Provide a command ‘hydra-init’ to initialise/upgrade the database

For schema upgrades, hydra-init executes the files
src/sql/upgrade-<N>.sql, each of which upgrades the schema from
version N-1 to N.  The upgrades are wrapped in a transaction.

src/lib/Hydra/Helper/Nix.pm

@@ -8,7 +8,7 @@ use Hydra::Helper::CatalystUtils;
 
 our @ISA = qw(Exporter);
 our @EXPORT = qw(
-    getHydraPath getHydraDBPath openHydraDB getHydraConf txn_do
+    getHydraPath getHydraHome getHydraDBPath openHydraDB getHydraConf txn_do
     registerRoot getGCRootsDir gcRootFor
     getPrimaryBuildsForView
     getPrimaryBuildTotal
@@ -21,6 +21,13 @@ sub getHydraPath {
     return $dir;
 }
 
+
+sub getHydraHome {
+    my $dir = $ENV{"HYDRA_HOME"} or die "The HYDRA_HOME directory does not exist!\n";
+    return $dir;
+}
+
+
 sub getHydraConf {
     my $conf = $ENV{"HYDRA_CONFIG"} || (getHydraPath . "/hydra.conf");
     die "The HYDRA_CONFIG file ($conf) does not exist!\n" unless -f $conf;

src/script/hydra-init

@@ -0,0 +1,58 @@
+#! /var/run/current-system/sw/bin/perl -w
+
+use strict;
+use Hydra::Schema;
+use Hydra::Helper::Nix;
+use File::Slurp;
+use SQL::SplitStatement;
+use List::Util qw(max);
+
+my $db = openHydraDB;
+my $dbh = $db->storage->dbh;
+$dbh->{RaiseError} = 1;
+
+my $home = getHydraHome;
+
+my $sql_splitter = SQL::SplitStatement->new;
+
+# Figure out the target schema version.
+my $maxSchemaVersion = max (map { /.*\/upgrade-(\d.*)\.sql/; $1 } (glob "$home/sql/upgrade-[0-9]*.sql")) || 1;
+
+# Check whether the database has been initialised.  If not, load the
+# schema.
+my @tables = $dbh->tables;
+if (! grep { /SchemaVersion/i } @tables) {
+    print STDERR "initialising the Hydra database schema...\n";
+    my $schema = read_file(
+	$dbh->{Driver}->{Name} eq 'SQLite' ? "$home/sql/hydra-sqlite.sql" :
+	$dbh->{Driver}->{Name} eq 'Pg' ? "$home/sql/hydra-postgresql.sql" :
+	die "unsupported database type\n");
+    my @statements = $sql_splitter->split($schema);
+    eval {
+	$dbh->begin_work;
+	$dbh->do($_) foreach @statements;
+	$db->resultset('SchemaVersion')->create({version => $maxSchemaVersion});
+	$dbh->commit;
+    };
+    die "schema initialisation failed: $@\n" if $@;
+    exit 0;
+}
+
+# Get the current schema version.
+my @versions = $db->resultset('SchemaVersion')->all;
+die "couldn't get Hydra schema version!" if scalar @versions != 1;
+my $schemaVersion = $versions[0]->version;
+
+for (my $n = $schemaVersion; $n < $maxSchemaVersion; $n++) {
+    my $m = $n + 1;
+    print STDERR "upgrading Hydra schema from version $n to $m\n";
+    my $schema = read_file("$home/sql/upgrade-$m.sql");
+    my @statements = $sql_splitter->split($schema);
+    eval {
+	$dbh->begin_work;
+	$dbh->do($_) foreach @statements;
+	$db->resultset('SchemaVersion')->update({version => $m});
+	$dbh->commit;
+    };
+    die "schema upgrade failed: $@\n" if $@;
+}

src/sql/Makefile.am

@@ -1,6 +1,6 @@
 EXTRA_DIST = hydra.sql hydra-postgresql.sql hydra-sqlite.sql
 
-sqldir = $(datadir)/hydra/sql
+sqldir = $(libexecdir)/hydra/sql
 nobase_sql_DATA = $(EXTRA_DIST)
 
 hydra-postgresql.sql: hydra.sql

src/sql/hydra.sql

@@ -3,8 +3,6 @@ create table SchemaVersion (
     version       integer not null
 );
 
-insert into SchemaVersion (version) values (1);
-
 
 create table Users (
     userName      text primary key not null,