Well, I guess this is looking more an more like a bug then.
I just went to the sqlite.org site to find out how I log a bug and it referred
me back to here. Perhaps this means I just need to *DECLARE BUG* here ;-)
Actually, I'll probably have some time soon to try out a profiler to see if I
can figure out which mutexes are involved in causing the synchonising behaviour
I seem to be experiencing.
>
> I'm out of ideas about this. I understand that it shouldn't work this
> way and I don't understand why it does.
> Is it possible for you to run application in some sort of profiler?
> Obviously it should show that a lot of time is spent in waiting on
> some mutex and it will be able to show where this mutex is held
> from...
>
>
> Pavel
>
> On Tue, Mar 9, 2010 at 1:02 PM, Luke Evans <luk...@me.com> wrote:
>> Hi guys,
>>
>> Had to take a break for a couple of days from my SQLite experiments, but
>> back on it now.
>>
>> Pavel, regarding the question about VFS, I'm not using one to my knowledge
>> and have set the "name of VFS module" to NULL in sqlite3_open_v2. Maybe
>> NULL means I'm using the standard VFS, but in any case, not a "non-standard"
>> one.
>> I'm selecting from a real table.
>>
>> Here are some more timings...
>>
>> Shared cache ON. 6 of the same query issued (as before) within the
>> multithreaded scenario. All the queries bunch up and report complete more
>> or less together.
>>
>> 2010-03-09 09:32:33.013 SQLiteTest[16208:a0f] SQLite says multithreading is
>> ON
>> 2010-03-09 09:32:33.015 SQLiteTest[16208:a0f] SQLite's multithreading value
>> is 2
>> 2010-03-09 09:32:33.015 SQLiteTest[16208:a0f] SHARED CACHE IS ON
>> 2010-03-09 09:32:33.017 SQLiteTest[16208:1b03] Starting query on thread
>> <NSThread: 0x10061e450>{name = (null), num = 3}
>> 2010-03-09 09:32:33.018 SQLiteTest[16208:5603] Starting query on thread
>> <NSThread: 0x117e071c0>{name = (null), num = 4}
>> 2010-03-09 09:32:33.017 SQLiteTest[16208:4403] Starting query on thread
>> <NSThread: 0x117e06760>{name = (null), num = 2}
>> 2010-03-09 09:32:33.018 SQLiteTest[16208:5503] Starting query on thread
>> <NSThread: 0x10061ea70>{name = (null), num = 5}
>> 2010-03-09 09:32:33.019 SQLiteTest[16208:5703] Starting query on thread
>> <NSThread: 0x10061e5a0>{name = (null), num = 6}
>> 2010-03-09 09:32:33.019 SQLiteTest[16208:5c03] Starting query on thread
>> <NSThread: 0x10061e680>{name = (null), num = 7}
>> 2010-03-09 09:32:41.359 SQLiteTest[16208:5603] Finished query on thread
>> <NSThread: 0x117e071c0>{name = (null), num = 4} in 8.34s
>> 2010-03-09 09:32:41.359 SQLiteTest[16208:1b03] Finished query on thread
>> <NSThread: 0x10061e450>{name = (null), num = 3} in 8.34s
>> 2010-03-09 09:32:41.359 SQLiteTest[16208:4403] Finished query on thread
>> <NSThread: 0x117e06760>{name = (null), num = 2} in 8.34s
>> 2010-03-09 09:32:41.359 SQLiteTest[16208:5503] Finished query on thread
>> <NSThread: 0x10061ea70>{name = (null), num = 5} in 8.34s
>> 2010-03-09 09:32:41.360 SQLiteTest[16208:5703] Finished query on thread
>> <NSThread: 0x10061e5a0>{name = (null), num = 6} in 8.34s
>> 2010-03-09 09:32:41.360 SQLiteTest[16208:5c03] Finished query on thread
>> <NSThread: 0x10061e680>{name = (null), num = 7} in 8.34s
>> 2010-03-09 09:32:41.360 SQLiteTest[16208:a0f] Finished all queries in 8.34s
>>
>>
>>
>> 6 of the same query executed in separate processes.
>> The query time is essentially the same as when you issue just a single query
>> in the 'multithreaded' configuration above - as one would expect.
>>
>> 2010-03-09 09:47:02.729 SQLiteTest[17083:a0f] SQLite says multithreading is
>> ON
>> 2010-03-09 09:47:02.731 SQLiteTest[17083:a0f] SQLite's multithreading value
>> is 2
>> SHARED CACHE IS OFFRead uncommitted is 1
>> SHARED CACHE IS OFFRead uncommitted is 1
>> SHARED CACHE IS OFFRead uncommitted is 1
>> SHARED CACHE IS OFFRead uncommitted is 1
>> SHARED CACHE IS OFFRead uncommitted is 1
>> SHARED CACHE IS OFFRead uncommitted is 1
>> Cache size is 100000
>> Page size is 32768
>> Temp store is 2
>> Synchronous is 0
>> Cache size is 100000
>> Page size is 32768
>> Temp store is 2
>> Synchronous is 0
>> Cache size is 100000
>> Page size is 32768
>> Temp store is 2
>> Synchronous is 0
>> Cache size is 100000
>> Page size is 32768
>> Temp store is 2
>> Synchronous is 0
>> Cache size is 100000
>> Page size is 32768
>> Temp store is 2
>> Synchronous is 0
>> Cache size is 100000
>> Page size is 32768
>> Temp store is 2
>> Synchronous is 0
>> On pid 17089, 3717 rows read in approx 2s
>> On pid 17088, 3717 rows read in approx 2s
>> On pid 17093, 3717 rows read in approx 2s
>> On pid 17090, 3717 rows read in approx 2s
>> On pid 17091, 3717 rows read in approx 2s
>> On pid 17092, 3717 rows read in approx 2s
>> 2010-03-09 09:47:04.323 SQLiteTest[17083:a0f] Finished all queries in 1.59s
>>
>>
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