mirror of
https://github.com/searxng/searxng.git
synced 2024-11-14 16:50:11 +01:00
[mod] sqlitedb: access to SQLite databases a little more convenient.
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
This commit is contained in:
Markus Heiser
Markus Heiser
parent
e17d7632d0
commit
c49a2707c1
8
docs/src/searx.sqlitedb.rst
Normal file
8
docs/src/searx.sqlitedb.rst
Normal file
@ -0,0 +1,8 @@
|
||||
.. _sqlite db:
|
||||
|
||||
=========
|
||||
SQLite DB
|
||||
=========
|
||||
|
||||
.. automodule:: searx.sqlitedb
|
||||
:members:
|
||||
323
searx/sqlitedb.py
Normal file
323
searx/sqlitedb.py
Normal file
@ -0,0 +1,323 @@
|
||||
# SPDX-License-Identifier: AGPL-3.0-or-later
|
||||
"""Implementations to make access to SQLite databases a little more convenient.
|
||||
|
||||
:py:obj:`SQLiteAppl`
|
||||
Abstract class with which DB applications can be implemented.
|
||||
|
||||
:py:obj:`SQLiteProperties`:
|
||||
Class to manage properties stored in a database.
|
||||
|
||||
----
|
||||
|
||||
"""
|
||||
from __future__ import annotations
|
||||
|
||||
import sys
|
||||
import re
|
||||
import sqlite3
|
||||
import threading
|
||||
import abc
|
||||
|
||||
from searx import logger
|
||||
|
||||
logger = logger.getChild('sqlitedb')
|
||||
|
||||
|
||||
class SQLiteAppl(abc.ABC):
|
||||
"""Abstract base class for implementing convenient DB access in SQLite
|
||||
applications. In the constructor, a :py:obj:`SQLiteProperties` instance is
|
||||
already aggregated under ``self.properties``."""
|
||||
|
||||
DDL_CREATE_TABLES: dict[str, str] = {}
|
||||
|
||||
DB_SCHEMA: int = 1
|
||||
"""As soon as changes are made to the DB schema, the version number must be
|
||||
increased. Changes to the version number require the DB to be recreated (or
|
||||
migrated / if an migration path exists and is implemented)."""
|
||||
|
||||
SQLITE_THREADING_MODE = {
|
||||
0: "single-thread",
|
||||
1: "multi-thread",
|
||||
3: "serialized"}[sqlite3.threadsafety] # fmt:skip
|
||||
"""Threading mode of the SQLite library. Depends on the options used at
|
||||
compile time and is different for different distributions and architectures.
|
||||
|
||||
Possible values are 0:``single-thread``, 1:``multi-thread``,
|
||||
3:``serialized`` (see :py:obj:`sqlite3.threadsafety`). Pre- Python 3.11
|
||||
this value was hard coded to 1.
|
||||
|
||||
Depending on this value, optimizations are made, e.g. in “serialized” mode
|
||||
it is not necessary to create a separate DB connector for each thread.
|
||||
"""
|
||||
|
||||
SQLITE_JOURNAL_MODE = "WAL"
|
||||
SQLITE_CONNECT_ARGS = {
|
||||
# "timeout": 5.0,
|
||||
# "detect_types": 0,
|
||||
"check_same_thread": bool(SQLITE_THREADING_MODE != "serialized"),
|
||||
"cached_statements": 0, # https://github.com/python/cpython/issues/118172
|
||||
# "uri": False,
|
||||
"autocommit": False,
|
||||
} # fmt:skip
|
||||
"""Connection arguments (:py:obj:`sqlite3.connect`)
|
||||
|
||||
``check_same_thread``:
|
||||
Is disabled by default when :py:obj:`SQLITE_THREADING_MODE` is
|
||||
``serialized``. The check is more of a hindrance in this case because it
|
||||
would prevent a DB connector from being used in multiple threads.
|
||||
|
||||
``autocommit``:
|
||||
Is disabled by default. Note: autocommit option has been added in Python
|
||||
3.12.
|
||||
|
||||
``cached_statements``:
|
||||
Is set to ``0`` by default. Note: Python 3.12+ fetch result are not
|
||||
consistent in multi-threading application and causing an API misuse error.
|
||||
|
||||
The multithreading use in SQLiteAppl is intended and supported if
|
||||
threadsafety is set to 3 (aka "serialized"). CPython supports “serialized”
|
||||
from version 3.12 on, but unfortunately only with errors:
|
||||
|
||||
- https://github.com/python/cpython/issues/118172
|
||||
- https://github.com/python/cpython/issues/123873
|
||||
|
||||
The workaround for SQLite3 multithreading cache inconsistency ist to set
|
||||
option ``cached_statements`` to ``0`` by default.
|
||||
"""
|
||||
|
||||
def __init__(self, db_url):
|
||||
|
||||
self.db_url = db_url
|
||||
self.properties = SQLiteProperties(db_url)
|
||||
self.thread_local = threading.local()
|
||||
self._init_done = False
|
||||
self._compatibility()
|
||||
|
||||
def _compatibility(self):
|
||||
|
||||
if self.SQLITE_THREADING_MODE == "serialized":
|
||||
self._DB = None
|
||||
else:
|
||||
msg = (
|
||||
f"SQLite library is compiled with {self.SQLITE_THREADING_MODE} mode,"
|
||||
" read https://docs.python.org/3/library/sqlite3.html#sqlite3.threadsafety"
|
||||
)
|
||||
if threading.active_count() > 1:
|
||||
logger.error(msg)
|
||||
else:
|
||||
logger.warning(msg)
|
||||
|
||||
if sqlite3.sqlite_version_info <= (3, 35):
|
||||
# See "Generalize UPSERT:" in https://sqlite.org/releaselog/3_35_0.html
|
||||
logger.critical(
|
||||
"SQLite runtime library version %s is not supported (require >= 3.35)", sqlite3.sqlite_version
|
||||
)
|
||||
|
||||
def connect(self) -> sqlite3.Connection:
|
||||
"""Creates a new DB connection (:py:obj:`SQLITE_CONNECT_ARGS`). If not
|
||||
already done, the DB schema is set up
|
||||
"""
|
||||
if sys.version_info < (3, 12):
|
||||
# Prior Python 3.12 there is no "autocommit" option
|
||||
self.SQLITE_CONNECT_ARGS.pop("autocommit", None)
|
||||
|
||||
self.init()
|
||||
logger.debug("%s: connect to DB: %s // %s", self.__class__.__name__, self.db_url, self.SQLITE_CONNECT_ARGS)
|
||||
conn = sqlite3.Connection(self.db_url, **self.SQLITE_CONNECT_ARGS) # type: ignore
|
||||
conn.execute(f"PRAGMA journal_mode={self.SQLITE_JOURNAL_MODE}")
|
||||
self.register_functions(conn)
|
||||
return conn
|
||||
|
||||
def register_functions(self, conn):
|
||||
"""Create user-defined_ SQL functions.
|
||||
|
||||
``REGEXP(<pattern>, <field>)`` : 0 | 1
|
||||
`re.search`_ returns (int) 1 for a match and 0 for none match of
|
||||
``<pattern>`` in ``<field>``.
|
||||
|
||||
.. code:: sql
|
||||
|
||||
SELECT '12' AS field WHERE REGEXP('^[0-9][0-9]$', field)
|
||||
-- 12
|
||||
|
||||
SELECT REGEXP('[0-9][0-9]', 'X12Y')
|
||||
-- 1
|
||||
SELECT REGEXP('[0-9][0-9]', 'X1Y')
|
||||
-- 0
|
||||
|
||||
.. _user-defined: https://docs.python.org/3/library/sqlite3.html#sqlite3.Connection.create_function
|
||||
.. _deterministic: https://sqlite.org/deterministic.html
|
||||
.. _re.search: https://docs.python.org/3/library/re.html#re.search
|
||||
"""
|
||||
|
||||
conn.create_function('regexp', 2, lambda x, y: 1 if re.search(x, y) else 0, deterministic=True)
|
||||
|
||||
@property
|
||||
def DB(self) -> sqlite3.Connection:
|
||||
"""Provides a DB connection. The connection is a *singleton* and
|
||||
therefore well suited for read access. If
|
||||
:py:obj:`SQLITE_THREADING_MODE` is ``serialized`` only one DB connection
|
||||
is created for all threads.
|
||||
|
||||
.. note::
|
||||
|
||||
For dedicated `transaction control`_, it is recommended to create a
|
||||
new connection (:py:obj:`SQLiteAppl.connect`).
|
||||
|
||||
.. _transaction control:
|
||||
https://docs.python.org/3/library/sqlite3.html#sqlite3-controlling-transactions
|
||||
"""
|
||||
|
||||
if getattr(self.thread_local, 'DB', None) is None:
|
||||
self.thread_local.DB = self.connect()
|
||||
|
||||
# Theoretically it is possible to reuse the DB cursor across threads as
|
||||
# of Python 3.12, in practice the threading of the cursor seems to me to
|
||||
# be so faulty that I prefer to establish one connection per thread
|
||||
|
||||
self.thread_local.DB.commit()
|
||||
return self.thread_local.DB
|
||||
|
||||
# In "serialized" mode, SQLite can be safely used by multiple threads
|
||||
# with no restriction.
|
||||
#
|
||||
# if self.SQLITE_THREADING_MODE != "serialized":
|
||||
# if getattr(self.thread_local, 'DB', None) is None:
|
||||
# self.thread_local.DB = self.connect()
|
||||
# return self.thread_local.DB
|
||||
#
|
||||
# if self._DB is None:
|
||||
# self._DB = self.connect() # pylint: disable=attribute-defined-outside-init
|
||||
# return self._DB
|
||||
|
||||
def init(self):
|
||||
"""Initializes the DB schema and properties, is only executed once even
|
||||
if called several times."""
|
||||
|
||||
if self._init_done:
|
||||
return
|
||||
self._init_done = True
|
||||
|
||||
logger.debug("init DB: %s", self.db_url)
|
||||
self.properties.init()
|
||||
ver = self.properties("DB_SCHEMA")
|
||||
if ver is None:
|
||||
with self.properties.DB:
|
||||
self.create_schema(self.properties.DB)
|
||||
else:
|
||||
ver = int(ver)
|
||||
if ver != self.DB_SCHEMA:
|
||||
raise sqlite3.DatabaseError("Expected DB schema v%s, DB schema is v%s" % (self.DB_SCHEMA, ver))
|
||||
logger.debug("DB_SCHEMA = %s", ver)
|
||||
|
||||
def create_schema(self, conn):
|
||||
|
||||
logger.debug("create schema ..")
|
||||
with conn:
|
||||
for table_name, sql in self.DDL_CREATE_TABLES.items():
|
||||
conn.execute(sql)
|
||||
self.properties.set(f"Table {table_name} created", table_name)
|
||||
self.properties.set("DB_SCHEMA", self.DB_SCHEMA)
|
||||
self.properties.set("LAST_MAINTENANCE", "")
|
||||
|
||||
|
||||
class SQLiteProperties(SQLiteAppl):
|
||||
"""Simple class to manage properties of a DB application in the DB. The
|
||||
object has its own DB connection and transaction area.
|
||||
|
||||
.. code:: sql
|
||||
|
||||
CREATE TABLE IF NOT EXISTS properties (
|
||||
name TEXT,
|
||||
value TEXT,
|
||||
m_time INTEGER DEFAULT (strftime('%s', 'now')),
|
||||
PRIMARY KEY (name))
|
||||
|
||||
"""
|
||||
|
||||
SQLITE_JOURNAL_MODE = "WAL"
|
||||
|
||||
DDL_PROPERTIES = """\
|
||||
CREATE TABLE IF NOT EXISTS properties (
|
||||
name TEXT,
|
||||
value TEXT,
|
||||
m_time INTEGER DEFAULT (strftime('%s', 'now')), -- last modified (unix epoch) time in sec.
|
||||
PRIMARY KEY (name))"""
|
||||
|
||||
"""Table to store properties of the DB application"""
|
||||
|
||||
SQL_GET = "SELECT value FROM properties WHERE name = ?"
|
||||
SQL_M_TIME = "SELECT m_time FROM properties WHERE name = ?"
|
||||
SQL_SET = (
|
||||
"INSERT INTO properties (name, value) VALUES (?, ?)"
|
||||
" ON CONFLICT(name) DO UPDATE"
|
||||
" SET value=excluded.value, m_time=strftime('%s', 'now')"
|
||||
)
|
||||
SQL_TABLE_EXISTS = (
|
||||
"SELECT name FROM sqlite_master"
|
||||
" WHERE type='table' AND name='properties'"
|
||||
) # fmt:skip
|
||||
SQLITE_CONNECT_ARGS = dict(SQLiteAppl.SQLITE_CONNECT_ARGS)
|
||||
SQLITE_CONNECT_ARGS["autocommit"] = True # This option has no effect before Python 3.12
|
||||
|
||||
def __init__(self, db_url: str): # pylint: disable=super-init-not-called
|
||||
|
||||
self.db_url = db_url
|
||||
self.thread_local = threading.local()
|
||||
self._init_done = False
|
||||
self._compatibility()
|
||||
|
||||
def init(self):
|
||||
"""Initializes DB schema of the properties in the DB."""
|
||||
|
||||
if self._init_done:
|
||||
return
|
||||
self._init_done = True
|
||||
logger.debug("init properties of DB: %s", self.db_url)
|
||||
with self.DB as conn:
|
||||
res = conn.execute(self.SQL_TABLE_EXISTS)
|
||||
if res.fetchone() is None: # DB schema needs to be be created
|
||||
self.create_schema(conn)
|
||||
|
||||
def __call__(self, name, default=None):
|
||||
"""Returns the value of the property ``name`` or ``default`` if property
|
||||
not exists in DB."""
|
||||
|
||||
res = self.DB.execute(self.SQL_GET, (name,)).fetchone()
|
||||
if res is None:
|
||||
return default
|
||||
return res[0]
|
||||
|
||||
def set(self, name, value):
|
||||
"""Set ``value`` of property ``name`` in DB. If property already
|
||||
exists, update the ``m_time`` (and the value)."""
|
||||
|
||||
self.DB.execute(self.SQL_SET, (name, value))
|
||||
|
||||
if sys.version_info <= (3, 12):
|
||||
# Prior Python 3.12 there is no "autocommit" option / lets commit
|
||||
# explicitely.
|
||||
self.DB.commit()
|
||||
|
||||
def row(self, name, default=None):
|
||||
"""Returns the DB row of property ``name`` or ``default`` if property
|
||||
not exists in DB."""
|
||||
|
||||
cur = self.DB.cursor()
|
||||
cur.execute("SELECT * FROM properties WHERE name = ?", (name,))
|
||||
res = cur.fetchone()
|
||||
if res is None:
|
||||
return default
|
||||
col_names = [column[0] for column in cur.description]
|
||||
return dict(zip(col_names, res))
|
||||
|
||||
def m_time(self, name, default: int = 0) -> int:
|
||||
"""Last modification time of this property."""
|
||||
res = self.DB.execute(self.SQL_M_TIME, (name,)).fetchone()
|
||||
if res is None:
|
||||
return default
|
||||
return int(res[0])
|
||||
|
||||
def create_schema(self, conn):
|
||||
with conn:
|
||||
conn.execute(self.DDL_PROPERTIES)
|
||||
Loading…
Reference in New Issue
Block a user