Implement brep-migrate utility

40 files changed, 1153 insertions, 183 deletions

diff --git a/INSTALL b/INSTALL
index 1944228..e37c806 100644
--- a/INSTALL
+++ b/INSTALL
@@ -122,10 +122,10 @@ To troubleshoot, see PostgreSQL logs.
 5. Create Database Schema and Load Repositories
 
 $ mkdir config
-$ edit config/brep-loader.conf # Loader configuration, see brep-loader(1).
+$ edit config/brep-load.conf # Loader configuration, see brep-load(1).
 
-$ psql --quiet -f install/share/brep/package.sql
-$ install/bin/brep-loader config/brep-loader.conf
+$ install/bin/brep-migrate
+$ install/bin/brep-load config/brep-load.conf
 
 To verify:
 
@@ -226,21 +226,21 @@ since we want the loader to run even when we are not logged in:
 $ sudo loginctl enable-linger brep
 
 $ mkdir -p .config/systemd/user
-$ cp install/share/brep/etc/systemd/brep-loader.* .config/systemd/user/
+$ cp install/share/brep/etc/systemd/brep-load.* .config/systemd/user/
 
 Start the service to make sure there are no issues:
 
-$ systemctl --user start brep-loader.service
+$ systemctl --user start brep-load.service
 $ journalctl
 
 Start the timer and monitor it to make sure it fires:
 
-$ systemctl --user start brep-loader.timer
+$ systemctl --user start brep-load.timer
 $ journalctl -f
 
 If everything looks good, enable the timer to be started at boot time:
 
-$ systemctl --user enable brep-loader.timer
+$ systemctl --user enable brep-load.timer
 
 
 8. Upgrade Procedure
@@ -262,8 +262,8 @@ $ bpkg -d brep build brep
 
 Stop and disable loader:
 
-$ systemctl --user disable --now brep-loader.timer
-$ systemctl --user stop brep-loader.service
+$ systemctl --user disable --now brep-load.timer
+$ systemctl --user stop brep-load.service
 
 Stop apache:
 
@@ -280,16 +280,16 @@ $ diff -u install/share/brep/etc/brep-module.conf config/brep-module.conf
 
 Update database schema:
 
-$ psql --quiet -f install/share/brep/package.sql
+$ install/bin/brep-migrate
 
 Start and enable loader:
 
-$ systemctl --user start brep-loader.service
-$ systemctl --user status brep-loader.service
+$ systemctl --user start brep-load.service
+$ systemctl --user status brep-load.service
 
 If everything looks good, enable periodic execution:
 
-$ systemctl --user enable --now brep-loader.timer
+$ systemctl --user enable --now brep-load.timer
 
 Start apache:
 
diff --git a/INSTALL-DEV b/INSTALL-DEV
index b81d7fb..6e23664 100644
--- a/INSTALL-DEV
+++ b/INSTALL-DEV
@@ -48,8 +48,8 @@ $ sudo tail -f /var/log/postgresql/*.log
 
 All the commands are executed from brep project root.
 
-$ psql --quiet -d brep -f brep/package.sql
-$ loader/brep-loader tests/loader/r.conf # Or some other loader config.
+$ migrate/brep-migrate
+$ load/brep-load tests/load/r.conf # Or some other loader config.
 
 To verify:
 
@@ -115,7 +115,7 @@ $ sudo tail -f /var/log/apache2/error.log
 To do a "complete reload" (i.e., recreate database schema, load the repository
 data, and reload the Apache2 plugin), execute the following from brep/:
 
-psql --quiet -d brep -f brep/package.sql
-loader/brep-loader tests/loader/r.conf
+migrate/brep-migrate --recreate
+load/brep-load tests/load/r.conf
 sudo /etc/init.d/apache2 restart
 sudo systemctl restart apache2
diff --git a/brep/.gitignore b/brep/.gitignore
index 2c23e23..852a40d 100644
--- a/brep/.gitignore
+++ b/brep/.gitignore
@@ -2,4 +2,4 @@ options
 options.?xx
 package-odb*
 package.sql
-
+package-extra
diff --git a/brep/buildfile b/brep/buildfile
index 9826504..1aa4d08 100644
--- a/brep/buildfile
+++ b/brep/buildfile
@@ -10,7 +10,7 @@ define sql: file
 sql{*}: extension = sql
 sql{*}: install = data
 
-./: lib{brep} mod{brep} sql{package}
+./: lib{brep} mod{brep} sql{package package-extra}
 
 # lib{brep}
 #
@@ -20,8 +20,10 @@ import libs += libbpkg%lib{bpkg}
 
 lib{brep}:                          \
 {hxx         cxx}{ package        } \
+{file           }{ package.xml    } \
 {hxx ixx     cxx}{ package-odb    } \
 {hxx         cxx}{ package-traits } \
+{hxx         cxx}{ database-lock  } \
 {hxx            }{ types          } \
 {hxx            }{ utility        } \
 {hxx            }{ version        } \
diff --git a/brep/database-lock b/brep/database-lock
new file mode 100644
index 0000000..72036a1
--- /dev/null
+++ b/brep/database-lock
@@ -0,0 +1,43 @@
+// file      : brep/database-lock -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BREP_DATABASE_LOCK
+#define BREP_DATABASE_LOCK
+
+#include <memory>    // unique_ptr
+#include <exception>
+
+#include <odb/pgsql/forward.hxx>    // database, transaction
+#include <odb/pgsql/connection.hxx>
+
+namespace brep
+{
+  struct database_locked: std::exception
+  {
+    virtual char const*
+    what () const throw () {return "database locked";}
+  };
+
+  // Try to "lock" the PostgreSQL database in the constructor and release the
+  // lock in the destructor. Throw database_locked if the database is already
+  // locked by someone else. May also throw odb::pgsql::database_exception.
+  //
+  // This mechanism is used by the brep loader and schema migration tool to
+  // make sure they don't step on each others toes.
+  //
+  // Note: movable but not copyable.
+  //
+  class database_lock
+  {
+  public:
+    explicit
+    database_lock (odb::pgsql::database&);
+
+  private:
+    odb::pgsql::connection_ptr connection_;
+    std::unique_ptr<odb::pgsql::transaction> transaction_;
+  };
+}
+
+#endif // BREP_DATABASE_LOCK
diff --git a/brep/database-lock.cxx b/brep/database-lock.cxx
new file mode 100644
index 0000000..3b8ae21
--- /dev/null
+++ b/brep/database-lock.cxx
@@ -0,0 +1,44 @@
+// file      : brep/database-lock.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <brep/database-lock>
+
+#include <odb/pgsql/database.hxx>
+#include <odb/pgsql/exceptions.hxx>
+#include <odb/pgsql/transaction.hxx>
+
+namespace brep
+{
+  using namespace odb::pgsql;
+
+  database_lock::
+  database_lock (database& db)
+  {
+    // Before locking the table make sure it exists.
+    //
+    {
+      transaction t (db.begin ());
+      db.execute ("CREATE TABLE IF NOT EXISTS database_mutex ()");
+      t.commit ();
+    }
+
+    connection_ = db.connection ();
+
+    // Don't make current. Will be rolled back in destructor.
+    //
+    transaction_.reset (new transaction (connection_->begin (), false));
+
+    try
+    {
+      connection_->execute ("LOCK TABLE database_mutex NOWAIT");
+    }
+    catch (const database_exception& e)
+    {
+      if (e.sqlstate () == "55P03") // The table is already locked.
+        throw database_locked ();
+
+      throw;
+    }
+  }
+}
diff --git a/brep/mod-package-search.cxx b/brep/mod-package-search.cxx
index 4326435..d649ff4 100644
--- a/brep/mod-package-search.cxx
+++ b/brep/mod-package-search.cxx
@@ -9,6 +9,7 @@
 #include <odb/session.hxx>
 #include <odb/database.hxx>
 #include <odb/transaction.hxx>
+#include <odb/schema-catalog.hxx>
 
 #include <web/xhtml>
 #include <web/module>
@@ -16,6 +17,7 @@
 
 #include <brep/types>
 #include <brep/utility>
+#include <brep/version>
 
 #include <brep/page>
 #include <brep/options>
@@ -38,6 +40,20 @@ init (scanner& s)
     options_->root (dir_path ("/"));
 
   db_ = shared_database (*options_);
+
+  // Check that the database schema matches the current one. It's enough to
+  // perform the check in just a single module implementation (and we don't
+  // do in the dispatcher because it doesn't use the database).
+  //
+  // Note that the failure can be reported by each web server worker process.
+  // While it could be tempting to move the check to the
+  // repository_root::version() function, it would be wrong. The function can
+  // be called by a different process (usually the web server root one) not
+  // having the proper permissions to access the database.
+  //
+  if (schema_catalog::current_version (*db_) != db_->schema_version ())
+    fail << "database schema differs from the current one (module "
+         << BREP_VERSION_STR << ")";
 }
 
 template <typename T>
diff --git a/brep/odb.sh b/brep/odb.sh
index 489d423..d68b28f 100755
--- a/brep/odb.sh
+++ b/brep/odb.sh
@@ -1,11 +1,13 @@
 #! /usr/bin/env bash
 
 odb -d pgsql --std c++11 --generate-query --generate-schema \
-               --odb-epilogue '#include <brep/wrapper-traits>' \
-               --hxx-prologue '#include <brep/wrapper-traits>' \
-	       --hxx-prologue "#include <brep/package-traits>" \
-	       --sql-epilogue-file package-extra.sql \
-	       -I .. -I ../../libbpkg -I ../../libbutl \
-               --hxx-suffix "" --include-with-brackets \
-               --include-prefix brep --guard-prefix BREP \
-	       package
+    --schema-format sql --schema-format embedded \
+    --odb-epilogue '#include <brep/wrapper-traits>' \
+    --hxx-prologue '#include <brep/wrapper-traits>' \
+    --hxx-prologue '#include <brep/package-traits>' \
+    -I .. -I ../../libbpkg -I ../../libbutl \
+    --hxx-suffix "" --include-with-brackets \
+    --include-prefix brep --guard-prefix BREP \
+    package
+
+xxd -i <package-extra.sql >package-extra
diff --git a/brep/package b/brep/package
index 92a2320..2700e8a 100644
--- a/brep/package
+++ b/brep/package
@@ -19,6 +19,12 @@
 #include <brep/types>
 #include <brep/utility>
 
+// Used by the data migration entries.
+//
+#define LIBBREP_SCHEMA_VERSION_BASE 1
+
+#pragma db model version(LIBBREP_SCHEMA_VERSION_BASE, 1, open)
+
 // The uint16_t value range is not fully covered by SMALLINT PostgreSQL type
 // to which uint16_t is mapped by default.
 //
diff --git a/brep/package-extra.sql b/brep/package-extra.sql
index dc37d1f..9a847e3 100644
--- a/brep/package-extra.sql
+++ b/brep/package-extra.sql
@@ -1,12 +1,22 @@
-DROP TYPE IF EXISTS weighted_text CASCADE;
-CREATE TYPE weighted_text AS (a TEXT, b TEXT, c TEXT, d TEXT);
-
+-- This file should be parsable by the brep-migrate utility. To decrease the
+-- parser complexity, the following restrictions are placed:
+--
+-- * comments must start with -- at the beginning of the line (ignoring
+--   leading spaces)
+-- * only CREATE and DROP statements for FUNCTION and TYPE
+-- * function bodies must be defined using $$-quoted strings
+-- * strings other then function bodies must be quoted with ' or "
+-- * statements must end with ";\n"
+--
 DROP FUNCTION IF EXISTS to_tsvector(IN document weighted_text);
 DROP FUNCTION IF EXISTS search_packages(IN query tsquery, INOUT name TEXT);
 DROP FUNCTION IF EXISTS search_latest_packages(IN query tsquery);
 DROP FUNCTION IF EXISTS latest_package(INOUT name TEXT);
 DROP FUNCTION IF EXISTS latest_packages();
 
+DROP TYPE IF EXISTS weighted_text CASCADE;
+CREATE TYPE weighted_text AS (a TEXT, b TEXT, c TEXT, d TEXT);
+
 -- Return the latest versions of internal packages as a set of package rows.
 --
 CREATE FUNCTION
@@ -72,9 +82,9 @@ $$ LANGUAGE SQL STABLE;
 -- Search for packages matching the search query and having the specified name.
 -- Return a set of rows containing the package id and search rank. If query
 -- is NULL, then match all packages and return 0 rank for all rows.
--- 
+--
 CREATE FUNCTION
-search_packages(IN query tsquery,             
+search_packages(IN query tsquery,
                 INOUT name TEXT,
                 OUT version_epoch INTEGER,
                 OUT version_canonical_upstream TEXT,
diff --git a/brep/package.xml b/brep/package.xml
new file mode 100644
index 0000000..9c88f25
--- /dev/null
+++ b/brep/package.xml
@@ -0,0 +1,406 @@
+<changelog xmlns="http://www.codesynthesis.com/xmlns/odb/changelog" database="pgsql" version="1">
+  <model version="1">
+    <table name="repository" kind="object">
+      <column name="name" type="TEXT" null="false"/>
+      <column name="location" type="TEXT" null="false"/>
+      <column name="display_name" type="TEXT" null="false"/>
+      <column name="priority" type="INTEGER" null="false"/>
+      <column name="url" type="TEXT" null="true"/>
+      <column name="email" type="TEXT" null="true"/>
+      <column name="summary" type="TEXT" null="true"/>
+      <column name="description" type="TEXT" null="true"/>
+      <column name="local_path" type="TEXT" null="false"/>
+      <column name="packages_timestamp" type="BIGINT" null="false"/>
+      <column name="repositories_timestamp" type="BIGINT" null="false"/>
+      <column name="internal" type="BOOLEAN" null="false"/>
+      <primary-key>
+        <column name="name"/>
+      </primary-key>
+    </table>
+    <table name="repository_complements" kind="container">
+      <column name="repository" type="TEXT" null="false"/>
+      <column name="index" type="BIGINT" null="false"/>
+      <column name="complement" type="TEXT" null="false"/>
+      <foreign-key name="repository_fk" on-delete="CASCADE">
+        <column name="repository"/>
+        <references table="repository">
+          <column name="name"/>
+        </references>
+      </foreign-key>
+      <index name="repository_complements_repository_i">
+        <column name="repository"/>
+      </index>
+      <index name="repository_complements_index_i">
+        <column name="index"/>
+      </index>
+      <foreign-key name="complement_fk" deferrable="DEFERRED">
+        <column name="complement"/>
+        <references table="repository">
+          <column name="name"/>
+        </references>
+      </foreign-key>
+    </table>
+    <table name="repository_prerequisites" kind="container">
+      <column name="repository" type="TEXT" null="false"/>
+      <column name="index" type="BIGINT" null="false"/>
+      <column name="prerequisite" type="TEXT" null="false"/>
+      <foreign-key name="repository_fk" on-delete="CASCADE">
+        <column name="repository"/>
+        <references table="repository">
+          <column name="name"/>
+        </references>
+      </foreign-key>
+      <index name="repository_prerequisites_repository_i">
+        <column name="repository"/>
+      </index>
+      <index name="repository_prerequisites_index_i">
+        <column name="index"/>
+      </index>
+      <foreign-key name="prerequisite_fk" deferrable="DEFERRED">
+        <column name="prerequisite"/>
+        <references table="repository">
+          <column name="name"/>
+        </references>
+      </foreign-key>
+    </table>
+    <table name="package" kind="object">
+      <column name="name" type="TEXT" null="false"/>
+      <column name="version_epoch" type="INTEGER" null="false"/>
+      <column name="version_canonical_upstream" type="TEXT" null="false"/>
+      <column name="version_canonical_release" type="TEXT" null="false" options="COLLATE &quot;C&quot;"/>
+      <column name="version_revision" type="INTEGER" null="false"/>
+      <column name="version_upstream" type="TEXT" null="false"/>
+      <column name="version_release" type="TEXT" null="true"/>
+      <column name="priority" type="INTEGER" null="false"/>
+      <column name="priority_comment" type="TEXT" null="false"/>
+      <column name="summary" type="TEXT" null="false"/>
+      <column name="description" type="TEXT" null="true"/>
+      <column name="changes" type="TEXT" null="false"/>
+      <column name="url" type="TEXT" null="false"/>
+      <column name="url_comment" type="TEXT" null="false"/>
+      <column name="package_url" type="TEXT" null="true"/>
+      <column name="package_url_comment" type="TEXT" null="true"/>
+      <column name="email" type="TEXT" null="false"/>
+      <column name="email_comment" type="TEXT" null="false"/>
+      <column name="package_email" type="TEXT" null="true"/>
+      <column name="package_email_comment" type="TEXT" null="true"/>
+      <column name="internal_repository" type="TEXT" null="true"/>
+      <column name="location" type="TEXT" null="true"/>
+      <column name="search_index" type="tsvector" null="true"/>
+      <primary-key>
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+      </primary-key>
+      <foreign-key name="internal_repository_fk" deferrable="DEFERRED">
+        <column name="internal_repository"/>
+        <references table="repository">
+          <column name="name"/>
+        </references>
+      </foreign-key>
+      <index name="package_search_index_i" method="GIN">
+        <column name="search_index"/>
+      </index>
+    </table>
+    <table name="package_license_alternatives" kind="container">
+      <column name="name" type="TEXT" null="false"/>
+      <column name="version_epoch" type="INTEGER" null="false"/>
+      <column name="version_canonical_upstream" type="TEXT" null="false"/>
+      <column name="version_canonical_release" type="TEXT" null="false" options="COLLATE &quot;C&quot;"/>
+      <column name="version_revision" type="INTEGER" null="false"/>
+      <column name="index" type="BIGINT" null="false"/>
+      <column name="comment" type="TEXT" null="false"/>
+      <foreign-key name="object_id_fk" on-delete="CASCADE">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+        <references table="package">
+          <column name="name"/>
+          <column name="version_epoch"/>
+          <column name="version_canonical_upstream"/>
+          <column name="version_canonical_release"/>
+          <column name="version_revision"/>
+        </references>
+      </foreign-key>
+      <index name="package_license_alternatives_object_id_i">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+      </index>
+      <index name="package_license_alternatives_index_i">
+        <column name="index"/>
+      </index>
+    </table>
+    <table name="package_licenses" kind="container">
+      <column name="name" type="TEXT" null="false"/>
+      <column name="version_epoch" type="INTEGER" null="false"/>
+      <column name="version_canonical_upstream" type="TEXT" null="false"/>
+      <column name="version_canonical_release" type="TEXT" null="false" options="COLLATE &quot;C&quot;"/>
+      <column name="version_revision" type="INTEGER" null="false"/>
+      <column name="alternative_index" type="BIGINT" null="false"/>
+      <column name="index" type="BIGINT" null="false"/>
+      <column name="license" type="TEXT" null="false"/>
+      <foreign-key name="object_id_fk" on-delete="CASCADE">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+        <references table="package">
+          <column name="name"/>
+          <column name="version_epoch"/>
+          <column name="version_canonical_upstream"/>
+          <column name="version_canonical_release"/>
+          <column name="version_revision"/>
+        </references>
+      </foreign-key>
+      <index name="package_licenses_object_id_i">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+      </index>
+    </table>
+    <table name="package_tags" kind="container">
+      <column name="name" type="TEXT" null="false"/>
+      <column name="version_epoch" type="INTEGER" null="false"/>
+      <column name="version_canonical_upstream" type="TEXT" null="false"/>
+      <column name="version_canonical_release" type="TEXT" null="false" options="COLLATE &quot;C&quot;"/>
+      <column name="version_revision" type="INTEGER" null="false"/>
+      <column name="index" type="BIGINT" null="false"/>
+      <column name="tag" type="TEXT" null="false"/>
+      <foreign-key name="object_id_fk" on-delete="CASCADE">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+        <references table="package">
+          <column name="name"/>
+          <column name="version_epoch"/>
+          <column name="version_canonical_upstream"/>
+          <column name="version_canonical_release"/>
+          <column name="version_revision"/>
+        </references>
+      </foreign-key>
+      <index name="package_tags_object_id_i">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+      </index>
+      <index name="package_tags_index_i">
+        <column name="index"/>
+      </index>
+    </table>
+    <table name="package_dependencies" kind="container">
+      <column name="name" type="TEXT" null="false"/>
+      <column name="version_epoch" type="INTEGER" null="false"/>
+      <column name="version_canonical_upstream" type="TEXT" null="false"/>
+      <column name="version_canonical_release" type="TEXT" null="false" options="COLLATE &quot;C&quot;"/>
+      <column name="version_revision" type="INTEGER" null="false"/>
+      <column name="index" type="BIGINT" null="false"/>
+      <column name="conditional" type="BOOLEAN" null="false"/>
+      <column name="comment" type="TEXT" null="false"/>
+      <foreign-key name="object_id_fk" on-delete="CASCADE">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+        <references table="package">
+          <column name="name"/>
+          <column name="version_epoch"/>
+          <column name="version_canonical_upstream"/>
+          <column name="version_canonical_release"/>
+          <column name="version_revision"/>
+        </references>
+      </foreign-key>
+      <index name="package_dependencies_object_id_i">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+      </index>
+      <index name="package_dependencies_index_i">
+        <column name="index"/>
+      </index>
+    </table>
+    <table name="package_dependency_alternatives" kind="container">
+      <column name="name" type="TEXT" null="false"/>
+      <column name="version_epoch" type="INTEGER" null="false"/>
+      <column name="version_canonical_upstream" type="TEXT" null="false"/>
+      <column name="version_canonical_release" type="TEXT" null="false" options="COLLATE &quot;C&quot;"/>
+      <column name="version_revision" type="INTEGER" null="false"/>
+      <column name="dependency_index" type="BIGINT" null="false"/>
+      <column name="index" type="BIGINT" null="false"/>
+      <column name="dep_name" type="TEXT" null="false"/>
+      <column name="dep_version_epoch" type="INTEGER" null="false"/>
+      <column name="dep_version_canonical_upstream" type="TEXT" null="false"/>
+      <column name="dep_version_canonical_release" type="TEXT" null="false" options="COLLATE &quot;C&quot;"/>
+      <column name="dep_version_revision" type="INTEGER" null="false"/>
+      <column name="dep_min_version_epoch" type="INTEGER" null="true"/>
+      <column name="dep_min_version_canonical_upstream" type="TEXT" null="true"/>
+      <column name="dep_min_version_canonical_release" type="TEXT" null="true"/>
+      <column name="dep_min_version_revision" type="INTEGER" null="true"/>
+      <column name="dep_min_version_upstream" type="TEXT" null="true"/>
+      <column name="dep_min_version_release" type="TEXT" null="true"/>
+      <column name="dep_max_version_epoch" type="INTEGER" null="true"/>
+      <column name="dep_max_version_canonical_upstream" type="TEXT" null="true"/>
+      <column name="dep_max_version_canonical_release" type="TEXT" null="true"/>
+      <column name="dep_max_version_revision" type="INTEGER" null="true"/>
+      <column name="dep_max_version_upstream" type="TEXT" null="true"/>
+      <column name="dep_max_version_release" type="TEXT" null="true"/>
+      <column name="dep_min_open" type="BOOLEAN" null="true"/>
+      <column name="dep_max_open" type="BOOLEAN" null="true"/>
+      <foreign-key name="object_id_fk" on-delete="CASCADE">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+        <references table="package">
+          <column name="name"/>
+          <column name="version_epoch"/>
+          <column name="version_canonical_upstream"/>
+          <column name="version_canonical_release"/>
+          <column name="version_revision"/>
+        </references>
+      </foreign-key>
+      <index name="package_dependency_alternatives_object_id_i">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+      </index>
+      <foreign-key name="dep_package_fk" deferrable="DEFERRED">
+        <column name="dep_name"/>
+        <column name="dep_version_epoch"/>
+        <column name="dep_version_canonical_upstream"/>
+        <column name="dep_version_canonical_release"/>
+        <column name="dep_version_revision"/>
+        <references table="package">
+          <column name="name"/>
+          <column name="version_epoch"/>
+          <column name="version_canonical_upstream"/>
+          <column name="version_canonical_release"/>
+          <column name="version_revision"/>
+        </references>
+      </foreign-key>
+    </table>
+    <table name="package_requirements" kind="container">
+      <column name="name" type="TEXT" null="false"/>
+      <column name="version_epoch" type="INTEGER" null="false"/>
+      <column name="version_canonical_upstream" type="TEXT" null="false"/>
+      <column name="version_canonical_release" type="TEXT" null="false" options="COLLATE &quot;C&quot;"/>
+      <column name="version_revision" type="INTEGER" null="false"/>
+      <column name="index" type="BIGINT" null="false"/>
+      <column name="conditional" type="BOOLEAN" null="false"/>
+      <column name="comment" type="TEXT" null="false"/>
+      <foreign-key name="object_id_fk" on-delete="CASCADE">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+        <references table="package">
+          <column name="name"/>
+          <column name="version_epoch"/>
+          <column name="version_canonical_upstream"/>
+          <column name="version_canonical_release"/>
+          <column name="version_revision"/>
+        </references>
+      </foreign-key>
+      <index name="package_requirements_object_id_i">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+      </index>
+      <index name="package_requirements_index_i">
+        <column name="index"/>
+      </index>
+    </table>
+    <table name="package_requirement_alternatives" kind="container">
+      <column name="name" type="TEXT" null="false"/>
+      <column name="version_epoch" type="INTEGER" null="false"/>
+      <column name="version_canonical_upstream" type="TEXT" null="false"/>
+      <column name="version_canonical_release" type="TEXT" null="false" options="COLLATE &quot;C&quot;"/>
+      <column name="version_revision" type="INTEGER" null="false"/>
+      <column name="requirement_index" type="BIGINT" null="false"/>
+      <column name="index" type="BIGINT" null="false"/>
+      <column name="id" type="TEXT" null="false"/>
+      <foreign-key name="object_id_fk" on-delete="CASCADE">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+        <references table="package">
+          <column name="name"/>
+          <column name="version_epoch"/>
+          <column name="version_canonical_upstream"/>
+          <column name="version_canonical_release"/>
+          <column name="version_revision"/>
+        </references>
+      </foreign-key>
+      <index name="package_requirement_alternatives_object_id_i">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+      </index>
+    </table>
+    <table name="package_other_repositories" kind="container">
+      <column name="name" type="TEXT" null="false"/>
+      <column name="version_epoch" type="INTEGER" null="false"/>
+      <column name="version_canonical_upstream" type="TEXT" null="false"/>
+      <column name="version_canonical_release" type="TEXT" null="false" options="COLLATE &quot;C&quot;"/>
+      <column name="version_revision" type="INTEGER" null="false"/>
+      <column name="index" type="BIGINT" null="false"/>
+      <column name="repository" type="TEXT" null="false"/>
+      <foreign-key name="object_id_fk" on-delete="CASCADE">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+        <references table="package">
+          <column name="name"/>
+          <column name="version_epoch"/>
+          <column name="version_canonical_upstream"/>
+          <column name="version_canonical_release"/>
+          <column name="version_revision"/>
+        </references>
+      </foreign-key>
+      <index name="package_other_repositories_object_id_i">
+        <column name="name"/>
+        <column name="version_epoch"/>
+        <column name="version_canonical_upstream"/>
+        <column name="version_canonical_release"/>
+        <column name="version_revision"/>
+      </index>
+      <index name="package_other_repositories_index_i">
+        <column name="index"/>
+      </index>
+      <foreign-key name="repository_fk" deferrable="DEFERRED">
+        <column name="repository"/>
+        <references table="repository">
+          <column name="name"/>
+        </references>
+      </foreign-key>
+    </table>
+  </model>
+</changelog>
diff --git a/buildfile b/buildfile
index 88a8c0b..60318fe 100644
--- a/buildfile
+++ b/buildfile
@@ -2,7 +2,7 @@
 # copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
 # license   : MIT; see accompanying LICENSE file
 
-d = brep/ etc/ loader/ tests/ www/
+d = brep/ etc/ load/ migrate/ tests/ www/
 ./: $d doc{INSTALL INSTALL-DEV LICENSE version} file{manifest}
 include $d
 
diff --git a/etc/buildfile b/etc/buildfile
index 9ebcf27..4910076 100644
--- a/etc/buildfile
+++ b/etc/buildfile
@@ -3,7 +3,7 @@
 # license   : MIT; see accompanying LICENSE file
 
 ./: file{brep-module.conf brep-apache2.conf} \
-systemd/file{brep-loader.service brep-loader.timer}
+systemd/file{brep-load.service brep-load.timer}
 
 install = data/etc
 systemd/: install = data/etc/systemd
diff --git a/etc/systemd/brep-loader.service b/etc/systemd/brep-load.service
index dec7944..34a7c9a 100644
--- a/etc/systemd/brep-loader.service
+++ b/etc/systemd/brep-load.service
@@ -3,7 +3,7 @@ Description=brep repository loader service
 
 [Service]
 Type=oneshot
-ExecStart=/home/brep/install/bin/brep-loader /home/brep/config/brep-loader.conf
+ExecStart=/home/brep/install/bin/brep-load /home/brep/config/brep-load.conf
 
 [Install]
 WantedBy=default.target
diff --git a/etc/systemd/brep-loader.timer b/etc/systemd/brep-load.timer
index 22ff22b..713cb31 100644
--- a/etc/systemd/brep-loader.timer
+++ b/etc/systemd/brep-load.timer
@@ -4,7 +4,7 @@ RefuseManualStart=no
 RefuseManualStop=no
 
 [Timer]
-Unit=brep-loader.service
+Unit=brep-load.service
 
 # Don't keep track of the timer across reboots.
 #
diff --git a/loader/.gitignore b/load/.gitignore
index 820b183..2f464c5 100644
--- a/loader/.gitignore
+++ b/load/.gitignore
@@ -1,3 +1,3 @@
 options
 options.?xx
-brep-loader
+brep-load
diff --git a/loader/buildfile b/load/buildfile
index 477cebd..c3a324f 100644
--- a/loader/buildfile
+++ b/load/buildfile
@@ -1,4 +1,4 @@
-# file      : loader/buildfile
+# file      : load/buildfile
 # copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
 # license   : MIT; see accompanying LICENSE file
 
@@ -9,12 +9,12 @@ import libs += libodb%lib{odb}
 
 include ../brep/
 
-exe{brep-loader}:            \
-{            cxx}{ loader  } \
+exe{brep-load}:              \
+{            cxx}{ load    } \
 {hxx ixx     cxx}{ options } \
 ../brep/lib{brep} $libs
 
-cli.options += -I $src_root --include-with-brackets --include-prefix loader \
---guard-prefix LOADER
+cli.options += -I $src_root --include-with-brackets --include-prefix load \
+--guard-prefix LOAD
 
 {hxx ixx cxx}{options}: cli{options}
diff --git a/loader/loader.cxx b/load/load.cxx
index b1b7706..9e6ee5d 100644
--- a/loader/loader.cxx
+++ b/load/load.cxx
@@ -1,9 +1,10 @@
-// file      : loader/loader.cxx -*- C++ -*-
+// file      : load/load.cxx -*- C++ -*-
 // copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
 // license   : MIT; see accompanying LICENSE file
 
 #include <sstream>
 #include <fstream>
+#include <ostream>
 #include <iostream>
 #include <stdexcept> // runtime_error, invalid_argument
 #include <algorithm> // find(), find_if()
@@ -11,11 +12,9 @@
 #include <odb/session.hxx>
 #include <odb/database.hxx>
 #include <odb/transaction.hxx>
+#include <odb/schema-catalog.hxx>
 
 #include <odb/pgsql/database.hxx>
-#include <odb/pgsql/exceptions.hxx>
-#include <odb/pgsql/connection.hxx>
-#include <odb/pgsql/transaction.hxx>
 
 #include <butl/filesystem>
 
@@ -27,8 +26,9 @@
 
 #include <brep/package>
 #include <brep/package-odb>
+#include <brep/database-lock>
 
-#include <loader/options>
+#include <load/options>
 
 using namespace std;
 using namespace odb::core;
@@ -36,12 +36,10 @@ using namespace butl;
 using namespace bpkg;
 using namespace brep;
 
-namespace pgsql = odb::pgsql;
-
 static void
 usage (ostream& os)
 {
-  os << "Usage: brep-loader [options] <file>" << endl
+  os << "Usage: brep-load [options] <file>" << endl
      << "File lists internal repositories." << endl
      << "Options:" << endl;
 
@@ -700,152 +698,141 @@ detect_dependency_cycle (const package_id& id, package_ids& chain, database& db)
 
 int
 main (int argc, char* argv[])
+try
 {
-  try
+  cli::argv_scanner scan (argc, argv, true);
+  options ops (scan);
+
+  // Version.
+  //
+  if (ops.version ())
   {
-    cli::argv_scanner scan (argc, argv, true);
-    options ops (scan);
+    cout << "brep-load " << BREP_VERSION_STR << endl
+         << "libbrep " << LIBBREP_VERSION_STR << endl
+         << "libbpkg " << LIBBPKG_VERSION_STR << endl
+         << "libbutl " << LIBBUTL_VERSION_STR << endl
+         << "Copyright (c) 2014-2016 Code Synthesis Ltd" << endl
+         << "MIT; see accompanying LICENSE file" << endl;
+
+    return 0;
+  }
 
-    // Version.
-    //
-    if (ops.version ())
-    {
-      cout << "brep-loader " << BREP_VERSION_STR << endl
-           << "libbrep " << LIBBREP_VERSION_STR << endl
-           << "libbpkg " << LIBBPKG_VERSION_STR << endl
-           << "libbutl " << LIBBUTL_VERSION_STR << endl
-           << "Copyright (c) 2014-2016 Code Synthesis Ltd" << endl
-           << "MIT; see accompanying LICENSE file" << endl;
-
-      return 0;
-    }
+  // Help.
+  //
+  if (ops.help ())
+  {
+    usage (cout);
+    return 0;
+  }
 
-    // Help.
-    //
-    if (ops.help ())
-    {
-      usage (cout);
-      return 0;
-    }
+  if (argc < 2)
+  {
+    cerr << "<file> argument not provided" << endl;
+    usage (cerr);
+    return 1;
+  }
 
-    if (argc < 2)
-    {
-      cerr << "<file> argument not provided" << endl;
-      usage (cerr);
-      return 1;
-    }
+  if (argc > 2)
+  {
+    cerr << "unexpected argument encountered" << endl;
+    usage (cerr);
+    return 1;
+  }
 
-    if (argc > 2)
-    {
-      cerr << "unexpected argument encountered" << endl;
-      usage (cerr);
-      return 1;
-    }
+  odb::pgsql::database db (ops.db_user (),
+                           ops.db_password (),
+                           ops.db_name (),
+                           ops.db_host (),
+                           ops.db_port ());
 
-    pgsql::database db (ops.db_user (),
-                        ops.db_password (),
-                        ops.db_name (),
-                        ops.db_host (),
-                        ops.db_port ());
+  // Prevent several brep-load/migrate instances from updating DB
+  // simultaneously.
+  //
+  database_lock l (db);
 
-    // Prevent several loader instances from updating DB simultaneously.
-    //
-    {
-      transaction t (db.begin ());
-      db.execute ("CREATE TABLE IF NOT EXISTS loader_mutex ()");
-      t.commit ();
-    }
+  transaction t (db.begin ());
 
-    pgsql::connection_ptr synch_c (db.connection ());
+  // Check that the database schema matches the current one.
+  //
+  if (schema_catalog::current_version (db) != db.schema_version ())
+  {
+    cerr << "database schema differs from the current one" << endl;
+    return 1;
+  }
+
+  // Load the description of all the internal repositories from the
+  // configuration file.
+  //
+  internal_repositories irs (load_repositories (path (argv[1])));
 
-    // Don't make current.
+  if (changed (irs, db))
+  {
+    // Rebuild repositories persistent state from scratch.
     //
-    pgsql::transaction synch_t (synch_c->begin (), false);
+    db.erase_query<package> ();
+    db.erase_query<repository> ();
 
-    try
-    {
-      synch_c->execute ("LOCK TABLE loader_mutex NOWAIT");
-    }
-    catch (const pgsql::database_exception& e)
+    // On the first pass over the internal repositories we load their
+    // packages.
+    //
+    uint16_t priority (1);
+    for (const auto& ir: irs)
     {
-      if (e.sqlstate () == "55P03")
-        return 2; // Other loader instance acquired the mutex.
+      shared_ptr<repository> r (
+        make_shared<repository> (ir.location,
+                                 move (ir.display_name),
+                                 move (ir.local_path),
+                                 priority++));
 
-      throw;
+      load_packages (r, db);
     }
 
-    // Load the description of all the internal repositories from the
-    // configuration file.
+    // On the second pass over the internal repositories we load their
+    // (not yet loaded) manifest values, complement, and prerequisite
+    // repositories.
     //
-    internal_repositories irs (load_repositories (path (argv[1])));
-
-    transaction t (db.begin ());
-
-    if (changed (irs, db))
+    for (const auto& ir: irs)
     {
-      // Rebuild repositories persistent state from scratch.
-      //
-      db.erase_query<package> ();
-      db.erase_query<repository> ();
-
-      // On the first pass over the internal repositories we load their
-      // packages.
-      //
-      uint16_t priority (1);
-      for (const auto& ir: irs)
-      {
-        shared_ptr<repository> r (
-          make_shared<repository> (ir.location,
-                                   move (ir.display_name),
-                                   move (ir.local_path),
-                                   priority++));
-
-        load_packages (r, db);
-      }
-
-      // On the second pass over the internal repositories we load their
-      // (not yet loaded) manifest values, complement, and prerequisite
-      // repositories.
-      //
-      for (const auto& ir: irs)
-      {
-        shared_ptr<repository> r (
-          db.load<repository> (ir.location.canonical_name ()));
+      shared_ptr<repository> r (
+        db.load<repository> (ir.location.canonical_name ()));
 
-        load_repositories (r, db);
-      }
-
-      session s;
-      using query = query<package>;
+      load_repositories (r, db);
+    }
 
-      // Resolve internal packages dependencies.
-      //
-      for (auto& p:
-             db.query<package> (query::internal_repository.is_not_null ()))
-        resolve_dependencies (p, db);
+    session s;
+    using query = query<package>;
 
-      // Ensure there is no package dependency cycles.
-      //
-      package_ids chain;
-      for (const auto& p:
-             db.query<package> (query::internal_repository.is_not_null ()))
-        detect_dependency_cycle (p.id, chain, db);
-    }
+    // Resolve internal packages dependencies.
+    //
+    for (auto& p:
+           db.query<package> (query::internal_repository.is_not_null ()))
+      resolve_dependencies (p, db);
 
-    t.commit ();
-    synch_t.commit (); // Release the mutex.
-  }
-  catch (const cli::exception& e)
-  {
-    cerr << e << endl;
-    usage (cerr);
-    return 1;
-  }
-  // Fully qualified to avoid ambiguity with odb exception.
-  //
-  catch (const std::exception& e)
-  {
-    cerr << e.what () << endl;
-    return 1;
+    // Ensure there is no package dependency cycles.
+    //
+    package_ids chain;
+    for (const auto& p:
+           db.query<package> (query::internal_repository.is_not_null ()))
+      detect_dependency_cycle (p.id, chain, db);
   }
+
+  t.commit ();
+}
+catch (const database_locked&)
+{
+  cerr << "brep-load or brep-migrate instance is running" << endl;
+  return 2;
+}
+catch (const cli::exception& e)
+{
+  cerr << e << endl;
+  usage (cerr);
+  return 1;
+}
+// Fully qualified to avoid ambiguity with odb exception.
+//
+catch (const std::exception& e)
+{
+  cerr << e.what () << endl;
+  return 1;
 }
diff --git a/loader/options.cli b/load/options.cli
index 0899156..df91606 100644
--- a/loader/options.cli
+++ b/load/options.cli
@@ -1,14 +1,37 @@
-// file      : loader/options.cli
+// file      : load/options.cli
 // copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
 // license   : MIT; see accompanying LICENSE file
 
 include <string>;
 include <cstdint>; // uint16_t
 
+"\section=1"
+"\name=brep-load"
+"\summary=load repositories into database"
+
+{
+  "<options> <file>",
+
+  "\h|SYNOPSIS|
+
+   \cb{brep-load --help}\n
+   \cb{brep-load --version}\n
+   \c{\b{brep-load} [<options>] <file>}
+
+   \h|DESCRIPTION|
+
+   \cb{brep-load} reads the list of repositories from the specified
+   configuration <file>, fetches their manifest files, and loads the repository
+   and package information into the database, suitable for consumption by the
+   \cb{brep} web module.
+
+   Note that \cb{brep-load} expects the database schema to have already been
+   created using \l{brep-migrate(1)}."
+}
+
 class options
 {
-  bool --help {"Print usage information and exit."}
-  bool --version {"Print version and exit."}
+  "\h|OPTIONS|"
 
   std::string --db-user|-u
   {
@@ -43,4 +66,7 @@ class options
     "<port>",
     "Database port number. If not specified, the default port is used."
   }
+
+  bool --help {"Print usage information and exit."}
+  bool --version {"Print version and exit."}
 };
diff --git a/migrate/.gitignore b/migrate/.gitignore
new file mode 100644
index 0000000..580958d
--- /dev/null
+++ b/migrate/.gitignore
@@ -0,0 +1,3 @@
+options
+options.?xx
+brep-migrate
diff --git a/migrate/buildfile b/migrate/buildfile
new file mode 100644
index 0000000..c42de5a
--- /dev/null
+++ b/migrate/buildfile
@@ -0,0 +1,18 @@
+# file      : migrate/buildfile
+# copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+import libs += libodb-pgsql%lib{odb-pgsql}
+import libs += libodb%lib{odb}
+
+include ../brep/
+
+exe{brep-migrate}:           \
+{            cxx}{ migrate } \
+{hxx ixx     cxx}{ options } \
+../brep/lib{brep} $libs
+
+cli.options += -I $src_root --include-with-brackets --include-prefix migrate \
+--guard-prefix MIGRATE
+
+{hxx ixx cxx}{options}: cli{options}
diff --git a/migrate/migrate.cxx b/migrate/migrate.cxx
new file mode 100644
index 0000000..aa71b67
--- /dev/null
+++ b/migrate/migrate.cxx
@@ -0,0 +1,317 @@
+// file      : migrate/migrate.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <strings.h> // strcasecmp()
+
+#include <string>
+#include <cassert>
+#include <ostream>
+#include <sstream>
+#include <iostream>
+#include <stdexcept> // runtime_error, invalid_argument
+
+#include <odb/database.hxx>
+#include <odb/transaction.hxx>
+#include <odb/schema-catalog.hxx>
+
+#include <odb/pgsql/database.hxx>
+
+#include <brep/types>
+#include <brep/utility>
+#include <brep/version>
+
+#include <brep/database-lock>
+
+#include <migrate/options>
+
+using namespace std;
+using namespace odb::core;
+using namespace brep;
+
+// Helper class that encapsulates both the ODB-generated schema and the
+// extra that comes from a .sql file (via xxd).
+//
+class schema
+{
+public:
+  explicit
+  schema (const char* extra);
+
+  void
+  create (database&) const;
+
+  void
+  drop (database&) const;
+
+private:
+  strings drop_statements_;
+  strings create_statements_;
+};
+
+schema::
+schema (const char* s)
+{
+  // Remove comments, saving the cleaned SQL code into statements.
+  //
+  string statements;
+  for (istringstream i (s); i; )
+  {
+    // Skip leading spaces (including consequtive newlines). In case we
+    // hit eof, keep c set to '\n'.
+    //
+    char c;
+    static const string spaces (" \t\n\r");
+    for (c = '\n'; i.get (c) && spaces.find (c) != string::npos; c = '\n')
+      ;
+
+    // First non-space character (or '\n' for eof). See if this is a comment.
+    //
+    bool skip (c == '\n' || (c == '-' && i.peek () == '-'));
+
+    // Read until newline (and don't forget the character we already have).
+    //
+    do
+    {
+      if (!skip)
+        statements.push_back (c);
+
+    } while (c != '\n' && i.get (c));
+  }
+
+  istringstream i (move (statements));
+
+  // Build CREATE and DROP statement lists.
+  //
+  while (i)
+  {
+    string op;
+    if (i >> op) // Get the first word.
+    {
+      string statement (op);
+
+      auto read_until = [&i, &statement](const char stop[2]) -> bool
+        {
+          for (char prev ('\0'), c; i.get (c); prev = c)
+          {
+            statement.push_back (c);
+
+            if (stop[0] == prev && stop[1] == c)
+              return true;
+          }
+
+          return false;
+        };
+
+      if (strcasecmp (op.c_str (), "CREATE") == 0)
+      {
+        string kw;
+        i >> kw;
+        statement += " " + kw;
+
+        if (strcasecmp (kw.c_str (), "FUNCTION") == 0)
+        {
+          if (!read_until ("$$") || !read_until ("$$"))
+            throw invalid_argument (
+              "function body must be defined using $$-quoted strings");
+        }
+        else if (strcasecmp (kw.c_str (), "TYPE") == 0)
+        {
+          // Fall through.
+        }
+        else
+          throw invalid_argument ("unexpected CREATE statement");
+
+        if (!read_until (";\n"))
+          throw invalid_argument (
+            "expected ';\\n' at the end of CREATE statement");
+
+        assert (!statement.empty ());
+        create_statements_.emplace_back (move (statement));
+      }
+      else if (strcasecmp (op.c_str (), "DROP") == 0)
+      {
+        if (!read_until (";\n"))
+          throw invalid_argument (
+            "expected ';\\n' at the end of DROP statement");
+
+        assert (!statement.empty ());
+        drop_statements_.emplace_back (move (statement));
+      }
+      else
+        throw invalid_argument (
+          "unexpected statement starting with '" + op + "'");
+    }
+  }
+}
+
+void schema::
+drop (database& db) const
+{
+  for (const auto& s: drop_statements_)
+    // If the statement execution fails, the corresponding source file line
+    // number is not reported. The line number could be usefull for the utility
+    // implementer only. The errors seen by the end-user should not be
+    // statement-specific.
+    //
+    db.execute (s);
+
+  schema_catalog::drop_schema (db);
+}
+
+void schema::
+create (database& db) const
+{
+  drop (db);
+
+  schema_catalog::create_schema (db);
+
+  for (const auto& s: create_statements_)
+    db.execute (s);
+}
+
+// Utility functions
+//
+static void
+usage (ostream& os)
+{
+  os << "Usage: brep-migrate [options]" << endl
+     << "Options:" << endl;
+
+  options::print_usage (os);
+}
+
+// main() function
+//
+int
+main (int argc, char* argv[])
+try
+{
+  cli::argv_scanner scan (argc, argv, true);
+  options ops (scan);
+
+  // Version.
+  //
+  if (ops.version ())
+  {
+    cout << "brep-migrate " << BREP_VERSION_STR << endl
+         << "libbrep " << LIBBREP_VERSION_STR << endl
+         << "libbpkg " << LIBBPKG_VERSION_STR << endl
+         << "libbutl " << LIBBUTL_VERSION_STR << endl
+         << "Copyright (c) 2014-2016 Code Synthesis Ltd" << endl
+         << "MIT; see accompanying LICENSE file" << endl;
+
+    return 0;
+  }
+
+  // Help.
+  //
+  if (ops.help ())
+  {
+    usage (cout);
+    return 0;
+  }
+
+  if (argc > 1)
+  {
+    cerr << "unexpected argument encountered" << endl;
+    usage (cerr);
+    return 1;
+  }
+
+  if (ops.recreate () && ops.drop ())
+  {
+    cerr << "inconsistent options specified" << endl;
+    usage (cerr);
+    return 1;
+  }
+
+  odb::pgsql::database db (ops.db_user (),
+                           ops.db_password (),
+                           ops.db_name (),
+                           ops.db_host (),
+                           ops.db_port ());
+
+  // Prevent several brep-migrate/load instances from updating DB
+  // simultaneously.
+  //
+  database_lock l (db);
+
+  // Need to obtain schema version out of the transaction. If the
+  // schema_version table does not exist, the SQL query fails, which makes the
+  // transaction useless as all consequitive queries in that transaction will
+  // be ignored by PostgreSQL.
+  //
+  schema_version schema_version (db.schema_version ());
+
+  // It is impossible to operate with the database which is out of the
+  // [base_version, current_version] range due to the lack of the knowlege
+  // required not just for migration, but for the database wiping as well.
+  //
+  if (schema_version > 0)
+  {
+    if (schema_version < schema_catalog::base_version (db))
+      throw runtime_error ("database schema is too old");
+
+    if (schema_version > schema_catalog::current_version (db))
+      throw runtime_error ("database schema is too new");
+  }
+
+  bool drop (ops.drop ());
+  bool create (ops.recreate () || (schema_version == 0 && !drop));
+  assert (!create || !drop);
+
+  // The database schema recreation requires dropping it initially, which is
+  // impossible before the database is migrated to the current schema version.
+  // Let the user decide if they want to migrate or just drop the entire
+  // database (followed with the database creation for the --recreate option).
+  //
+  if ((create || drop) && schema_version != 0 &&
+      schema_version != schema_catalog::current_version (db))
+    throw runtime_error ("database schema requires migration");
+
+  transaction t (db.begin ());
+
+  if (create || drop)
+  {
+    static const char extras[] = {
+#include <brep/package-extra>
+      , '\0'};
+
+    schema s (extras);
+
+    if (create)
+      s.create (db);
+    else if (drop)
+      s.drop (db);
+  }
+  else
+  {
+    // Register the data migration functions.
+    //
+    // static const data_migration_entry<2, LIBBREP_SCHEMA_VERSION_BASE>
+    // migrate_v2_entry (&migrate_v2);
+    //
+    schema_catalog::migrate (db);
+  }
+
+  t.commit ();
+}
+catch (const database_locked&)
+{
+  cerr << "brep-migrate or brep-load instance is running" << endl;
+  return 2;
+}
+catch (const cli::exception& e)
+{
+  cerr << e << endl;
+  usage (cerr);
+  return 1;
+}
+// Fully qualified to avoid ambiguity with odb exception.
+//
+catch (const std::exception& e)
+{
+  cerr << e.what () << endl;
+  return 1;
+}
diff --git a/migrate/options.cli b/migrate/options.cli
new file mode 100644
index 0000000..e36155c
--- /dev/null
+++ b/migrate/options.cli
@@ -0,0 +1,90 @@
+// file      : migrate/options.cli
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+include <string>;
+include <cstdint>; // uint16_t
+
+"\section=1"
+"\name=brep-migrate"
+"\summary=create/drop/migrate brep database"
+
+{
+  "<options>",
+
+  "\h|SYNOPSIS|
+
+   \cb{brep-migrate --help}\n
+   \cb{brep-migrate --version}\n
+   \c{\b{brep-migrate} [<options>]}
+
+   \h|DESCRIPTION|
+
+   In its default mode \cb{brep-migrate} creates the database schema if it
+   doesn't already exist. Otherwise, it migrates the existing schema and data
+   to the current version, if needed.
+
+   If the \cb{--recreate} option is specified, then \cb{brep-migrate} instead
+   recreates the database schema. That is, it drops all the existing tables
+   (and their data) and then creates them from scratch.
+
+   If the \cb{--drop} option is specified, then \cb{brep-migrate} drops all the
+   existing tables (and their data).
+
+   The \cb{--recreate} and \cb{--drop} options are mutually exclusive. When
+   specified, they will cause \cb{brep-migrate} to fail if the database schema
+   requires migration. In this case you can either migrate the database first
+   or drop the entire database using, for example, \cb{psql(1)}."
+}
+
+class options
+{
+  "\h|OPTIONS|"
+
+  bool --recreate
+  {
+    "Recreate the database schema (all the existing data will be lost)."
+  }
+
+  bool --drop
+  {
+    "Drop the database schema (all the existing data will be lost)."
+  }
+
+  std::string --db-user|-u
+  {
+    "<user>",
+    "Database user name. If not specified, then operating system (login)
+     name is used."
+  }
+
+  std::string --db-password
+  {
+    "<pass>",
+    "Database password. If not specified, then login without password is
+     expected to work."
+  }
+
+  std::string --db-name|-n = "brep"
+  {
+    "<name>",
+    "Database name. If not specified, then '\cb{brep}' is used by default."
+  }
+
+  std::string --db-host|-h
+  {
+    "<host>",
+    "Database host name, address, or socket. If not specified, then connect
+     to \cb{localhost} using the operating system-default mechanism
+     (Unix-domain socket, etc)."
+  }
+
+  std::uint16_t --db-port|-p = 0
+  {
+    "<port>",
+    "Database port number. If not specified, the default port is used."
+  }
+
+  bool --help {"Print usage information and exit."}
+  bool --version {"Print version and exit."}
+};
diff --git a/tests/buildfile b/tests/buildfile
index ca46f59..2bdea00 100644
--- a/tests/buildfile
+++ b/tests/buildfile
@@ -2,6 +2,6 @@
 # copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
 # license   : MIT; see accompanying LICENSE file
 
-d = loader/ web/
+d = load/ web/
 ./: $d
 include $d
diff --git a/tests/loader/1/basics/packages b/tests/load/1/basics/packages
index 86c20c1..86c20c1 100644
--- a/tests/loader/1/basics/packages
+++ b/tests/load/1/basics/packages
diff --git a/tests/loader/1/basics/repositories b/tests/load/1/basics/repositories
index 57a1c7a..57a1c7a 100644
--- a/tests/loader/1/basics/repositories
+++ b/tests/load/1/basics/repositories
diff --git a/tests/loader/1/math/packages b/tests/load/1/math/packages
index 7b81c5e..7b81c5e 100644
--- a/tests/loader/1/math/packages
+++ b/tests/load/1/math/packages
diff --git a/tests/loader/1/math/repositories b/tests/load/1/math/repositories
index 20aa30d..20aa30d 100644
--- a/tests/loader/1/math/repositories
+++ b/tests/load/1/math/repositories
diff --git a/tests/loader/1/misc/packages b/tests/load/1/misc/packages
index fec3780..fec3780 100644
--- a/tests/loader/1/misc/packages
+++ b/tests/load/1/misc/packages
diff --git a/tests/loader/1/misc/repositories b/tests/load/1/misc/repositories
index 1a41290..1a41290 100644
--- a/tests/loader/1/misc/repositories
+++ b/tests/load/1/misc/repositories
diff --git a/tests/loader/1/stable/packages b/tests/load/1/stable/packages
index afa168a..afa168a 100644
--- a/tests/loader/1/stable/packages
+++ b/tests/load/1/stable/packages
diff --git a/tests/loader/1/stable/repositories b/tests/load/1/stable/repositories
index b692ebe..b692ebe 100644
--- a/tests/loader/1/stable/repositories
+++ b/tests/load/1/stable/repositories
diff --git a/tests/loader/1/staging/packages b/tests/load/1/staging/packages
index e7b22b0..e7b22b0 100644
--- a/tests/loader/1/staging/packages
+++ b/tests/load/1/staging/packages
diff --git a/tests/loader/1/staging/repositories b/tests/load/1/staging/repositories
index d72a3f8..d72a3f8 100644
--- a/tests/loader/1/staging/repositories
+++ b/tests/load/1/staging/repositories
diff --git a/tests/loader/1/testing/packages b/tests/load/1/testing/packages
index bdebece..bdebece 100644
--- a/tests/loader/1/testing/packages
+++ b/tests/load/1/testing/packages
diff --git a/tests/loader/1/testing/repositories b/tests/load/1/testing/repositories
index a218d5c..a218d5c 100644
--- a/tests/loader/1/testing/repositories
+++ b/tests/load/1/testing/repositories
diff --git a/tests/loader/buildfile b/tests/load/buildfile
index d8ab9ac..e68fd1f 100644
--- a/tests/loader/buildfile
+++ b/tests/load/buildfile
@@ -1,4 +1,4 @@
-# file      : tests/loader/buildfile
+# file      : tests/load/buildfile
 # copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
 # license   : MIT; see accompanying LICENSE file
 
@@ -18,4 +18,4 @@ exe{driver}: test = false
 
 # precondition: PostgreSQL server running port 8432 with brep schema created.
 # test:
-# ./driver ../../loader/brep-loader --db-host localhost --db-port 8432 ./r.conf
+# ./driver ../../load/brep-load --db-host localhost --db-port 8432 ./r.conf
diff --git a/tests/loader/driver.cxx b/tests/load/driver.cxx
index 67093d9..7a70ff5 100644
--- a/tests/loader/driver.cxx
+++ b/tests/load/driver.cxx
@@ -1,4 +1,4 @@
-// file      : tests/loader/driver.cxx -*- C++ -*-
+// file      : tests/load/driver.cxx -*- C++ -*-
 // copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
 // license   : MIT; see accompanying LICENSE file
 
diff --git a/tests/loader/r.conf b/tests/load/r.conf
index 8da4b77..8da4b77 100644
--- a/tests/loader/r.conf
+++ b/tests/load/r.conf
diff --git a/web/apache/service.cxx b/web/apache/service.cxx
index c4fe462..96ff855 100644
--- a/web/apache/service.cxx
+++ b/web/apache/service.cxx
@@ -125,7 +125,7 @@ namespace web
 
         // Terminate the root apache process. Indeed we can only try to
         // terminate the process, and most likely will fail in a production
-        // environment where the apache root process usually runs under root
+        // environment where the apache root process usually runs under root,
         // and worker processes run under some other user. This is why the
         // implementation should consider the possibility of not being
         // initialized at the time of HTTP request processing. In such a case