elasticsearch的mapping疑问

今天导入了一些日志，看到mapping是这样的：
"logstash-2014.11.24" : {
"mappings" : {
"logs" : {
"dynamic_templates" : [ {
"string_fields" : {
"mapping" : {
"index" : "analyzed",
"omit_norms" : true,
"type" : "string",
"fields" : {
"raw" : {
"index" : "not_analyzed",
"ignore_above" : 256,
"type" : "string"
}
}
},
"match" : "*",
"match_mapping_type" : "string"
}
} ],
"properties" : {
"@timestamp" : {
"type" : "date",
"format" : "dateOptionalTime"
},
"@version" : {
"type" : "string",
"index" : "not_analyzed"
},
"geoip" : {
"dynamic" : "true",
"properties" : {
"location" : {
"type" : "geo_point"
}
}
},
"host" : {
"type" : "string",
"norms" : {
"enabled" : false
},
"fields" : {
"raw" : {
"type" : "string",
"index" : "not_analyzed",
"ignore_above" : 256
}
}
},
"lineno" : {
"type" : "long"
},
"message" : {
"type" : "string",
"norms" : {
"enabled" : false
},
"fields" : {
"raw" : {
"type" : "string",
"index" : "not_analyzed",
"ignore_above" : 256
}
}
},
"path" : {
"type" : "string",
"norms" : {
"enabled" : false
},
"fields" : {
"raw" : {
"type" : "string",
"index" : "not_analyzed",
"ignore_above" : 256
}
}
}
}
}
}
}
请问dynamic_templates里面是什么意思？还有下面 "raw" : {
"type" : "string",
"index" : "not_analyzed",
"ignore_above" : 256
}
这种又有什么作用呢？