For the cost of a single table scan, you may be better with:
select max(foo) - min(foo) where etc.
S.
--
Anyone using floating point for financial computations needs their head
examined.
On 12/20/18 4:32 PM, Jens Alfke wrote:
On Dec 20, 2018, at 4:21 PM, Jungle Boogie wrote:
select
In the nolock IOMETHODS:
https://github.com/mackyle/sqlite/blob/7bd4fc81a71bdc777151c747b2e6d3ee58994251/src/os_unix.c#L5203
Either the constant should be '1' or the comment should permit mmap. I
suspect the constant should be 1?
S.
___
On 08/03/2018 12:55 PM, Simon Slavin wrote:
On 3 Aug 2018, at 8:36pm, Shevek wrote:
We are running a 100Gb sqlite database, which we mmap entirely into RAM. We are
having trouble with parts of the disk file being evicted from RAM during
periods of low activity causing slow responses
Hi,
We are running a 100Gb sqlite database, which we mmap entirely into RAM.
We are having trouble with parts of the disk file being evicted from
RAM during periods of low activity causing slow responses, particularly
before 9am. Has anybody played with mlock and/or madvise within the
You may find it faster to do:
select c from t where rowid in (list-of-constants)
and generate the list of constants using something like a blackrock
permutation generator. That takes linear time, whereas all the order-by
variants are n.log(n). You need some sort of row-id generator function,
SQL overall is phenomenally ambiguous about group-by:
1) select a0 + 1 as a0 from a group by a0
has a different behaviour in different SQL implementations, depending on
whether the group-by prefers the underlying column or the projection alias.
2) As you rightly point out, group by integer
About storing the whole result set: Note that in postgresql-derivatives
(and Oracle? maybe Teradata?), this is valid:
select lag(a0, a0) over () from a;
whereas many other servers (which I won't name) require the second
argument of lag() to be constant. If it is constant (even in
Opinion: Of all the DBMS's UPSERT/MERGE semantics, postgresql's is the
least useful because it's very limited: It can only do a check against a
constraint, and the cost of evaluating that constraint has to be carried
by all other statements which mutate the table. Oracle/Teradata MERGE is
a
It has to be a subscriber. I just got spam in the form of an
almost-immediate reply to my last message to the list, including
message-ids. Web wouldn't bother including that metadata, and is
unlikely to be quite so real-time.
On 04/18/2018 11:35 PM, Simon Slavin wrote:
On 18 Apr 2018, at
1. Xerial
2. A year or so, relatively heavily.
3.
* MAX_MMAP_SIZE is too small by a few hundred megabytes. It's safe to
set to around a terabyte.
* No way to effectively use multiple threads, even on a read-only
mmap'd database.
* Planner sometimes misses plans - does it need better STAT
Nachricht-
Von: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org] Im
Auftrag von Shevek
Gesendet: Donnerstag, 01. März 2018 09:10
An: SQLite mailing list <sqlite-users@mailinglists.sqlite.org>; Simon Slavin
<slav...@bigfraud.org>
Betreff: [EXTERNAL] Re: [
On 02/28/2018 11:45 PM, Simon Slavin wrote:
On 1 Mar 2018, at 7:24am, Shevek <sql...@anarres.org> wrote:
What I think is happening is that either a pthread mutex or a database lock is
serializing the accesses, so each thread blocks the others.
To be specific, I'm concerned
Hi,
I would like to have truly concurrent access to an sqlite database, that
is, the ability for multiple connections to read from the database
simultaneously. I'm using Java with xerial's sqlite-jdbc, customized to
let me mmap the entire database into RAM, and with additional debugging
If I create a partial index:
create table a (a0, a1)
create index idx on a (a0) where a1 is null;
Then we have several issues:
1) This should be a covering index for
select a0, a1 from a where a1 is null;
It isn't. It's a great index, but we still defer to the table to look up
the (always
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