diff --git a/src/main.rs b/src/main.rs
index 81feaf8..07e0900 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -9,7 +9,7 @@ extern crate zip;
 use clap::{Parser, Subcommand};
 use rand::seq::IteratorRandom;
 
-use std::io::{Read, Write};
+use std::io::{Read, Seek, Write};
 use std::path::PathBuf;
 use std::time::Instant;
 use std::{fs, io, sync::mpsc, thread};
@@ -230,12 +230,6 @@ fn main() {
     action();
 }
 
-#[derive(bincode::Decode, bincode::Encode)]
-struct VEntry {
-    pos: u32,
-    len: u16,
-}
-
 fn read_from_db2(id: u32) -> Option<Question> {
     use std::io::Cursor;
     const LEN_SIZE: usize = std::mem::size_of::<u64>();
@@ -253,17 +247,33 @@ fn read_from_db2(id: u32) -> Option<Question> {
     let mut zdata = vec![0u8; len];
     input.read_exact(&mut zdata[..len]).expect("read ztab");
     let tab_data = zstd::decode_all(Cursor::new(zdata)).expect("zstd decode table");
-    let tab: (Vec<VEntry>, usize) =
+    let tab: (Vec<u32>, usize) =
         bincode::decode_from_slice(&tab_data, cfg).expect("bincode decode tab");
     let tab = tab.0;
 
-    //println!("read tab done");
+    //println!("read tab done, len {}", tab.len());
+    let index = match id {
+        0 => {
+            let mut rng = rand::thread_rng();
+            (1..tab.len()).into_iter().choose(&mut rng).unwrap()
+        }
+        _ => (id - 1) as usize,
+    };
 
-    let choosen = tab.get(id as usize).expect("get by id");
-    input.seek_relative(choosen.pos as i64).expect("q seek");
-    let reader = input.take(choosen.len as u64);
+    //println!("index {}", index);
+
+    let pos = *tab.get(index).expect("get pos");
+    let pos_next = *tab.get((index + 1) as usize).expect("get pos next");
+    let len = pos_next - pos;
+
+    //println!("pos {} | next {} | len {}", pos, pos_next, len);
+
+    input.seek_relative(pos as i64).expect("q seek");
+    let reader = input.take(len as u64);
     let data = zstd::decode_all(reader).expect("zstd decode data");
 
+    //println!("zstd decoded len {}", data.len());
+
     let question: (Question, usize) =
         bincode::decode_from_slice(&data, cfg).expect("bincode decode q");
     let question = question.0;
@@ -284,35 +294,42 @@ fn write_db2() {
 }
 fn db_writer2_task(rx: mpsc::Receiver<Question>) {
     const LEN_SIZE: usize = std::mem::size_of::<u64>();
+    const COMP_DATA_LEVEL: i32 = 2;
+    const COMP_HDR_LEVEL: i32 = 2;
 
     let cfg = bincode::config::standard().with_fixed_int_encoding();
-    let mut table: Vec<VEntry> = vec![];
+    let mut table: Vec<u32> = vec![];
 
     let buf_data: Vec<u8> = Vec::with_capacity(500 * 1024 * 1024);
     use std::io::Cursor;
     let mut buf = Cursor::new(buf_data);
     let mut pos: u32 = 0;
-
-    rx.into_iter().for_each(|q| {
+    let mut num = 1;
+    rx.into_iter().for_each(|mut q| {
+        q.num = num;
         let data = bincode::encode_to_vec(q, cfg).expect("bincode q encode");
-        let data = zstd::encode_all(Cursor::new(data), 3).expect("zstd q encode");
+        let data = zstd::encode_all(Cursor::new(data), COMP_DATA_LEVEL).expect("zstd q encode");
         let len = buf.write(&data).expect("write question");
-        table.push(VEntry {
-            pos,
-            len: len.try_into().expect("len try_into len"),
-        });
+        table.push(pos);
+
         pos += len as u32;
+        num += 1;
     });
+    table.push(pos);
+
+    println!(
+        "zbuf done, tab len {}, buf size {}",
+        table.len(),
+        buf.position()
+    );
 
     buf.set_position(0);
 
-    println!("zbuf done");
-
     let tab_data = bincode::encode_to_vec(&table, cfg).expect("encode table");
-    let zdata = zstd::encode_all(Cursor::new(tab_data), 3).expect("zstd enc table");
+    let zdata = zstd::encode_all(Cursor::new(tab_data), COMP_HDR_LEVEL).expect("zstd enc table");
     let zlen = zdata.len() as u64;
 
-    println!("z tab done");
+    println!("z tab done, tab data_len = {}", zlen);
 
     let out = fs::File::create("test.bin").expect("out create");
     let mut out = std::io::BufWriter::with_capacity(500 * 1024 * 1024, out);
@@ -321,6 +338,9 @@ fn db_writer2_task(rx: mpsc::Receiver<Question>) {
     let ztab_writed = out.write(&zdata).expect("write tab zdata");
     assert_eq!(ztab_writed, zdata.len());
     drop(zdata);
+
+    println!("header write done, pos: {}", out.stream_position().unwrap());
+
     std::io::copy(&mut buf, &mut out).expect("copy z buf");
     drop(buf);
     out.flush().expect("out flush");