Fix panic on query error with nil stmtcache

fixes #895

query_test.go

@@ -1973,6 +1973,31 @@ func TestQueryStatementCacheModes(t *testing.T) {
 	}
 }
 
+// https://github.com/jackc/pgx/issues/895
+func TestQueryErrorWithNilStatementCacheMode(t *testing.T) {
+	t.Parallel()
+
+	config := mustParseConfig(t, os.Getenv("PGX_TEST_DATABASE"))
+	config.BuildStatementCache = nil
+
+	conn := mustConnect(t, config)
+	defer closeConn(t, conn)
+
+	_, err := conn.Exec(context.Background(), "create temporary table t_unq(id text primary key);")
+	require.NoError(t, err)
+
+	_, err = conn.Exec(context.Background(), "insert into t_unq (id) values ($1)", "abc")
+	require.NoError(t, err)
+
+	rows, err := conn.Query(context.Background(), "insert into t_unq (id) values ($1)", "abc")
+	require.NoError(t, err)
+	rows.Close()
+	err = rows.Err()
+	require.EqualError(t, err, `ERROR: duplicate key value violates unique constraint "t_unq_pkey" (SQLSTATE 23505)`)
+
+	ensureConnValid(t, conn)
+}
+
 func TestConnQueryFunc(t *testing.T) {
 	t.Parallel()
 

rows.go

@@ -150,7 +150,7 @@ func (rows *connRows) Close() {
 			if rows.logger.shouldLog(LogLevelError) {
 				rows.logger.log(rows.ctx, LogLevelError, "Query", map[string]interface{}{"err": rows.err, "sql": rows.sql, "args": logQueryArgs(rows.args)})
 			}
-			if rows.err != nil {
+			if rows.err != nil && rows.conn.stmtcache != nil {
 				rows.conn.stmtcache.StatementErrored(rows.sql, rows.err)
 			}
 		}