Cache path info lookups in SQLite

This re-implements the binary cache database in C++, allowing it to be
used by other Store backends, in particular the S3 backend.

src/libstore/nar-info-disk-cache.cc

@@ -0,0 +1,217 @@
+#include "nar-info-disk-cache.hh"
+#include "sync.hh"
+#include "sqlite.hh"
+#include "globals.hh"
+
+#include <sqlite3.h>
+
+namespace nix {
+
+static const char * schema = R"sql(
+
+create table if not exists BinaryCaches (
+    id        integer primary key autoincrement not null,
+    url       text unique not null,
+    timestamp integer not null,
+    storeDir  text not null,
+    wantMassQuery integer not null,
+    priority  integer not null
+);
+
+create table if not exists NARs (
+    cache            integer not null,
+    storePath        text not null,
+    url              text,
+    compression      text,
+    fileHash         text,
+    fileSize         integer,
+    narHash          text,
+    narSize          integer,
+    refs             text,
+    deriver          text,
+    sigs             text,
+    timestamp        integer not null,
+    primary key (cache, storePath),
+    foreign key (cache) references BinaryCaches(id) on delete cascade
+);
+
+create table if not exists NARExistence (
+    cache            integer not null,
+    storePath        text not null,
+    exist            integer not null,
+    timestamp        integer not null,
+    primary key (cache, storePath),
+    foreign key (cache) references BinaryCaches(id) on delete cascade
+);
+
+)sql";
+
+class NarInfoDiskCacheImpl : public NarInfoDiskCache
+{
+public:
+
+    /* How long negative lookups are valid. */
+    const int ttlNegative = 3600;
+
+    struct State
+    {
+        SQLite db;
+        SQLiteStmt insertCache, queryCache, insertNAR, queryNAR, insertNARExistence, queryNARExistence;
+        std::map<std::string, int> caches;
+    };
+
+    Sync<State> _state;
+
+    NarInfoDiskCacheImpl()
+    {
+        auto state(_state.lock());
+
+        Path dbPath = getCacheDir() + "/nix/binary-cache-v3.sqlite";
+        createDirs(dirOf(dbPath));
+
+        if (sqlite3_open_v2(dbPath.c_str(), &state->db.db,
+                SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, 0) != SQLITE_OK)
+            throw Error(format("cannot open store cache ‘%s’") % dbPath);
+
+        if (sqlite3_busy_timeout(state->db, 60 * 60 * 1000) != SQLITE_OK)
+            throwSQLiteError(state->db, "setting timeout");
+
+        // We can always reproduce the cache.
+        if (sqlite3_exec(state->db, "pragma synchronous = off", 0, 0, 0) != SQLITE_OK)
+            throwSQLiteError(state->db, "making database asynchronous");
+        if (sqlite3_exec(state->db, "pragma main.journal_mode = truncate", 0, 0, 0) != SQLITE_OK)
+            throwSQLiteError(state->db, "setting journal mode");
+
+        if (sqlite3_exec(state->db, schema, 0, 0, 0) != SQLITE_OK)
+            throwSQLiteError(state->db, "initialising database schema");
+
+        state->insertCache.create(state->db,
+            "insert or replace into BinaryCaches(url, timestamp, storeDir, wantMassQuery, priority) values (?, ?, ?, ?, ?)");
+
+        state->queryCache.create(state->db,
+            "select id, storeDir, wantMassQuery, priority from BinaryCaches where url = ?");
+
+        state->insertNAR.create(state->db,
+            "insert or replace into NARs(cache, storePath, url, compression, fileHash, fileSize, narHash, "
+            "narSize, refs, deriver, sigs, timestamp) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)");
+
+        state->queryNAR.create(state->db,
+            "select * from NARs where cache = ? and storePath = ?");
+
+        state->insertNARExistence.create(state->db,
+            "insert or replace into NARExistence(cache, storePath, exist, timestamp) values (?, ?, ?, ?)");
+
+        state->queryNARExistence.create(state->db,
+            "select exist, timestamp from NARExistence where cache = ? and storePath = ?");
+    }
+
+    int uriToInt(State & state, const std::string & uri)
+    {
+        auto i = state.caches.find(uri);
+        if (i == state.caches.end()) abort();
+        return i->second;
+    }
+
+    void createCache(const std::string & uri) override
+    {
+        auto state(_state.lock());
+
+        // FIXME: race
+
+        state->insertCache.use()(uri)(time(0))(settings.nixStore)(1)(0).exec();
+        assert(sqlite3_changes(state->db) == 1);
+        state->caches[uri] = sqlite3_last_insert_rowid(state->db);
+    }
+
+    bool cacheExists(const std::string & uri) override
+    {
+        auto state(_state.lock());
+
+        auto i = state->caches.find(uri);
+        if (i != state->caches.end()) return true;
+
+        auto queryCache(state->queryCache.use()(uri));
+
+        if (queryCache.next()) {
+            state->caches[uri] = queryCache.getInt(0);
+            return true;
+        }
+
+        return false;
+    }
+
+    std::pair<Outcome, std::shared_ptr<NarInfo>> lookupNarInfo(
+        const std::string & uri, const Path & storePath) override
+    {
+        auto state(_state.lock());
+
+        auto queryNAR(state->queryNAR.use()
+            (uriToInt(*state, uri))
+            (baseNameOf(storePath)));
+
+        if (!queryNAR.next())
+            // FIXME: check NARExistence
+            return {oUnknown, 0};
+
+        auto narInfo = make_ref<NarInfo>();
+
+        // FIXME: implement TTL.
+
+        narInfo->path = storePath;
+        narInfo->url = queryNAR.getStr(2);
+        narInfo->compression = queryNAR.getStr(3);
+        if (!queryNAR.isNull(4))
+            narInfo->fileHash = parseHash(queryNAR.getStr(4));
+        narInfo->fileSize = queryNAR.getInt(5);
+        narInfo->narHash = parseHash(queryNAR.getStr(6));
+        narInfo->narSize = queryNAR.getInt(7);
+        for (auto & r : tokenizeString<Strings>(queryNAR.getStr(8), " "))
+            narInfo->references.insert(settings.nixStore + "/" + r);
+        if (!queryNAR.isNull(9))
+            narInfo->deriver = settings.nixStore + "/" + queryNAR.getStr(9);
+        for (auto & sig : tokenizeString<Strings>(queryNAR.getStr(10), " "))
+            narInfo->sigs.insert(sig);
+
+        return {oValid, narInfo};
+    }
+
+    void upsertNarInfo(
+        const std::string & uri, std::shared_ptr<ValidPathInfo> info) override
+    {
+        auto state(_state.lock());
+
+        if (info) {
+
+            auto narInfo = std::dynamic_pointer_cast<NarInfo>(info);
+
+            state->insertNAR.use()
+                (uriToInt(*state, uri))
+                (baseNameOf(info->path))
+                (narInfo ? narInfo->url : "", narInfo != 0)
+                (narInfo ? narInfo->compression : "", narInfo != 0)
+                (narInfo && narInfo->fileHash ? narInfo->fileHash.to_string() : "", narInfo && narInfo->fileHash)
+                (narInfo ? narInfo->fileSize : 0, narInfo != 0 && narInfo->fileSize)
+                (info->narHash.to_string())
+                (info->narSize)
+                (concatStringsSep(" ", info->shortRefs()))
+                (info->deriver != "" ? baseNameOf(info->deriver) : "", info->deriver != "")
+                (concatStringsSep(" ", info->sigs))
+                (time(0)).exec();
+
+        } else {
+            // not implemented
+            abort();
+        }
+    }
+};
+
+ref<NarInfoDiskCache> getNarInfoDiskCache()
+{
+    static Sync<std::shared_ptr<NarInfoDiskCache>> cache;
+
+    auto cache_(cache.lock());
+    if (!*cache_) *cache_ = std::make_shared<NarInfoDiskCacheImpl>();
+    return ref<NarInfoDiskCache>(*cache_);
+}
+
+}