diff --git a/pkg/sql/opt/memo/cost.go b/pkg/sql/opt/memo/cost.go
index 3ee6ce0a140d..309613b1c2de 100644
--- a/pkg/sql/opt/memo/cost.go
+++ b/pkg/sql/opt/memo/cost.go
@@ -36,7 +36,7 @@ type Cost struct {
 // member will have a lower cost.
 var MaxCost = Cost{
 	C:         math.Inf(+1),
-	Penalties: HugeCostPenalty | FullScanPenalty | UnboundedCardinalityPenalty,
+	Penalties: HugeCostPenalty | FullScanPenalty | PlanGramMismatchPenalty | UnboundedCardinalityPenalty,
 }
 
 // Less returns true if this cost is lower than the given cost.
@@ -105,6 +105,11 @@ const (
 	// plan is possible.
 	FullScanPenalty
 
+	// PlanGramMismatchPenalty is true if the plan does not match the required
+	// PlanGram pattern, indicating that this plan should only be used if no
+	// PlanGram-matching plan is possible.
+	PlanGramMismatchPenalty
+
 	// UnboundedCardinalityPenalty is true if the operator or any of its
 	// descendants have no guaranteed upperbound on the number of rows that they
 	// can produce. See props.AnyCardinality.
@@ -121,8 +126,9 @@ const (
 // Where:
 //
 //	<Cost> is the floating point cost value.
-//	<Penalties> contains "H", "F", or "U" for HugeCostPenalty, FullScanPenalty,
-//	  and UnboundedCardinalityPenalty, respectively.
+//	<Penalties> contains "H", "F", "P", or "U" for HugeCostPenalty,
+//	  FullScanPenalty, PlanGramMismatchPenalty, and
+//	  UnboundedCardinalityPenalty, respectively.
 //	<aux> contains the number of full scans and unbounded reads.
 //
 // For example, the summary "1.23:HF:5f6u" indicates a cost of 1.23 with the
@@ -137,6 +143,9 @@ func (c Cost) Summary() string {
 	if c.Penalties&FullScanPenalty != 0 {
 		sb.WriteByte('F')
 	}
+	if c.Penalties&PlanGramMismatchPenalty != 0 {
+		sb.WriteByte('P')
+	}
 	if c.Penalties&UnboundedCardinalityPenalty != 0 {
 		sb.WriteByte('U')
 	}
diff --git a/pkg/sql/opt/memo/cost_test.go b/pkg/sql/opt/memo/cost_test.go
index da0cd078d747..9c503c454678 100644
--- a/pkg/sql/opt/memo/cost_test.go
+++ b/pkg/sql/opt/memo/cost_test.go
@@ -36,8 +36,12 @@ func TestCostLess(t *testing.T) {
 		{MaxCost, MaxCost, false},
 		{MaxCost, Cost{C: 1.0, Penalties: FullScanPenalty}, false},
 		{Cost{C: 1.0, Penalties: HugeCostPenalty}, MaxCost, true},
+		{Cost{C: 2.0}, Cost{C: 1.0, Penalties: PlanGramMismatchPenalty}, true},
+		{Cost{C: 1.0, Penalties: PlanGramMismatchPenalty}, Cost{C: 2.0}, false},
 		{Cost{C: 2.0}, Cost{C: 1.0, Penalties: UnboundedCardinalityPenalty}, true},
 		{Cost{C: 1.0, Penalties: UnboundedCardinalityPenalty}, Cost{C: 2.0}, false},
+		{Cost{C: 1.0, Penalties: UnboundedCardinalityPenalty}, Cost{C: 1.0, Penalties: PlanGramMismatchPenalty}, true},
+		{Cost{C: 1.0, Penalties: PlanGramMismatchPenalty}, Cost{C: 1.0, Penalties: FullScanPenalty}, true},
 		// Auxiliary information should not affect the comparison.
 		{Cost{C: 1.0, aux: testAux{0, 0}}, Cost{C: 1.0, aux: testAux{1, 1}}, false},
 		{Cost{C: 1.0, aux: testAux{1, 1}}, Cost{C: 1.0, aux: testAux{0, 0}}, false},
@@ -59,6 +63,8 @@ func TestCostAdd(t *testing.T) {
 		{Cost{C: 1.5}, Cost{C: 2.5}, Cost{C: 4.0}},
 		{Cost{C: 1.0, Penalties: FullScanPenalty}, Cost{C: 2.0}, Cost{C: 3.0, Penalties: FullScanPenalty}},
 		{Cost{C: 1.0}, Cost{C: 2.0, Penalties: HugeCostPenalty}, Cost{C: 3.0, Penalties: HugeCostPenalty}},
+		{Cost{C: 1.0, Penalties: PlanGramMismatchPenalty}, Cost{C: 2.0, Penalties: FullScanPenalty}, Cost{C: 3.0, Penalties: FullScanPenalty | PlanGramMismatchPenalty}},
+		{Cost{C: 1.0, Penalties: PlanGramMismatchPenalty}, Cost{C: 2.0, Penalties: PlanGramMismatchPenalty}, Cost{C: 3.0, Penalties: PlanGramMismatchPenalty}},
 		{Cost{C: 1.0, Penalties: UnboundedCardinalityPenalty}, Cost{C: 2.0, Penalties: HugeCostPenalty}, Cost{C: 3.0, Penalties: HugeCostPenalty | UnboundedCardinalityPenalty}},
 		{Cost{C: 1.0, aux: testAux{1, 4}}, Cost{C: 1.0, aux: testAux{2, 5}}, Cost{C: 2.0, aux: testAux{3, 9}}},
 		{Cost{C: 1.0, aux: testAux{65530, 65530}}, Cost{C: 1.0, aux: testAux{100, 100}}, Cost{C: 2.0, aux: testAux{65535, 65535}}},
@@ -81,8 +87,9 @@ func TestCostSummary(t *testing.T) {
 		{Cost{C: 1.23456}, "1.23456::0f0u"},
 		{Cost{C: 1.23, Penalties: HugeCostPenalty}, "1.23:H:0f0u"},
 		{Cost{C: 1.23, Penalties: FullScanPenalty}, "1.23:F:0f0u"},
+		{Cost{C: 1.23, Penalties: PlanGramMismatchPenalty}, "1.23:P:0f0u"},
 		{Cost{C: 1.23, Penalties: UnboundedCardinalityPenalty}, "1.23:U:0f0u"},
-		{Cost{C: 1.23, Penalties: HugeCostPenalty | FullScanPenalty | UnboundedCardinalityPenalty}, "1.23:HFU:0f0u"},
+		{Cost{C: 1.23, Penalties: HugeCostPenalty | FullScanPenalty | PlanGramMismatchPenalty | UnboundedCardinalityPenalty}, "1.23:HFPU:0f0u"},
 		{Cost{C: 1.23, Penalties: HugeCostPenalty | FullScanPenalty | UnboundedCardinalityPenalty}, "1.23:HFU:0f0u"},
 		{Cost{C: 1.23, aux: testAux{5, 0}}, "1.23::5f0u"},
 		{Cost{C: 1.23, aux: testAux{0, 6}}, "1.23::0f6u"},
diff --git a/pkg/sql/opt/memo/expr_format.go b/pkg/sql/opt/memo/expr_format.go
index 90ca7bc87fb6..1c952122f316 100644
--- a/pkg/sql/opt/memo/expr_format.go
+++ b/pkg/sql/opt/memo/expr_format.go
@@ -933,6 +933,9 @@ func (f *ExprFmtCtx) formatRelational(e RelExpr, tp treeprinter.Node) {
 			if cost.Penalties&HugeCostPenalty != 0 {
 				b.WriteString(" huge-cost-penalty")
 			}
+			if cost.Penalties&PlanGramMismatchPenalty != 0 {
+				b.WriteString(" plangram-mismatch")
+			}
 			if cost.Penalties&UnboundedCardinalityPenalty != 0 {
 				b.WriteString(" unbounded-cardinality")
 			}