9 files changed, 278 insertions, 297 deletions

diff --git a/crates/ra_analysis/src/completion.rs b/crates/ra_analysis/src/completion.rs
index a0fd6828d..0a2f99575 100644
--- a/crates/ra_analysis/src/completion.rs
+++ b/crates/ra_analysis/src/completion.rs
@@ -6,13 +6,15 @@ use ra_syntax::{
 
 use crate::{
     FileId, Cancelable,
+    input::FilesDatabase,
     db::{self, SyntaxDatabase},
     descriptors::module::{ModulesDatabase, ModuleTree, ModuleId},
 };
 
 pub(crate) fn resolve_based_completion(db: &db::RootDatabase, file_id: FileId, offset: TextUnit) -> Cancelable<Option<Vec<CompletionItem>>> {
+    let source_root_id = db.file_source_root(file_id);
     let file = db.file_syntax(file_id);
-    let module_tree = db.module_tree()?;
+    let module_tree = db.module_tree(source_root_id)?;
     let file = {
         let edit = AtomEdit::insert(offset, "intellijRulezz".to_string());
         file.reparse(&edit)
diff --git a/crates/ra_analysis/src/db.rs b/crates/ra_analysis/src/db.rs
index b527cde61..3ca14af79 100644
--- a/crates/ra_analysis/src/db.rs
+++ b/crates/ra_analysis/src/db.rs
@@ -1,12 +1,9 @@
 use std::{
-    fmt,
-    hash::{Hash, Hasher},
     sync::Arc,
 };
 
 use ra_editor::LineIndex;
 use ra_syntax::File;
-use rustc_hash::FxHashSet;
 use salsa;
 
 use crate::{
@@ -14,20 +11,14 @@ use crate::{
     Cancelable, Canceled,
     descriptors::module::{SubmodulesQuery, ModuleTreeQuery, ModulesDatabase},
     symbol_index::SymbolIndex,
-    FileId, FileResolverImp,
+    FileId,
 };
 
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub(crate) struct RootDatabase {
     runtime: salsa::Runtime<RootDatabase>,
 }
 
-impl fmt::Debug for RootDatabase {
-    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        fmt.write_str("RootDatabase { ... }")
-    }
-}
-
 impl salsa::Database for RootDatabase {
     fn salsa_runtime(&self) -> &salsa::Runtime<RootDatabase> {
         &self.runtime
@@ -58,9 +49,13 @@ impl Clone for RootDatabase {
 
 salsa::database_storage! {
     pub(crate) struct RootDatabaseStorage for RootDatabase {
-        impl FilesDatabase {
-            fn file_text() for FileTextQuery;
-            fn file_set() for FileSetQuery;
+        impl crate::input::FilesDatabase {
+            fn file_text() for crate::input::FileTextQuery;
+            fn file_source_root() for crate::input::FileSourceRootQuery;
+            fn source_root() for crate::input::SourceRootQuery;
+            fn libraries() for crate::input::LibrarieseQuery;
+            fn library_symbols() for crate::input::LibrarySymbolsQuery;
+            fn crate_graph() for crate::input::CrateGraphQuery;
         }
         impl SyntaxDatabase {
             fn file_syntax() for FileSyntaxQuery;
@@ -75,40 +70,7 @@ salsa::database_storage! {
 }
 
 salsa::query_group! {
-    pub(crate) trait FilesDatabase: salsa::Database {
-        fn file_text(file_id: FileId) -> Arc<String> {
-            type FileTextQuery;
-            storage input;
-        }
-        fn file_set() -> Arc<FileSet> {
-            type FileSetQuery;
-            storage input;
-        }
-    }
-}
-
-#[derive(Default, Debug, Eq)]
-pub(crate) struct FileSet {
-    pub(crate) files: FxHashSet<FileId>,
-    pub(crate) resolver: FileResolverImp,
-}
-
-impl PartialEq for FileSet {
-    fn eq(&self, other: &FileSet) -> bool {
-        self.files == other.files && self.resolver == other.resolver
-    }
-}
-
-impl Hash for FileSet {
-    fn hash<H: Hasher>(&self, hasher: &mut H) {
-        let mut files = self.files.iter().cloned().collect::<Vec<_>>();
-        files.sort();
-        files.hash(hasher);
-    }
-}
-
-salsa::query_group! {
-    pub(crate) trait SyntaxDatabase: FilesDatabase {
+    pub(crate) trait SyntaxDatabase: crate::input::FilesDatabase {
         fn file_syntax(file_id: FileId) -> File {
             type FileSyntaxQuery;
         }
diff --git a/crates/ra_analysis/src/descriptors/module/imp.rs b/crates/ra_analysis/src/descriptors/module/imp.rs
index 22e4bd785..aecf6e29a 100644
--- a/crates/ra_analysis/src/descriptors/module/imp.rs
+++ b/crates/ra_analysis/src/descriptors/module/imp.rs
@@ -8,8 +8,8 @@ use ra_syntax::{
 };
 
 use crate::{
-    FileId, Cancelable, FileResolverImp,
-    db,
+    FileId, Cancelable, FileResolverImp, db,
+    input::{SourceRoot, SourceRootId},
 };
 
 use super::{
@@ -35,9 +35,12 @@ pub(super) fn modules(root: ast::Root<'_>) -> impl Iterator<Item = (SmolStr, ast
     })
 }
 
-pub(super) fn module_tree(db: &impl ModulesDatabase) -> Cancelable<Arc<ModuleTree>> {
+pub(super) fn module_tree(
+    db: &impl ModulesDatabase,
+    source_root: SourceRootId,
+) -> Cancelable<Arc<ModuleTree>> {
     db::check_canceled(db)?;
-    let res = create_module_tree(db)?;
+    let res = create_module_tree(db, source_root)?;
     Ok(Arc::new(res))
 }
 
@@ -50,6 +53,7 @@ pub struct Submodule {
 
 fn create_module_tree<'a>(
     db: &impl ModulesDatabase,
+    source_root: SourceRootId,
 ) -> Cancelable<ModuleTree> {
     let mut tree = ModuleTree {
         mods: Vec::new(),
@@ -59,12 +63,13 @@ fn create_module_tree<'a>(
     let mut roots = FxHashMap::default();
     let mut visited = FxHashSet::default();
 
-    for &file_id in db.file_set().files.iter() {
+    let source_root = db.source_root(source_root);
+    for &file_id in source_root.files.iter() {
         if visited.contains(&file_id) {
             continue; // TODO: use explicit crate_roots here
         }
         assert!(!roots.contains_key(&file_id));
-        let module_id = build_subtree(db, &mut tree, &mut visited, &mut roots, None, file_id)?;
+        let module_id = build_subtree(db, &source_root, &mut tree, &mut visited, &mut roots, None, file_id)?;
         roots.insert(file_id, module_id);
     }
     Ok(tree)
@@ -72,6 +77,7 @@ fn create_module_tree<'a>(
 
 fn build_subtree(
     db: &impl ModulesDatabase,
+    source_root: &SourceRoot,
     tree: &mut ModuleTree,
     visited: &mut FxHashSet<FileId>,
     roots: &mut FxHashMap<FileId, ModuleId>,
@@ -84,10 +90,8 @@ fn build_subtree(
         parent,
         children: Vec::new(),
     });
-    let file_set = db.file_set();
-    let file_resolver = &file_set.resolver;
     for name in db.submodules(file_id)?.iter() {
-        let (points_to, problem) = resolve_submodule(file_id, name, file_resolver);
+        let (points_to, problem) = resolve_submodule(file_id, name, &source_root.file_resolver);
         let link = tree.push_link(LinkData {
             name: name.clone(),
             owner: id,
@@ -102,7 +106,7 @@ fn build_subtree(
                     tree.module_mut(module_id).parent = Some(link);
                     Ok(module_id)
                 }
-                None => build_subtree(db, tree, visited, roots, Some(link), file_id),
+                None => build_subtree(db, source_root, tree, visited, roots, Some(link), file_id),
             })
             .collect::<Cancelable<Vec<_>>>()?;
         tree.link_mut(link).points_to = points_to;
diff --git a/crates/ra_analysis/src/descriptors/module/mod.rs b/crates/ra_analysis/src/descriptors/module/mod.rs
index 52da650b3..8968c4afd 100644
--- a/crates/ra_analysis/src/descriptors/module/mod.rs
+++ b/crates/ra_analysis/src/descriptors/module/mod.rs
@@ -8,11 +8,12 @@ use ra_syntax::{ast::{self, NameOwner, AstNode}, SmolStr, SyntaxNode};
 use crate::{
     FileId, Cancelable,
     db::SyntaxDatabase,
+    input::SourceRootId,
 };
 
 salsa::query_group! {
     pub(crate) trait ModulesDatabase: SyntaxDatabase {
-        fn module_tree() -> Cancelable<Arc<ModuleTree>> {
+        fn module_tree(source_root_id: SourceRootId) -> Cancelable<Arc<ModuleTree>> {
             type ModuleTreeQuery;
             use fn imp::module_tree;
         }
@@ -110,15 +111,9 @@ impl ModuleId {
 }
 
 impl LinkId {
-    pub(crate) fn name(self, tree: &ModuleTree) -> SmolStr {
-        tree.link(self).name.clone()
-    }
     pub(crate) fn owner(self, tree: &ModuleTree) -> ModuleId {
         tree.link(self).owner
     }
-    fn points_to(self, tree: &ModuleTree) -> &[ModuleId] {
-        &tree.link(self).points_to
-    }
     pub(crate) fn bind_source<'a>(
         self,
         tree: &ModuleTree,
diff --git a/crates/ra_analysis/src/imp.rs b/crates/ra_analysis/src/imp.rs
index f3e5b2887..5a6e2450d 100644
--- a/crates/ra_analysis/src/imp.rs
+++ b/crates/ra_analysis/src/imp.rs
@@ -1,7 +1,5 @@
 use std::{
-    fmt,
     hash::{Hash, Hasher},
-    iter,
     sync::Arc,
 };
 
@@ -14,12 +12,17 @@ use ra_syntax::{
 };
 use relative_path::RelativePath;
 use rustc_hash::FxHashSet;
+use salsa::{ParallelDatabase, Database};
 
 use crate::{
-    db::SyntaxDatabase,
+    AnalysisChange,
+    db::{
+        self, SyntaxDatabase,
+
+    },
+    input::{SourceRootId, FilesDatabase, SourceRoot, WORKSPACE},
     descriptors::module::{ModulesDatabase, ModuleTree, Problem},
     descriptors::{FnDescriptor},
-    roots::{ReadonlySourceRoot, SourceRoot, WritableSourceRoot},
     CrateGraph, CrateId, Diagnostic, FileId, FileResolver, FileSystemEdit, Position,
     Query, SourceChange, SourceFileEdit, Cancelable,
 };
@@ -80,96 +83,128 @@ impl Default for FileResolverImp {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub(crate) struct AnalysisHostImpl {
-    data: WorldData,
+    db: db::RootDatabase,
 }
 
+
 impl AnalysisHostImpl {
     pub fn new() -> AnalysisHostImpl {
-        AnalysisHostImpl {
-            data: WorldData::default(),
-        }
+        AnalysisHostImpl::default()
     }
     pub fn analysis(&self) -> AnalysisImpl {
         AnalysisImpl {
-            data: self.data.clone(),
+            db: self.db.fork() // freeze revision here
         }
     }
-    pub fn change_files(&mut self, changes: &mut dyn Iterator<Item = (FileId, Option<String>)>) {
-        self.data_mut().root.apply_changes(changes, None);
-    }
-    pub fn set_file_resolver(&mut self, resolver: FileResolverImp) {
-        self.data_mut()
-            .root
-            .apply_changes(&mut iter::empty(), Some(resolver));
-    }
-    pub fn set_crate_graph(&mut self, graph: CrateGraph) {
-        let mut visited = FxHashSet::default();
-        for &file_id in graph.crate_roots.values() {
-            if !visited.insert(file_id) {
-                panic!("duplicate crate root: {:?}", file_id);
+    pub fn apply_change(&mut self, change: AnalysisChange) {
+        log::info!("apply_change {:?}", change);
+
+        for (file_id, text) in change.files_changed {
+            self.db
+                .query(crate::input::FileTextQuery)
+                .set(file_id, Arc::new(text))
+        }
+        if !(change.files_added.is_empty() && change.files_removed.is_empty()) {
+            let file_resolver = change.file_resolver
+                .expect("change resolver when changing set of files");
+            let mut source_root = SourceRoot::clone(&self.db.source_root(WORKSPACE));
+            for (file_id, text) in change.files_added {
+                self.db
+                    .query(crate::input::FileTextQuery)
+                    .set(file_id, Arc::new(text));
+                self.db
+                    .query(crate::input::FileSourceRootQuery)
+                    .set(file_id, crate::input::WORKSPACE);
+                source_root.files.insert(file_id);
+            }
+            for file_id in change.files_removed {
+                self.db
+                    .query(crate::input::FileTextQuery)
+                    .set(file_id, Arc::new(String::new()));
+                source_root.files.remove(&file_id);
             }
+            source_root.file_resolver = file_resolver;
+            self.db
+                .query(crate::input::SourceRootQuery)
+                .set(WORKSPACE, Arc::new(source_root))
+        }
+        if !change.libraries_added.is_empty() {
+            let mut libraries = Vec::clone(&self.db.libraries());
+            for library in change.libraries_added {
+                let source_root_id = SourceRootId(1 + libraries.len() as u32);
+                libraries.push(source_root_id);
+                let mut files = FxHashSet::default();
+                for (file_id, text) in library.files {
+                    files.insert(file_id);
+                    self.db
+                        .query(crate::input::FileSourceRootQuery)
+                        .set_constant(file_id, source_root_id);
+                    self.db
+                        .query(crate::input::FileTextQuery)
+                        .set_constant(file_id, Arc::new(text));
+                }
+                let source_root = SourceRoot {
+                    files,
+                    file_resolver: library.file_resolver,
+                };
+                self.db
+                    .query(crate::input::SourceRootQuery)
+                    .set(source_root_id, Arc::new(source_root));
+                self.db
+                    .query(crate::input::LibrarySymbolsQuery)
+                    .set(source_root_id, Arc::new(library.symbol_index));
+            }
+            self.db
+                .query(crate::input::LibrarieseQuery)
+                .set((), Arc::new(libraries));
+        }
+        if let Some(crate_graph) = change.crate_graph {
+            self.db.query(crate::input::CrateGraphQuery)
+                .set((), Arc::new(crate_graph))
         }
-        self.data_mut().crate_graph = graph;
-    }
-    pub fn add_library(&mut self, root: ReadonlySourceRoot) {
-        self.data_mut().libs.push(root);
-    }
-    fn data_mut(&mut self) -> &mut WorldData {
-        &mut self.data
     }
 }
 
+#[derive(Debug)]
 pub(crate) struct AnalysisImpl {
-    data: WorldData,
-}
-
-impl fmt::Debug for AnalysisImpl {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.data.fmt(f)
-    }
+    db: db::RootDatabase,
 }
 
 impl AnalysisImpl {
-    fn root(&self, file_id: FileId) -> &SourceRoot {
-        if self.data.root.contains(file_id) {
-            return &self.data.root;
-        }
-        self
-            .data
-            .libs
-            .iter()
-            .find(|it| it.contains(file_id))
-            .unwrap()
-    }
     pub fn file_syntax(&self, file_id: FileId) -> File {
-        self.root(file_id).db().file_syntax(file_id)
+        self.db.file_syntax(file_id)
     }
     pub fn file_line_index(&self, file_id: FileId) -> Arc<LineIndex> {
-        self.root(file_id).db().file_lines(file_id)
+        self.db.file_lines(file_id)
     }
     pub fn world_symbols(&self, query: Query) -> Cancelable<Vec<(FileId, FileSymbol)>> {
         let mut buf = Vec::new();
         if query.libs {
-            for lib in self.data.libs.iter() {
-                lib.symbols(&mut buf)?;
+            for &lib_id in self.db.libraries().iter() {
+                buf.push(self.db.library_symbols(lib_id));
             }
         } else {
-            self.data.root.symbols(&mut buf)?;
+            for &file_id in self.db.source_root(WORKSPACE).files.iter() {
+                buf.push(self.db.file_symbols(file_id)?);
+            }
         }
         Ok(query.search(&buf))
     }
+    fn module_tree(&self, file_id: FileId) -> Cancelable<Arc<ModuleTree>> {
+        let source_root = self.db.file_source_root(file_id);
+        self.db.module_tree(source_root)
+    }
     pub fn parent_module(&self, file_id: FileId) -> Cancelable<Vec<(FileId, FileSymbol)>> {
-        let root = self.root(file_id);
-        let module_tree = root.db().module_tree()?;
+        let module_tree = self.module_tree(file_id)?;
 
         let res = module_tree.modules_for_file(file_id)
             .into_iter()
             .filter_map(|module_id| {
                 let link = module_id.parent_link(&module_tree)?;
                 let file_id = link.owner(&module_tree).file_id(&module_tree);
-                let syntax = root.db().file_syntax(file_id);
+                let syntax = self.db.file_syntax(file_id);
                 let decl = link.bind_source(&module_tree, syntax.ast());
 
                 let sym = FileSymbol {
@@ -183,8 +218,8 @@ impl AnalysisImpl {
         Ok(res)
     }
     pub fn crate_for(&self, file_id: FileId) -> Cancelable<Vec<CrateId>> {
-        let module_tree = self.root(file_id).db().module_tree()?;
-        let crate_graph = &self.data.crate_graph;
+        let module_tree = self.module_tree(file_id)?;
+        let crate_graph = self.db.crate_graph();
         let res = module_tree.modules_for_file(file_id)
             .into_iter()
             .map(|it| it.root(&module_tree))
@@ -195,7 +230,7 @@ impl AnalysisImpl {
         Ok(res)
     }
     pub fn crate_root(&self, crate_id: CrateId) -> FileId {
-        self.data.crate_graph.crate_roots[&crate_id]
+        self.db.crate_graph().crate_roots[&crate_id]
     }
     pub fn completions(&self, file_id: FileId, offset: TextUnit) -> Cancelable<Option<Vec<CompletionItem>>> {
         let mut res = Vec::new();
@@ -205,8 +240,7 @@ impl AnalysisImpl {
             res.extend(scope_based);
             has_completions = true;
         }
-        let root = self.root(file_id);
-        if let Some(scope_based) = crate::completion::resolve_based_completion(root.db(), file_id, offset)? {
+        if let Some(scope_based) = crate::completion::resolve_based_completion(&self.db, file_id, offset)? {
             res.extend(scope_based);
             has_completions = true;
         }
@@ -222,9 +256,8 @@ impl AnalysisImpl {
         file_id: FileId,
         offset: TextUnit,
     ) -> Cancelable<Vec<(FileId, FileSymbol)>> {
-        let root = self.root(file_id);
-        let module_tree = root.db().module_tree()?;
-        let file = root.db().file_syntax(file_id);
+        let module_tree = self.module_tree(file_id)?;
+        let file = self.db.file_syntax(file_id);
         let syntax = file.syntax();
         if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(syntax, offset) {
             // First try to resolve the symbol locally
@@ -273,8 +306,7 @@ impl AnalysisImpl {
     }
 
     pub fn find_all_refs(&self, file_id: FileId, offset: TextUnit) -> Vec<(FileId, TextRange)> {
-        let root = self.root(file_id);
-        let file = root.db().file_syntax(file_id);
+        let file = self.db.file_syntax(file_id);
         let syntax = file.syntax();
 
         let mut ret = vec![];
@@ -305,9 +337,8 @@ impl AnalysisImpl {
     }
 
     pub fn diagnostics(&self, file_id: FileId) -> Cancelable<Vec<Diagnostic>> {
-        let root = self.root(file_id);
-        let module_tree = root.db().module_tree()?;
-        let syntax = root.db().file_syntax(file_id);
+        let module_tree = self.module_tree(file_id)?;
+        let syntax = self.db.file_syntax(file_id);
 
         let mut res = ra_editor::diagnostics(&syntax)
             .into_iter()
@@ -396,8 +427,7 @@ impl AnalysisImpl {
         file_id: FileId,
         offset: TextUnit,
     ) -> Cancelable<Option<(FnDescriptor, Option<usize>)>> {
-        let root = self.root(file_id);
-        let file = root.db().file_syntax(file_id);
+        let file = self.db.file_syntax(file_id);
         let syntax = file.syntax();
 
         // Find the calling expression and it's NameRef
@@ -412,9 +442,10 @@ impl AnalysisImpl {
 
         // Resolve the function's NameRef (NOTE: this isn't entirely accurate).
         let file_symbols = self.index_resolve(name_ref)?;
-        for (_, fs) in file_symbols {
+        for (fn_fiel_id, fs) in file_symbols {
             if fs.kind == FN_DEF {
-                if let Some(fn_def) = find_node_at_offset(syntax, fs.node_range.start()) {
+                let fn_file = self.db.file_syntax(fn_fiel_id);
+                if let Some(fn_def) = find_node_at_offset(fn_file.syntax(), fs.node_range.start()) {
                     if let Some(descriptor) = FnDescriptor::new(fn_def) {
                         // If we have a calling expression let's find which argument we are on
                         let mut current_parameter = None;
@@ -491,13 +522,6 @@ impl AnalysisImpl {
     }
 }
 
-#[derive(Default, Clone, Debug)]
-struct WorldData {
-    crate_graph: CrateGraph,
-    root: WritableSourceRoot,
-    libs: Vec<ReadonlySourceRoot>,
-}
-
 impl SourceChange {
     pub(crate) fn from_local_edit(file_id: FileId, label: &str, edit: LocalEdit) -> SourceChange {
         let file_edit = SourceFileEdit {
diff --git a/crates/ra_analysis/src/input.rs b/crates/ra_analysis/src/input.rs
new file mode 100644
index 000000000..e64fad40c
--- /dev/null
+++ b/crates/ra_analysis/src/input.rs
@@ -0,0 +1,79 @@
+use std::{
+    sync::Arc,
+    fmt,
+};
+
+use salsa;
+use rustc_hash::FxHashSet;
+use relative_path::RelativePath;
+use rustc_hash::FxHashMap;
+
+use crate::{symbol_index::SymbolIndex, FileResolverImp};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct FileId(pub u32);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct CrateId(pub u32);
+
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
+pub struct CrateGraph {
+    pub(crate) crate_roots: FxHashMap<CrateId, FileId>,
+}
+
+impl CrateGraph {
+    pub fn new() -> CrateGraph {
+        CrateGraph::default()
+    }
+    pub fn add_crate_root(&mut self, file_id: FileId) -> CrateId{
+        let crate_id = CrateId(self.crate_roots.len() as u32);
+        let prev = self.crate_roots.insert(crate_id, file_id);
+        assert!(prev.is_none());
+        crate_id
+    }
+}
+
+pub trait FileResolver: fmt::Debug + Send + Sync + 'static {
+    fn file_stem(&self, file_id: FileId) -> String;
+    fn resolve(&self, file_id: FileId, path: &RelativePath) -> Option<FileId>;
+}
+
+salsa::query_group! {
+    pub(crate) trait FilesDatabase: salsa::Database {
+        fn file_text(file_id: FileId) -> Arc<String> {
+            type FileTextQuery;
+            storage input;
+        }
+        fn file_source_root(file_id: FileId) -> SourceRootId {
+            type FileSourceRootQuery;
+            storage input;
+        }
+        fn source_root(id: SourceRootId) -> Arc<SourceRoot> {
+            type SourceRootQuery;
+            storage input;
+        }
+        fn libraries() -> Arc<Vec<SourceRootId>> {
+            type LibrarieseQuery;
+            storage input;
+        }
+        fn library_symbols(id: SourceRootId) -> Arc<SymbolIndex> {
+            type LibrarySymbolsQuery;
+            storage input;
+        }
+        fn crate_graph() -> Arc<CrateGraph> {
+            type CrateGraphQuery;
+            storage input;
+        }
+    }
+}
+
+#[derive(Default, Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub(crate) struct SourceRootId(pub(crate) u32);
+
+#[derive(Clone, Default, Debug, PartialEq, Eq)]
+pub(crate) struct SourceRoot {
+    pub(crate) file_resolver: FileResolverImp,
+    pub(crate) files: FxHashSet<FileId>,
+}
+
+pub(crate) const WORKSPACE: SourceRootId = SourceRootId(0);
diff --git a/crates/ra_analysis/src/lib.rs b/crates/ra_analysis/src/lib.rs
index 7078e2d31..a67cac21e 100644
--- a/crates/ra_analysis/src/lib.rs
+++ b/crates/ra_analysis/src/lib.rs
@@ -6,23 +6,30 @@ extern crate relative_path;
 extern crate rustc_hash;
 extern crate salsa;
 
+mod input;
 mod db;
 mod descriptors;
 mod imp;
-mod roots;
 mod symbol_index;
 mod completion;
 
-use std::{fmt::Debug, sync::Arc};
+use std::{
+    fmt,
+    sync::Arc,
+};
 
 use ra_syntax::{AtomEdit, File, TextRange, TextUnit};
-use relative_path::{RelativePath, RelativePathBuf};
-use rustc_hash::FxHashMap;
+use relative_path::RelativePathBuf;
+use rayon::prelude::*;
 
-use crate::imp::{AnalysisHostImpl, AnalysisImpl, FileResolverImp};
+use crate::{
+    imp::{AnalysisHostImpl, AnalysisImpl, FileResolverImp},
+    symbol_index::SymbolIndex,
+};
 
 pub use crate::{
     descriptors::FnDescriptor,
+    input::{FileId, FileResolver, CrateGraph, CrateId}
 };
 pub use ra_editor::{
     CompletionItem, FileSymbol, Fold, FoldKind, HighlightedRange, LineIndex, Runnable,
@@ -43,20 +50,52 @@ impl std::fmt::Display for Canceled {
 impl std::error::Error for Canceled {
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct FileId(pub u32);
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct CrateId(pub u32);
+#[derive(Default)]
+pub struct AnalysisChange {
+    files_added: Vec<(FileId, String)>,
+    files_changed: Vec<(FileId, String)>,
+    files_removed: Vec<(FileId)>,
+    libraries_added: Vec<LibraryData>,
+    crate_graph: Option<CrateGraph>,
+    file_resolver: Option<FileResolverImp>,
+}
 
-#[derive(Debug, Clone, Default)]
-pub struct CrateGraph {
-    pub crate_roots: FxHashMap<CrateId, FileId>,
+impl fmt::Debug for AnalysisChange {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("AnalysisChange")
+            .field("files_added", &self.files_added.len())
+            .field("files_changed", &self.files_changed.len())
+            .field("files_removed", &self.files_removed.len())
+            .field("libraries_added", &self.libraries_added.len())
+            .field("crate_graph", &self.crate_graph)
+            .field("file_resolver", &self.file_resolver)
+            .finish()
+    }
 }
 
-pub trait FileResolver: Debug + Send + Sync + 'static {
-    fn file_stem(&self, file_id: FileId) -> String;
-    fn resolve(&self, file_id: FileId, path: &RelativePath) -> Option<FileId>;
+
+impl AnalysisChange {
+    pub fn new() -> AnalysisChange {
+        AnalysisChange::default()
+    }
+    pub fn add_file(&mut self, file_id: FileId, text: String) {
+        self.files_added.push((file_id, text))
+    }
+    pub fn change_file(&mut self, file_id: FileId, new_text: String) {
+        self.files_changed.push((file_id, new_text))
+    }
+    pub fn remove_file(&mut self, file_id: FileId) {
+        self.files_removed.push(file_id)
+    }
+    pub fn add_library(&mut self, data: LibraryData) {
+        self.libraries_added.push(data)
+    }
+    pub fn set_crate_graph(&mut self, graph: CrateGraph) {
+        self.crate_graph = Some(graph);
+    }
+    pub fn set_file_resolver(&mut self, file_resolver: Arc<FileResolver>) {
+        self.file_resolver = Some(FileResolverImp::new(file_resolver));
+    }
 }
 
 #[derive(Debug)]
@@ -75,20 +114,8 @@ impl AnalysisHost {
             imp: self.imp.analysis(),
         }
     }
-    pub fn change_file(&mut self, file_id: FileId, text: Option<String>) {
-        self.change_files(::std::iter::once((file_id, text)));
-    }
-    pub fn change_files(&mut self, mut changes: impl Iterator<Item = (FileId, Option<String>)>) {
-        self.imp.change_files(&mut changes)
-    }
-    pub fn set_file_resolver(&mut self, resolver: Arc<FileResolver>) {
-        self.imp.set_file_resolver(FileResolverImp::new(resolver));
-    }
-    pub fn set_crate_graph(&mut self, graph: CrateGraph) {
-        self.imp.set_crate_graph(graph)
-    }
-    pub fn add_library(&mut self, data: LibraryData) {
-        self.imp.add_library(data.root)
+    pub fn apply_change(&mut self, change: AnalysisChange) {
+        self.imp.apply_change(change)
     }
 }
 
@@ -266,14 +293,18 @@ impl Analysis {
 
 #[derive(Debug)]
 pub struct LibraryData {
-    root: roots::ReadonlySourceRoot,
+    files: Vec<(FileId, String)>,
+    file_resolver: FileResolverImp,
+    symbol_index: SymbolIndex,
 }
 
 impl LibraryData {
     pub fn prepare(files: Vec<(FileId, String)>, file_resolver: Arc<FileResolver>) -> LibraryData {
-        let file_resolver = FileResolverImp::new(file_resolver);
-        let root = roots::ReadonlySourceRoot::new(files, file_resolver);
-        LibraryData { root }
+        let symbol_index = SymbolIndex::for_files(files.par_iter().map(|(file_id, text)| {
+            let file = File::parse(text);
+            (*file_id, file)
+        }));
+        LibraryData { files, file_resolver: FileResolverImp::new(file_resolver), symbol_index }
     }
 }
 
diff --git a/crates/ra_analysis/src/roots.rs b/crates/ra_analysis/src/roots.rs
deleted file mode 100644
index 1e9e613ac..000000000
--- a/crates/ra_analysis/src/roots.rs
+++ /dev/null
@@ -1,116 +0,0 @@
-use std::{sync::Arc};
-
-use rustc_hash::FxHashSet;
-use rayon::prelude::*;
-use salsa::Database;
-
-use crate::{
-    Cancelable,
-    db::{self, FilesDatabase, SyntaxDatabase},
-    imp::FileResolverImp,
-    symbol_index::SymbolIndex,
-    FileId,
-};
-
-pub(crate) trait SourceRoot {
-    fn contains(&self, file_id: FileId) -> bool;
-    fn db(&self) -> &db::RootDatabase;
-    fn symbols(&self, acc: &mut Vec<Arc<SymbolIndex>>) -> Cancelable<()>;
-}
-
-#[derive(Default, Debug, Clone)]
-pub(crate) struct WritableSourceRoot {
-    db: db::RootDatabase,
-}
-
-impl WritableSourceRoot {
-    pub fn apply_changes(
-        &mut self,
-        changes: &mut dyn Iterator<Item = (FileId, Option<String>)>,
-        file_resolver: Option<FileResolverImp>,
-    ) {
-        let mut changed = FxHashSet::default();
-        let mut removed = FxHashSet::default();
-        for (file_id, text) in changes {
-            match text {
-                None => {
-                    removed.insert(file_id);
-                }
-                Some(text) => {
-                    self.db
-                        .query(db::FileTextQuery)
-                        .set(file_id, Arc::new(text));
-                    changed.insert(file_id);
-                }
-            }
-        }
-        let file_set = self.db.file_set();
-        let mut files: FxHashSet<FileId> = file_set.files.clone();
-        for file_id in removed {
-            files.remove(&file_id);
-        }
-        files.extend(changed);
-        let resolver = file_resolver.unwrap_or_else(|| file_set.resolver.clone());
-        self.db
-            .query(db::FileSetQuery)
-            .set((), Arc::new(db::FileSet { files, resolver }));
-    }
-}
-
-impl SourceRoot for WritableSourceRoot {
-    fn contains(&self, file_id: FileId) -> bool {
-        self.db.file_set().files.contains(&file_id)
-    }
-    fn db(&self) -> &db::RootDatabase {
-        &self.db
-    }
-    fn symbols<'a>(&'a self, acc: &mut Vec<Arc<SymbolIndex>>) -> Cancelable<()> {
-        for &file_id in self.db.file_set().files.iter() {
-            let symbols = self.db.file_symbols(file_id)?;
-            acc.push(symbols)
-        }
-        Ok(())
-    }
-}
-
-#[derive(Debug, Clone)]
-pub(crate) struct ReadonlySourceRoot {
-    db: db::RootDatabase,
-    symbol_index: Arc<SymbolIndex>,
-}
-
-impl ReadonlySourceRoot {
-    pub(crate) fn new(
-        files: Vec<(FileId, String)>,
-        resolver: FileResolverImp,
-    ) -> ReadonlySourceRoot {
-        let db = db::RootDatabase::default();
-        let mut file_ids = FxHashSet::default();
-        for (file_id, text) in files {
-            file_ids.insert(file_id);
-            db.query(db::FileTextQuery).set(file_id, Arc::new(text));
-        }
-
-        db.query(db::FileSetQuery)
-            .set((), Arc::new(db::FileSet { files: file_ids, resolver }));
-        let file_set = db.file_set();
-        let symbol_index =
-            SymbolIndex::for_files(file_set.files.par_iter()
-                .map_with(db.clone(), |db, &file_id| (file_id, db.file_syntax(file_id))));
-
-        ReadonlySourceRoot { db, symbol_index: Arc::new(symbol_index) }
-    }
-}
-
-impl SourceRoot for ReadonlySourceRoot {
-    fn contains(&self, file_id: FileId) -> bool {
-        self.db.file_set().files.contains(&file_id)
-    }
-    fn db(&self) -> &db::RootDatabase {
-        &self.db
-    }
-    fn symbols(&self, acc: &mut Vec<Arc<SymbolIndex>>) -> Cancelable<()> {
-        acc.push(Arc::clone(&self.symbol_index));
-        Ok(())
-    }
-}
diff --git a/crates/ra_analysis/src/symbol_index.rs b/crates/ra_analysis/src/symbol_index.rs
index e5c8d8870..5f302cbda 100644
--- a/crates/ra_analysis/src/symbol_index.rs
+++ b/crates/ra_analysis/src/symbol_index.rs
@@ -13,7 +13,7 @@ use rayon::prelude::*;
 
 use crate::{FileId, Query};
 
-#[derive(Debug)]
+#[derive(Default, Debug)]
 pub(crate) struct SymbolIndex {
     symbols: Vec<(FileId, FileSymbol)>,
     map: fst::Map,