store: Add derivation dependency graph query

src/main.rs

@@ -97,6 +97,7 @@ fn main() {
     println!("<<< {}", args.path.to_string_lossy());
     println!(">>> {}", args.path2.to_string_lossy());
 
+
     // handles to the threads collecting closure size information
     // We do this as early as possible because nix is slow.
     let closure_size_handles = if args.closure_size {
@@ -115,7 +116,7 @@ fn main() {
     let package_list_pre = match store::get_packages(&args.path) {
         Ok(packages) => {
             debug!("Found {} packages in first closure", packages.len());
-            packages
+            packages.into_iter().map(|(_, path)| path).collect()
         }
         Err(e) => {
             error!(
@@ -135,7 +136,7 @@ fn main() {
     let package_list_post = match store::get_packages(&args.path2) {
         Ok(packages) => {
             debug!("Found {} packages in second closure", packages.len());
-            packages
+            packages.into_iter().map(|(_, path)| path).collect()
         }
         Err(e) => {
             error!(
@@ -184,6 +185,7 @@ fn main() {
 
     // Difference gives us added and removed packages
     let added: HashSet<&str> = &post_keys - &pre_keys;
+
     let removed: HashSet<&str> = &pre_keys - &post_keys;
     // Get the intersection of the package names for version changes
     let changed: HashSet<&str> = &pre_keys & &post_keys;

src/store.rs

@@ -1,3 +1,5 @@
+use std::collections::HashMap;
+
 use crate::error::AppError;
 use rusqlite::Connection;
 
@@ -14,7 +16,7 @@ WITH RECURSIVE
 		SELECT reference FROM Refs
 		JOIN graph ON referrer = p
 	)
-SELECT path from graph
+SELECT id, path from graph
 JOIN ValidPaths ON id = p;
 ";
 
@@ -32,18 +34,37 @@ SELECT SUM(narSize) as sum from graph
 JOIN ValidPaths ON p = id;
 ";
 
+const QUERY_DEPENDENCY_GRAPH: &str = "
+WITH RECURSIVE
+	graph(p, c) AS (
+		SELECT id as par, reference as chd 
+		FROM ValidPaths
+		JOIN Refs ON referrer = id
+		WHERE path = ?
+	UNION
+		SELECT referrer as par, reference as chd FROM Refs
+		JOIN graph ON referrer = c
+	)
+SELECT p, c from graph;
+";
+
 /// executes a query on the nix db directly
 /// to gather all derivations that the derivation given by the path
 /// depends on
 ///
+/// The ids of the derivations in the database are returned as well, since these
+/// can be used to later convert nodes (represented by the the ids) of the
+/// dependency graph to actual paths
+///
 /// in the future, we might wan't to switch to async
-pub fn get_packages(path: &std::path::Path) -> Result<Vec<String>> {
+pub fn get_packages(path: &std::path::Path) -> Result<Vec<(i64, String)>> {
     let p: String = path.canonicalize()?.to_string_lossy().into_owned();
     let conn = Connection::open("/nix/var/nix/db/db.sqlite")?;
 
     let mut stmt = conn.prepare(QUERY_PKGS)?;
-    let queried_pkgs: std::result::Result<Vec<String>, _> =
-        stmt.query_map([p], |row| row.get(0))?.collect();
+    let queried_pkgs: std::result::Result<Vec<(i64, String)>, _> =
+        stmt.query_map([p], |row| Ok((row.get(0)?, row.get(1)?)))?
+        	.collect();
     Ok(queried_pkgs?)
 }
 
@@ -61,3 +82,30 @@ pub fn get_closure_size(path: &std::path::Path) -> Result<i64> {
     let queried_sum = stmt.query_row([p], |row| row.get(0))?;
     Ok(queried_sum)
 }
+
+
+/// returns the complete dependency graph of
+/// of the derivation as an adjacency list. The nodes are
+/// represented by the DB ids
+///
+/// We might want to collect the paths in the graph directly as
+/// well in the future, depending on how much we use them
+/// in the operations on the graph
+///
+/// The mapping from id to graph can be obtained by using [get_packages]
+pub fn get_dependency_graph(path: &std::path::Path) -> Result<HashMap<i64, Vec<i64>>> {
+    let p: String = path.canonicalize()?.to_string_lossy().into_owned();
+    let conn = Connection::open("/nix/var/nix/db/db.sqlite")?;
+
+    let mut stmt = conn.prepare(QUERY_DEPENDENCY_GRAPH)?;
+    let mut adj = HashMap::<i64, Vec<i64>>::new();
+    let queried_sum = stmt.query_map(
+    	[p],
+    		|row| Ok::<(i64, i64), _>((row.get(0)?, row.get(1)?)))?;
+    for row in queried_sum {
+    	let (from, to) = row?;
+		adj.entry(from).or_default().push(to);
+    }
+
+    Ok(adj)
+}