLRecoveryTest, AttachFailure) {
+  // Create a valid database, then write junk over the header.  This should lead
+  // to SQLITE_NOTADB, which will cause ATTACH to fail.
+  ASSERT_TRUE(db().Execute("CREATE TABLE x (t TEXT)"));
+  ASSERT_TRUE(db().Execute("INSERT INTO x VALUES ('This is a test')"));
+  db().Close();
+  WriteJunkToDatabase(SQLTestBase::TYPE_OVERWRITE);
+
+  const char kEventHistogramName[] = "Sqlite.RecoveryEvents";
+  const int kEventEnum = 5;  // RECOVERY_FAILED_ATTACH
+  const char kErrorHistogramName[] = "Sqlite.RecoveryAttachError";
+  base::HistogramTester tester;
+
+  {
+    sql::test::ScopedErrorExpecter expecter;
+    expecter.ExpectError(SQLITE_NOTADB);
+
+    // Reopen() here because it will see SQLITE_NOTADB.
+    ASSERT_TRUE(Reopen());
+
+    // Begin() should fail.
+    std::unique_ptr<sql::Recovery>
+        recovery = sql::Recovery::Begin(&db(), db_path());
+    ASSERT_FALSE(recovery.get());
+
+    ASSERT_TRUE(expecter.SawExpectedErrors());
+  }
+
+  // Verify that the failure was in the right place with the expected code.
+  tester.ExpectBucketCount(kEventHistogramName, kEventEnum, 1);
+  tester.ExpectBucketCount(kErrorHistogramName, SQLITE_NOTADB, 1);
+}
+
 }  // namespace

tools/metrics/histograms/histograms.xml

@@ -57060,6 +57060,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Errors truncating database for Raze().</summary>
 </histogram>
 
+<histogram name="Sqlite.RecoveryAttachError" enum="SqliteErrorCode">
+  <owner>shess@chromium.org</owner>
+  <summary>
+    SQLite error code from failed ATTACH in sql::Recovery::Init().
+  </summary>
+</histogram>
+
 <histogram name="Sqlite.RecoveryEvents" enum="SqliteRecoveryEventEnum">
   <owner>shess@chromium.org</owner>
   <summary>