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# Copyright 2016 Virgil Dupras
#
# This software is licensed under the "GPLv3" License as described in the "LICENSE" file,
# which should be included with this package. The terms are also available at
# http://www.gnu.org/licenses/gpl-3.0.html
import os
import os.path as op
import logging
import sqlite3 as sqlite
from core.pe.cache import string_to_colors, colors_to_string
class SqliteCache:
"""A class to cache picture blocks in a sqlite backend."""
def __init__(self, db=":memory:", readonly=False):
# readonly is not used in the sqlite version of the cache
self.dbname = db
self.con = None
self._create_con()
def __contains__(self, key):
sql = "select count(*) from pictures where path = ?"
result = self.con.execute(sql, [key]).fetchall()
return result[0][0] > 0
def __delitem__(self, key):
if key not in self:
raise KeyError(key)
sql = "delete from pictures where path = ?"
self.con.execute(sql, [key])
# Optimized
def __getitem__(self, key):
if isinstance(key, int):
sql = "select blocks from pictures where rowid = ?"
else:
sql = "select blocks from pictures where path = ?"
result = self.con.execute(sql, [key]).fetchone()
if result:
result = string_to_colors(result[0])
return result
else:
raise KeyError(key)
def __iter__(self):
sql = "select path from pictures"
result = self.con.execute(sql)
return (row[0] for row in result)
def __len__(self):
sql = "select count(*) from pictures"
result = self.con.execute(sql).fetchall()
return result[0][0]
def __setitem__(self, path_str, blocks):
blocks = colors_to_string(blocks)
if op.exists(path_str):
mtime = int(os.stat(path_str).st_mtime)
else:
mtime = 0
if path_str in self:
sql = "update pictures set blocks = ?, mtime = ? where path = ?"
else:
sql = "insert into pictures(blocks,mtime,path) values(?,?,?)"
try:
self.con.execute(sql, [blocks, mtime, path_str])
except sqlite.OperationalError:
logging.warning("Picture cache could not set value for key %r", path_str)
except sqlite.DatabaseError as e:
logging.warning("DatabaseError while setting value for key %r: %s", path_str, str(e))
def _create_con(self, second_try=False):
def create_tables():
logging.debug("Creating picture cache tables.")
self.con.execute("drop table if exists pictures")
self.con.execute("drop index if exists idx_path")
self.con.execute("create table pictures(path TEXT, mtime INTEGER, blocks TEXT)")
self.con.execute("create index idx_path on pictures (path)")
self.con = sqlite.connect(self.dbname, isolation_level=None)
try:
self.con.execute("select path, mtime, blocks from pictures where 1=2")
except sqlite.OperationalError: # new db
create_tables()
except sqlite.DatabaseError as e: # corrupted db
if second_try:
raise # Something really strange is happening
logging.warning("Could not create picture cache because of an error: %s", str(e))
self.con.close()
os.remove(self.dbname)
self._create_con(second_try=True)
def clear(self):
self.close()
if self.dbname != ":memory:":
os.remove(self.dbname)
self._create_con()
def close(self):
if self.con is not None:
self.con.close()
self.con = None
def filter(self, func):
to_delete = [key for key in self if not func(key)]
for key in to_delete:
del self[key]
def get_id(self, path):
sql = "select rowid from pictures where path = ?"
result = self.con.execute(sql, [path]).fetchone()
if result:
return result[0]
else:
raise ValueError(path)
def get_multiple(self, rowids):
sql = "select rowid, blocks from pictures where rowid in (%s)" % ",".join(map(str, rowids))
cur = self.con.execute(sql)
return ((rowid, string_to_colors(blocks)) for rowid, blocks in cur)
def purge_outdated(self):
"""Go through the cache and purge outdated records.
A record is outdated if the picture doesn't exist or if its mtime is greater than the one in
the db.
"""
todelete = []
sql = "select rowid, path, mtime from pictures"
cur = self.con.execute(sql)
for rowid, path_str, mtime in cur:
if mtime and op.exists(path_str):
picture_mtime = os.stat(path_str).st_mtime
if int(picture_mtime) <= mtime:
# not outdated
continue
todelete.append(rowid)
if todelete:
sql = "delete from pictures where rowid in (%s)" % ",".join(map(str, todelete))
self.con.execute(sql)
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