Default shards/replicas count

and some clarificaitons in the README

joins/README.md

@@ -28,7 +28,8 @@ Main index:
 ```
 
 The cardinality of the keys is the same as the key name, eg. `key_1000` will have 1000 different values in the dataset,
-from `0` to `999`.
+from `0` to `999` (unless the dataset is not big enough to contain all the keys of a given cardinality, 
+eg. with a dataset of 1000 documents, `key_100000000` will contain only 1000 distinct keys, one per document).
 The IDs and the timestamps are sequential.
 
 ### Parameters
@@ -38,11 +39,10 @@ This track allows to overwrite the following parameters using `--track-params`:
 * `bulk_size` (default: 10000)
 * `bulk_indexing_clients` (default: 8): Number of clients that issue bulk indexing requests.
 * `ingest_percentage` (default: 100): A number between 0 and 100 that defines how much of the document corpus should be ingested. It will be applied to the main index and to the large join indexes (ie. not to join indexes with up to 500K documents)
-* `number_of_replicas` (default: 0)
 * `number_of_shards` (default: 1)
 * `source_mode` (default: stored): Should the `_source` be `stored` to disk exactly as sent (the default), thrown away (`disabled`), or reconstructed on the fly (`synthetic`)
 * `force_merge_max_num_segments` (default: unset): An integer specifying the max amount of segments the force-merge operation should use.
-* `index_settings`: A list of index settings. Index settings defined elsewhere (e.g. `number_of_replicas`) need to be overridden explicitly.
+* `index_settings`: A list of index settings. Index settings defined elsewhere need to be overridden explicitly.
 * `cluster_health` (default: "green"): The minimum required cluster health.
 * `error_level` (default: "non-fatal"): Available for bulk operations only to specify ignore-response-error-level.
 * `detailed_results` (default: `false`): Adds additional [metadata](https://esrally.readthedocs.io/en/latest/track.html?highlight=detailed-results#meta-data) to challenges using the track `update` operation. Be aware using this option can add client side overhead due to the deserialization of API responses.

joins/index-join_base_idx.json

@@ -3,10 +3,6 @@
 {
   "settings": {
     {# non-serverless-index-settings-marker-start #}{%- if build_flavor != "serverless" or serverless_operator == true -%}
-      {% if p_include_non_serverless_index_settings %}
-    "index.number_of_shards": {{number_of_shards | default(1)}},
-    "index.number_of_replicas": {{number_of_replicas | default(0)}},
-      {% endif %}
     "index.requests.cache.enable": false
     {%- endif -%}{# non-serverless-index-settings-marker-end #}
   },