python - SQLite3 Request Hangs in Twisted -


i trying write script automatically update schema of database. however, reason twisted hangs during second request make on adbapi.connectionpool. here code:

update.py

import os import glob import imp  twisted.internet import reactor twisted.enterprise import adbapi twisted.internet import defer  @defer.inlinecallbacks def get_schema_version(conn):     schema_exists = yield conn.runquery("select name sqlite_master type='table' , name='schema_meta';")     defer.returnvalue(0)  def add_schema_files(schemas):     # finds , imports schema_*.py files list     module_files = glob.glob(os.path.dirname(os.path.abspath(__file__)) + "/schema_*.py")     mod in module_files:         module_name = os.path.basename(os.path.splitext(mod)[0])         newmod = imp.load_source('%s'%module_name, mod)         schemas.append( (module_name, newmod) )  @defer.inlinecallbacks def update_schema(conn):     # update database schema latest version     schema_version = yield get_schema_version(conn)     print "at schema version %d" % schema_version     schemas = []     add_schema_files(schemas)     schemas = sorted(schemas, key=lambda tup: tup[0])     in range(schema_version, len(schemas)):         # schemas[0] v1, schemas[1] v2, etc         print "updating version %d" % (i+1)         yield schemas[i][1].update(conn)  if __name__ == '__main__':     conn = adbapi.connectionpool("sqlite3", "data.db", check_same_thread=false)     d = update_schema(conn)     d.addcallback(exit)     reactor.run()

schema_1.py

from twisted.internet import defer  update_query = """ create table schema_meta ( version int not null ); insert schema_meta (version) values (1); """  @defer.inlinecallbacks def update(conn):     yield conn.runquery(update_query)

it hangs on yield conn.runquery(update_query) in schema_1.py.

in addition, when inturrupt script, following sqlite error:

sqlite3.warning: can execute 1 statement @ time.

sqlite allows run 1 writing query @ time. code asynchronous , new query can started before first 1 finished.

to handle have serialize queries or use database server instead of sqlite.


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