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+[[mapping-all-field]]
+=== `_all`
+
+The idea of the `_all` field is that it includes the text of one or more
+other fields within the document indexed. It can come very handy
+especially for search requests, where we want to execute a search query
+against the content of a document, without knowing which fields to
+search on. This comes at the expense of CPU cycles and index size.
+
+The `_all` fields can be completely disabled. Explicit field mapping and
+object mapping can be excluded / included in the `_all` field. By
+default, it is enabled and all fields are included in it for ease of
+use.
+
+When disabling the `_all` field, it is a good practice to set
+`index.query.default_field` to a different value (for example, if you
+have a main "message" field in your data, set it to `message`).
+
+One of the nice features of the `_all` field is that it takes into
+account specific fields boost levels. Meaning that if a title field is
+boosted more than content, the title (part) in the `_all` field will
+mean more than the content (part) in the `_all` field.
+
+Here is a sample mapping:
+
+[source,js]
+--------------------------------------------------
+{
+    "person" : {
+        "_all" : {"enabled" : true},
+        "properties" : {
+            "name" : {
+                "type" : "object",
+                "dynamic" : false,
+                "properties" : {
+                    "first" : {"type" : "string", "store" : true , "include_in_all" : false},
+                    "last" : {"type" : "string", "index" : "not_analyzed"}
+                }
+            },
+            "address" : {
+                "type" : "object",
+                "include_in_all" : false,
+                "properties" : {
+                    "first" : {
+                        "properties" : {
+                            "location" : {"type" : "string", "store" : true, "index_name" : "firstLocation"}
+                        }
+                    },
+                    "last" : {
+                        "properties" : {
+                            "location" : {"type" : "string"}
+                        }
+                    }
+                }
+            },
+            "simple1" : {"type" : "long", "include_in_all" : true},
+            "simple2" : {"type" : "long", "include_in_all" : false}
+        }
+    }
+}
+--------------------------------------------------
+
+The `_all` fields allows for `store`, `term_vector` and `analyzer` (with
+specific `index_analyzer` and `search_analyzer`) to be set.
+
+[float]
+[[highlighting]]
+==== Highlighting
+
+For any field to allow
+<<search-request-highlighting,highlighting>> it has
+to be either stored or part of the `_source` field. By default `_all`
+field does not qualify for either, so highlighting for it does not yield
+any data.
+
+Although it is possible to `store` the `_all` field, it is basically an
+aggregation of all fields, which means more data will be stored, and
+highlighting it might produce strange results.