information_schema uppercase rule doesn't apply to processlist table (#2764)

Author: jycor

enginetest/enginetests.go

@@ -313,6 +313,51 @@ func TestInfoSchema(t *testing.T, h Harness) {
 		}, nil, nil, nil)
 	})
 
+	t.Run("information_schema.processlist projection case", func(t *testing.T) {
+		e := mustNewEngine(t, h)
+		defer e.Close()
+
+		if IsServerEngine(e) {
+			t.Skip("skipping for server engine as the processlist returned from server differs")
+		}
+		p := sqle.NewProcessList()
+		p.AddConnection(1, "localhost")
+
+		ctx := NewContext(h)
+		ctx.Session.SetClient(sql.Client{Address: "localhost", User: "root"})
+		ctx.Session.SetConnectionId(1)
+		ctx.ProcessList = p
+		ctx.SetCurrentDatabase("")
+
+		p.ConnectionReady(ctx.Session)
+
+		ctx, err := p.BeginQuery(ctx, "SELECT foo")
+		require.NoError(t, err)
+
+		p.AddConnection(2, "otherhost")
+		sess2 := sql.NewBaseSessionWithClientServer("localhost", sql.Client{Address: "otherhost", User: "root"}, 2)
+		sess2.SetCurrentDatabase("otherdb")
+		p.ConnectionReady(sess2)
+		ctx2 := sql.NewContext(context.Background(), sql.WithPid(2), sql.WithSession(sess2))
+		ctx2, err = p.BeginQuery(ctx2, "SELECT bar")
+		require.NoError(t, err)
+		p.EndQuery(ctx2)
+
+		TestQueryWithContext(t, ctx, e, h,
+			"SELECT id, uSeR, hOST FROM information_schema.processlist ORDER BY id",
+			[]sql.Row{
+				{uint64(1), "root", "localhost"},
+				{uint64(2), "root", "otherhost"},
+			},
+			sql.Schema{
+				{Name: "id", Type: types.Uint64},
+				{Name: "uSeR", Type: types.MustCreateString(sqltypes.VarChar, 96, sql.Collation_Information_Schema_Default)},
+				{Name: "hOST", Type: types.MustCreateString(sqltypes.VarChar, 783, sql.Collation_Information_Schema_Default)},
+			},
+			nil, nil,
+		)
+	})
+
 	for _, tt := range queries.SkippedInfoSchemaQueries {
 		t.Run(tt.Query, func(t *testing.T) {
 			t.Skip()

sql/planbuilder/scope.go

@@ -613,8 +613,9 @@ func (c scopeColumn) unwrapGetFieldAliasId() columnId {
 }
 
 func (c scopeColumn) withOriginal(col string) scopeColumn {
-	if !strings.EqualFold(c.db, sql.InformationSchemaDatabaseName) {
-		// info schema columns always presented as uppercase
+	// info schema columns always presented as uppercase, except for processlist
+	// can't reference information_schema.ProcessListTableName because of import cycles
+	if !strings.EqualFold(c.db, sql.InformationSchemaDatabaseName) || (strings.EqualFold(c.db, sql.InformationSchemaDatabaseName) && strings.EqualFold(c.table, "processlist")) {
 		c.originalCol = col
 	}
 	return c