elasticsearch-painless - Manipulate date - elasticsearch

Question

I am trying to manipulate date in elasticsearch's scripting language painless.
Specifically, I am trying to add 4 hours, which is 14,400 seconds.
{
"script_fields": {
"new_date_field": {
"script": {
"inline": "doc['date_field'] + 14400"
}
}
}
}
This throws Cannot apply [+] operation to types [org.elasticsearch.index.fielddata.ScriptDocValues.Longs] and [java.lang.Integer].
Thanks

Answer 1

The solution was to use .value
{
"script_fields": {
"new_date_field": {
"script": {
"inline": "doc['date_field'].value + 14400"
}
}
}
}
However, I actually wanted to use it for reindexing, where the format is a bit different.
Here is my version for manipulating time in the _reindex api
POST _reindex
{
"source": {
"index": "some_index_v1"
},
"dest": {
"index": "some_index_v2"
},
"script": {
"inline": "def sf = new SimpleDateFormat(\"yyyy-MM-dd'T'HH:mm:ss\"); def dt = sf.parse(ctx._source.date_field); def calendar = sf.getCalendar(); calendar.setTime(dt); def instant = calendar.toInstant(); def localDateTime = LocalDateTime.ofInstant(instant, ZoneOffset.UTC); ctx._source.date_field = localDateTime.plusHours(4);"
}
}
Here is the inline script in a readable version
def sf = new SimpleDateFormat(\"yyyy-MM-dd'T'HH:mm:ss\");
def dt = sf.parse(ctx._source.date_field);
def calendar = sf.getCalendar();
calendar.setTime(dt);
def instant = calendar.toInstant();
def localDateTime = LocalDateTime.ofInstant(instant, ZoneOffset.UTC);
ctx._source.date_field = localDateTime.plusHours(4);
Here is the list of functions supported by painless, it was painful.

Answer 2

An addition. Converting date to a string, your first part I believe, can be done with:
def dt = String.valueOf(ctx._source.date_field);
Just spent a couple of hours playing with this.. so I can concantenate a date field (in UTC format with 00:00:00 added).. to a string with the time, to get a valid datetime to add to ES. Don't ask why it was split.. its an old Oracle system