Disregard migrations older than the schema

septentrion/core.py

@@ -145,6 +145,11 @@ def build_migration_plan(settings: configuration.Settings) -> Iterable[Dict[str,
             "version {} not found.".format(settings.TARGET_VERSION)
         )
 
+    if settings.SCHEMA_VERSION:
+        versions_to_apply = list(
+            utils.since(versions_to_apply, settings.SCHEMA_VERSION)
+        )
+
     # get plan for each version to apply
     for version in versions_to_apply:
         version_plan = []
@@ -177,6 +182,14 @@ def describe_migration_plan(
     with stylist.activate("title") as echo:
         echo("Current version is {}".format(current_version))
 
+    schema_version = settings.SCHEMA_VERSION
+    if schema_version:
+        with stylist.activate("title") as echo:
+            echo("Schema version is {}".format(schema_version))
+    else:
+        with stylist.activate("title") as echo:
+            echo("No explicit schema version. All migrations are considered.")
+
     target_version = settings.TARGET_VERSION
     with stylist.activate("title") as echo:
         echo("Target version is {}".format(target_version))

septentrion/utils.py

@@ -2,6 +2,7 @@
 All functions in here should be easily unit testable
 """
 
+import itertools
 from typing import Iterable, TypeVar
 
 from septentrion import exceptions, versions
@@ -37,3 +38,15 @@ def until(iterable: Iterable[T], value: T) -> Iterable[T]:
             break
     else:
         raise ValueError("{} not found".format(value))
+
+
+def since(iterable: Iterable[T], value: T) -> Iterable[T]:
+    """
+    Returns the values from iterable starting after the element is found
+    >>> list(until(range(300), 297))
+    [298, 299]
+    """
+    it = itertools.dropwhile((lambda x: x != value), iterable)
+    # Drop the first element
+    next(it)
+    yield from it