From 1c467275d07167c13cb69782ce64c6d116a44d9d Mon Sep 17 00:00:00 2001
From: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>
Date: Wed, 5 Jun 2024 13:47:02 +0300
Subject: [PATCH 1/2] schemadiff: adding a FK dependency unit test

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>
---
 go/vt/schemadiff/schema_diff_test.go | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/go/vt/schemadiff/schema_diff_test.go b/go/vt/schemadiff/schema_diff_test.go
index 3dc1ab291fd..75b5599f39c 100644
--- a/go/vt/schemadiff/schema_diff_test.go
+++ b/go/vt/schemadiff/schema_diff_test.go
@@ -977,6 +977,22 @@ func TestSchemaDiff(t *testing.T) {
 			conflictingDiffs:  2,
 			instantCapability: InstantDDLCapabilityImpossible,
 		},
+		{
+			name: "add and drop FK, add and drop respective tables",
+			fromQueries: []string{
+				"create table t1 (id int primary key, p int, key p_idx (p));",
+				"create table t2 (id int primary key, p int, key p_idx (p), foreign key (p) references t1 (p) on delete no action);",
+			},
+			toQueries: []string{
+				"create table t2 (id int primary key, p int, key p_idx (p), foreign key (p) references t3 (p) on delete no action);",
+				"create table t3 (id int primary key, p int, key p_idx (p));",
+			},
+			expectDiffs:       3,
+			expectDeps:        2,
+			sequential:        true,
+			entityOrder:       []string{"t3", "t2", "t1"},
+			instantCapability: InstantDDLCapabilityImpossible,
+		},
 		{
 			name: "two identical foreign keys in table, drop one",
 			fromQueries: []string{
@@ -1051,7 +1067,7 @@ func TestSchemaDiff(t *testing.T) {
 			for _, dep := range deps {
 				depsKeys = append(depsKeys, dep.hashKey())
 			}
-			assert.Equalf(t, tc.expectDeps, len(deps), "found deps: %v", depsKeys)
+			assert.Equalf(t, tc.expectDeps, len(deps), "found %v deps: %v", len(depsKeys), depsKeys)
 			assert.Equal(t, tc.sequential, schemaDiff.HasSequentialExecutionDependencies())
 
 			orderedDiffs, err := schemaDiff.OrderedDiffs(ctx)

From b2d882a9b576a5fa49aaeffa64af5ecc5a2c6474 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>
Date: Wed, 5 Jun 2024 13:59:11 +0300
Subject: [PATCH 2/2] code comment

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>
---
 go/vt/schemadiff/schema_diff_test.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/go/vt/schemadiff/schema_diff_test.go b/go/vt/schemadiff/schema_diff_test.go
index 75b5599f39c..cf8a85fcff2 100644
--- a/go/vt/schemadiff/schema_diff_test.go
+++ b/go/vt/schemadiff/schema_diff_test.go
@@ -988,7 +988,7 @@ func TestSchemaDiff(t *testing.T) {
 				"create table t3 (id int primary key, p int, key p_idx (p));",
 			},
 			expectDiffs:       3,
-			expectDeps:        2,
+			expectDeps:        2, // [alter t2]/[drop t1], [alter t2]/[create t3]
 			sequential:        true,
 			entityOrder:       []string{"t3", "t2", "t1"},
 			instantCapability: InstantDDLCapabilityImpossible,