diff --git a/elastic search/02_elastic_search_index.md b/elastic search/02_elastic_search_index.md
index c3701af..632ef03 100644
--- a/elastic search/02_elastic_search_index.md	
+++ b/elastic search/02_elastic_search_index.md	
@@ -16,6 +16,12 @@
       - [path param](#path-param)
       - [query param](#query-param)
       - [示例](#示例)
+  - [Similarity module](#similarity-module)
+    - [配置similarity](#配置similarity)
+  - [slow query](#slow-query)
+    - [Search Slow log](#search-slow-log)
+    - [identify search log origin](#identify-search-log-origin)
+    - [index slow log](#index-slow-log)
 
 
 # index modules
@@ -133,5 +139,140 @@ PUT /my-index-000001/_block/write
   } ]
 }
 ```
+## Similarity module
+similarity moudle（scoring/ranking model）定义了如何对匹配到的document进行打分。similaity是针对单个字段的，这意味着可以通过mapping为每个字段都定义不同的mapping。
 
+similarity仅适用于text类型和keyword类型的字段。
 
+### 配置similarity
+大多similarity都可以通过如下方式进行配置：
+```
+PUT /index
+{
+  "settings": {
+    "index": {
+      "similarity": {
+        "my_similarity": {
+          "type": "DFR",
+          "basic_model": "g",
+          "after_effect": "l",
+          "normalization": "h2",
+          "normalization.h2.c": "3.0"
+        }
+      }
+    }
+  }
+}
+```
+上述示例中，配置了DFR similarity，故而，在mapping中，即可通过`my_similarity`来进行引用，示例如下所示：
+```
+PUT /index/_mapping
+{
+  "properties" : {
+    "title" : { "type" : "text", "similarity" : "my_similarity" }
+  }
+}
+```
+## slow query
+### Search Slow log
+shard level slow search log允许将slow query记录到特定的日志文件中。
+
+对于threshold，可以对query阶段和fetch阶段分别进行配置，示例如下所示：
+```
+index.search.slowlog.threshold.query.warn: 10s
+index.search.slowlog.threshold.query.info: 5s
+index.search.slowlog.threshold.query.debug: 2s
+index.search.slowlog.threshold.query.trace: 500ms
+
+index.search.slowlog.threshold.fetch.warn: 1s
+index.search.slowlog.threshold.fetch.info: 800ms
+index.search.slowlog.threshold.fetch.debug: 500ms
+index.search.slowlog.threshold.fetch.trace: 200ms
+```
+上述所有的配置都是`dynamic`的，并且可以针对每个index单独进行设置，示例如下所示：
+```
+PUT /my-index-000001/_settings
+{
+  "index.search.slowlog.threshold.query.warn": "10s",
+  "index.search.slowlog.threshold.query.info": "5s",
+  "index.search.slowlog.threshold.query.debug": "2s",
+  "index.search.slowlog.threshold.query.trace": "500ms",
+  "index.search.slowlog.threshold.fetch.warn": "1s",
+  "index.search.slowlog.threshold.fetch.info": "800ms",
+  "index.search.slowlog.threshold.fetch.debug": "500ms",
+  "index.search.slowlog.threshold.fetch.trace": "200ms"
+}
+```
+
+默认情况下，threshold为`-1`，代表threshold被停用。
+
+该日志针对的是shard的范围。
+
+search slow log file在`log4j2.properties`文件中进行配置。
+
+### identify search log origin
+通过将`index.search.slowlog.include.user`配置项设置为true，可以在slow log中输出`触发该slow query的用户信息`，示例如下：
+```
+PUT /my-index-000001/_settings
+{
+  "index.search.slowlog.include.user": true
+}
+```
+上述设置将导致用户信息将会被包含在slow log中：
+```json
+{
+  "@timestamp": "2024-02-21T12:42:37.255Z",
+  "log.level": "WARN",
+  "auth.type": "REALM",
+  "elasticsearch.slowlog.id": "tomcat-123",
+  "elasticsearch.slowlog.message": "[index6][0]",
+  "elasticsearch.slowlog.search_type": "QUERY_THEN_FETCH",
+  "elasticsearch.slowlog.source": "{\"query\":{\"match_all\":{\"boost\":1.0}}}",
+  "elasticsearch.slowlog.stats": "[]",
+  "elasticsearch.slowlog.took": "747.3micros",
+  "elasticsearch.slowlog.took_millis": 0,
+  "elasticsearch.slowlog.total_hits": "1 hits",
+  "elasticsearch.slowlog.total_shards": 1,
+  "user.name": "elastic",
+  "user.realm": "reserved",
+  "ecs.version": "1.2.0",
+  "service.name": "ES_ECS",
+  "event.dataset": "elasticsearch.index_search_slowlog",
+  "process.thread.name": "elasticsearch[runTask-0][search][T#5]",
+  "log.logger": "index.search.slowlog.query",
+  "elasticsearch.cluster.uuid": "Ui23kfF1SHKJwu_hI1iPPQ",
+  "elasticsearch.node.id": "JK-jn-XpQ3OsDUsq5ZtfGg",
+  "elasticsearch.node.name": "node-0",
+  "elasticsearch.cluster.name": "distribution_run"
+}
+```
+### index slow log
+index slow log和search slow log类似，其log file名称以`_index_indexing_slowlog.json`结尾。index slow log的配置如下所示：
+```
+index.indexing.slowlog.threshold.index.warn: 10s
+index.indexing.slowlog.threshold.index.info: 5s
+index.indexing.slowlog.threshold.index.debug: 2s
+index.indexing.slowlog.threshold.index.trace: 500ms
+index.indexing.slowlog.source: 1000
+```
+index slow log的配置也是dynamic的，可以通过如下示例来进行配置：
+```
+PUT /my-index-000001/_settings
+{
+  "index.indexing.slowlog.threshold.index.warn": "10s",
+  "index.indexing.slowlog.threshold.index.info": "5s",
+  "index.indexing.slowlog.threshold.index.debug": "2s",
+  "index.indexing.slowlog.threshold.index.trace": "500ms",
+  "index.indexing.slowlog.source": "1000"
+}
+```
+如果想要在日志中包含触发该slow index请求的用户，可以通过如下方式进行请求：
+```
+PUT /my-index-000001/_settings
+{
+  "index.indexing.slowlog.include.user": true
+}
+```
+默认情况下，elasticsearch会打印slow log中头1000个字符。可以通过`index.indexing.slowlog.source`来修改该配置。
+- 如果将`indexing.slowlog.source`设置为false或0，将会跳过对`source`的输出
+- 如果将`indexing.slowlog.source`设置为true，将会输出所有`source`的内容