fix: use ms in prepareFillZeroArgsWithStep (#11196)

frontend/src/lib/uPlotV2/components/Tooltip/Tooltip.tsx

@@ -24,15 +24,10 @@ export default function Tooltip({
 	);
 
 	const showHeader = showTooltipHeader || activeItem != null;
-	// A single row collapses into the header when it's the active item, but
-	// must stay in the list when there's no active item (e.g. sync-driven
-	// tooltips with no focused series) — otherwise the row would vanish.
-	const showList =
-		tooltipContent.length > 1 ||
-		(tooltipContent.length === 1 && activeItem == null);
-	// The divider separates the active row in the header from the list; with
-	// no active item it has nothing to separate.
-	const showDivider = showList && showHeader && activeItem != null;
+	// With a single series the active item is fully represented in the header —
+	// hide the divider and list to avoid showing a duplicate row.
+	const showList = tooltipContent.length > 1;
+	const showDivider = showList && showHeader;
 
 	return (
 		<div

frontend/src/lib/uPlotV2/plugins/TooltipPlugin/syncDisplayHook.ts

@@ -137,7 +137,7 @@ function applyReceiverSync({
 
 	if (commonKeys.length === 0) {
 		uPlotInstance.setSeries(null, { focus: false });
-		return noMatchResult;
+		return [];
 	}
 
 	if ((uPlotInstance.cursor.left ?? -1) < 0) {

pkg/querier/postprocess.go

@@ -12,6 +12,7 @@ import (
 	"github.com/SigNoz/govaluate"
 
 	"github.com/SigNoz/signoz/pkg/errors"
+	"github.com/SigNoz/signoz/pkg/querybuilder"
 	qbtypes "github.com/SigNoz/signoz/pkg/types/querybuildertypes/querybuildertypesv5"
 	"github.com/SigNoz/signoz/pkg/types/telemetrytypes"
 )
@@ -969,11 +970,19 @@ func (q *querier) prepareFillZeroArgsWithStep(functions []qbtypes.Function, req
 	updatedFunctions := make([]qbtypes.Function, len(functions))
 	copy(updatedFunctions, functions)
 
+	// funcFillZero expects start/end in milliseconds. req.Start/req.End may
+	// arrive in s/ms/μs/ns depending on the caller; normalize via ToNanoSecs
+	// (same pattern used elsewhere in the codebase, e.g. RecommendedStepInterval)
+	// then convert to ms. Without this, an ns payload makes (end-start)/step
+	// 10^6× too large and OOMs the process.
+	startMs := querybuilder.ToNanoSecs(req.Start) / 1_000_000
+	endMs := querybuilder.ToNanoSecs(req.End) / 1_000_000
+
 	for i, fn := range updatedFunctions {
 		if fn.Name == qbtypes.FunctionNameFillZero && len(fn.Args) == 0 {
 			fn.Args = []qbtypes.FunctionArg{
-				{Value: float64(req.Start)},
-				{Value: float64(req.End)},
+				{Value: float64(startMs)},
+				{Value: float64(endMs)},
 				{Value: float64(step)},
 			}
 			updatedFunctions[i] = fn