From 78a3f9d2223a7c6477036c8bd6fb8a6f188f344f Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Sat, 28 Sep 2013 13:15:48 +0200
Subject: Rework migration API in schema_catalog

Specifically:

 - Rename latest_version() to current_version().
 - Change next_version() to return one past current instead of 0 if
   passed current.
 - migrate() will now do schema creation if current database version
   is 0 (no schema).
---
 odb/schema-catalog.cxx | 54 ++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 39 insertions(+), 15 deletions(-)

(limited to 'odb/schema-catalog.cxx')

diff --git a/odb/schema-catalog.cxx b/odb/schema-catalog.cxx
index 15cdcb9..bec13a7 100644
--- a/odb/schema-catalog.cxx
+++ b/odb/schema-catalog.cxx
@@ -250,15 +250,30 @@ namespace odb
   void schema_catalog::
   migrate (database& db, schema_version v, const string& name)
   {
-    schema_version latest (latest_version (db, name));
+    schema_version cur (current_version (db, name));
 
     if (v == 0)
-      v = latest;
-    else if (v > latest)
+      v = cur;
+    else if (v > cur)
       throw unknown_schema_version (v);
 
-    for (schema_version i (next_version (db, 0, name));
-         i != 0 && i <= v;
+    schema_version i (db.schema_version (name));
+
+    // If there is no schema, then "migrate" by creating it.
+    //
+    if (i == 0)
+    {
+      // Schema creation can only "migrate" straight to current.
+      //
+      if (v != cur)
+        throw unknown_schema_version (v);
+
+      create_schema (db, name, false);
+      return;
+    }
+
+    for (i = next_version (db, i, name);
+         i <= v;
          i = next_version (db, i, name))
     {
       migrate_schema_pre (db, i, name);
@@ -268,7 +283,7 @@ namespace odb
   }
 
   schema_version schema_catalog::
-  next_version (database_id id, schema_version current, const string& name)
+  current_version (database_id id, const string& name)
   {
     const schema_catalog_impl& c (*schema_catalog_init::catalog);
     schema_map::const_iterator i (c.schema.find (key (id, name)));
@@ -277,22 +292,31 @@ namespace odb
       throw unknown_schema (name);
 
     const version_map& vm (i->second.migrate);
-    version_map::const_iterator j (vm.upper_bound (current));
-    return j != vm.end () ? j->first : 0;
+    assert (!vm.empty ());
+    return vm.rbegin ()->first;
   }
 
   schema_version schema_catalog::
-  latest_version (database_id id, const string& name)
+  next_version (database_id id, schema_version v, const string& name)
   {
-    const schema_catalog_impl& c (*schema_catalog_init::catalog);
-    schema_map::const_iterator i (c.schema.find (key (id, name)));
+    const schema_catalog_impl& sc (*schema_catalog_init::catalog);
+    schema_map::const_iterator i (sc.schema.find (key (id, name)));
 
-    if (i == c.schema.end ())
+    if (i == sc.schema.end ())
       throw unknown_schema (name);
 
-    const version_map& vm (i->second.migrate);
-    assert (!vm.empty ());
-    return vm.rbegin ()->first;
+    const version_map& vm (i->second.migrate); // Cannot be empty.
+
+    schema_version b (vm.begin ()->first);
+    schema_version c (vm.rbegin ()->first);
+
+    if (v == 0)
+      return c; // "Migration" to the current via schema creation.
+    else if (v < b)
+      throw unknown_schema_version (v); // Unsupported migration.
+
+    version_map::const_iterator j (vm.upper_bound (v));
+    return j != vm.end () ? j->first : c + 1;
   }
 
   // schema_catalog_init
-- 
cgit v1.1