Refactor MetaTableHelper to remove redundant table name prefixing with database

name. Also, PrimeCache logic duplicated in HistoryBackend and
SQLitePersistentCookieStore is moved to this class.

BUG=none
TEST=n/a

Review URL: http://codereview.chromium.org/150094

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@19802 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 74 insertions, 17 deletions

diff --git a/chrome/browser/meta_table_helper.cc b/chrome/browser/meta_table_helper.cc
index 6667197..5ce6aea 100644
--- a/chrome/browser/meta_table_helper.cc
+++ b/chrome/browser/meta_table_helper.cc
@@ -12,6 +12,24 @@
 static const char kVersionKey[] = "version";
 static const char kCompatibleVersionKey[] = "last_compatible_version";
 
+// static
+void MetaTableHelper::PrimeCache(const std::string& db_name, sqlite3* db) {
+  // A statement must be open for the preload command to work. If the meta
+  // table doesn't exist, it probably means this is a new database and there
+  // is nothing to preload (so it's OK we do nothing).
+  SQLStatement dummy;
+  if (!DoesSqliteTableExist(db, db_name.c_str(), "meta"))
+    return;
+  std::string sql("SELECT * from ");
+  appendMetaTableName(db_name, &sql);
+  if (dummy.prepare(db, sql.c_str()) != SQLITE_OK)
+    return;
+  if (dummy.step() != SQLITE_ROW)
+    return;
+
+  sqlite3Preload(db);
+}
+
 MetaTableHelper::MetaTableHelper() : db_(NULL) {
 }
 
@@ -28,13 +46,9 @@ bool MetaTableHelper::Init(const std::string& db_name,
   if (!DoesSqliteTableExist(db_, db_name.c_str(), "meta")) {
     // Build the sql.
     std::string sql("CREATE TABLE ");
-    if (!db_name.empty()) {
-      // Want a table name of the form db_name.meta
-      sql.append(db_name);
-      sql.push_back('.');
-    }
-    sql.append("meta(key LONGVARCHAR NOT NULL UNIQUE PRIMARY KEY,"
-                    "value LONGVARCHAR)");
+    appendMetaTableName(db_name, &sql);
+    sql.append("(key LONGVARCHAR NOT NULL UNIQUE PRIMARY KEY,"
+               "value LONGVARCHAR)");
 
     if (sqlite3_exec(db_, sql.c_str(), NULL, NULL, NULL) != SQLITE_OK)
       return false;
@@ -130,15 +144,22 @@ int MetaTableHelper::GetCompatibleVersionNumber() {
   return version;
 }
 
+// static
+void MetaTableHelper::appendMetaTableName(const std::string& db_name,
+                                          std::string* sql) {
+  if (!db_name.empty()) {
+    sql->append(db_name);
+    sql->push_back('.');
+  }
+  sql->append("meta");
+}
+
 bool MetaTableHelper::PrepareSetStatement(SQLStatement* statement,
                                           const std::string& key) {
   DCHECK(db_ && statement);
   std::string sql("INSERT OR REPLACE INTO ");
-  if (db_name_.size() > 0) {
-    sql.append(db_name_);
-    sql.push_back('.');
-  }
-  sql.append("meta(key,value) VALUES(?,?)");
+  appendMetaTableName(db_name_, &sql);
+  sql.append("(key,value) VALUES(?,?)");
   if (statement->prepare(db_, sql.c_str()) != SQLITE_OK) {
     NOTREACHED() << sqlite3_errmsg(db_);
     return false;
@@ -151,11 +172,8 @@ bool MetaTableHelper::PrepareGetStatement(SQLStatement* statement,
                                           const std::string& key) {
   DCHECK(db_ && statement);
   std::string sql("SELECT value FROM ");
-  if (db_name_.size() > 0) {
-    sql.append(db_name_);
-    sql.push_back('.');
-  }
-  sql.append("meta WHERE key = ?");
+  appendMetaTableName(db_name_, &sql);
+  sql.append(" WHERE key = ?");
   if (statement->prepare(db_, sql.c_str()) != SQLITE_OK) {
     NOTREACHED() << sqlite3_errmsg(db_);
     return false;
diff --git a/chrome/browser/meta_table_helper.h b/chrome/browser/meta_table_helper.h
index 027ea5d..a55f136 100644
--- a/chrome/browser/meta_table_helper.h
+++ b/chrome/browser/meta_table_helper.h
@@ -20,6 +20,12 @@ class SQLStatement;
 // database to use.
 class MetaTableHelper {
  public:
+  // Primes the sqlite cache by filling it with the file in sequence
+  // until there is no more data or the cache is full. Since this is one
+  // contiguous read operation, it is much faster than letting the pages come
+  // in on-demand (which causes lots of seeks).
+  static void PrimeCache(const std::string& db_name, sqlite3* db);
+
   // Creates a new MetaTableHelper. After construction you must invoke
   // Init with the appropriate database.
   MetaTableHelper();
@@ -69,6 +75,11 @@ class MetaTableHelper {
   bool GetValue(const std::string& key, int64* value);
 
  private:
+  friend class MetaTableHelperTest;
+
+  // Appends the meta table name to the SQL statement.
+  static void appendMetaTableName(const std::string& db_name, std::string* sql);
+
   // Conveniences to prepare the two types of statements used by
   // MetaTableHelper.
   bool PrepareSetStatement(SQLStatement* statement, const std::string& key);
diff --git a/chrome/browser/meta_table_helper_unittest.cc b/chrome/browser/meta_table_helper_unittest.cc
new file mode 100644
index 0000000..0d8ae5b
--- /dev/null
+++ b/chrome/browser/meta_table_helper_unittest.cc
@@ -0,0 +1,28 @@
+// Copyright (c) 2009 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.
+
+// Tests for MetaTableHelper.
+
+#include "chrome/browser/meta_table_helper.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+class MetaTableHelperTest : public testing::Test {
+ public:
+  static void appendMetaTableName(const std::string& db_name,
+                                  std::string* sql) {
+    MetaTableHelper::appendMetaTableName(db_name, sql);
+  }
+};
+
+TEST_F(MetaTableHelperTest, EmptyDbName) {
+  std::string sql("select * from ");
+  MetaTableHelperTest::appendMetaTableName(std::string(), &sql);
+  EXPECT_EQ("select * from meta", sql);
+}
+
+TEST_F(MetaTableHelperTest, NonEmptyDbName) {
+  std::string sql("select * from ");
+  MetaTableHelperTest::appendMetaTableName(std::string("mydb"), &sql);
+  EXPECT_EQ("select * from mydb.meta", sql);
+}