While working on a VFS for use in 3.5.1, I was looking at the winLock()
and have a question.
Is it possible for the lock on a winFile object to progress from
SHARED_LOCK to EXCLUSIVE_LOCK without first acquiring a RESERVED_LOCK?
Assuming that it is, it seems that the comments at the start of
The prepare creates a virtual machine which can be rused. A useful way
to implement Sqlite is to use prepare to compile all the SQL in the
initialization phase of the program and then to execute the virutal
machines using step.
By compiling a SQL in advance you can ensure that the program
PostgreSQL has the capability of storing pre-compiled SQL so that it can
be reused and have data bound to the compiled statement. I have not
looked at the mechanics, but it would be of interest and educational for
you to see the PostgreSQL approach.
Sqlite does cache the results of a query.
Think about it. A transaction does not affect SELECts, it only defers
the processing of the journal until there is a COMMIT.
According to your version of Sqlite you may get some benefit from
SELECTs within a transaction by retaining the cache.
Ken wrote:
Thomas, if i understand you
Babu, Lokesh wrote:
sorry I forgot to mention the sqlite version that I'm using, its SQLite
3.3.8.
Below is the sample code that I tried,
static char *database_name = ":memory:";
static sqlite3* db_handle;
#define PRINT_TIME \
{ \
unsigned long millisec = clock(); \
This is a working proof of concept patch against sqlite 3.5.1 that
can improve query speed by as much as 50% when floating point or
64 bit integer constants are used. It does so by eliminating repeated
parsing of numbers from strings in OP_Real and OP_Int64 by storing
the parsed binary numbers
Hi,
Uma Krishnan wrote:
In SQLite3 one uses prepare/step to execute query. The question that I have is,
when your stepping yields no more rows, and one has to re-execute the query,
does one have to call the prepare statement again. If that's the case, what's
the advantage of pre-compiling.
In SQLite3 one uses prepare/step to execute query. The question that I have is,
when your stepping yields no more rows, and one has to re-execute the query,
does one have to call the prepare statement again. If that's the case, what's
the advantage of pre-compiling. If not, how does Sqlite3
I am not changing the ordering, but i do not want to copy the primary
key field since it is auto increment (I neglected too mention that
before, sorry).
On 10/16/07, Vitali Lovich <[EMAIL PROTECTED]> wrote:
> Well, you don't have to list the columns if you're not changing the
> ordering.
>
>
Yes. Makes sense (not to cache query results for embedded apps). So what is
cached. Just dirty pages? or are raw tables cached when queried?
Thanks
Uma
Scott Hess <[EMAIL PROTECTED]> wrote: On 10/17/07, Trevor Talbot wrote:
> On 10/17/07, Uma Krishnan wrote:
> > One other question, when a
Thomas DILIGENT <[EMAIL PROTECTED]> wrote: Hi Ken,
Ken wrote:
> Thomas, if i understand you correctly:
>
> 1. Place the writing of multiple rows of data inside a transaction.
> 2. Querry performance will not be affected by the transaction.
>
> So, If you have multiple rows and are doing
On 10/17/07, Trevor Talbot <[EMAIL PROTECTED]> wrote:
> On 10/17/07, Uma Krishnan <[EMAIL PROTECTED]> wrote:
> > One other question, when a query is issued, does SQLite cache the results,
> > so that future queries can be processed off the cache (I think not)
>
> Like the "query cache" in some
Thomas DILIGENT <[EMAIL PROTECTED]> wrote:
>
> That's it. This is what I want to do.
> From this point, I have the following questions :
> 1) Will this increase speed compared to a basic solution where I would
> use autocommit mode ? (in other words, is it worthy implementing such a
> solution
On 10/17/07, Uma Krishnan <[EMAIL PROTECTED]> wrote:
> As far as I know, Postgres does not have a virtual engine. I could be wrong.
It's not a virtual machine style, where it has a specific instruction
set; instead it's more like a graph of operations. Execution means
walking a graph instead of
On 10/17/07, Uma Krishnan <[EMAIL PROTECTED]> wrote:
> One other question, when a query is issued, does SQLite cache the results, so
> that future queries can be processed off the cache (I think not)
Like the "query cache" in some other databases? No.
SQLite does have a cache of database
Regarding: "... when a query is issued, does SQLite cache the results,
so that future queries can be processed off the cache (I think not) "
...
=
P.S. And I should certainly have mentioned the sqlite items below:
http://sqlite.org/pragma.html
PRAGMA cache_size=
Hi Ken,
Ken wrote:
Thomas, if i understand you correctly:
1. Place the writing of multiple rows of data inside a transaction.
2. Querry performance will not be affected by the transaction.
So, If you have multiple rows and are doing something like the following:
1. Begin Transaction
Hi,
with sqlite3_update_hook I can get the rowid of the row AFTER it has
been INSERTed, DELETEd or UPDATEd.
Is there a way to get the rowid of a row BEFORE it is DELETEd or
UPDATEd ?
If not, can someone suggest a good approach to this problem?
Thanks a lot,
---
Marco Bambini
Regarding: "... when a query is issued, does SQLite cache the results,
so that future queries can be processed off the cache (I think not) "
Hi Uma,
In effect, powerful caching effects *do* occur because of the disk cache
provided by modern operating systems. Since the hard disk operations
Thanks John and Joe for your responses.
As far as I know, Postgres does not have a virtual engine. I could be wrong.
One other question, when a query is issued, does SQLite cache the results, so
that future queries can be processed off the cache (I think not)
Thanks
Uma
John Stanton <[EMAIL
Thomas, if i understand you correctly:
1. Place the writing of multiple rows of data inside a transaction.
2. Querry performance will not be affected by the transaction.
So, If you have multiple rows and are doing something like the following:
1. Begin Transaction
2. Read data from
Richard,
this helped me greatly! I also derived from your example that I can use
multiple characters without conflicts like this:
---
doc ::= inline_list.
// List of allowed characters. Add more as you like.
c ::= CHAR.
c ::= SPACE.
// The c character repeat.
chars ::= c.
chars
Richard,
this helped me greatly! I also derived from your example that I can use
multiple characters without conflicts like this:
---
doc ::= inline_list.
// List of allowed characters. Add more as you like.
c ::= CHAR.
c ::= SPACE.
// The c character repeat.
chars ::= c.
chars
sorry I forgot to mention the sqlite version that I'm using, its SQLite
3.3.8.
Below is the sample code that I tried,
static char *database_name = ":memory:";
static sqlite3* db_handle;
#define PRINT_TIME \
{ \
unsigned long millisec = clock(); \
printf("milliseconds = %ld\n",
Igor Tandetnik wrote:
Thomas DILIGENT <[EMAIL PROTECTED]> wrote:
What about the performance issue ?
What about it?
You need to provide some context. Your questions, standing alone,
don't make much sense, no offence intended. What problem are you
trying to solve, and what specifically are
Ralf Junker <[EMAIL PROTECTED]> wrote:
> I am writing to ask for help about how to solve The Lemon parser conflicts.
>
> As part of a larger grammar, I am need to implement this regular expression
> in Lemon:
>
> (.+|'.+')+
>
> I tried lots of grammars, but all of them generated Lemon
Well, rough calculations indicate that the situation that sqlite
preallocates about an additional 3 rows every time a new ROWID is
assigned (on the fairly common use case that ROWID is always
monotonically increasing). Assuming that this corner case is not
accounted for, it could be that when
Thomas DILIGENT <[EMAIL PROTECTED]> wrote:
I would like to know what is the behavior of sqlite when performing a
SELECT query during a transaction ?
The same as outside the transaction.
CREATE TABLE thebeatles (_ID INTEGER PRIMARY KEY, name TEXT);
BEGIN TRANSACTION;
INSERT INTO thebeatles
"B V, Phanisekhar" <[EMAIL PROTECTED]> wrote:
> > A database is in the EXCLUSIVE state if one of the processes has an
> > EXCLUSIVE lock. Only *one* process at a time can hold an EX- CLUSIVE
> > lock. The process holding the EXCLUSIVE lock is currently writing to
> > the database file. Every
Could it be that you're seeing the btree optimization around in-order
insertion? From btree.c:
#ifndef SQLITE_OMIT_QUICKBALANCE
/*
** A special case: If a new entry has just been inserted into a
** table (that is, a btree with integer keys and all data at the leaves)
** and the new entry
I am writing to ask for help about how to solve The Lemon parser conflicts.
As part of a larger grammar, I am need to implement this regular expression in
Lemon:
(.+|'.+')+
I tried lots of grammars, but all of them generated Lemon warnings.
Maybe someone could have a look at the grammar
Hi all !
I would like to know what is the behavior of sqlite when performing a
SELECT query during a transaction ?
For example :
CREATE TABLE thebeatles (_ID INTEGER PRIMARY KEY, name TEXT);
BEGIN TRANSACTION;
INSERT INTO thebeatles (name) VALUES ('john');
INSERT INTO thebeatles (name)
> A database is in the EXCLUSIVE state if one of the processes has an
> EXCLUSIVE lock. Only *one* process at a time can hold an EX- CLUSIVE
> lock. The process holding the EXCLUSIVE lock is currently writing to
> the database file. Every other process must hold *no* lock. No other
>
Dear all,
I'll reframe the question again, If ROWID(hidden column/b-tree key/internal
to all table) is changed manually, means I'll insert some unique values in
random order / in descending order (say from 1 to 1), the memory
occupied increases more. why? I observed entire table is getting
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