[sql] Remove misleading AutoRecoverTable() parameter.

sql/recovery.cc

 // Copyright 2013 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.
 
 #include "sql/recovery.h"
 
 #include <stddef.h>
 
 #include "base/files/file_path.h"
 #include "base/format_macros.h"
@@ skipping 331 matching lines @@
   recover_db_.Close();
   if (raze == RAZE_AND_POISON) {
     db_->RazeAndClose();
   } else if (raze == POISON) {
     db_->Poison();
   }
   db_ = NULL;
 }
 
 bool Recovery::AutoRecoverTable(const char* table_name,
-                                size_t extend_columns,
                                 size_t* rows_recovered) {
   // Query the info for the recovered table in database [main].
   std::string query(
       base::StringPrintf("PRAGMA main.table_info(%s)", table_name));
   Statement s(db()->GetUniqueStatement(query.c_str()));
 
   // The columns of the recover virtual table.
   std::vector<std::string> create_column_decls;
 
   // The columns to select from the recover virtual table when copying
@@ skipping 89 matching lines @@
   // Receiving no column information implies that the table doesn't exist.
   if (create_column_decls.empty()) {
     RecordRecoveryEvent(RECOVERY_FAILED_AUTORECOVER_MISSING_TABLE);
     return false;
   }
 
   // If the PRIMARY KEY was a single INTEGER column, convert it to ROWID.
   if (pk_column_count == 1 && !rowid_decl.empty())
     create_column_decls[rowid_ofs] = rowid_decl;
 
-  // Additional columns accept anything.
-  // TODO(shess): ignoreN isn't well namespaced.  But it will fail to
-  // execute in case of conflicts.
-  for (size_t i = 0; i < extend_columns; ++i) {
-    create_column_decls.push_back(
-        base::StringPrintf("ignore%" PRIuS " ANY", i));
-  }

[Scott Hess - ex-Googler, 2016/02/03 20:36:18]

Summary of "why": Recovery works by defining a virtual table over the data of a
real table.  That virtual table allows the regular SQLite case of "row has fewer
columns than expected, return NULL for extras", but if there are more columns
than requested it assumes the row is corrupt.  This code was meant to handle the
fewer-columns-than-requested case, but actually handles the
more-columns-than-requested case.  So it is unnecessary.

[Ryan Hamilton, 2016/02/04 01:36:34]

Cute!

[Scott Hess - ex-Googler, 2016/02/04 18:39:59]

I was prototyping an alternative recovery method which didn't use the virtual
table, and found that in that case I _did_ have to actually implement this, and
that my test which tested that implementation broke this implementation.  It was
embarrassing.

-
   std::string recover_create(base::StringPrintf(
       "CREATE VIRTUAL TABLE temp.recover_%s USING recover(corrupt.%s, %s)",
       table_name,
       table_name,
       base::JoinString(create_column_decls, ",").c_str()));
 
   std::string recover_insert(base::StringPrintf(
       "INSERT OR REPLACE INTO main.%s SELECT %s FROM temp.recover_%s",
       table_name,
       base::JoinString(insert_columns, ",").c_str(),
@@ skipping 57 matching lines @@
     }
     return false;
   }
 
   RecordRecoveryEvent(RECOVERY_SUCCESS_META_VERSION);
   *version = recovery_version.ColumnInt(0);
   return true;
 }
 
 }  // namespace sql