Elasticsearch 1.7.3: doc_values treated as fielddata - elasticsearch

Question

I'm new to ElasticSearch, started working with ElasticSearch 1.7.3 as part of a Logstash-ElasticSearch-Kibana deployment.
I've defined a mapping template for my log messages, this is the interesting part:
{
"template" : "logstash-*",
"settings" : { "index.refresh_interval" : "5s" },
"mappings" : {
"_default_" : {
"_all" : {"enabled" : true, "omit_norms" : true},
"dynamic_templates" : [ {
"date_fields" : {
"match" : "*",
"match_mapping_type" : "date",
"mapping" : { "type" : "date", "doc_values" : true }
}
}],
"properties" : {
"#version" : { "type" : "string", "index" : "not_analyzed" },
"#timestamp" : { "type" : "date", "format" : "dateOptionalTime" },
"message" : { "type" : "string" }
}
} ,
"my_log" : {
"_all" : { "enabled" : true, "omit_norms" : true },
"dynamic_templates" : [ {
"date_fields" : {
"match" : "*",
"match_mapping_type" : "date",
"mapping" : { "type" : "date", "doc_values" : true }
}
}],
"properties" : {
"#timestamp" : { "type" : "date", "format" : "dateOptionalTime" },
"file" : { "type" : "string" },
"message" : { "type" : "string" }
"geolocation" : { "type" : "string" },
}
}
}
}
Although the #timestamp field is defined as doc_value:true I have an error of MemoryException because it is a fielddata:
[FIELDDATA] Data too large, data for [#timestamp] would be larger than
limit of [633785548/604.4 mb]
NOTE:
I know I can change the memory or add more nodes to the cluster, but in my point of view this is a design problem where this field should not be indexed in memory.