If a search after request targets multiple indices and some of its sort
field has type `date` in one index but `date_nanos` in other indices,
then Elasticsearch won't interpret the search_after parameter correctly
in every target index. The sort value of a date field by default is a
long of milliseconds since the epoch while a date_nanos field is a long
of nanoseconds.
This commit introduces the `format` parameter in the sort field so a
sort value of a date or date_nanos will be formatted using a date format
in a search response.
The below example illustrates how to use this new parameter.
```js
{
"query": {
"match_all": {}
},
"sort": [
{
"timestamp": {
"order": "asc",
"format": "strict_date_optional_time_nanos"
}
}
]
}
```
```js
{
"query": {
"match_all": {}
},
"sort": [
{
"timestamp": {
"order": "asc",
"format": "strict_date_optional_time_nanos"
}
}
],
"search_after": [
"2015-01-01T12:10:30.123456789Z" // in `strict_date_optional_time_nanos` format
]
}
```
Closes#69192
8b5aa84647