Fix create_bwc_index for 5.x (#19469)

`create_bwc_index.py` has some cruft in it that only works on 2.x or
even before. This commit make the tool functional, yet there might still
be some bwc relevant things missing here.

Closes #19253

dev-tools/create_bwc_index.py

@@ -31,7 +31,6 @@ DEFAULT_HTTP_TCP_PORT = 9200
 if sys.version_info[0] < 3:
   print('%s must use python 3.x (for the ES python client)' % sys.argv[0])
 
-from datetime import datetime
 try:
   from elasticsearch import Elasticsearch
   from elasticsearch.exceptions import ConnectionError
@@ -178,9 +177,15 @@ def generate_index(client, version, index_name):
   logging.info('Create single shard test index')
 
   mappings = {}
-  if not version.startswith('2.'):
-    # TODO: we need better "before/onOr/after" logic in python
-
+  warmers = {}
+  if parse_version(version) < parse_version('2.0.0-alpha1'):
+    warmers['warmer1'] = {
+      'source': {
+        'query': {
+          'match_all': {}
+        }
+      }
+    }
     # backcompat test for legacy type level analyzer settings, see #8874
     mappings['analyzer_type1'] = {
       'analyzer': 'standard',
@@ -219,15 +224,9 @@ def generate_index(client, version, index_name):
       }
     }
     mappings['meta_fields'] = {
-      '_id': {
-        'path': 'myid'
-      },
       '_routing': {
-        'path': 'myrouting'
+        'required': 'false'
       },
-      '_boost': {
-        'null_value': 2.0
-      }     
     }
     mappings['custom_formats'] = {
       'properties': {
@@ -246,34 +245,57 @@ def generate_index(client, version, index_name):
         'auto_boost': True
       }
     }
-
-  mappings['norms'] = {
-    'properties': {
-      'string_with_norms_disabled': {
-        'type': 'string',
-        'norms': {
-          'enabled': False
-        }
-      },
-      'string_with_norms_enabled': {
-        'type': 'string',
-        'index': 'not_analyzed',
-        'norms': {
-          'enabled': True,
-          'loading': 'eager'
+  if parse_version(version) < parse_version("5.0.0-alpha1"):
+    mappings['norms'] = {
+      'properties': {
+        'string_with_norms_disabled': {
+          'type': 'string',
+          'norms' : {
+            'enabled' : False
+          }
+        },
+        'string_with_norms_enabled': {
+          'type': 'string',
+          'index': 'not_analyzed',
+          'norms': {
+            'enabled' : True,
+            'loading': 'eager'
+          }
         }
       }
     }
-  }
 
-  mappings['doc'] = {
-    'properties': {
-      'string': {
-        'type': 'string',
-        'boost': 4
+    mappings['doc'] = {
+      'properties': {
+        'string': {
+          'type': 'string',
+          'boost': 4
+        }
+      }
+    }
+  else: # current version of the norms mapping
+    mappings['norms'] = {
+      'properties': {
+        'string_with_norms_disabled': {
+          'type': 'text',
+          'norms' : False
+        },
+        'string_with_norms_enabled': {
+          'type': 'keyword',
+          'index': 'not_analyzed',
+          'norms': True,
+          'eager_global_ordinals' : True
+        }
+      }
+    }
+    mappings['doc'] = {
+      'properties': {
+        'string': {
+          'type': 'text',
+          'boost': 4
+        }
       }
     }
-  }
 
   settings = {
     'number_of_shards': 1,
@@ -284,21 +306,14 @@ def generate_index(client, version, index_name):
     settings['gc_deletes'] = '60000',
     # Same as ES default (5 GB), but missing the units to make sure they are inserted on upgrade:
     settings['merge.policy.max_merged_segment'] = '5368709120'
-    
-  warmers = {}
-  warmers['warmer1'] = {
-    'source': {
-      'query': {
-        'match_all': {}
-      }
-    }
+  body = {
+    'settings': settings,
+    'mappings': mappings,
   }
 
-  client.indices.create(index=index_name, body={
-      'settings': settings,
-      'mappings': mappings,
-      'warmers': warmers
-  })
+  if warmers:
+    body['warmers'] = warmers
+  client.indices.create(index=index_name, body=body)
   health = client.cluster.health(wait_for_status='green', wait_for_relocating_shards=0)
   assert health['timed_out'] == False, 'cluster health timed out %s' % health
 
@@ -313,15 +328,17 @@ def generate_index(client, version, index_name):
   run_basic_asserts(client, index_name, 'doc', num_docs)
 
 def snapshot_index(client, version, repo_dir):
+  persistent = {
+    'cluster.routing.allocation.exclude.version_attr': version
+  }
+  if parse_version(version) < parse_version('5.0.0-alpha1'):
+    # Same as ES default (30 seconds), but missing the units to make sure they are inserted on upgrade:
+    persistent['discovery.zen.publish_timeout'] = '30000'
+    # Same as ES default (512 KB), but missing the units to make sure they are inserted on upgrade:
+    persistent['indices.recovery.file_chunk_size'] = '524288'
   # Add bogus persistent settings to make sure they can be restored
   client.cluster.put_settings(body={
-    'persistent': {
-      'cluster.routing.allocation.exclude.version_attr': version,
-      # Same as ES default (30 seconds), but missing the units to make sure they are inserted on upgrade:
-      'discovery.zen.publish_timeout': '30000',
-      # Same as ES default (512 KB), but missing the units to make sure they are inserted on upgrade:
-      'indices.recovery.file_chunk_size': '524288',
-    }
+    'persistent': persistent
   })
   client.indices.put_template(name='template_' + version.lower(), order=0, body={
     "template": "te*",
@@ -446,7 +463,24 @@ def shutdown_node(node):
   logging.info('Shutting down node with pid %d', node.pid)
   node.terminate()
   node.wait()
-    
+
+def parse_version(version):
+  import re
+  splitted = re.split('[.-]', version)
+  if len(splitted) == 3:
+    splitted = splitted + ['GA']
+  splitted = [s.lower() for s in splitted]
+  assert len(splitted) == 4;
+  return splitted
+
+assert parse_version('5.0.0-alpha1') == parse_version('5.0.0-alpha1')
+assert parse_version('5.0.0-alpha1') < parse_version('5.0.0-alpha2')
+assert parse_version('5.0.0-alpha1') < parse_version('5.0.0-beta1')
+assert parse_version('5.0.0-beta1') < parse_version('5.0.0')
+assert parse_version('1.2.3') < parse_version('2.1.0')
+assert parse_version('1.2.3') < parse_version('1.2.4')
+assert parse_version('1.1.0') < parse_version('1.2.0')
+
 def main():
   logging.basicConfig(format='[%(levelname)s] [%(asctime)s] %(message)s', level=logging.INFO,
                       datefmt='%Y-%m-%d %I:%M:%S %p')
@@ -461,3 +495,4 @@ if __name__ == '__main__':
     main()
   except KeyboardInterrupt:
     print('Caught keyboard interrupt, exiting...')
+