World: r3wp

<<SQLite "databases" act more like traditional "tablespaces">>
That's a nice flexible approach.

It may add an apparent unnecessary level of complexity for small 
databases, but the tablespace approach is intended to scale almost 
unlimitedly.

Think to when REBOL has taken over the world, and we have tables 
that exceed a single disk drive. Tablespaces exist (in part) to handle 
that sort of issue.

what is tablespace?

It's a data space that contains tables.

A tablespace can be split across disk volumes (or servers or machines)
And a table is defined as residing in one or more tablespaces.


The unit of back up is a tablespace -- or a database (which consists 
of 1 or more tablespaces)

It adds a lot of flexibility for large systems. But can be overkill 
for smaller ones....Where you probably just have one tablespace that 
lives in one folder.

OK, initial beta release can be found at: http://www.dobeash.com/files/SQLite.r

ok, please inform us here, if you do some changes/fixes :-) Thanks 
a lot ...

Ashley - maybe I vote for functions having sql- or sqlite- prefix 
.... sql then could become sql-query .... because ... standalone 
"disconnect" in rebol script is a bit strangely looking .... in rebol 
you can disconnect from many things ... it does not look obvisous 
at first sight .... what do others think?

also open, close vs connect, disconnect ... evne rebdb has db-open 
.... looks good ... maybe db- would be nice, telling and short prefix 
...

hmm, now I found oconnect refinements uncomfort ....

I would prefer setting /blocked or not, /direct or not, as a result 
fo query, so maybe those refinements should be available with /sql 
function instead?

could we mark this group [web-public]? Would anyone be offended?

Done. I've also updated SQLite.r to correct its mold/all handling 
and changed the /blocked refinement to /flat (the driver now returns 
rows as blocks by default).

Bumped the version to 0.1.2 with three enhancements:

1) Automatic NULL -> none! conversion (and vice versa)

2) 'sql now handles a SQLITE_BUSY return code by retrying the failing 
sqlite3_step 5 times at one second intervals

3) About value (number of retries) can be set with a new connect/timeout 
refinement

About -> Above

Ashley - why did you name somehow not traditionally functions as 
connect and disconnect? To not clash with open and close natives? 
:-)

Ashley - why can't we support multiple name-spaces?

can we have opened only one db at a time? And if we want to open 
other, do we have to attach, no other chance?

Would it also be possible to extend e.g. 'headings to return non-string 
 values? (but I wonder if heading can contain space, if so, that 
is bad) .... because it would allow for following contstructs:

cols: headings
== [ID Name Address]

values: [1 "Petr" "Czech Republic"]

set cols values

I also don't agree with exposing functions as you did it, without 
prefix of sqlite or db .... that aproach is flat ... and unless it 
is not forbidden by sqlite itself, I don't see a reason to limit 
ourselves to have just one openened database .... I will shortly 
try it ...

I assigned whole anonymous context to sqlite: , to have access to 
sqlite/dbid, which can be submitted to other library wrapper functions 
to try some stuff. In current state, 'connect returns true or false, 
I want handler though ...

maybe it would be better to introduce one more function - if connect? 
db1: connect %my-db.db

It seems you want cursors.

Then you can separate preparing of an sql statement and fetching 
from the cursor.

This would allow to reset an already compiled statement and to redo 
 do it without a new compilation.
Or even to cache compiled statements as Caché does it.

I am not sure I want cursors - I just want to be able to work with 
multiple databases, without the need to close prior one ....

the problem imo is, that current driver does not return db handler 
anymore, but only true or false ...

1) why did you name somehow not traditionally functions as connect 
and disconnect?


open and close are already taken and I wanted to avoid pathing (sqlite/open) 
or prefixes (sqlite-open) as the number of words added to the global 
context is relatively few and I wanted them to be meaningful words 
in their own right (same reason why VID doesn't have vid-layout, 
vid-center-face, etc). Connect and disconnect are the commands used 
to login/logout of another user in many databases; so while the context 
is not strictly correct, they are recognisable DB words.

2) why can't we support multiple name-spaces?


You can via the connect/attach refinement (and this lets you transparently 
reference tables across multiple "databases"). Why would you want 
to concurrently access multiple databases that are *not* related 
to each other in any way?

3) can we have opened only one db at a time?


Yes, bar /attach as above. The benefit of this approach is that you 
minimise the number of file locks a single process obtains, and you 
don't have to track state information (i.e. you don't need to tell 
'sql which DB you are referring to).


4) Would it also be possible to extend e.g. 'headings to return non-string 
 values?

No, as it may contain strings like "count(*)"

5) don't agree with exposing functions as you did


I tend to write CONNECT, SQL, etc in upper-case so db references 
embedded in my code stand out. Come up with a better naming scheme 
that everyone likes though and I'll adopt it. ;)

ad 1) I was referring to the context of foreign script reader understanding 
- you used db-open even for rebDB - as I said, it is a detail, but 
makes sometimes things more clearer ...


ad 2) I was imagining simply kind of server product, which can open 
multiple unrelated databases ....


ad 3) kind of disadvantage here to not refer by pointer. We are used 
to it, no? Look at /Command or other schemes - db: open some-db://..... 
conn1: first db conn2: first db ... db2: open some-db://..../other-db

ad 4) OK


ad 5) db- or sqlite- prefix or let it the way it is, I will assign 
it to sqlite: context [] directly in %sqlite.r

you used db-open even for RebDB

 ... that's because it needed to define about 20 low-level SQL statement 
 functions like 'select, 'delete, ''show, 'close, 'insert, etc that 
 conflicted with existing REBOL words and could not be easily renamed 
 (folks expect a SELECT statement, an UPDATE statement, etc or something 
 that resembles it). With the SQLite driver, all these statements 
 are handled by the SQLite library itself so we only need to provide 
 a few high-level accessor functions like SQL and DESCRIBE; these 
 types of words don't conflict with REBOL's lower-level atomic action 
 type words so there isn't the same need to group and isolate them 
 by prefix and/or context.


kind of disadvantage here to not refer by pointer. We are used to 
it, no?

 But is it *needed*? If you *must* work with multiple databases concurrently 
 and *cannot* have them attached, then SQLite is probably not the 
 right solution for you anyway ... it's an embedded C library with 
 limited concurrency and no user rights management after all. ;)

:-)

New revision available at: http://www.dobeash.com/SQLite/sqlite.r

thanks a lot :-)

It's designed to create the database in a Rebol's root dir? (if the 
path is not fully specified) I would expect to create the database 
in the folder where I'm (and where is the SQLite)

hehe, forget that ....

not sure ... it was really strange ... it created dbs at path of 
dll or so, dunno now ...

but I think that it is easy by simply setting db-path: your-dir-here 
... and then connect join db-path %my-db-name.db

While testing I started a script using sqlite several times, at about 
the 17th call I get this error:

** Script Error: Library error: Max Callbacks
** Where: context
** Near: sqlite-trace: make routine! [
    db [integer!]
    clb [callback! [int string!]]
    ptr [integer!]
] SQLite3lib

I'm using the following version:

	Title:		"SQLite driver"
	Owner:		"Ashley G. Trüter"
	Version:	0.1.3
	Date:		22-Feb-2006

And another question ... I have a table which conains string data 
...

sql {select * from person where firstname = "Ingo"}


does not find the row (tried with singel quotes, too). What am I 
doing wrong? It goes without saying, that the data is actually there, 
and I can find it using the following SQL

sql {select * from person where firstname like "%ingo%"}

REBOL supports a maximum of 16 callbacks; so to avoid this error 
don't do %sqlite.r more than once within a script (and there is no 
sensible reason to do so anyway).


As for strings, remember that the driver mold's them; so they are 
actually stored as "string" (inclusive of quotes). You can reference 
them in one of two ways:

	sql {select * from table where col = '"string"'}

or

	sql ["select * from table where col = ?" "string"]


The second form is preferred as the binding is handled for you by 
the driver. I'm in the process of writing a SQLite Driver Guide (that 
covers this and other tricks) but it's a week or two away at the 
moment.

Thanks Ashley,

I found out the first point by myself, and just added a check whether 
'sql has already been set before doing sqlite.r.

But so far I had no idea about the molding of strings, I could have 
tried for months, I guess ;-)

Hi Ashlsy, I found a bug in sqlite.r. 'sql reuses its own return 
value on subsequent calls. so ...

>> all: sql "select * from persons"
== [["Ivo" "Hohmann" ...] ....]
>> me: sql {select * from persons where firstname = '"ingo"'}
== [["Ingo" "Hohmann" ...] ...]
>> all =? me
== true

Deliberate design that. The last line of 'sql is simply:

	buffer

not:

	copy/deep buffer


This is important when dealing with a large number of values as you 
want to pass a reference not double the amount of memory used with 
a redundant copy/deep! I'll add this "gotcha" to the documentation 
I'm writing.

Actually, there is no need to copy/deep buffer.
Just change 
	clear buffer
to
	buffer: copy []

there is no problem with integer, decimal, and none values regarding 
sharing.
Blob data is debased, which implicitly creates a new string.

Strings are normally loaded, which creates a new string. only when 
you use /raw, you are dependend on the sqlite.dll having a sane interface 
and not reusing the returned string data. You could add this as a 
possible gotcha.

clear buffer

 is also an optimization as it defaults to 32K values (make block! 
 1032 * 32) and I don't won't to reallocate it each SQL call. The 
 following benchmarks (Transactions Per Second) give some backround 
 to the design decisions I made:

	buffer				1744718
	copy buffer			282
	copy/deep buffer		76

	clear buffer			1144733
	buffer: copy []			824352
	buffer: make block! 32768	387


So the approach I took optimizes for large result sets by allocating 
a large buffer once up-front and then just referencing it thereafter.

0.1.4 of the driver available at:http://www.dobeash.com/SQLite/sqlite.r


Plus new documentation now available at: http://www.dobeash.com/SQLite/

Enjoy!

Well, OK, I'm just not sure it's worth it. On the other hand, I don't 
expect a high volume access on my databases ...

I think it *is* worth it, because it gives the choice to copy or 
not to the user, instead of deciding beforehand for the user.  It 
being a somewhat unexpected optimization, however, means that it 
should be documented clearly, which Ashley is doing.

just would like to say, that I don't like the last line:
any [system/script/parent/header halt]

which throws an error if you run the script as a part of bigger context
I would use:
any [error? try [system/script/parent/header] halt]

run the script as a part of bigger context

 Not sure I understand what the issue is; do you have a small example?

not small, but imagine, that I can include your code to other script, 
which for example require sqlite

and I don't want to halt the code

and I'm using modified attempt, which will print out all errors without 
halting the script as well so I can see, what's going on - and your 
code is not clear it throws error when system/script is not defined

>> rss/run %sqlite
!!! ERRROR:
make object! [
    code: 312
    type: 'script
    id: 'cannot-use
    arg1: 'path
    arg2: 'none!
    arg3: none
    near: [any [system/script/parent/header halt]]
    where: 'attempt
]