[sql] Allow storing mmap status in a VIEW instead of meta table.
Some databases do not use the sql::MetaTable to handle versioning.
The mmap verification pass uses the [meta] table to store progress for
larger databases, and it uses detection of the [meta] table to
distinguish new/empty databases from existing databases. For
non-[meta] databases, store the status in an MmapStatus view.
BUG=652359
Review-Url: https://codereview.chromium.org/2397753005
Cr-Commit-Position: refs/heads/master@{#430343}
diff --git a/sql/connection.cc b/sql/connection.cc
index 073b032..788329b 100644
--- a/sql/connection.cc
+++ b/sql/connection.cc
@@ -318,6 +318,7 @@
needs_rollback_(false),
in_memory_(false),
poisoned_(false),
+ mmap_alt_status_(false),
mmap_disabled_(false),
mmap_enabled_(false),
total_changes_at_last_release_(0),
@@ -840,6 +841,49 @@
return debug_info;
}
+bool Connection::GetMmapAltStatus(int64_t* status) {
+ // The [meta] version uses a missing table as a signal for a fresh database.
+ // That will not work for the view, which would not exist in either a new or
+ // an existing database. A new database _should_ be only one page long, so
+ // just don't bother optimizing this case (start at offset 0).
+ // TODO(shess): Could the [meta] case also get simpler, then?
+ if (!DoesViewExist("MmapStatus")) {
+ *status = 0;
+ return true;
+ }
+
+ const char* kMmapStatusSql = "SELECT * FROM MmapStatus";
+ Statement s(GetUniqueStatement(kMmapStatusSql));
+ if (s.Step())
+ *status = s.ColumnInt64(0);
+ return s.Succeeded();
+}
+
+bool Connection::SetMmapAltStatus(int64_t status) {
+ if (!BeginTransaction())
+ return false;
+
+ // View may not exist on first run.
+ if (!Execute("DROP VIEW IF EXISTS MmapStatus")) {
+ RollbackTransaction();
+ return false;
+ }
+
+ // Views live in the schema, so they cannot be parameterized. For an integer
+ // value, this construct should be safe from SQL injection, if the value
+ // becomes more complicated use "SELECT quote(?)" to generate a safe quoted
+ // value.
+ const std::string createViewSql =
+ base::StringPrintf("CREATE VIEW MmapStatus (value) AS SELECT %" PRId64,
+ status);
+ if (!Execute(createViewSql.c_str())) {
+ RollbackTransaction();
+ return false;
+ }
+
+ return CommitTransaction();
+}
+
size_t Connection::GetAppropriateMmapSize() {
AssertIOAllowed();
@@ -854,27 +898,27 @@
// percentile of Chrome databases in the wild, so this should be good.
const size_t kMmapEverything = 256 * 1024 * 1024;
- // If the database doesn't have a place to track progress, assume the best.
- // This will happen when new databases are created, or if a database doesn't
- // use a meta table. sql::MetaTable::Init() will preload kMmapSuccess.
- // TODO(shess): Databases not using meta include:
- // DOMStorageDatabase (localstorage)
- // ActivityDatabase (extensions activity log)
- // PredictorDatabase (prefetch and autocomplete predictor data)
- // SyncDirectory (sync metadata storage)
- // For now, these all have mmap disabled to allow other databases to get the
- // default-enable path. sqlite-diag could be an alternative for all but
- // DOMStorageDatabase, which creates many small databases.
- // http://crbug.com/537742
- if (!MetaTable::DoesTableExist(this)) {
- RecordOneEvent(EVENT_MMAP_META_MISSING);
- return kMmapEverything;
- }
-
+ // Progress information is tracked in the [meta] table for databases which use
+ // sql::MetaTable, otherwise it is tracked in a special view.
+ // TODO(shess): Move all cases to the view implementation.
int64_t mmap_ofs = 0;
- if (!MetaTable::GetMmapStatus(this, &mmap_ofs)) {
- RecordOneEvent(EVENT_MMAP_META_FAILURE_READ);
- return 0;
+ if (mmap_alt_status_) {
+ if (!GetMmapAltStatus(&mmap_ofs)) {
+ RecordOneEvent(EVENT_MMAP_STATUS_FAILURE_READ);
+ return 0;
+ }
+ } else {
+ // If [meta] doesn't exist, yet, it's a new database, assume the best.
+ // sql::MetaTable::Init() will preload kMmapSuccess.
+ if (!MetaTable::DoesTableExist(this)) {
+ RecordOneEvent(EVENT_MMAP_META_MISSING);
+ return kMmapEverything;
+ }
+
+ if (!MetaTable::GetMmapStatus(this, &mmap_ofs)) {
+ RecordOneEvent(EVENT_MMAP_META_FAILURE_READ);
+ return 0;
+ }
}
// Database read failed in the past, don't memory map.
@@ -949,9 +993,16 @@
event = EVENT_MMAP_FAILED_NEW;
}
- if (!MetaTable::SetMmapStatus(this, mmap_ofs)) {
- RecordOneEvent(EVENT_MMAP_META_FAILURE_UPDATE);
- return 0;
+ if (mmap_alt_status_) {
+ if (!SetMmapAltStatus(mmap_ofs)) {
+ RecordOneEvent(EVENT_MMAP_STATUS_FAILURE_UPDATE);
+ return 0;
+ }
+ } else {
+ if (!MetaTable::SetMmapStatus(this, mmap_ofs)) {
+ RecordOneEvent(EVENT_MMAP_META_FAILURE_UPDATE);
+ return 0;
+ }
}
RecordOneEvent(event);
@@ -1503,15 +1554,19 @@
return true;
}
-bool Connection::DoesTableExist(const char* table_name) const {
- return DoesTableOrIndexExist(table_name, "table");
-}
-
bool Connection::DoesIndexExist(const char* index_name) const {
- return DoesTableOrIndexExist(index_name, "index");
+ return DoesSchemaItemExist(index_name, "index");
}
-bool Connection::DoesTableOrIndexExist(
+bool Connection::DoesTableExist(const char* table_name) const {
+ return DoesSchemaItemExist(table_name, "table");
+}
+
+bool Connection::DoesViewExist(const char* view_name) const {
+ return DoesSchemaItemExist(view_name, "view");
+}
+
+bool Connection::DoesSchemaItemExist(
const char* name, const char* type) const {
const char* kSql =
"SELECT name FROM sqlite_master WHERE type=? AND name=? COLLATE NOCASE";
