sqlite: accept -d URI, where query string can configure the DB connection

neo.conf

@@ -6,7 +6,7 @@
 # for more information about the syntax.
 
 # ~ and ~user constructions are expanded for all paths, even for those that
-# may appear in 'database' option.
+# may appear in 'database' option (except SQLite URI).
 
 # Common parameters.
 [DEFAULT]
@@ -58,7 +58,12 @@ partitions: 12
 # database: Storage nodes only. Syntax for:
 #   - MySQL: [user[:password]@]database[unix_socket]
 #     Database must be created manually.
-#   - SQLite: path
+#   - SQLite: path or URI
+#     URI extends the https://www.sqlite.org/c3ref/open.html syntax
+#     by accepting some PRAGMA settings via the query string
+#     (currently supported: cache_size, journal_mode, synchronous),
+#     but it can't be used yet to pass open options
+#     because Python 2.7's sqlite3.connect does not support URIs.
 # engine: Optional parameter for MySQL.
 #         Can be InnoDB (default) or RocksDB.
 

neo/storage/database/sqlite.py

@@ -20,8 +20,9 @@ import sqlite3
 from hashlib import sha1
 import string
 import traceback
+from urlparse import urlsplit, parse_qsl
 
-from . import LOG_QUERIES
+from . import LOG_QUERIES, DatabaseFailure
 from .manager import DatabaseManager, splitOIDField
 from neo.lib import logging, util
 from neo.lib.exception import NonReadableCell, UndoPackError
@@ -72,7 +73,22 @@ class SQLiteDatabaseManager(DatabaseManager):
     VERSION = 4
 
     def _parse(self, database):
+        pragmas = self.pragmas = {}
+        if database.startswith('file:'):
+            database = urlsplit(database)
+            for k, v in parse_qsl(database.query, keep_blank_values=True,
+                                  strict_parsing=True):
+                if k in pragmas:
+                    raise DatabaseFailure("duplicate pragma: " + k)
+                if k not in ('cache_size', 'journal_mode', 'synchronous'):
+                    raise DatabaseFailure("unsupported pragma: " + k)
+                pragmas[k] = v
+            self.db = database.path
+        else:
             self.db = os.path.expanduser(database)
+        if self.UNSAFE:
+            pragmas.setdefault('synchronous', 'OFF')
+            pragmas.setdefault('journal_mode', 'MEMORY')
 
     def _close(self):
         self.conn.close()
@@ -82,10 +98,14 @@ class SQLiteDatabaseManager(DatabaseManager):
         self.conn = sqlite3.connect(self.db, check_same_thread=False)
         self.conn.text_factory = str
         self.lockFile(self.db)
-        if self.UNSAFE:
-            q = self.query
-            q("PRAGMA synchronous = OFF").fetchall()
-            q("PRAGMA journal_mode = MEMORY").fetchall()
+        try:
+            for pragma in map("PRAGMA %s = %s".__mod__,
+                              self.pragmas.iteritems()):
+                logging.info(pragma)
+                self.query(pragma).fetchall()
+        except Exception:
+            self.close()
+            raise
         self._config = {}
 
     def _getDevPath(self):