OpenSearch/watcher/docs/reference/condition/compare.asciidoc

99 lines
3.9 KiB
Plaintext

[[condition-compare]]
==== Compare Condition
A watch <<condition, condition>> that simply compares a value in the <<watch-execution-context, Watch Execution Context Model>>
to given value. The value in the model is identified by a path within that model.
While limited in its functionality, the advantage of this condition over the <<condition-script, Script Condition>>
is that you do not have to enable dynamic scripting to use compare conditions.
===== Using a Compare Condition
The following snippet configures a `compare` condition that returns `true` if the number of
the total hits in the search result (typically loaded by the <<input-search, Search Input>>) is
higher or equals 5:
[source,json]
--------------------------------------------------
{
...
"condition" : {
"compare" : {
"ctx.payload.hits.total" : { <1>
"gte" : 5 <2>
}
}
...
}
--------------------------------------------------
<1> The field name is the path to the execution context model
<2> The field name (here `gte`) is the comparison operator, and the value is the value to compare to.
The path is a "dot-notation" expression that can reference the following variables in the watch context:
[options="header"]
|======
| Name | Description
| `ctx.watch_id` | The id of the watch that is currently executing.
| `ctx.execution_time` | The time execution of this watch started.
| `ctx.trigger.triggered_time` | The time this watch was triggered.
| `ctx.trigger.scheduled_time` | The time this watch was supposed to be triggered.
| `ctx.metadata.*` | Any metadata associated with the watch.
| `ctx.payload.*` | The payload data loaded by the watch's input.
|======
TIP: You can reference entries in arrays using their zero-based array indices. For example, to access the third
element of the `ctx.payload.hits.hits` array, use `ctx.payload.hits.hits.2`.
[[condition-compare-operators]]
The comparison operator can be any one of the following:
[options="header"]
|======
| Name | Description
| `eq` | Returns `true` when the resolved value equals the given one (applies to numeric, string, list, object and values)
| `not_eq` | Returns `true` when the resolved value does not equal the given one (applies to numeric, string, list, object and null values)
| `gt` | Returns `true` when the resolved value is greater than the given one (applies to numeric and string values)
| `gte` | Returns `true` when the resolved value is greater/equal than/to the given one (applies to numeric and string values)
| `lt` | Returns `true` when the resolved value is less than the given one (applies to numeric and string values)
| `lte` | Returns `true` when the resolved value is less/equal than/to the given one (applies to numeric and string values)
|======
When dealing with dates/times, the specified value can hold date math expression in the form of `<{expression}>`. For example, one
can compare the watch execution time as follows:
[source,json]
--------------------------------------------------
{
...
"condition" : {
"compare" : {
"ctx.execution_time" : {
"gte" : "<{now-5m}>"
}
}
...
}
--------------------------------------------------
It is also possible to compare one value in the context model to another value in the same model. This can be done by
specifying the compared value as a path in the form of `{{path}}`. The following snippet shows a condition that compares
two values in the payload
[source,json]
--------------------------------------------------
{
...
"condition" : {
"compare" : {
"ctx.payload.aggregations.status.buckets.error.doc_count" : {
"not_eq" : "{{ctx.payload.aggregations.handled.buckets.true.doc_count}}"
}
}
...
}
--------------------------------------------------