@Anthony
If I try for_update=True in the 1st SELECT I get this error
sqlite3.OperationalError: near "FOR": syntax error.
My original code
row = db.wo_counter(year_=request.now.year)
My interpretation of your suggestion
row = db(db.wo_counter.year_ == request.now.year).select(
db.wo_counter.year_, db.wo_counter.last_assigned, for_update=True).first
()
The error I get
File "C:\web2py\applications\ajc\controllers/open_wo.py", line 319, in
new_par
t2
db.wo_counter.year_, db.wo_counter.last_assigned, for_update=True).first
()
File "C:\web2py\gluon\packages\dal\pydal\objects.py", line 2378, in select
return adapter.select(self.query, fields, attributes)
File "C:\web2py\gluon\packages\dal\pydal\adapters\sqlite.py", line 82, in
sele
ct
return super(SQLite, self).select(query, fields, attributes)
File "C:\web2py\gluon\packages\dal\pydal\adapters\base.py", line 763, in
selec
t
return self._select_aux(sql, fields, attributes, colnames)
File "C:\web2py\gluon\packages\dal\pydal\adapters\base.py", line 719, in
_sele
ct_aux
rows = self._select_aux_execute(sql)
File "C:\web2py\gluon\packages\dal\pydal\adapters\base.py", line 713, in
_sele
ct_aux_execute
self.execute(sql)
File "C:\web2py\gluon\packages\dal\pydal\adapters\__init__.py", line 66,
in wr
ap
return f(*args, **kwargs)
File "C:\web2py\gluon\packages\dal\pydal\adapters\base.py", line 413, in
execu
te
rv = self.cursor.execute(command, *args[1:], **kwargs)
sqlite3.OperationalError: near "FOR": syntax error
If I remove the for_update=True from the 1st SELECT and add it to the 2nd I
get a different error sqlite3.OperationalError: cannot start a transaction
within a transaction.
My original code
sn_counter_id = db.equipment(session.new_form_part1.equipment_id).
sn_counter_id
My interpretation of your suggestion
sn_counter_id = db(db.equipment.id == session.new_form_part1.
equipment_id).select(db.equipment.sn_counter_id, for_update=True).first().
sn_counter_id
The error I get
ERROR:web2py:Traceback (most recent call last):
File "C:\web2py\gluon\restricted.py", line 219, in restricted
exec(ccode, environment)
File "C:\web2py\applications\ajc\controllers/open_wo.py", line 708, in <
module
>
File "C:\web2py\gluon\globals.py", line 421, in <lambda>
self._caller = lambda f: f()
File "C:\web2py\gluon\tools.py", line 3868, in f
return action(*a, **b)
File "C:\web2py\applications\ajc\controllers/open_wo.py", line 331, in
new_par
t2
).select(db.equipment.sn_counter_id, for_update=True).first().
sn_counter_id
File "C:\web2py\gluon\packages\dal\pydal\objects.py", line 2378, in select
return adapter.select(self.query, fields, attributes)
File "C:\web2py\gluon\packages\dal\pydal\adapters\sqlite.py", line 81, in
sele
ct
self.execute('BEGIN IMMEDIATE TRANSACTION;')
File "C:\web2py\gluon\packages\dal\pydal\adapters\__init__.py", line 66,
in wr
ap
return f(*args, **kwargs)
File "C:\web2py\gluon\packages\dal\pydal\adapters\base.py", line 413, in
execu
te
rv = self.cursor.execute(command, *args[1:], **kwargs)
sqlite3.OperationalError: cannot start a transaction within a transaction
If I remove the for_update=True everything works either with my original
code and with the changes made to be able to add the for_update=True.
I'm confused regarding the 1st error.
The 2nd error might be because there is already an implicit transaction
from web2py itself?
I'm using SQLite.
quinta-feira, 21 de Março de 2019 às 15:36:56 UTC, Anthony escreveu:
>
> On Wednesday, March 20, 2019 at 9:56:11 PM UTC-4, João Matos wrote:
>>
>> What I read about the commit/rollback "wrapping" that web2py does, it
>> doesn't seem to solve my problem.
>>
>> Let me explain.
>> I have 3 tables (sn_counter, wo_counter and wo).
>> The procedure I must do is the following:
>> 1. Get the record from wo_counter table a extract the counter value (read
>> operation), let's suppose I get the number 10.
>>
>
> At this step, you can lock this particular wo_counter record using
> for_update:
>
> row = db(query).select(db.wo_counter.counter, for_update=True).first()
>
> The above will (a) wait until the relevant rows are unlocked via a similar
> query in another request before doing the select and then (b) lock the
> relevant rows until the current transaction is complete. So, once you've
> read the counter value, you can proceed with the rest of the transaction
> without worrying about other requests making intervening changes.
>
> Anthony
>
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