search database has to be a file, as in-memory dbs are per connection

calibre-db/Cargo.toml

@@ -12,5 +12,6 @@ r2d2 = "0.8.10"
 r2d2_sqlite = "0.24.0"
 rusqlite = { version = "0.31.0", features = ["bundled", "time"] }
 serde = { workspace = true }
+tempfile = "3.10.1"
 thiserror = { workspace = true }
 time = { workspace = true }

calibre-db/src/data/error.rs

@@ -1,5 +1,8 @@
 //! Error handling for calibre database access.
 
+use std::io;
+
+use tempfile::PersistError;
 use thiserror::Error;
 use time::error::Parse;
 
@@ -16,9 +19,15 @@ pub enum DataStoreError {
     /// Error connecting to the database.
     #[error("connection error")]
     ConnectionError(#[from] r2d2::Error),
-    /// Error wparsing a datetime from the database.
+    /// Error parsing a datetime from the database.
     #[error("failed to parse datetime")]
     DateTimeError(#[from] Parse),
+    /// Error creating the search database.
+    #[error("failed to create search database")]
+    SearchDbError(#[from] io::Error),
+    /// Error marking the search database as persistent.
+    #[error("failed to persist search database")]
+    PersistSearchDbError(#[from] PersistError),
 }
 
 /// Convert an SQLite error into a proper NoResults one if the query

calibre-db/src/search.rs

@@ -1,13 +1,14 @@
 //! Provide search funcitonality for calibre.
 //!
 //! Because the calibre database can not be disturbed (it is treated as read-only)
-//! it attaches an in-memory database and inserts the relevant data into a
+//! it attaches a temporary database and inserts the relevant data into a
 //! virtual table leveraging fts5 (https://www.sqlite.org/fts5.html). Full-text search is run on
 //! that virtual table.
 
 use r2d2::{Pool, PooledConnection};
 use r2d2_sqlite::SqliteConnectionManager;
 use rusqlite::named_params;
+use tempfile::NamedTempFile;
 
 use crate::data::{book::Book, error::DataStoreError};
 
@@ -31,11 +32,16 @@ const SEARCH_INIT_QUERY: &str = "INSERT INTO search.fts(book_id, data)
       LEFT JOIN main.series AS s ON b2s.series = s.id
     GROUP BY b.id";
 
-/// Attach the fts in-memory database to the read-only calibre database.
+/// Attach the fts temporary database to the read-only calibre database.
 pub(crate) fn attach(pool: &Pool<SqliteConnectionManager>) -> Result<(), DataStoreError> {
     let conn = pool.get()?;
+    let tmpfile = NamedTempFile::new()?;
+    let (_, path) = tmpfile.keep()?;
 
-    conn.execute("ATTACH DATABASE ':memory:' AS search", [])?;
+    conn.execute(
+        &format!("ATTACH DATABASE '{}' AS search", path.to_string_lossy()),
+        [],
+    )?;
     init(&conn)?;
 
     Ok(())