[sql] Disable memory-mapping under sql::Recovery.

sql/connection.cc

Index: sql/connection.cc
diff --git a/sql/connection.cc b/sql/connection.cc
index a904632eb517e066596855ab980fe3ce8a80aff3..79264916c0274c3cda466ccee94750b35e3f798d 100644
--- a/sql/connection.cc
+++ b/sql/connection.cc
@@ -1628,18 +1628,6 @@ bool Connection::OpenInternal(const std::string& file_name,
   // secure_delete.
   ignore_result(Execute("PRAGMA journal_mode = TRUNCATE"));
 
-  // Enable memory-mapped access.  This value will be capped by
-  // SQLITE_MAX_MMAP_SIZE, which could be different between 32-bit and 64-bit
-  // platforms.
-  mmap_enabled_ = false;
-  if (!mmap_disabled_)
-    ignore_result(Execute("PRAGMA mmap_size = 268435456"));  // 256MB.
-  {
-    Statement s(GetUniqueStatement("PRAGMA mmap_size"));
-    if (s.Step() && s.ColumnInt64(0) > 0)
-      mmap_enabled_ = true;
-  }
-
   const base::TimeDelta kBusyTimeout =
     base::TimeDelta::FromSeconds(kBusyTimeoutSeconds);
 
@@ -1668,6 +1656,25 @@ bool Connection::OpenInternal(const std::string& file_name,
     return false;
   }
 
+  // Enable memory-mapped access.  The explicit-disable case is because SQLite
+  // can be built to default-enable mmap.  This value will be capped by
+  // SQLITE_MAX_MMAP_SIZE, which could be different between 32-bit and 64-bit
+  // platforms.
+  if (mmap_disabled_) {
+    ignore_result(Execute("PRAGMA mmap_size = 0"));
+  } else {
+    ignore_result(Execute("PRAGMA mmap_size = 268435456"));  // 256MB.
+  }
+
+  // Determine if memory-mapping has actually been enabled.  The Execute() above
+  // can succeed without changing the amount mapped.
+  mmap_enabled_ = false;
+  {
+    Statement s(GetUniqueStatement("PRAGMA mmap_size"));
+    if (s.Step() && s.ColumnInt64(0) > 0)
+      mmap_enabled_ = true;
+  }
+

[Scott Hess - ex-Googler, 2015/11/04 23:36:42]

Hmm, and I moved the stanza down here because it seemed like the thing most
sensitive to database problems should come as late as possible to give other
statements a chance to flush out problems.

   return true;
 }