Fix acceptance test failures

Signed-off-by: 🌲 Harry 🌊 John 🏔 <[email protected]>

Author: harry671003

engine/engine_test.go

@@ -250,7 +250,7 @@ func TestQueriesAgainstOldEngine(t *testing.T) {
 			load: `load 30s
 			    http_requests_total{pod="nginx-1"} 1+1.1x10
 			    http_requests_total{pod="nginx-2"} 2+2.3x50`,
-			query: `predict_linear({__name__="http_requests_total", pod!~"nginx-1"}[5m] @ start(), -0.37690610678629094)`,
+			query: `predict_linear({__name__="http_requests_total",pod!~"nginx-1"}[5m] @ start(), -0.37690610678629094)`,
 			end:   time.Unix(600, 0),
 			start: time.Unix(300, 0),
 		},

logicalplan/logical_nodes.go

@@ -115,6 +115,7 @@ func (f *VectorSelector) ReturnType() parser.ValueType { return parser.ValueType
 type MatrixSelector struct {
 	VectorSelector *VectorSelector `json:"-"`
 	Range          time.Duration
+	Timestamp      *int64
 
 	// Needed because this operator is used in the distributed mode
 	OriginalString string

logicalplan/plan.go

@@ -248,7 +248,13 @@ func replacePrometheusNodes(plan parser.Expr) Node {
 		// parents of matrixselector nodes are always expected to be functions, not step invariant
 		// operators.
 		if m, ok := t.Expr.(*parser.MatrixSelector); ok {
-			return replacePrometheusNodes(m)
+			n := replacePrometheusNodes(m)
+			if ms, ok := n.(*MatrixSelector); ok {
+				// For cases such as predict_linear(metric[5m] @start() , 0.3), we mark the
+				// matrix selector to be invariant. The scanner will only scan points once in such cases.
+				ms.Timestamp = ms.VectorSelector.Timestamp
+			}
+			return n
 		}
 		return &StepInvariantExpr{Expr: replacePrometheusNodes(t.Expr)}
 	case *parser.MatrixSelector:

storage/prometheus/scanners.go

@@ -134,7 +134,7 @@ func (p Scanners) NewMatrixSelector(
 			call.Func.Name,
 			arg,
 			arg2,
-			logicalNode.VectorSelector.Timestamp,
+			logicalNode.Timestamp,
 			opts,
 			logicalNode.Range,
 			vs.Offset,