* Upgraded to Berkeley DB 4.2.52. The main advantage of 4.2 is that

it automatically removes log files when they are no longer needed.

  *** IMPORTANT ***

  If you have an existing Nix installation, you must checkpoint the
  Nix database to prevent recent transactions from being undone.  Do
  the following:

  - optional: make a backup of $prefix/var/nix/db.

  - run `db_checkpoint' from Berkeley DB 4.1:
  
    $ db_checkpoint -h $prefix/var/nix/db -1

  - optional (?): run `db_recover' from Berkeley DB 4.1:

    $ db_recover -h $prefix/var/nix/db

  - remove $prefix/var/nix/db/log* and $prefix/var/nix/db/__db*

externals/Makefile.am

@@ -1,11 +1,11 @@
 # Berkeley DB
 
-DB = db-4.1.25
+DB = db-4.2.52
 
 $(DB).tar.gz:
 	@echo "Nix requires Berkeley DB to build."
-	@echo "Please download version 4.1.25 from"
-	@echo "  http://www.sleepycat.com/update/snapshot/db-4.1.25.tar.gz"
+	@echo "Please download version 4.2.52 from"
+	@echo "  http://www.sleepycat.com/update/snapshot/db-4.2.52.tar.gz"
 	@echo "and place it in the externals/ directory."
 	false
 
@@ -21,7 +21,8 @@ build-db: have-db
 	cd $(DB)/build_unix && \
 	CC="$(CC)" CXX="$(CXX)" CFLAGS="$(CFLAGS)" CXXFLAGS="$(CXXFLAGS)" \
 	 ../dist/configure --prefix=$$pfx/inst \
-	 --enable-cxx --disable-shared && \
+	 --enable-cxx --disable-shared --disable-cryptography \
+         --disable-replication --disable-verify && \
 	make && \
 	make install)
 	touch build-db

src/libstore/db.cc

@@ -160,7 +160,7 @@ void Database::open(const string & path)
         env->set_lg_bsize(32 * 1024); /* default */
         env->set_lg_max(256 * 1024); /* must be > 4 * lg_bsize */
         env->set_lk_detect(DB_LOCK_DEFAULT);
-        env->set_flags(DB_TXN_WRITE_NOSYNC, 1);
+        env->set_flags(DB_TXN_WRITE_NOSYNC | DB_LOG_AUTOREMOVE, 1);
         
 
         /* The following code provides automatic recovery of the