sql::MetaTable.next_download_id, DownloadManager::GetNextId()

chrome/browser/history/download_database.cc

 // Copyright (c) 2011 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 "chrome/browser/history/download_database.h"
 
 #include <limits>
 #include <vector>
 
 #include "base/file_path.h"
@@ skipping 34 matching lines @@
 // See above.
 void BindFilePath(sql::Statement& statement, const FilePath& path, int col) {
   statement.BindString(col, UTF16ToUTF8(path.value()));
 }
 FilePath ColumnFilePath(sql::Statement& statement, int col) {
   return FilePath(UTF8ToUTF16(statement.ColumnString(col)));
 }
 
 #endif
 
+// Key in the meta_table containing the next id to use for a new download in
+// this profile.
+static const char kNextDownloadId[] = "next_download_id";
+
 }  // namespace
 
-DownloadDatabase::DownloadDatabase() {
+DownloadDatabase::DownloadDatabase()
+  : next_id_(0) {
 }
 
 DownloadDatabase::~DownloadDatabase() {
 }
 
 bool DownloadDatabase::InitDownloadTable() {
   if (!GetDB().DoesTableExist("downloads")) {
     if (!GetDB().Execute(
         "CREATE TABLE downloads ("
         "id INTEGER PRIMARY KEY,"
         "full_path LONGVARCHAR NOT NULL,"
         "url LONGVARCHAR NOT NULL,"
         "start_time INTEGER NOT NULL,"
         "received_bytes INTEGER NOT NULL,"
         "total_bytes INTEGER NOT NULL,"
         "state INTEGER NOT NULL)"))
       return false;
   }
+  meta_table_.Init(&GetDB(), 0, 0);
+  meta_table_.GetValue(kNextDownloadId, &next_id_);
   return true;
 }
 
 bool DownloadDatabase::DropDownloadTable() {
   return GetDB().Execute("DROP TABLE downloads");
 }
 
 void DownloadDatabase::QueryDownloads(
     std::vector<DownloadHistoryInfo>* results) {
   results->clear();
@@ skipping 67 matching lines @@
   if (!statement)
     return 0;
 
   BindFilePath(statement, info.path, 0);
   statement.BindString(1, info.url.spec());
   statement.BindInt64(2, info.start_time.ToTimeT());
   statement.BindInt64(3, info.received_bytes);
   statement.BindInt64(4, info.total_bytes);
   statement.BindInt(5, info.state);
 
-  if (statement.Run())
-    return GetDB().GetLastInsertRowId();
+  if (statement.Run()) {
+    int64 db_handle = GetDB().GetLastInsertRowId();
+    // TODO(benjhayden) if(info.id>next_id_){setvalue;next_id_=info.id;}
+    meta_table_.SetValue(kNextDownloadId, ++next_id_);

[Randy Smith (Not in Mondays), 2011/07/25 20:20:12]

Is there a reason why it's safe not to implement the TODO?  The current behavior
looks like an obvious, dangerous race which the TODO is needed to fix.

[benjhayden, 2011/07/27 19:40:54]

This next_id_ is only communicated to DownloadManager once, and is not used to
allocate ids.
The todo cannot be implemented until id is added to DownloadHistoryInfo.

[Randy Smith (Not in Mondays), 2011/07/28 21:03:16]

Sorry, still having problems distinguishing non-persistent and persistent ids in
my head.  I think this is ok, since we're not actually storing anything in the
next_id_ namespace on a per-entry basis in the database.

[benjhayden, 2011/08/03 17:44:46]

Done.

+    return db_handle;
+  }
   return 0;
 }
 
 void DownloadDatabase::RemoveDownload(DownloadID db_handle) {
   sql::Statement statement(GetDB().GetCachedStatement(SQL_FROM_HERE,
       "DELETE FROM downloads WHERE id=?"));
   if (!statement)
     return;
 
   statement.BindInt64(0, db_handle);
@@ skipping 16 matching lines @@
   statement.BindInt64(
       1,
       end_time ? end_time : std::numeric_limits<int64>::max());
   statement.BindInt(2, DownloadItem::COMPLETE);
   statement.BindInt(3, DownloadItem::CANCELLED);
   statement.BindInt(4, DownloadItem::INTERRUPTED);
   statement.Run();
 }
 
 }  // namespace history