hgsubversion: use a single transaction for hgsubversion pull

Summary:
hgsubversion was doing one transaction per commit, which is both slow
and also causes a lot of packs to be created when operating on a remotefilelog
client.

Let's make it use a single transaction instead. Unfortunately the svn metadata
is not integrated with Mercurial transactions. If we're using a normal flat-text
revmap, if there is an exception when running pull, it will need to svn rebuild
the metadata to remove the bad data and continue.

If we're using a sqlite revmap, then we've integrated with the sqlite
transaction, so it should work as expected.

Reviewed By: quark-zju

Differential Revision: D13433557

fbshipit-source-id: 809abb57839213302eb856ec19a113097be624e8

hgext/hgsubversion/maps.py

@@ -608,6 +608,7 @@ class SqliteRevMap(collections.MutableMapping):
         self._lastpulledpath = lastpulled_path
 
         self._db = None
+        self._txndb = None
         self._sqlitepragmas = sqlitepragmas
         self.firstpulled = 0
         self._updatefirstlastpulled()
@@ -733,18 +734,23 @@ class SqliteRevMap(collections.MutableMapping):
 
     @contextlib.contextmanager
     def _transaction(self, mode="IMMEDIATE"):
-        if self._db is None:
-            self._opendb()
-        with self._db as db:
-            # wait indefinitely for database lock
-            while True:
-                try:
-                    db.execute("BEGIN %s" % mode)
-                    break
-                except sqlite3.OperationalError as ex:
-                    if str(ex) != "database is locked":
-                        raise
-            yield db
+        if self._txndb is not None:
+            yield self._txndb
+        else:
+            if self._db is None:
+                self._opendb()
+            with self._db as db:
+                # wait indefinitely for database lock
+                while True:
+                    try:
+                        db.execute("BEGIN %s" % mode)
+                        break
+                    except sqlite3.OperationalError as ex:
+                        if str(ex) != "database is locked":
+                            raise
+                self._txndb = db
+                yield db
+                self._txndb = None
 
     def _query(self, sql, params=()):
         with self._transaction() as db:

hgext/hgsubversion/wrappers.py

@@ -501,7 +501,13 @@ def pull(repo, source, heads=None, force=False, meta=None):
         try:
             # start converting revisions
             firstrun = True
-            with progress.bar(ui, "pull", total=total) as prog:
+            with repo.wlock(), repo.lock(), repo.transaction(
+                "svn"
+            ), meta.revmap._transaction() if hgutil.safehasattr(
+                meta.revmap, "_transaction"
+            ) else hgutil.nullcontextmanager(), progress.bar(
+                ui, "pull", total=total
+            ) as prog:
                 for r in svn.revisions(start=start, stop=stopat_rev):
                     if r.revnum in skiprevs or (
                         r.author is None
@@ -536,7 +542,6 @@ def pull(repo, source, heads=None, force=False, meta=None):
                                     continue
                                 meta.delbranch(branch, parent, r)
 
-                            meta.save()
                             converted = True
                             firstrun = False
 
@@ -557,6 +562,7 @@ def pull(repo, source, heads=None, force=False, meta=None):
                                 raise hgutil.Abort(*e.args)
 
                     lastpulled = r.revnum
+                meta.save()
 
         except KeyboardInterrupt:
             ui.traceback()