Add first multi threaded test which fails.

tests/integration/wal/test_wal.rs

@@ -1,7 +1,9 @@
 use crate::common::{do_flush, TempDatabase};
 use limbo_core::{Connection, LimboError, Result, StepResult};
 use std::cell::RefCell;
+use std::ops::{Add, Deref};
 use std::rc::Rc;
+use std::sync::{Arc, Mutex};
 
 #[allow(clippy::arc_with_non_send_sync)]
 #[test]
@@ -29,6 +31,87 @@ fn test_wal_checkpoint_result() -> Result<()> {
     Ok(())
 }
 
+#[test]
+#[ignore = "Multi threaded seems to not work but this tests proves the point for later fiixes"]
+fn test_wal_1_writer_1_reader() -> Result<()> {
+    let tmp_db = Arc::new(Mutex::new(TempDatabase::new("test_wal.db")));
+    let db = tmp_db.lock().unwrap().limbo_database();
+
+    {
+        let conn = db.connect().unwrap();
+        match conn.query("CREATE TABLE t (id)")? {
+            Some(ref mut rows) => loop {
+                match rows.step().unwrap() {
+                    StepResult::Row => {}
+                    StepResult::IO => {
+                        tmp_db.lock().unwrap().io.run_once().unwrap();
+                    }
+                    StepResult::Interrupt => break,
+                    StepResult::Done => break,
+                    StepResult::Busy => unreachable!(),
+                }
+            },
+            None => todo!(),
+        }
+        do_flush(&conn, tmp_db.lock().unwrap().deref()).unwrap();
+    }
+    let rows = Arc::new(std::sync::Mutex::new(0));
+    let rows_ = rows.clone();
+    const ROWS_WRITE: usize = 1000;
+    let tmp_db_w = db.clone();
+    let writer_thread = std::thread::spawn(move || {
+        let conn = tmp_db_w.connect().unwrap();
+        for i in 0..ROWS_WRITE {
+            println!("adding {}", i);
+            conn.execute(format!("INSERT INTO t values({})", i).as_str())
+                .unwrap();
+            let _ = rows_.lock().unwrap().add(1);
+        }
+    });
+    let rows_ = rows.clone();
+    let reader_thread = std::thread::spawn(move || {
+        let conn = db.connect().unwrap();
+        loop {
+            let rows = *rows_.lock().unwrap();
+            let mut i = 0;
+            // println!("reading {}", rows);
+            match conn.query("SELECT * FROM t") {
+                Ok(Some(ref mut rows)) => loop {
+                    match rows.step().unwrap() {
+                        StepResult::Row => {
+                            let row = rows.row().unwrap();
+                            let first_value = row.get_value(0);
+                            let id = match first_value {
+                                limbo_core::OwnedValue::Integer(i) => *i as i32,
+                                _ => unreachable!(),
+                            };
+                            assert_eq!(id, i);
+                            i += 1;
+                        }
+                        StepResult::IO => {
+                            tmp_db.lock().unwrap().io.run_once().unwrap();
+                        }
+                        StepResult::Interrupt => break,
+                        StepResult::Done => break,
+                        StepResult::Busy => unreachable!(),
+                    }
+                },
+                Ok(None) => {}
+                Err(err) => {
+                    eprintln!("{}", err);
+                }
+            }
+            if rows == ROWS_WRITE {
+                break;
+            }
+        }
+    });
+
+    writer_thread.join().unwrap();
+    reader_thread.join().unwrap();
+    Ok(())
+}
+
 /// Execute a statement and get strings result
 pub(crate) fn execute_and_get_strings(
     tmp_db: &TempDatabase,