Janky Fix for #43 Data Corruption with Multiple Connections

src/dict_management.rs

@@ -1,10 +1,17 @@
 use anyhow::Context as AContext;
-use rusqlite::{functions::Context, params};
+use rusqlite::{functions::Context, params, Connection, Result};
 use std::sync::{Arc, RwLock};
 use std::time::Duration;
+use lazy_static::__Deref;
 
 use zstd::dict::{DecoderDictionary, EncoderDictionary};
 
+fn get_db_path(conn: &Connection) -> Result<String> {
+    conn.query_row("PRAGMA database_list", [], |row| row.get(2))
+        .map(|path: String| path)
+        .or_else(|_| Ok("<unknown>".to_string()))
+}
+
 // TODO: the rust interface currently requires a level when preparing a dictionary, but the zstd interface (ZSTD_CCtx_loadDictionary) does not.
 // TODO: Using LruCache here isn't very smart
 pub fn encoder_dict_from_ctx(
@@ -16,20 +23,23 @@
     // we cache the instantiated encoder dictionaries keyed by (DbConnection, dict_id, compression_level)
     // DbConnection would ideally be db.path() because it's the same for multiple connections to the same db, but that would be less robust (e.g. in-memory databases)
     lazy_static::lazy_static! {
-        static ref DICTS: RwLock<LruCache<(usize, i32, i32), Arc<EncoderDictionary<'static>>>> = RwLock::new(LruCache::with_expiry_duration(Duration::from_secs(10)));
+        static ref DICTS: RwLock<LruCache<(usize, i32, i32, String), Arc<EncoderDictionary<'static>>>> = RwLock::new(LruCache::with_expiry_duration(Duration::from_secs(10)));
     }
     let id: i32 = ctx.get(arg_index)?;
     let db = unsafe { ctx.get_connection()? }; // SAFETY: This might be unsafe depending on how the connection is used. See https://github.com/rusqlite/rusqlite/issues/643#issuecomment-640181213
     let db_handle_pointer = unsafe { db.handle() } as usize; // SAFETY: We're only getting the pointer as an int, not using the raw connection
+    let conn: &Connection = db.deref();
+    let path = get_db_path(conn)?;
 
     let mut dicts_write = DICTS.write().unwrap();
-    let entry = dicts_write.entry((db_handle_pointer, id, level));
+    let entry = dicts_write.entry((db_handle_pointer, id, level, path.clone()));
     let res = match entry {
         lru_time_cache::Entry::Vacant(e) => e.insert({
             log::debug!(
-                "loading encoder dictionary {} level {} (should only happen once per 10s)",
+                "loading encoder dictionary {} level {} @ {} (should only happen once per 10s)",
                 id,
-                level
+                level,
+                path
             );
 
             let dict_raw: Vec<u8> = db
@@ -56,18 +66,21 @@
     // we cache the instantiated decoder dictionaries keyed by (DbConnection, dict_id)
     // DbConnection would ideally be db.path() because it's the same for multiple connections to the same db, but that would be less robust (e.g. in-memory databases)
     lazy_static::lazy_static! {
-        static ref DICTS: RwLock<LruCache<(usize, i32), Arc<DecoderDictionary<'static>>>> = RwLock::new(LruCache::with_expiry_duration(Duration::from_secs(10)));
+        static ref DICTS: RwLock<LruCache<(usize, i32, String), Arc<DecoderDictionary<'static>>>> = RwLock::new(LruCache::with_expiry_duration(Duration::from_secs(10)));
     }
     let id: i32 = ctx.get(arg_index)?;
     let db = unsafe { ctx.get_connection()? }; // SAFETY: This might be unsafe depending on how the connection is used. See https://github.com/rusqlite/rusqlite/issues/643#issuecomment-640181213
+    let conn: &Connection = db.deref();
+    let path = get_db_path(conn)?;
     let db_handle_pointer = unsafe { db.handle() } as usize; // SAFETY: We're only getting the pointer as an int, not using the raw connection
     let mut dicts_write = DICTS.write().unwrap();
-    let entry = dicts_write.entry((db_handle_pointer, id));
+    let entry = dicts_write.entry((db_handle_pointer, id, path.clone()));
     let res = match entry {
         lru_time_cache::Entry::Vacant(e) => e.insert({
             log::debug!(
-                "loading decoder dictionary {} (should only happen once per 10s)",
-                id
+                "loading decoder dictionary {} @ {} (should only happen once per 10s)",
+                id, 
+                path
             );
             let db = unsafe { ctx.get_connection()? };
             let dict_raw: Vec<u8> = db