From: Daira Hopwood Date: Fri, 17 Apr 2015 16:57:49 +0000 (+0100) Subject: Add util/dbutil.py: open/create/update sqlite databases given some schema. X-Git-Url: https://git.rkrishnan.org/?a=commitdiff_plain;h=e5c62e55d014c02dff48602d3f3008cb062443c6;p=tahoe-lafs%2Ftahoe-lafs.git Add util/dbutil.py: open/create/update sqlite databases given some schema. Author: Brian Warner Signed-off-by: Daira Hopwood --- diff --git a/src/allmydata/util/dbutil.py b/src/allmydata/util/dbutil.py new file mode 100644 index 00000000..f098f1c1 --- /dev/null +++ b/src/allmydata/util/dbutil.py @@ -0,0 +1,66 @@ + +import os, sys + +import sqlite3 +from sqlite3 import IntegrityError +[IntegrityError] + + +class DBError(Exception): + pass + + +def get_db(dbfile, stderr=sys.stderr, + create_version=(None, None), updaters={}, just_create=False, dbname="db", + journal_mode=None, synchronous=None): + """Open or create the given db file. The parent directory must exist. + create_version=(SCHEMA, VERNUM), and SCHEMA must have a 'version' table. + Updaters is a {newver: commands} mapping, where e.g. updaters[2] is used + to get from ver=1 to ver=2. Returns a (sqlite3,db) tuple, or raises + DBError. + """ + must_create = not os.path.exists(dbfile) + try: + db = sqlite3.connect(dbfile) + except (EnvironmentError, sqlite3.OperationalError), e: + raise DBError("Unable to create/open %s file %s: %s" % (dbname, dbfile, e)) + + schema, target_version = create_version + c = db.cursor() + + # Enabling foreign keys allows stricter integrity checking. + # The default is unspecified according to . + c.execute("PRAGMA foreign_keys = ON;") + + if journal_mode is not None: + c.execute("PRAGMA journal_mode = %s;" % (journal_mode,)) + + if synchronous is not None: + c.execute("PRAGMA synchronous = %s;" % (synchronous,)) + + if must_create: + c.executescript(schema) + c.execute("INSERT INTO version (version) VALUES (?)", (target_version,)) + db.commit() + + try: + c.execute("SELECT version FROM version") + version = c.fetchone()[0] + except sqlite3.DatabaseError, e: + # this indicates that the file is not a compatible database format. + # Perhaps it was created with an old version, or it might be junk. + raise DBError("%s file is unusable: %s" % (dbname, e)) + + if just_create: # for tests + return (sqlite3, db) + + while version < target_version and version+1 in updaters: + c.executescript(updaters[version+1]) + db.commit() + version = version+1 + if version != target_version: + raise DBError("Unable to handle %s version %s" % (dbname, version)) + + return (sqlite3, db) + +