* Read manifests directly into the database, rather than first reading

them into memory.  This brings memory use down to (more or less)
  O(1).  For instance, on my test case, the maximum resident size of
  download-using-manifests while filling the DB went from 142 MiB to
  11 MiB.

scripts/NixManifest.pm.in

@@ -6,6 +6,23 @@ use File::Path;
 use Fcntl ':flock';
 
 
+sub addNAR {
+    my ($narFiles, $storePath, $info) = @_;
+    
+    $$narFiles{$storePath} = []
+        unless defined $$narFiles{$storePath};
+
+    my $narFileList = $$narFiles{$storePath};
+
+    my $found = 0;
+    foreach my $narFile (@{$narFileList}) {
+        $found = 1 if $narFile->{url} eq $info->{url};
+    }
+    
+    push @{$narFileList}, $info if !$found;
+}
+
+
 sub addPatch {
     my ($patches, $storePath, $patch) = @_;
 
@@ -27,8 +44,8 @@ sub addPatch {
 }
 
 
-sub readManifest {
+sub readManifest_ {
-    my ($manifest, $narFiles, $patches) = @_;
+    my ($manifest, $addNAR, $addPatch) = @_;
 
     open MANIFEST, "<$manifest"
         or die "cannot open `$manifest': $!";
@@ -72,35 +89,22 @@ sub readManifest {
                 $inside = 0;
 
                 if ($type eq "narfile") {
-
+                    &$addNAR($storePath,
-                    $$narFiles{$storePath} = []
-                        unless defined $$narFiles{$storePath};
-
-                    my $narFileList = $$narFiles{$storePath};
-
-                    my $found = 0;
-                    foreach my $narFile (@{$narFileList}) {
-                        $found = 1 if $narFile->{url} eq $url;
-                    }
-                    if (!$found) {
-                        push @{$narFileList},
                         { url => $url, hash => $hash, size => $size
                         , narHash => $narHash, narSize => $narSize
                         , references => $references
                         , deriver => $deriver
                         , system => $system
-                            };
+                        });
-                    }
-                
                 }
 
                 elsif ($type eq "patch") {
-                    addPatch $patches, $storePath,
+                    &$addPatch($storePath,
                         { url => $url, hash => $hash, size => $size
                         , basePath => $basePath, baseHash => $baseHash
                         , narHash => $narHash, narSize => $narSize
                         , patchType => $patchType
-                        };
+                        });
                 }
 
             }
@@ -134,6 +138,14 @@ sub readManifest {
 }
 
 
+sub readManifest {
+    my ($manifest, $narFiles, $patches) = @_;
+    readManifest_($manifest,
+        sub { addNAR($narFiles, @_); },
+        sub { addPatch($patches, @_); } );
+}
+
+
 sub writeManifest {
     my ($manifest, $narFiles, $patches, $noCompress) = @_;
 
@@ -205,7 +217,7 @@ sub updateManifestDB {
     my $dbPath = "$manifestDir/cache.sqlite";
 
     # Open/create the database.
-    my $dbh = DBI->connect("dbi:SQLite:dbname=$dbPath", "", "")
+    our $dbh = DBI->connect("dbi:SQLite:dbname=$dbPath", "", "")
         or die "cannot open database `$dbPath'";
     $dbh->{AutoCommit} = 0;
     $dbh->{RaiseError} = 1;
@@ -279,47 +291,40 @@ EOF
             "select 1 from Manifests where path = ? and timestamp = ?",
             {}, $manifest, $timestamp)} == 1;
 
-        # !!! Insert directly into the DB.
-        my %narFiles;
-        my %patches;
-        my $version = readManifest($manifest, \%narFiles, \%patches);
-        
-        if ($version < 3) {
-            die "you have an old-style manifest `$manifest'; please delete it";
-        }
-        if ($version >= 10) {
-            die "manifest `$manifest' is too new; please delete it or upgrade Nix";
-        }
-
         $dbh->do("delete from Manifests where path = ?", {}, $manifest);
                  
         $dbh->do("insert into Manifests(path, timestamp) values (?, ?)",
                  {}, $manifest, $timestamp);
 
-        my $id = $dbh->sqlite_last_insert_rowid();
+        our $id = $dbh->sqlite_last_insert_rowid();
 
-        foreach my $storePath (keys %narFiles) {
+        sub addNARToDB {
-            my $narFileList = $narFiles{$storePath};
+            my ($storePath, $narFile) = @_;
-            foreach my $narFile (@{$narFiles{$storePath}}) {
             $dbh->do(
                 "insert into NARs(manifest, storePath, url, hash, size, narHash, " .
                 "narSize, refs, deriver, system) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)",
                 {}, $id, $storePath, $narFile->{url}, $narFile->{hash}, $narFile->{size},
                 $narFile->{narHash}, $narFile->{narSize}, $narFile->{references},
                 $narFile->{deriver}, $narFile->{system});
-            }
+        };
-        }
         
-        foreach my $storePath (keys %patches) {
+        sub addPatchToDB {
-            my $patchList = $patches{$storePath};
+            my ($storePath, $patch) = @_;
-            foreach my $patch (@{$patchList}) {
             $dbh->do(
                 "insert into Patches(manifest, storePath, basePath, baseHash, url, hash, " .
                 "size, narHash, narSize, patchType) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)",
                 {}, $id, $storePath, $patch->{basePath}, $patch->{baseHash}, $patch->{url},
                 $patch->{hash}, $patch->{size}, $patch->{narHash}, $patch->{narSize},
                 $patch->{patchType});
+        };
+
+        my $version = readManifest_($manifest, \&addNARToDB, \&addPatchToDB);
+        
+        if ($version < 3) {
+            die "you have an old-style manifest `$manifest'; please delete it";
         }
+        if ($version >= 10) {
+            die "manifest `$manifest' is too new; please delete it or upgrade Nix";
         }
     }