Esql compare nanos and millis (elastic#118027)

Resolves elastic#116281 Introduces support for comparing millisecond dates with nanosecond dates, without the need for casting. Millisecond dates outside of the nanosecond date range are handled correctly.
not-napoleon · Dec 6, 2024 · fdb36aa · fdb36aa
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diff --git a/docs/changelog/118027.yaml b/docs/changelog/118027.yaml
@@ -0,0 +1,6 @@
+pr: 118027
+summary: Esql compare nanos and millis
+area: ES|QL
+type: enhancement
+issues:
+ - 116281
diff --git a/docs/reference/esql/functions/kibana/definition/equals.json b/docs/reference/esql/functions/kibana/definition/equals.json
diff --git a/docs/reference/esql/functions/kibana/definition/greater_than.json b/docs/reference/esql/functions/kibana/definition/greater_than.json
diff --git a/docs/reference/esql/functions/kibana/definition/greater_than_or_equal.json b/docs/reference/esql/functions/kibana/definition/greater_than_or_equal.json
diff --git a/docs/reference/esql/functions/kibana/definition/less_than.json b/docs/reference/esql/functions/kibana/definition/less_than.json
diff --git a/docs/reference/esql/functions/kibana/definition/less_than_or_equal.json b/docs/reference/esql/functions/kibana/definition/less_than_or_equal.json
diff --git a/docs/reference/esql/functions/kibana/definition/not_equals.json b/docs/reference/esql/functions/kibana/definition/not_equals.json
diff --git a/docs/reference/esql/functions/types/equals.asciidoc b/docs/reference/esql/functions/types/equals.asciidoc
diff --git a/docs/reference/esql/functions/types/greater_than.asciidoc b/docs/reference/esql/functions/types/greater_than.asciidoc
diff --git a/docs/reference/esql/functions/types/greater_than_or_equal.asciidoc b/docs/reference/esql/functions/types/greater_than_or_equal.asciidoc
diff --git a/docs/reference/esql/functions/types/less_than.asciidoc b/docs/reference/esql/functions/types/less_than.asciidoc
diff --git a/docs/reference/esql/functions/types/less_than_or_equal.asciidoc b/docs/reference/esql/functions/types/less_than_or_equal.asciidoc
diff --git a/docs/reference/esql/functions/types/not_equals.asciidoc b/docs/reference/esql/functions/types/not_equals.asciidoc
diff --git a/server/src/main/java/org/elasticsearch/common/time/DateUtils.java b/server/src/main/java/org/elasticsearch/common/time/DateUtils.java
@@ -298,6 +298,37 @@ public static long toMilliSeconds(long nanoSecondsSinceEpoch) {
         return nanoSecondsSinceEpoch / 1_000_000;
     }
 
+    /**
+     * Compare an epoch nanosecond date (such as returned by {@link DateUtils#toLong}
+     * to an epoch millisecond date (such as returned by {@link Instant#toEpochMilli()}}.
+     * <p>
+     * NB: This function does not implement {@link java.util.Comparator} in
+     * order to avoid performance costs of autoboxing the input longs.
+     *
+     * @param nanos Epoch date represented as a long number of nanoseconds.
+     *              Note that Elasticsearch does not support nanosecond dates
+     *              before Epoch, so this number should never be negative.
+     * @param millis Epoch date represented as a long number of milliseconds.
+     *               This parameter does not have to be constrained to the
+     *               range of long nanosecond dates.
+     * @return -1 if the nanosecond date is before the millisecond date,
+     *         0  if the two dates represent the same instant,
+     *         1  if the nanosecond date is after the millisecond date
+     */
+    public static int compareNanosToMillis(long nanos, long millis) {
+        assert nanos >= 0;
+        if (millis < 0) {
+            return 1;
+        }
+        if (millis > MAX_NANOSECOND_IN_MILLIS) {
+            return -1;
+        }
+        // This can't overflow, because we know millis is between 0 and MAX_NANOSECOND_IN_MILLIS,
+        // and MAX_NANOSECOND_IN_MILLIS * 1_000_000 doesn't overflow.
+        long diff = nanos - (millis * 1_000_000);
+        return diff == 0 ? 0 : diff < 0 ? -1 : 1;
+    }
+
     /**
      * Rounds the given utc milliseconds sicne the epoch down to the next unit millis
      *