From 2981677158f90654c6e08082b177a5b4ee35a159 Mon Sep 17 00:00:00 2001
From: Nick Travers <travers@cockroachlabs.com>
Date: Wed, 1 Sep 2021 09:05:14 -0700
Subject: [PATCH] metamorphic: transform percentage of SINGLEDEL ops to DELETE
 ops

Generated SINGLEDEL operations are eligible for transformation into less
restrictive DELETE operations.

Transform a fixed percentage of SINGLEDEL operations at generation time
into DELETEs to further exercise the delete execution paths.

Related to cockroachdb/cockroach#69414.
---
 internal/metamorphic/generator.go | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/internal/metamorphic/generator.go b/internal/metamorphic/generator.go
index 7d8cc5f863..173199cf58 100644
--- a/internal/metamorphic/generator.go
+++ b/internal/metamorphic/generator.go
@@ -840,10 +840,20 @@ func (g *generator) writerSingleDelete() {
 	if key == nil {
 		return
 	}
-	g.add(&singleDeleteOp{
-		writerID: writerID,
-		key:      key,
-	})
+
+	// Keys eligible for single deletes can be removed with a regular delete.
+	// Mutate a percentage of SINGLEDEL ops into DELETEs.
+	if g.rng.Float64() < 0.25 {
+		g.add(&deleteOp{
+			writerID:        writerID,
+			key:             key,
+		})
+	} else {
+		g.add(&singleDeleteOp{
+			writerID: writerID,
+			key:      key,
+		})
+	}
 	g.tryRepositionBatchIters(writerID)
 }