failed to parse date field Elasticsearch - elasticsearch

Question

I have an index in elasticsearch 6.2.4, for which i created a new index in new elasticsearch cluster 7.6.1.
I have copied the mapping for this index from 6.2.4 to 7.6.1, but when i tried to _reindex from 6.2.4 to 7.6.1.
I get the below error.
"failures" : [
{
"index" : "newindex",
"type" : "_doc",
"id" : "someid",
"cause" : {
"type" : "mapper_parsing_exception",
"reason" : "failed to parse field [UPDATES.when] of type [date] in document with id 'someid'. Preview of field's value: '1.528501444E9'",
"caused_by" : {
"type" : "illegal_argument_exception",
"reason" : "failed to parse date field [1.528501444E9] with format [epoch_second]",
"caused_by" : {
"type" : "date_time_parse_exception",
"reason" : "Failed to parse with all enclosed parsers"
}
}
},
"status" : 400
}
_reindex call done at 7.6.1's kibana
POST _reindex/?pretty
{
"source": {
"remote": {
"host": "http://oldserver:9200"
},
"index": "oldindex",
"query": {
"match_all": {}
}
},
"dest": {
"index": "newindex"
}
}
Mapping of updates field is same in both places
"UPDATES" : {
"properties" : {
"key" : {
"type" : "text",
"fields" : {
"keyword" : {
"type" : "keyword",
"ignore_above" : 256
}
}
},
"when" : {
"type" : "date",
"format" : "epoch_second"
}
What am I missing here ?

Answer 1

I guess the timestamp which is appearing in one of your date feild 1.528501444E9 is UNIX timestamp in scientific notation.
But Elasticsearch fails because it can't parse 1.528501444E9 since I suppose as per you exception the format that you have given for this field is epoch_second which does not take this format.
You can read futher related to this format from here https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping-date-format.html