[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-14 Thread az

On Saturday 14 June 2008 06:50:23 Russell Warren wrote:
  so far i have found these ways to hack somebeody else's source:
   a) inherit the class, replace whatever, use the new version -
  works if it is just you using the new-stuff
   b) complete replacement: import thatclass; thatclass.method =
  your-own-version
   c) partial hacks: inspect.get_source( that method); replace some
  lines in that with yours; compile; replace the method with the
  new version. this works if u have sources; if its just *.pyc,
  sorry.

 All good ways.  I was planning on b), but I just couldn't (can't)
 locate the right replacement location underneath the SQLA classes
 I'm using (Session, Engine, Metadata, etc).  Where the heck is the
 Compiler?
it depends.. there is DefaultCompiler (called AnsiCompiler in 0.3) 
which is used when u do not have an engine yet (meta =Metadata()). 
and all dialects inherit from it. 
see dbcook/misc/aggregator/tests/convertertest.py for another hack for 
better visibility/str() of bindparams.
also dbcook/misc/metadata/autoload is fiddling a bit with dialects.

grep - and your very own eyes - are your friends. 
and of course trial+error...

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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-14 Thread az

On Saturday 14 June 2008 06:28:58 Russell Warren wrote:
  if you'd like to specify a value generator for the columns, just
  use a ColumnDefault.  Whatever function or SQL you like will be
  called if no value is present - its just in this case we can't
  rely upon SQLite's OID generation.

 Thanks - I'll look into that.  I just have to figure out how to
 make ColumnDefault dialect dependent.

  I wouldn't favor a built in system of guessing within the
  sqlite dialect how to autoincrement a composite PK field without
  explicit user intervention.

 Why not?  Is it really guessing when the table has been defined
 precisely within SQLA?  If you have a Column that has been defined
 to be an Integer primary key that is supposed to autoincrement, and
 you are using sqlite... how could you be wrong?  The worst case I
 can think of is if sqlite changes in the future to actually support
 it, in which case you'd either change the dialect or get an error. 
 No?
maybe the user should request it somehow. Here come extra 
dialect-preferences. e.g. Column may mantain an attribute 
extras4sqlite, eventualy containing a dict of sqlite-specific 
settings; same for postgres etc. Then the specific dialect can look 
the column and get his own extra-settings - if any. This gives 
explicitness, separation of concerns (generic vs specific), and 
flexibility together. And this can be applied to other objects, e.g. 
tables or whatever. i'm sure thre are things u can do with tables in 
postgress and u cannot do in sqlite. 
Once some feature/attribute is considered generic/unified, it is moved 
from those extra* settings into the usual place -- or vice versa if 
stops being generic.

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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-14 Thread Michael Bayer

Russell Warren wrote:

 Why not?  Is it really guessing when the table has been defined
 precisely within SQLA?  If you have a Column that has been defined to
 be an Integer primary key that is supposed to autoincrement, and you
 are using sqlite... how could you be wrong?

autoincrement is very difficult to implement in application code in an
atomic and high performing fashion.  If we're not using what the DB engine
provides natively, then the user has to pick the method he or she wishes
to use, since each would have caveats the user needs to be aware of.  I'm
not opposed to having a catalog of id generator tools within the distro
but as of yet nobody has offered any.  A key philosophy of SQLA is that we
don't make choices for the user without explicit statement.

 But at the same time the dialect is also abstracting out many of the
 annoying backend type differences.  I thought that a big part of SQLA
 was going to be allowing the use of any back end.

We abstract as much as is reasonably possible.  But we also honor and make
explicit the differences between those databases so that each backend can
be used to its fullest potential.  Another big philosophy of ours is to
not pretend the database doesn't exist by forcing all the various vendors
into the lowest denominator of functionality.  Practices like that are
what give object relational tools as well as RDBMS overall a bad name.




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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-13 Thread az

 And a related question:  What is the general feeling on how well
 SQLA abtstracts the underlying database away?  Am I expecting too
 much to be able to write my application using SQLA-only from the
 beginning and have it work on any of the popular databases without
 much tweaking?
YMMV. it is actualy you who break things. e.g. if u dont rely much on 
specific SQldialect notions, or better, on specific SQL notions, 
you'r settled.
i've made dbcook over SA and ever since the team have forgotten about 
what SQL is, except some very tricky things which has to be SQL 
aware, as they rely on DB-structure being what it is. But dialects... 
only come to play when something is not supported, and my way of 
handling this so far is to avoid using any stuff that is not 
supported everywhere - workaround on lowe or higher level, including 
model refactoring.

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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-13 Thread az

 3. What internal SQLA structures can I count on staying fixed
 through revisions?  
everything changes/can change. 
so just do it, and keep doors opened for being version-aware (or 
actualy make them later).
i have a lot of this stuff, look in the dbcook sources. e.g. after 
rev260 i've whacked 0.3/0.4beta1 support out.

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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-13 Thread Egil Möller


 YMMV. it is actualy you who break things. e.g. if u dont rely much on 
 specific SQldialect notions, or better, on specific SQL notions, 
 you'r settled.
 i've made dbcook over SA and ever since the team have forgotten about 
 what SQL is, except some very tricky things which has to be SQL 
 aware, as they rely on DB-structure being what it is. But dialects... 
 only come to play when something is not supported, and my way of 
 handling this so far is to avoid using any stuff that is not 
 supported everywhere - workaround on lowe or higher level, including 
 model refactoring
I don't think that is a very workable strategy in the long run :( There 
are far to many bogus restrictions in some databases, e.g. Oracle, for 
any meaningful program to
be written to work on all platforms w/o support/wrapping/hiding of ugly 
details by SA.

I and a coworker are currently working on a patch-set to the oracle 
driver for SA for this very reason, fixing issues like:

* broken mangling of forbidden/to long table/column names
* missing support for the BOOL data type
* missing support for boolean expressions in the column list ( 
select([tbl.c.col1 == tbl.c.col2]) ) (related to the last one above)

You might think that you could easily get around the name-length barrier 
using the shortnames-option. But SA combines table names with column 
names to form aliases in select column lists, and the length quickly 
exceeds 32 characters (Oracles limit). In addition, do _you_ know which 
words are forbidden as column names in Oracle? I can assure you that 
there is at least a few you don't remember (and I wouldn't remember 
either :P)...

Just a point of measurement (ok, oracle is the worst one...)

Best regards,
Egil




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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-13 Thread Paul Johnston
Hi,

I don't think that is a very workable strategy in the long run :( There
 are far to many bogus restrictions in some databases, e.g. Oracle, for
 any meaningful program to
 be written to work on all platforms w/o support/wrapping/hiding of ugly
 details by SA.


This is often a difficulty for libraries that provide a portable layer over
different implementations. GUI toolkits are a good example. The library
essentially has three choices:
1) Only expose functionality that exists on all the implementations
2) Expose the user to the slight differences between implementations
3) Expose consistent functionality, and where an implementation lacks
support, fake it
In practice, (1) is usually a poor option as it's too restrictive.
SQLAlchemy currently takes approach (2). There is definitely consistency
merit for approach (3), but it comes at a cost - there's more magic going
on, which could be confusing in some circumstances.

Paul

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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-13 Thread az

On Friday 13 June 2008 16:34:47 Paul Johnston wrote:
 Hi,

 I don't think that is a very workable strategy in the long run :(
 There

  are far to many bogus restrictions in some databases, e.g.
  Oracle, for any meaningful program to
  be written to work on all platforms w/o support/wrapping/hiding
  of ugly details by SA.

 This is often a difficulty for libraries that provide a portable
 layer over different implementations. GUI toolkits are a good
 example. The library essentially has three choices:
 1) Only expose functionality that exists on all the implementations
 2) Expose the user to the slight differences between
 implementations 
 3) Expose consistent functionality, and where an 
 implementation lacks support, fake it
 In practice, (1) is usually a poor option as it's too restrictive.
 SQLAlchemy currently takes approach (2). There is definitely
 consistency merit for approach (3), but it comes at a cost -
 there's more magic going on, which could be confusing in some
 circumstances.
i think there's something 2.5, allow user to make his own 
support/settings, let him take the decision - preferences-like; e.g. 
a widget with a set of general attributes and several sets of 
implementation-dependent extra attributes, switched depending on 
implementation - the user can setup them all.

well maybe i got a mix of all them 3, for different aspects.
e.g. if oracle db will disallow me to use my 50-long names, i'll 
mangle them somewhere in the middle, but will not allow such 
meaningless restriction to cripple all the model above.
while for other things i just surrender and dont use the features... 

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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-13 Thread Michael Bayer


On Jun 13, 2008, at 1:00 AM, Russell Warren wrote:


 Any help is appreciated.  I expect I'm in over my head trying to mess
 with a dialect implementation.  I'm also worried that this will just
 be the first of many things like this I'll be trying to overcome to
 get SQLA to truly abstract the database implementations away...

 And a related question:  What is the general feeling on how well SQLA
 abtstracts the underlying database away?  Am I expecting too much to
 be able to write my application using SQLA-only from the beginning and
 have it work on any of the popular databases without much tweaking?


if you'd like to specify a value generator for the columns, just use a  
ColumnDefault.  Whatever function or SQL you like will be called if no  
value is present - its just in this case we can't rely upon SQLite's  
OID generation.

I wouldn't favor a built in system of guessing within the sqlite  
dialect how to autoincrement a composite PK field without explicit  
user intervention.  The dialects don't intend to build a completely  
uniform layer over all database backends (for example, when using  
Oracle, you are required to set up a default generator, usually a  
Sequence, in all cases) - the idea of a dialect's default behavior is  
that it uses what the database backend provides by default and that's  
it.

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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-13 Thread Michael Bayer


On Jun 13, 2008, at 3:58 AM, Egil Möller wrote:

 I and a coworker are currently working on a patch-set to the oracle
 driver for SA for this very reason, fixing issues like:

 * broken mangling of forbidden/to long table/column names

really ?  we have a lot of tests which pass fine for that, including  
when aliases are created, etc.  In compiler.py, all names go through  
the same length filter no matter how they got generated (the only  
exception to this is the too long index names ticket which is  
strictly a schema thing).   We have a long labels test specifically  
for this, and lots of ORM tests generate very long names as well (all  
of which work fine with Oracle).  We did a tremendous amount of  
development on this a few years back and noone has had issues since.

can you post a ticket with an example ?Also if producing fixes,  
keep in mind theres some compiler differences between 0.4 and 0.5, 0.5  
is the direction we're heading


 * missing support for the BOOL data type

there may or may not be a ticket for this (please post one if not)


 * missing support for boolean expressions in the column list (
 select([tbl.c.col1 == tbl.c.col2]) ) (related to the last one above)

ditto
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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-13 Thread Michael Bayer

for example, heres a beast of a unit test:

python test/orm/inheritance/query.py --log-debug=sqlalchemy.engine -- 
db oracle PolymorphicUnionsTest.test_primary_eager_aliasing

When you run on SQLite, one of the queries is:

SELECT anon_1.people_person_id AS anon_1_people_person_id,  
anon_1.people_company_id AS anon_1_people_company_id,  
anon_1.people_name AS anon_1_people_name, anon_1.people_type AS  
anon_1_people_type, anon_1.engineers_person_id AS  
anon_1_engineers_person_id, anon_1.engineers_status AS  
anon_1_engineers_status, anon_1.engineers_engineer_name AS  
anon_1_engineers_engineer_name, anon_1.engineers_primary_language AS  
anon_1_engineers_primary_language, anon_1.managers_person_id AS  
anon_1_managers_person_id, anon_1.managers_status AS  
anon_1_managers_status, anon_1.managers_manager_name AS  
anon_1_managers_manager_name, anon_1.boss_boss_id AS  
anon_1_boss_boss_id, anon_1.boss_golf_swing AS anon_1_boss_golf_swing,  
machines_1.machine_id AS machines_1_machine_id, machines_1.name AS  
machines_1_name, machines_1.engineer_id AS machines_1_engineer_id
FROM (SELECT people.person_id AS people_person_id, people.company_id  
AS people_company_id, people.name AS people_name, people.type AS  
people_type, engineers.person_id AS engineers_person_id,  
engineers.status AS engineers_status, engineers.engineer_name AS  
engineers_engineer_name, engineers.primary_language AS  
engineers_primary_language, managers.person_id AS managers_person_id,  
managers.status AS managers_status, managers.manager_name AS  
managers_manager_name, boss.boss_id AS boss_boss_id, boss.golf_swing  
AS boss_golf_swing
FROM people LEFT OUTER JOIN engineers ON people.person_id =  
engineers.person_id LEFT OUTER JOIN managers ON people.person_id =  
managers.person_id LEFT OUTER JOIN boss ON managers.person_id =  
boss.boss_id ORDER BY people.person_id
  LIMIT 2 OFFSET 1) AS anon_1 LEFT OUTER JOIN machines AS machines_1  
ON anon_1.engineers_person_id = machines_1.engineer_id ORDER BY  
anon_1.people_person_id, machines_1.oid

of note is the anonymous label anon_1_engineers_primary_language, 34  
characters.   This label is generated from an anonymous alias name  
combined with a column name, which is itself a combination of the  
original table name and column name.  So theres three stages of name  
generation represented here.

Here it is on oracle, including the result rows:

SELECT anon_1.people_person_id AS anon_1_people_person_id,  
anon_1.people_company_id AS anon_1_people_company_id,  
anon_1.people_name AS anon_1_people_name, anon_1.people_type AS  
anon_1_people_type, anon_1.managers_person_id AS  
anon_1_managers_person_id, anon_1.managers_status AS  
anon_1_managers_status, anon_1.managers_manager_name AS  
anon_1_managers_manager_name, anon_1.boss_boss_id AS  
anon_1_boss_boss_id, anon_1.boss_golf_swing AS anon_1_boss_golf_swing,  
anon_1.engineers_person_id AS anon_1_engineers_person_id,  
anon_1.engineers_status AS anon_1_engineers_status,  
anon_1.engineers_engineer_name AS anon_1_engineers_engineer_name,  
anon_1.engineers_primary_language AS anon_1_engineers_primary_1,  
machines_1.machine_id AS machines_1_machine_id, machines_1.name AS  
machines_1_name, machines_1.engineer_id AS machines_1_engineer_id
FROM (SELECT people_person_id, people_company_id, people_name,  
people_type, managers_person_id, managers_status,  
managers_manager_name, boss_boss_id, boss_golf_swing,  
engineers_person_id, engineers_status, engineers_engineer_name,  
engineers_primary_language
FROM (SELECT people.person_id AS people_person_id, people.company_id  
AS people_company_id, people.name AS people_name, people.type AS  
people_type, managers.person_id AS managers_person_id, managers.status  
AS managers_status, managers.manager_name AS managers_manager_name,  
boss.boss_id AS boss_boss_id, boss.golf_swing AS boss_golf_swing,  
engineers.person_id AS engineers_person_id, engineers.status AS  
engineers_status, engineers.engineer_name AS engineers_engineer_name,  
engineers.primary_language AS engineers_primary_language, ROW_NUMBER()  
OVER (ORDER BY people.person_id) AS ora_rn
FROM people LEFT OUTER JOIN managers ON people.person_id =  
managers.person_id LEFT OUTER JOIN boss ON managers.person_id =  
boss.boss_id LEFT OUTER JOIN engineers ON people.person_id =  
engineers.person_id)
WHERE ora_rn1 AND ora_rn=3) anon_1 LEFT OUTER JOIN machines  
machines_1 ON anon_1.engineers_person_id = machines_1.engineer_id  
ORDER BY anon_1.people_person_id, machines_1.machine_id
INFO:sqlalchemy.engine.base.Engine.0x..4c:{}
DEBUG:sqlalchemy.engine.base.Engine.0x..4c:Col  
('ANON_1_PEOPLE_PERSON_ID', 'ANON_1_PEOPLE_COMPANY_ID',  
'ANON_1_PEOPLE_NAME', 'ANON_1_PEOPLE_TYPE',  
'ANON_1_MANAGERS_PERSON_ID', 'ANON_1_MANAGERS_STATUS',  
'ANON_1_MANAGERS_MANAGER_NAME', 'ANON_1_BOSS_BOSS_ID',  
'ANON_1_BOSS_GOLF_SWING', 'ANON_1_ENGINEERS_PERSON_ID',  
'ANON_1_ENGINEERS_STATUS', 'ANON_1_ENGINEERS_ENGINEER_NAME',  
'ANON_1_ENGINEERS_PRIMARY_1', 

[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-13 Thread Russell Warren

 if you'd like to specify a value generator for the columns, just use a
 ColumnDefault.  Whatever function or SQL you like will be called if no
 value is present - its just in this case we can't rely upon SQLite's
 OID generation.

Thanks - I'll look into that.  I just have to figure out how to make
ColumnDefault dialect dependent.

 I wouldn't favor a built in system of guessing within the sqlite
 dialect how to autoincrement a composite PK field without explicit
 user intervention.

Why not?  Is it really guessing when the table has been defined
precisely within SQLA?  If you have a Column that has been defined to
be an Integer primary key that is supposed to autoincrement, and you
are using sqlite... how could you be wrong?  The worst case I can
think of is if sqlite changes in the future to actually support it, in
which case you'd either change the dialect or get an error.  No?

 The dialects don't intend to build a completely
 uniform layer over all database backends (for example, when using
 Oracle, you are required to set up a default generator, usually a
 Sequence, in all cases) - the idea of a dialect's default behavior is
 that it uses what the database backend provides by default and that's
 it.

But at the same time the dialect is also abstracting out many of the
annoying backend type differences.  I thought that a big part of SQLA
was going to be allowing the use of any back end.  Maybe I'll have to
re-evaluate my approach... more likely I'll just keep plugging away
and see what obstacles I hit!

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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-13 Thread Russell Warren

 so far i have found these ways to hack somebeody else's source:
  a) inherit the class, replace whatever, use the new version - works
 if it is just you using the new-stuff
  b) complete replacement: import thatclass; thatclass.method =
 your-own-version
  c) partial hacks: inspect.get_source( that method); replace some
 lines in that with yours; compile; replace the method with the new
 version. this works if u have sources; if its just *.pyc, sorry.

All good ways.  I was planning on b), but I just couldn't (can't)
locate the right replacement location underneath the SQLA classes I'm
using (Session, Engine, Metadata, etc).  Where the heck is the
Compiler?

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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-06-12 Thread Russell Warren

 judging by the slapdown in this ticket, and it looks safe to say that
 this behavior in SQLite will never change:

 http://www.sqlite.org/cvstrac/tktview?tn=2553 backend of

Yow - that is a pretty terse slapdown!  It doesn't seem like sqlite
will ever support it.

I keep hoping that sqlalchemy can be abstract enough that it will
enable the use of any database backend.  Stuff like this sqlite
composite PK hiccup is discouraging, but I'm convinced there is a
workaround to make this work!  I don't care if it is the fastest way,
it just has to work.

I'm trying to get this to work with logic along these lines:

1. Identify in SQLiteCompiler.visit_insert when a primary key is
missing from the insert (insert_stmt)

2. If the missing key is tagged as autoincrement, auto-add it to the
insert object with a bogus value before the insert is processed (and
flag it for use later when working with the execution context)

3. When subbing the variables into the INSERT statement later, replace
the bogus value with something like: (SELECT max(id) FROM user)+1


It seems somewhat reasonable in principle to me, but the problems I'm
having in reality are:


1. How do I override SQLiteCompiler.visit_insert without modifying
SQLA's sqlite.py?  I of course want to avoid trashing the base SQLA
install, but can't find an override location in the object tree from
my session or engine or anything.

2. Even if I could find a way to override visit_insert, I'm having
trouble locating a location to stuff the select max code in place.
Tweaking the statement by creating an SQLiteDialect.do_execute
implementation seems like it might work, but it also doesn't seem lke
the cleanest way.

3. What internal SQLA structures can I count on staying fixed through
revisions?  eg: in visit_insert I can use self._get_colparams to
figure out what columns have been requested, and I can use
insert_stmt.table._columns to figure out what primary key is missing
(and if it is supposed to be autoincrement).  But I don't know which
of those I can actually count on being there in the future!  Plus,
crawling around internal objects like this just seems like a bad idea.


Any help is appreciated.  I expect I'm in over my head trying to mess
with a dialect implementation.  I'm also worried that this will just
be the first of many things like this I'll be trying to overcome to
get SQLA to truly abstract the database implementations away...

And a related question:  What is the general feeling on how well SQLA
abtstracts the underlying database away?  Am I expecting too much to
be able to write my application using SQLA-only from the beginning and
have it work on any of the popular databases without much tweaking?

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[sqlalchemy] Re: sqlite PK autoincrement not working when you do a composite PK?

2008-05-31 Thread Michael Bayer


On May 31, 2008, at 12:38 AM, Russell Warren wrote:


 I've tried sifting through the sqlite dialect to figure out what is
 going on and have even tried forcing supports_pk_autoincrement to be
 true, but it rapidly became clear I hadn't a clue what I was doing in
 the sqlalchemy guts.

 Does anyone know why autoincrement on id stopped working, and how I
 can fix it?


this is not a SQLA behavior, its a known behavior of sqlite3 - its  
autoincrement feature ceases to work with a composite primary key.   
I've never known any workaround for it (with the possible exception of  
declaring the second column in the PK as unique, instead of it  
actually being part of the PK).

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