From cb18653c9fa6ef3366729ee36a3d221d9e158df4 Mon Sep 17 00:00:00 2001
From: discord9 <55937128+discord9@users.noreply.github.com>
Date: Tue, 29 Sep 2026 19:38:50 +0800
Subject: [PATCH] fix(promql): report dropped modulo histogram samples

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>
---
 src/query/src/promql/planner.rs      | 22 ++++++++++++++++++++--
 src/query/src/promql/planner/test.rs |  3 +++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/query/src/promql/planner.rs b/src/query/src/promql/planner.rs
index 8984ce9c205..32320144c02 100644
--- a/src/query/src/promql/planner.rs
+++ b/src/query/src/promql/planner.rs
@@ -1620,6 +1620,23 @@ impl PromPlanner {
                 {
                     float_pairs.extend(std::mem::take(&mut invalid_field_pairs));
                 }
+                // `%` over a mixed float/histogram vector and a native-histogram vector supports
+                // none of its pairs, so `align_binary_field_columns` falls back to a single lane
+                // that holds nothing but the discarded pairs. Record the dropped samples from
+                // that lane instead of a standalone annotation filter: `%` is not a comparison,
+                // so each lane expression is a `Float64(NULL)` drop UDF, and the outer non-null
+                // filter still discards those rows.
+                else if op.id() == token::T_MOD
+                    && self.promql_annotations.is_some()
+                    && !invalid_field_pairs.is_empty()
+                    && field_groups.len() == 1
+                    && field_groups[0]
+                        .1
+                        .iter()
+                        .all(|pair| invalid_field_pairs.contains(pair))
+                {
+                    field_groups[0].1 = std::mem::take(&mut invalid_field_pairs);
+                }
                 let mut field_groups = field_groups.into_iter();
                 // `vector()` uses EmptyMetric and keeps GreptimeDB's timestamp broadcast.
                 let has_empty_metric_operand = left_is_empty_metric || right_is_empty_metric;
@@ -1685,8 +1702,9 @@ impl PromPlanner {
                 let promql_annotations = self.promql_annotations.clone();
                 // These predicates always pass; they only evaluate otherwise-discarded pairs
                 // while collecting annotations. `+`/`-` over two alternative float/histogram
-                // operands already consumed its mixed pairs into the float lane above, where
-                // the physical plan cannot short-circuit them away.
+                // operands and `%` over a mixed vector and a native-histogram vector already
+                // consumed their mixed pairs into their only output lane above, where the
+                // physical plan cannot short-circuit them away.
                 let invalid_pair_predicates = invalid_field_pairs
                     .into_iter()
                     .filter(|_| promql_annotations.is_some())
diff --git a/src/query/src/promql/planner/test.rs b/src/query/src/promql/planner/test.rs
index 4f845450d6d..55964305689 100644
--- a/src/query/src/promql/planner/test.rs
+++ b/src/query/src/promql/planner/test.rs
@@ -8267,6 +8267,9 @@ async fn test_mixed_binary_operator_reports_only_dropped_samples() {
             0,
         ),
         ("(lf or on(tag) lh) % on(tag) lh", 0, 1),
+        // A non-bool comparison drops its unsupported pairs through the standalone annotation
+        // filter, not through the lane, so the dropped samples are still reported.
+        ("(lf or on(tag) lh) > on(tag) lh", 0, 1),
     ] {
         let state = build_query_engine_state();
         let annotations = PromqlAnnotationCollector::default();