wip: use Nix's sqlite db "directly"

this might not be a safe assumption, but we're gonna try

Cargo.lock

@@ -1642,6 +1642,18 @@ version = "2.5.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0206175f82b8d6bf6652ff7d71a1e27fd2e4efde587fd368662814d6ec1d9ce0"
 
+[[package]]
+name = "fallible-iterator"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2acce4a10f12dc2fb14a218589d4f1f62ef011b2d0cc4b3cb1bba8e94da14649"
+
+[[package]]
+name = "fallible-streaming-iterator"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7360491ce676a36bf9bb3c56c1aa791658183a54d2744120f27285738d90465a"
+
 [[package]]
 name = "fastcdc"
 version = "3.1.0"
@@ -2544,6 +2556,7 @@ dependencies = [
  "is_ci",
  "netrc-rs",
  "reqwest",
+ "rusqlite",
  "serde",
  "serde_json",
  "sha2",
@@ -3411,6 +3424,20 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "rusqlite"
+version = "0.30.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a78046161564f5e7cd9008aff3b2990b3850dc8e0349119b98e8f251e099f24d"
+dependencies = [
+ "bitflags 2.4.2",
+ "fallible-iterator",
+ "fallible-streaming-iterator",
+ "hashlink",
+ "libsqlite3-sys",
+ "smallvec",
+]
+
 [[package]]
 name = "rust_decimal"
 version = "1.34.3"

magic-nix-cache/Cargo.toml

@@ -33,6 +33,7 @@ uuid = { version = "1.4.0", features = ["serde", "v7", "rand", "std"] }
 futures = "0.3"
 async-compression = "0.4"
 tracing-appender = "0.2.3"
+rusqlite = { version = "0.30", features = ["bundled"] }
 
 [dependencies.tokio]
 version = "1.28.0"

magic-nix-cache/src/util.rs

@@ -9,34 +9,19 @@ use crate::error::Result;
 
 /// Returns the list of store paths that are currently present.
 pub async fn get_store_paths(store: &NixStore) -> Result<HashSet<PathBuf>> {
-    // FIXME: use the Nix API.
-    let store_dir = store.store_dir();
-    let mut listing = tokio::fs::read_dir(store_dir).await?;
-    let mut paths = HashSet::new();
-    while let Some(entry) = listing.next_entry().await? {
-        let file_name = entry.file_name();
-        let file_name = Path::new(&file_name);
+    // FIXME(cole-h): update the nix bindings to get the dbdir of the localstore?
+    let db =
+        rusqlite::Connection::open("file:/nix/var/nix/db/db.sqlite?immutable=1").expect("FIXME");
 
-        if let Some(extension) = file_name.extension() {
-            match extension.to_str() {
-                None | Some("drv") | Some("chroot") => {
-                    tracing::debug!(
-                        "skipping file with weird or uninteresting extension {extension:?}"
-                    );
-                    continue;
-                }
-                _ => {}
-            }
-        }
+    let mut stmt = db.prepare("SELECT path FROM ValidPaths").expect("FIXME");
+    let paths = stmt
+        .query_map([], |row| -> std::result::Result<PathBuf, rusqlite::Error> {
+            Ok(PathBuf::from(row.get::<_, String>(0)?))
+        })
+        .expect("FIXME")
+        .into_iter()
+        .map(|r| r.expect("FIXME"))
+        .collect::<HashSet<_>>();
 
-        if let Some(s) = file_name.to_str() {
-            // Special paths (so far only `.links`)
-            if s == ".links" {
-                continue;
-            }
-        }
-
-        paths.insert(store_dir.join(file_name));
-    }
     Ok(paths)
 }