3 files changed, 22 insertions, 4 deletions
diff --git a/src/libstore/db.cc b/src/libstore/db.cc
index 4a815a5f90a8..82211bd1dee8 100644
--- a/src/libstore/db.cc
+++ b/src/libstore/db.cc
@@ -33,11 +33,9 @@ Transaction::Transaction()
 
 
 Transaction::Transaction(Database & db)
+    : txn(0)
 {
-    db.requireEnv();
-    try {
-        db.env->txn_begin(0, &txn, 0);
-    } catch (DbException e) { rethrow(e); }
+    begin(db);
 }
 
 
@@ -47,6 +45,16 @@ Transaction::~Transaction()
 }
 
 
+void Transaction::begin(Database & db)
+{
+    assert(txn == 0);
+    db.requireEnv();
+    try {
+        db.env->txn_begin(0, &txn, 0);
+    } catch (DbException e) { rethrow(e); }
+}
+
+
 void Transaction::commit()
 {
     if (!txn) throw Error("commit called on null transaction");
diff --git a/src/libstore/db.hh b/src/libstore/db.hh
index d566fdad1e1c..8418364929db 100644
--- a/src/libstore/db.hh
+++ b/src/libstore/db.hh
@@ -27,6 +27,7 @@ public:
     Transaction(Database & _db);
     ~Transaction();
 
+    void begin(Database & db);
     void abort();
     void commit();
 
diff --git a/src/libstore/store.cc b/src/libstore/store.cc
index 5516dc8016c1..f73e993b880e 100644
--- a/src/libstore/store.cc
+++ b/src/libstore/store.cc
@@ -824,6 +824,7 @@ static void upgradeStore()
     PathSet validPaths(validPaths2.begin(), validPaths2.end());
 
     cerr << "hashing paths...";
+    int n = 0;
     for (PathSet::iterator i = validPaths.begin(); i != validPaths.end(); ++i) {
         checkInterrupt();
         string s;
@@ -832,10 +833,18 @@ static void upgradeStore()
             Hash hash = hashPath(htSHA256, *i);
             setHash(txn, *i, hash);
             cerr << ".";
+            if (++n % 1000 == 0) {
+                txn.commit();
+                txn.begin(nixDB);
+            }
         }
     }
     cerr << "\n";
 
+    txn.commit();
+
+    txn.begin(nixDB);
+    
     cerr << "processing closures...";
     for (PathSet::iterator i = validPaths.begin(); i != validPaths.end(); ++i) {
         checkInterrupt();