Hello
I do not have clear examples to post on this but would like to report
findings around multi threaded read access (single process) in a large
system that uses sqlite.
This may be a known issue/restriction of memory sqlite behaviour, but
wanted to check with the list first:
1. Running 2, 3,
David Burgess wrote:
>> Where do the quotes around the value come from?
>
> I typed them. Simgle set of double quotes
I meant the quotes around the entire value returned by the SELECT.
>> Are you using the standard command-line shell, and which output mode?
>
> yes and the default mode
The defau
Techno Magos wrote:
> So, memory sqlite is not really usable with multiple threads (readers).
> While one might expect that multiple readers of *memory *content could
> scale even better than with file content.
Concurrent accesses to the same in-memory data structures must be
serialized. In shar
Clemens Ladisch wrote:
Techno Magos wrote:
So, memory sqlite is not really usable with multiple threads (readers).
While one might expect that multiple readers of *memory *content could
scale even better than with file content.
Concurrent accesses to the same in-memory data structures must be
I have a few ideas you could try with a file db.
1. Use VFS with no locks - named "win32-none" or "unix-none" depending
on your system (4th argument to sqlite_open_v2).
2. Run "pragma locking_mode=exclusive;" on each connection or compile
SQLite with -DSQLITE_DEFAULT_LOCKING_MODE=1
3. Compile SQ
Say Hi to Gene!
https://en.wikipedia.org/wiki/Amdahl%27s_law
So I believe what you are saying is something like this: If I take a child and
have it count as fast as it can then it can count to X in an hour. However, I
take the same child but have it count as fast as it can at five minute
st
It's not clear to me why reads must be serialized at all. Maybe this could
be re-thought? Maybe there should be a way to tell SQLite that a certain
DB or table is to be read-only and unserialized?
On Sun, May 13, 2018 at 7:15 AM, Keith Medcalf wrote:
>
> Say Hi to Gene!
>
> https://en.wikipedi
On 13 May 2018, at 11:50am, Techno Magos wrote:
> So, memory sqlite is not really usable with multiple threads (readers).
> While one might expect that multiple readers of *memory *content could
> scale even better than with file content.
>
> Can this restriction be lifted?
It's not a pointles
>2. Running the same example on sqlite *file *(multi threaded mode;
>WAL journal) scales almost linearly; so 6 threads provide nearly 6xN
>throughput. Single threaded throughput is a bit slower (around 15-
>20%) than single threaded in-memory access (expected).
So, there is some "part" of the pr
The arguments here are simplified, and assume some things that may or may
not be true. The server I keep in my garage has 16 real cores, 32
threads. More importantly, it uses DDR4 memory which I think means there
are 4 channels to memory which can be used in parallel -- perhaps not on
exactly th
On 05/13/2018 11:57 AM, Kevin O'Gorman wrote:
The arguments here are simplified
Will you stop top posting please?
I am trying to follow along here about some x86 boxen stuff but
you are top posting madly. Also is that a single socket machine
with a single big memory bank or is it NUMA and mul
On 13 May 2018, at 4:57pm, Kevin O'Gorman wrote:
> More importantly, it uses DDR4 memory which I think means there
> are 4 channels to memory which can be used in parallel -- perhaps not on
> exactly the same address but the memory is spread among 16 DIMMs.
Suppose your different threads are rea
Kevin O'Gorman wrote:
> why is a read-only database being serialized at all?
The database file is read only, the in-memory data structures are not.
For example, when the cache size is smaller than the DB size, pages
must be removed from and added to the internal list of cached pages.
When using m
On 13 May 2018, at 17:01, Dennis Clarke wrote:
> On 05/13/2018 11:57 AM, Kevin O'Gorman wrote:
> Also is that a single socket machine with a single big memory bank or
> is it NUMA and multiple sockets or is it just a single motherboard unit?
And I'd be curious to know whether memory is interlea
On 5/13/18 11:57 AM, Kevin O'Gorman wrote:
> More importantly, it uses DDR4 memory which I think means there
> are 4 channels to memory which can be used in parallel
DDR4 does NOT have 4 independent memory channels. DDR4 is the forth
generation of the Double Data Rate interface standard. DDR memo
On 9 May 2018 at 08:56, Richard Hipp wrote:
> But with
> SQLite, there is no round-trip latency. A "round-trip" to and
> database is just a function call, and is very very cheap.
>
I want to emphasise that Dr. Hipp's usage of "round-trip" only includes the
latency of _communication_ between t
On 5/13/18 12:55 PM, Rowan Worth wrote:
> On 9 May 2018 at 08:56, Richard Hipp wrote:
>
>> But with
>> SQLite, there is no round-trip latency. A "round-trip" to and
>> database is just a function call, and is very very cheap.
>>
> I want to emphasise that Dr. Hipp's usage of "round-trip" only i
On Sun, May 13, 2018 at 9:01 AM, Dennis Clarke
wrote:
> On 05/13/2018 11:57 AM, Kevin O'Gorman wrote:
>
>> The arguments here are simplified
>>
>
>
> Will you stop top posting please?
>
> I am trying to follow along here about some x86 boxen stuff but
> you are top posting madly. Also is that a s
Try to open N separate database connections (without shared cache) and
load content using sqlite3_deserialize with
SQLITE_DESERIALIZE_READONLY flag.
http://www.sqlite.org/c3ref/deserialize.html
SQLite won't copy data but use provided buffer so you won't have N
copies of databse.
2018-05-13 12:50 G
Hi,
I am having problems building sqlite with the android NDK for macos.
Weirdly, it *does* build fine on windows ndk.
The errors I am getting are shown below.
Bye,
Mark
'-- errors building sqlite on macOS android ndk
jni/../../../sqlite-amalgamation/sqlite3.c:
> And it works for me:
I'm pleased for you.
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On 14 May 2018 at 01:08, Richard Damon wrote:
> On 5/13/18 12:55 PM, Rowan Worth wrote:
> > On 9 May 2018 at 08:56, Richard Hipp wrote:
> >
> >> But with
> >> SQLite, there is no round-trip latency. A "round-trip" to and
> >> database is just a function call, and is very very cheap.
> >>
> >
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