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Add flake evaluation cache

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This exploits the hermetic nature of flake evaluation to speed up
repeated evaluations of a flake output attribute.

For example (doing 'nix build' on an already present package):

  $ time nix build nixpkgs:firefox

  real    0m1.497s
  user    0m1.160s
  sys     0m0.139s

  $ time nix build nixpkgs:firefox

  real    0m0.052s
  user    0m0.038s
  sys     0m0.007s

The cache is ~/.cache/nix/eval-cache-v1.sqlite, which has entries like

  INSERT INTO Attributes VALUES(
    X'92a907d4efe933af2a46959b082cdff176aa5bfeb47a98fabd234809a67ab195',
    'packages.firefox',
    1,
    '/nix/store/pbalzf8x19hckr8cwdv62rd6g0lqgc38-firefox-67.0.drv /nix/store/g6q0gx0v6xvdnizp8lrcw7c4gdkzana0-firefox-67.0 out');

where the hash 92a9... is a fingerprint over the flake store path and
the contents of the lockfile. Because flakes are evaluated in pure
mode, this uniquely identifies the evaluation result.
This commit is contained in:
Eelco Dolstra 2019-06-07 22:25:48 +02:00
parent 671f16aee0
commit 6644b6099b
No known key found for this signature in database
GPG key ID: 8170B4726D7198DE
9 changed files with 293 additions and 49 deletions
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25
src/libstore/sqlite.cc
View file

@ -25,11 +25,16 @@ namespace nix {
throw SQLiteError("%s: %s (in '%s')", fs.s, sqlite3_errstr(exterr), path);
}
SQLite::SQLite(const Path & path)
SQLite::SQLite(const Path & path, bool create)
{
if (sqlite3_open_v2(path.c_str(), &db,
SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, 0) != SQLITE_OK)
SQLITE_OPEN_READWRITE | (create ? SQLITE_OPEN_CREATE : 0), 0) != SQLITE_OK)
throw Error(format("cannot open SQLite database '%s'") % path);
if (sqlite3_busy_timeout(db, 60 * 60 * 1000) != SQLITE_OK)
throwSQLiteError(db, "setting timeout");
exec("pragma foreign_keys = 1");
}
SQLite::~SQLite()
@ -42,6 +47,12 @@ SQLite::~SQLite()
}
}
void SQLite::isCache()
{
exec("pragma synchronous = off");
exec("pragma main.journal_mode = truncate");
}
void SQLite::exec(const std::string & stmt)
{
retrySQLite<void>([&]() {
@ -94,6 +105,16 @@ SQLiteStmt::Use & SQLiteStmt::Use::operator () (const std::string & value, bool
return *this;
}
SQLiteStmt::Use & SQLiteStmt::Use::operator () (const unsigned char * data, size_t len, bool notNull)
{
if (notNull) {
if (sqlite3_bind_blob(stmt, curArg++, data, len, SQLITE_TRANSIENT) != SQLITE_OK)
throwSQLiteError(stmt.db, "binding argument");
} else
bind();
return *this;
}
SQLiteStmt::Use & SQLiteStmt::Use::operator () (int64_t value, bool notNull)
{
if (notNull) {