Re: [PATCHES] ALTER TABLE modifications

2003-11-16 Thread Hannu Krosing
Rod Taylor kirjutas L, 08.11.2003 kell 18:55:
 A general re-organization of Alter Table. Node wise, it is a
 AlterTableStmt with a list of AlterTableCmds.  The Cmds are the
 individual actions to be completed (Add constraint, drop constraint, add
 column, etc.)
 
 Processing is done in 2 phases. The first phase updates the system
 catalogs and creates a work queue for the table scan. The second phase
 is to conduct the actual table scan evaluating all constraints and other
 per tuple processing simultaneously, as required. This has no effect on
 single step operations, but has a large benefit for combinational logic
 where multiple table scans would otherwise be required.

...

 ALTER TABLE tab ALTER COLUMN col TYPE text TRANSFORM ...; 
 Currently migrates indexes, check constraints, defaults, and the
 column definition to the new type with optional transform. If
 the tranform is not supplied, a standard assignment cast is
 attempted.

Do you have special cases for type changes which don't need data
transforms. 

I mean things like changing VARCHAR(10) to VARCHAR(20), dropping the NOT
NULL constraint or changing CHECK A  3 to CHECK A  4. 

All these could be done with no data migration or extra checking.

So how much of it should PG attemt to detect automatically and should
there be NOSCAN option when progremmer knows better 
(changing CHECK ABS(A)  3 into CHECK 9  (A*A) )


Hannu


---(end of broadcast)---
TIP 4: Don't 'kill -9' the postmaster


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Dave Cramer
Rod,

I tried the current patch on a RC2 release, and I noticed one
undesirable side affect. 

Modifying a column  moves it to the end. In high availability situations
this would not be desirable, I would imagine it would break lots of
code.

Dave
On Thu, 2003-11-13 at 11:35, Hannu Krosing wrote:
 Rod Taylor kirjutas N, 13.11.2003 kell 16:59:
 
  
  Can you please suggest a better term to use in place of TRANSFORM? 
  Perhaps UPDATE WITH?
 
 or perhaps USING, based loosely on our use of USING in CREATE INDEX ?
 
 --
 Hannu
 
 
 ---(end of broadcast)---
 TIP 3: if posting/reading through Usenet, please send an appropriate
   subscribe-nomail command to [EMAIL PROTECTED] so that your
   message can get through to the mailing list cleanly
 
 


---(end of broadcast)---
TIP 4: Don't 'kill -9' the postmaster


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Alvaro Herrera
On Fri, Nov 14, 2003 at 08:59:05AM -0500, Dave Cramer wrote:

 I tried the current patch on a RC2 release, and I noticed one
 undesirable side affect. 
 
 Modifying a column  moves it to the end. In high availability situations
 this would not be desirable, I would imagine it would break lots of
 code.

This is expected.  Doing otherwise would incur into a much bigger
performance hit.

Anyway, IMHO no code should use SELECT * in any case, which is the only
scenario where one would expect physical column order to matter, isn't
it?

-- 
Alvaro Herrera (alvherre[a]dcc.uchile.cl)
La primera ley de las demostraciones en vivo es: no trate de usar el sistema.
Escriba un guión que no toque nada para no causar daños. (Jakob Nielsen)

---(end of broadcast)---
TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Hannu Krosing
Alvaro Herrera kirjutas R, 14.11.2003 kell 16:17:
 On Fri, Nov 14, 2003 at 08:59:05AM -0500, Dave Cramer wrote:
 
  I tried the current patch on a RC2 release, and I noticed one
  undesirable side affect. 
  
  Modifying a column  moves it to the end. In high availability situations
  this would not be desirable, I would imagine it would break lots of
  code.
 
 This is expected.  Doing otherwise would incur into a much bigger
 performance hit.

Not neccessarily, but it would make the patch much bigger ;)

IIRC there was discussion about splitting colum numbers into physical
and logical numbers at the time when DROP COLUMN was done.

 Anyway, IMHO no code should use SELECT * in any case, which is the only
 scenario where one would expect physical column order to matter, isn't
 it?

and this could also break when just changing the column type.


Hannu

---(end of broadcast)---
TIP 4: Don't 'kill -9' the postmaster


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Peter Eisentraut
Rod Taylor writes:

 The method is rename old column, add new column, move data across, move
 or reform dependencies, drop old column.

I can do this by hand.  If we have an explicit command to do it, then it
needs to preserve the table schema.  Else, this feature would be mostly
useless and a certain source of complaints.

-- 
Peter Eisentraut   [EMAIL PROTECTED]


---(end of broadcast)---
TIP 7: don't forget to increase your free space map settings


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Rod Taylor
On Fri, 2003-11-14 at 09:57, Peter Eisentraut wrote:
 Rod Taylor writes:
 
  The method is rename old column, add new column, move data across, move
  or reform dependencies, drop old column.
 
 I can do this by hand.  If we have an explicit command to do it, then it
 needs to preserve the table schema.  Else, this feature would be mostly
 useless and a certain source of complaints.

The method was agreed to on -hackers prior to any code having been
written. Unless I'm mistaken, the method was suggested to me by other on
-hackers.

Can you give me an alternative on how to approach this problem without
relying on another TODO item labelled ALTER TABLE .. POSITION?

The point of the command isn't to accomplish anything magical, simply to
make it easier.

begin;
Rename old column
Add new column
Copy data
Recreate default
Recreate NOT NULL constraint
Recreate index 1
Recreate index 2 (multi-key)
Recreate check constraint 1
Recreate check constraint 2
Recreate check constraint 3
Recreate foreign key 1
remove old column
commit;
vacuum full table (to get rid of 2x problem since the user was unable to
do a fileswap)


The above is by hand, the below is with this command:

begin;
Alter table .. type ..
commit;

If it becomes possible to change the order without having to goto an
exceptional amount of work (that POSITION item) then it would only be
obvious to attempt to preserve the position.


---(end of broadcast)---
TIP 5: Have you checked our extensive FAQ?

   http://www.postgresql.org/docs/faqs/FAQ.html


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Dave Cramer
OK,

Here is another approach, that would retain column order. It will
require that the table be locked while this proceeds, but I think this
is a good idea anyway.

lock table
create newtable as select c1, c2, c3::newtype
modify pg_class to point to the new filename
modify existing pg_attribute for the column in question
recreate indexes that exist on the column
unlock table

Dave

On Fri, 2003-11-14 at 09:57, Peter Eisentraut wrote:
 Rod Taylor writes:
 
  The method is rename old column, add new column, move data across, move
  or reform dependencies, drop old column.
 
 I can do this by hand.  If we have an explicit command to do it, then it
 needs to preserve the table schema.  Else, this feature would be mostly
 useless and a certain source of complaints.


---(end of broadcast)---
TIP 4: Don't 'kill -9' the postmaster


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Tom Lane
Rod Taylor [EMAIL PROTECTED] writes:
 On Fri, 2003-11-14 at 09:57, Peter Eisentraut wrote:
 I can do this by hand.  If we have an explicit command to do it, then it
 needs to preserve the table schema.  Else, this feature would be mostly
 useless and a certain source of complaints.

 The method was agreed to on -hackers prior to any code having been
 written.

I believe the consensus was that automating what you could do by hand
is still a step forward.

It clearly would be better if we could relabel the logical column
position after finishing the whole process, but I agree with Rod that
that is an independent patch.  Combining them into one mega-patch
doesn't sound like good engineering.

I guess the real question here is whether we would want to revert this
capability if a patch to adjust logical column orderings doesn't appear
before 7.5.  My vote would be no, but apparently Peter's is yes.
Any other opinions?

regards, tom lane

---(end of broadcast)---
TIP 5: Have you checked our extensive FAQ?

   http://www.postgresql.org/docs/faqs/FAQ.html


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Rod Taylor
 lock table
 create newtable as select c1, c2, c3::newtype
 modify pg_class to point to the new filename
 modify existing pg_attribute for the column in question
 recreate indexes that exist on the column
 unlock table

I actually tried this to start with an ran into several dead-ends in
trying to rebuild constraints, defaults, etc.  In order to do this I
think you would need to create a second pg_class entry and do a full
table swap.

By far, the easiest method to preserve order without writing a ton of
additional code is to do something that is on the TODO list already,
separate the visible position from physical position.

Doing the above has lots of added benefits, where spending a ton of time
on TYPE change has very few benefits.


---(end of broadcast)---
TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Peter Eisentraut
Tom Lane writes:

 I believe the consensus was that automating what you could do by hand
 is still a step forward.

I don't recall that, but if so, I would like to revisit that consensus.

AFAICT, this patch does not buy us anything at all.  It's just a different
spelling of existing functionality.  We have never done that before.  It
just makes the system harder to maintain and use.  All commands should be
reasonably independent, or at least add some functionality of their own.

 It clearly would be better if we could relabel the logical column
 position after finishing the whole process, but I agree with Rod that
 that is an independent patch.  Combining them into one mega-patch
 doesn't sound like good engineering.

Good engineering would be if the logical column number patch comes first.
We cannot possibly leave this patch as is.  People expect in-place column
changes.  Things will break left and right, users will complain all over
the place if we offer a way to change a column, but yeah, by the way it
changes the structure of the table as well.  We've had these kinds of good
idea/right direction/better than nothing approaches in areas like DROP
COLUMN and CLUSTER already, and they were no good.  Except in this case,
better than nothing doesn't even apply, because there is already
something.

-- 
Peter Eisentraut   [EMAIL PROTECTED]


---(end of broadcast)---
TIP 5: Have you checked our extensive FAQ?

   http://www.postgresql.org/docs/faqs/FAQ.html


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Hannu Krosing
Peter Eisentraut kirjutas R, 14.11.2003 kell 18:51:
 Tom Lane writes:
 
  I believe the consensus was that automating what you could do by hand
  is still a step forward.
 
 I don't recall that, but if so, I would like to revisit that consensus.
 
 AFAICT, this patch does not buy us anything at all.  It's just a different
 spelling of existing functionality.  We have never done that before.

what about DROP COLUMN - this is also just a different spelling for

SELECT INTO, migrate all constraints, DROP OLD TABLE, RENAME.

 It just makes the system harder to maintain and use. All commands should be
 reasonably independent, or at least add some functionality of their own.
 
  It clearly would be better if we could relabel the logical column
  position after finishing the whole process, but I agree with Rod that
  that is an independent patch.  Combining them into one mega-patch
  doesn't sound like good engineering.
 
 Good engineering would be if the logical column number patch comes first.

Agreed, it would be nice.

 We cannot possibly leave this patch as is.  People expect in-place column
 changes.

Does SQL spec even require that SELECT * always returns columns in the
same order ? I don't think that relational model assigns any 'order' to
columns.

BTW, SELECT * is just a different spelling of existing functionality ;) 

 Things will break left and right, users will complain all over
 the place if we offer a way to change a column, but yeah, by the way it
 changes the structure of the table as well. 

ALTER TABLE ADD/DROP COLUMN would also break SELECT *.

as would type change in many cases (query expects int but gets string)

  We've had these kinds of good
 idea/right direction/better than nothing approaches in areas like DROP
 COLUMN and CLUSTER already, and they were no good.  Except in this case,
 better than nothing doesn't even apply, because there is already
 something.

We have always had DUMP - sed - LOAD too.

This patch is *MUCH* better than nothing for performance. Instead of
being N times SEQSCAN (+ intervening VACUUM FULLs to reclaim space), it
can do it all in one pass. If that pass takes 1.5 hours, we have a very
big win here.

-
Hannu


---(end of broadcast)---
TIP 6: Have you searched our list archives?

   http://archives.postgresql.org


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Tom Lane
Hannu Krosing [EMAIL PROTECTED] writes:
 Peter Eisentraut kirjutas R, 14.11.2003 kell 18:51:
 I don't recall that, but if so, I would like to revisit that consensus.

 [ Hannu disagrees ]

Please take this thread to pgsql-hackers; if the issue is going to be
contentious then we should try to get a wider spectrum of opinion than
just people who follow -patches.

regards, tom lane

---(end of broadcast)---
TIP 4: Don't 'kill -9' the postmaster


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Christopher Kings-Lynne
This is expected.  Doing otherwise would incur into a much bigger
performance hit.
Anyway, IMHO no code should use SELECT * in any case, which is the only
scenario where one would expect physical column order to matter, isn't
it?
Well, we can always bring back the old idea of a attlognum which is the 
logical order of the columns.  Then we use that to expand *

Chris



---(end of broadcast)---
TIP 2: you can get off all lists at once with the unregister command
   (send unregister YourEmailAddressHere to [EMAIL PROTECTED])


Re: [PATCHES] ALTER TABLE modifications

2003-11-14 Thread Christopher Kings-Lynne

I guess the real question here is whether we would want to revert this
capability if a patch to adjust logical column orderings doesn't appear
before 7.5.  My vote would be no, but apparently Peter's is yes.
Any other opinions?
The fact that it deals with the nightmare of dropping and recreating 
indexes and fk's makes it worth it to me.

How about functions and views and rules that depend on it though?

Chris

---(end of broadcast)---
TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]


Re: [PATCHES] ALTER TABLE modifications

2003-11-13 Thread Hannu Krosing
Peter Eisentraut kirjutas K, 12.11.2003 kell 21:02:
 Rod Taylor writes:
 
  ALTER TABLE tab ADD COLUMN col DEFAULT 3, ADD CHECK (anothercol  3);
  The above combinational syntax is commented out in gram.y. The
  support framework is used in both the above and below items, but
  arbitrary statements probably have some issues -- I've not
  tested enough to determine.
 
  If it is useful, it will be submitted at a later date.
 
 I think it's perfectly fine to write two separate ALTER TABLE statements.

I guess the difference is that each pass (i.e. ALTER TABLE) needs to do
another scan and copy of the table. Putting them in one statement allows
all the alterations to be done in one pass.

 No need to introduce this nonstandard syntax.
 
  ALTER TABLE tab ALTER COLUMN col TYPE text TRANSFORM ...;
  Currently migrates indexes, check constraints, defaults, and the
  column definition to the new type with optional transform. If
  the tranform is not supplied, a standard assignment cast is
  attempted.
 
 Please don't use the term transform.  It is used by the SQL standard for
 other purposes. 

Is the other use conflicting with this syntax ?

I think we have preferred reusing existing keywords to adding new ones
in the past.

-
Hannu


---(end of broadcast)---
TIP 2: you can get off all lists at once with the unregister command
(send unregister YourEmailAddressHere to [EMAIL PROTECTED])


Re: [PATCHES] ALTER TABLE modifications

2003-11-13 Thread Peter Eisentraut
Rod Taylor writes:

 Yes, it is certainly fine to do so, but much faster to do the above.

Are table schema changes performance-sensitive operations, and are they
usually done in bulk?  I doubt it.

 I've not found another database which allows this syntax. The suggestion
 of TRANSFORM was Toms and was a result of using an assignment cast by
 default. Do you have a better term I can use?

I'm not sure I buy this whole concept in the first place.  If there is
no cast between type A and type B, then surely changing a table column
from A to B is nonsensical.

 -- or say Bytes to MBytes  (original column is int8)
 ALTER TABLE tab ALTER col TYPE integer TRANSFORM col / (1024 * 1024);

You can do this using a plain column type change plus an UPDATE.  I'd
prefer to keep these operations independent.

-- 
Peter Eisentraut   [EMAIL PROTECTED]


---(end of broadcast)---
TIP 3: if posting/reading through Usenet, please send an appropriate
  subscribe-nomail command to [EMAIL PROTECTED] so that your
  message can get through to the mailing list cleanly


Re: [PATCHES] ALTER TABLE modifications

2003-11-13 Thread Peter Eisentraut
Hannu Krosing writes:

  Please don't use the term transform.  It is used by the SQL standard for
  other purposes.

 Is the other use conflicting with this syntax ?

 I think we have preferred reusing existing keywords to adding new ones
 in the past.

Maybe (although I don't agree). but we've never intentionally done
terminology overloading.

-- 
Peter Eisentraut   [EMAIL PROTECTED]


---(end of broadcast)---
TIP 4: Don't 'kill -9' the postmaster



Re: [PATCHES] ALTER TABLE modifications

2003-11-13 Thread Rod Taylor
On Thu, 2003-11-13 at 09:18, Peter Eisentraut wrote:
 Rod Taylor writes:
 
  Yes, it is certainly fine to do so, but much faster to do the above.
 
 Are table schema changes performance-sensitive operations, and are they
 usually done in bulk?  I doubt it.

Perhaps not for you. But I would disagree with both of those points for
a majority of companies.

If the system has high uptime requirements, the timeframe to accomplish
maintenance decreases substantially. For example, I have two 1.5 hour
maintenance windows per year for maintenance. This is a requirement
given by our clients, nearly all of whom insist on it. Telcos and other
enterprise level environments with 24 / 7 usage patterns have different
demands.

So.. Adding 2 new check constraints to a table with 500million entries
takes way way too much time in my eyes.

Toms request (when I initially brought up fixing ADD COLUMN) was that it
would process the DEFAULT and other new constraints in a single pass.
The above syntax simply uses the framework put in place for ADD COLUMN.

I'll not push it if it does not function with complex combinations,
which has not been tested, as such is not included in this patch.

  -- or say Bytes to MBytes  (original column is int8)
  ALTER TABLE tab ALTER col TYPE integer TRANSFORM col / (1024 * 1024);
 
 You can do this using a plain column type change plus an UPDATE.  I'd
 prefer to keep these operations independent.

Yes, if you can do the update first.

Ok.. How about boolean to int2 as the user discovered they require a
third or fouth state? Or vice-versa. An MSSQL, MySQL, etc. migration
would leave a bunch of int2's (since they do not support boolean) in the
PostgreSQL database which have a boolean meaning.

rbt=# select '1'::int4::boolean
rbt-# ;
ERROR:  cannot cast type integer to boolean
rbt=# select '1'::boolean;
 bool
--
 t
(1 row)

Are you going to tell these people to write down the Default, add a new
column, copy the data, remove the old column, re-add the default, and
rename the new column to the old column name?

This is the exact reason many folks have asked for this ALTER form to be
added.

Considering there are already 2 sites out there running with this patch
(I have been asked for advance copies) I do not believe the
functionality is overkill in any respect.

Can you please suggest a better term to use in place of TRANSFORM? 
Perhaps UPDATE WITH?



---(end of broadcast)---
TIP 9: the planner will ignore your desire to choose an index scan if your
  joining column's datatypes do not match


Re: [PATCHES] ALTER TABLE modifications

2003-11-13 Thread Hannu Krosing
Rod Taylor kirjutas N, 13.11.2003 kell 16:59:

 
 Can you please suggest a better term to use in place of TRANSFORM? 
 Perhaps UPDATE WITH?

or perhaps USING, based loosely on our use of USING in CREATE INDEX ?

--
Hannu


---(end of broadcast)---
TIP 3: if posting/reading through Usenet, please send an appropriate
  subscribe-nomail command to [EMAIL PROTECTED] so that your
  message can get through to the mailing list cleanly


Re: [PATCHES] ALTER TABLE modifications

2003-11-12 Thread Rod Taylor
On Tue, 2003-11-11 at 23:46, Tom Lane wrote:
 Bruce Momjian [EMAIL PROTECTED] writes:
  Is this to be applied to CVS HEAD?
 
 It sounded like large portions were still at the request-for-comment
 stage...

It can be applied to -HEAD without breaking anything or backtracking in
feature set (that I can see) but there is substantial change in the way
things work so a pre-review is warranted and I'm sure changes will be
requested.

If I don't receive comments for corrections by the weekend, I'll finish
off one of the missing components (foreign keys) and submit a
replacement.


---(end of broadcast)---
TIP 4: Don't 'kill -9' the postmaster


Re: [PATCHES] ALTER TABLE modifications

2003-11-12 Thread Peter Eisentraut
Rod Taylor writes:

 ALTER TABLE tab ADD COLUMN col DEFAULT 3, ADD CHECK (anothercol  3);
 The above combinational syntax is commented out in gram.y. The
 support framework is used in both the above and below items, but
 arbitrary statements probably have some issues -- I've not
 tested enough to determine.

 If it is useful, it will be submitted at a later date.

I think it's perfectly fine to write two separate ALTER TABLE statements.
No need to introduce this nonstandard syntax.

 ALTER TABLE tab ALTER COLUMN col TYPE text TRANSFORM ...;
 Currently migrates indexes, check constraints, defaults, and the
 column definition to the new type with optional transform. If
 the tranform is not supplied, a standard assignment cast is
 attempted.

Please don't use the term transform.  It is used by the SQL standard for
other purposes.  What kind of object would you put in place of the ...
anyway?  A function?  What syntax do other databases use?

-- 
Peter Eisentraut   [EMAIL PROTECTED]


---(end of broadcast)---
TIP 2: you can get off all lists at once with the unregister command
(send unregister YourEmailAddressHere to [EMAIL PROTECTED])


Re: [PATCHES] ALTER TABLE modifications

2003-11-12 Thread Rod Taylor
On Wed, 2003-11-12 at 14:02, Peter Eisentraut wrote:
 Rod Taylor writes:
 
  ALTER TABLE tab ADD COLUMN col DEFAULT 3, ADD CHECK (anothercol  3);

 I think it's perfectly fine to write two separate ALTER TABLE statements.
 No need to introduce this nonstandard syntax.

Yes, it is certainly fine to do so, but much faster to do the above.

The command shown executes nearly 40% faster than 2 independent
statements in a single transaction -- the difference is even more
significant with additional sub-commands.

  ALTER TABLE tab ALTER COLUMN col TYPE text TRANSFORM ...;
  Currently migrates indexes, check constraints, defaults, and the
  column definition to the new type with optional transform. If
  the tranform is not supplied, a standard assignment cast is
  attempted.
 
 Please don't use the term transform.  It is used by the SQL standard for
 other purposes.  What kind of object would you put in place of the ...
 anyway?  A function?  What syntax do other databases use?

I've not found another database which allows this syntax. The suggestion
of TRANSFORM was Toms and was a result of using an assignment cast by
default. Do you have a better term I can use?

http://groups.google.ca/groups?hl=enlr=ie=UTF-8oe=UTF-8frame=rightth=266b02a270a164aaseekm=1064805960.60248.24.camel%40jester#link4


The ... is an A_Expr which does not accept (among other things)
subselects. CASE statements, equations, etc. work fine.

CREATE TABLE tab (col int2);
-- integer to boolean
ALTER TABLE tab ALTER col TYPE boolean
TRANSFORM CASE WHEN col = 1 THEN true ELSE false END;

-- or say Bytes to MBytes  (original column is int8)
ALTER TABLE tab ALTER col TYPE integer TRANSFORM col / (1024 * 1024);



---(end of broadcast)---
TIP 8: explain analyze is your friend


Re: [PATCHES] ALTER TABLE modifications

2003-11-11 Thread Bruce Momjian

Is this to be applied to CVS HEAD?

---

Rod Taylor wrote:
 A general re-organization of Alter Table. Node wise, it is a
 AlterTableStmt with a list of AlterTableCmds.  The Cmds are the
 individual actions to be completed (Add constraint, drop constraint, add
 column, etc.)
 
 Processing is done in 2 phases. The first phase updates the system
 catalogs and creates a work queue for the table scan. The second phase
 is to conduct the actual table scan evaluating all constraints and other
 per tuple processing simultaneously, as required. This has no effect on
 single step operations, but has a large benefit for combinational logic
 where multiple table scans would otherwise be required.
 
 Steps for the table scan include expression processing (default or
 transform expressions), not null constraint process, other constraints.
 
 
 The code has been simplified a little. Simple permission and recursion
 checks are conducted in the common area and an enum for the command type
 is used rather than a Char.
 
 
 ALTER TABLE ADD COLUMN col DEFAULT 3 NOT NULL; 
 Allow creation of a column with a default (filled) and not null
 constraint. This is internally subdivided into 3 actions much
 like the below syntax.
 
 ALTER TABLE tab ADD COLUMN col DEFAULT 3, ADD CHECK (anothercol  3); 
 The above combinational syntax is commented out in gram.y. The
 support framework is used in both the above and below items, but
 arbitrary statements probably have some issues -- I've not
 tested enough to determine.
 
 If it is useful, it will be submitted at a later date.
 
 ALTER TABLE tab ALTER COLUMN col TYPE text TRANSFORM ...; 
 Currently migrates indexes, check constraints, defaults, and the
 column definition to the new type with optional transform. If
 the tranform is not supplied, a standard assignment cast is
 attempted.
 
 One issue is that it detects dependencies way too late in the
 game (after the TRANFORM has been applied). I tried mucking up
 performDeletion to have a RESTRICT that did not throw the error
 at the end (or physically remove the items) but that didn't work
 out. Any bright ideas on how to achieve the NOTICES from a
 failed DROP COLUMN earlier? Otherwise, I can put in single
 object detection at that point.
 
 It does not migrate foreign keys yet (should be easy to add) and
 will be forwarded as an independent patch at a later time.
 Currently foreign keys are rejected like views, functions, etc.
 
 
 Comments appreciated.
 -- 
 Rod Taylor pg [at] rbt [dot] ca
 
 Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL

[ Attachment, skipping... ]

 
 ---(end of broadcast)---
 TIP 2: you can get off all lists at once with the unregister command
 (send unregister YourEmailAddressHere to [EMAIL PROTECTED])

-- 
  Bruce Momjian|  http://candle.pha.pa.us
  [EMAIL PROTECTED]   |  (610) 359-1001
  +  If your life is a hard drive, |  13 Roberts Road
  +  Christ can be your backup.|  Newtown Square, Pennsylvania 19073

---(end of broadcast)---
TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]


Re: [PATCHES] ALTER TABLE modifications

2003-11-11 Thread Tom Lane
Bruce Momjian [EMAIL PROTECTED] writes:
 Is this to be applied to CVS HEAD?

It sounded like large portions were still at the request-for-comment
stage...

regards, tom lane

---(end of broadcast)---
TIP 8: explain analyze is your friend