Make sql::Connection::Raze() more robust against corruptions.

sql/connection.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SQL_CONNECTION_H_
 #define SQL_CONNECTION_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 177 matching lines @@
   // process.  RazeWithTimeout() may be used if appropriate.
   //
   // NOTE(shess): Raze() will DCHECK in the following situations:
   // - database is not open.
   // - the connection has a transaction open.
   // - a SQLite issue occurs which is structural in nature (like the
   //   statements used are broken).
   // Since Raze() is expected to be called in unexpected situations,
   // these all return false, since it is unlikely that the caller
   // could fix them.
+  //
+  // The database's page size is taken from |page_size_|.  The
+  // existing database's |auto_vacuum| setting is lost (the
+  // possibility of corruption makes it unreliable to pull it from the
+  // existing database).  To re-enable on the empty database requires
+  // running "PRAGMA auto_vacuum = 1;" then "VACUUM".
+  //
+  // NOTE(shess): For Android, SQLITE_DEFAULT_AUTOVACUUM is set to 1,
+  // so Raze() sets auto_vacuum to 1.
+  //
+  // TODO(shess): Raze() needs a connection so cannot clear SQLITE_NOTADB.
+  // TODO(shess): Bake auto_vacuum into Connection's API so it can
+  // just pick up the default.
   bool Raze();
   bool RazeWithTimout(base::TimeDelta timeout);
 
   // Transactions --------------------------------------------------------------
 
   // Transaction management. We maintain a virtual transaction stack to emulate
   // nested transactions since sqlite can't do nested transactions. The
   // limitation is you can't roll back a sub transaction: if any transaction
   // fails, all transactions open will also be rolled back. Any nested
   // transactions after one has rolled back will return fail for Begin(). If
@@ skipping 235 matching lines @@
   // This object handles errors resulting from all forms of executing sqlite
   // commands or statements. It can be null which means default handling.
   scoped_ptr<ErrorDelegate> error_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(Connection);
 };
 
 }  // namespace sql
 
 #endif  // SQL_CONNECTION_H_