Changed DB to store node positions as Ordinals.

sync/syncable/directory_backing_store.cc

Index: sync/syncable/directory_backing_store.cc
diff --git a/sync/syncable/directory_backing_store.cc b/sync/syncable/directory_backing_store.cc
index 9b8e0dba855edc22128e0cb4aab84d96ec485da5..c1e8254a90ebe42aaaa5742cb5356001a6ec20b6 100644
--- a/sync/syncable/directory_backing_store.cc
+++ b/sync/syncable/directory_backing_store.cc
@@ -27,6 +27,8 @@
 #include "sync/syncable/syncable-inl.h"
 #include "sync/syncable/syncable_columns.h"
 #include "sync/util/time.h"
+#include "sync/internal_api/public/base/ordinal.h"
+#include "sync/internal_api/public/base/node_ordinal.h"
 
 using std::string;
 
@@ -39,7 +41,7 @@ static const string::size_type kUpdateStatementBufferSize = 2048;
 
 // Increment this version whenever updating DB tables.
 extern const int32 kCurrentDBVersion;  // Global visibility for our unittest.
-const int32 kCurrentDBVersion = 80;
+const int32 kCurrentDBVersion = 81;
 
 // Iterate over the fields of |entry| and bind each to |statement| for
 // updating.  Returns the number of args bound.
@@ -48,6 +50,14 @@ void BindFields(const EntryKernel& entry,
   int index = 0;
   int i = 0;
   for (i = BEGIN_FIELDS; i < INT64_FIELDS_END; ++i) {
+    // Store SERVER_POSITION_IN_PARENT as a string for eventual shift
+    // to using ordinals instead of int64's
+    if(i == SERVER_POSITION_IN_PARENT) {
+      NodeOrdinal ordinal = Int64ToNodeOrdinal(
+          entry.ref(SERVER_POSITION_IN_PARENT));
+      statement->BindString(index++, ordinal.ToInternalValue());
+      continue;
+    }
     statement->BindInt64(index++, entry.ref(static_cast<Int64Field>(i)));
   }
   for ( ; i < TIME_FIELDS_END; ++i) {
@@ -78,6 +88,14 @@ EntryKernel* UnpackEntry(sql::Statement* statement) {
   DCHECK_EQ(statement->ColumnCount(), static_cast<int>(FIELD_COUNT));
   int i = 0;
   for (i = BEGIN_FIELDS; i < INT64_FIELDS_END; ++i) {
+    // Store SERVER_POSITION_IN_PARENT as a string for eventual shift
+    // to using ordinals instead of int64's
+    if(i == SERVER_POSITION_IN_PARENT) {
+      int64 server_position = NodeOrdinalToInt64(
+          NodeOrdinal(statement->ColumnString(i)));
+      kernel->put(static_cast<Int64Field>(i), server_position);
+      continue;
+    }
     kernel->put(static_cast<Int64Field>(i), statement->ColumnInt64(i));
   }
   for ( ; i < TIME_FIELDS_END; ++i) {
@@ -323,6 +341,13 @@ bool DirectoryBackingStore::InitializeTables() {
       version_on_disk = 80;
   }
 
+  // Version 81 changes the server_position_in_parent_field from an int64
+  // to a string.
+  if (version_on_disk == 80) {
+    if (MigrateVersion80To81())
+      version_on_disk = 81;
+  }
+
   // If one of the migrations requested it, drop columns that aren't current.
   // It's only safe to do this after migrating all the way to the current
   // version.
@@ -968,6 +993,7 @@ bool DirectoryBackingStore::MigrateVersion78To79() {
   SetVersion(79);
   return true;
 }
+
 bool DirectoryBackingStore::MigrateVersion79To80() {
   if (!db_->Execute(
           "ALTER TABLE share_info ADD COLUMN bag_of_chips BLOB"))
@@ -982,6 +1008,18 @@ bool DirectoryBackingStore::MigrateVersion79To80() {
   return true;
 }
 
+bool DirectoryBackingStore::MigrateVersion80To81() {
+  // Version 81 changes server_position_in_parent from a potentially lossy
+  // bigint to an unbounded fidelity ordinal represented as a varchar
+  if (!db_->Execute(
+          "ALTER TABLE metas"
+          "ALTER COLUMN server_position_in_parent VARCHAR(255)")) {
+    return false;
+  }
+  SetVersion(81);
+  return true;
+}
+
 bool DirectoryBackingStore::CreateTables() {
   DVLOG(1) << "First run, creating tables";
   // Create two little tables share_version and share_info