Re: [HACKERS] [PATCHES] Inherited Constraints
Ühel kenal päeval, E, 2006-03-06 kell 17:25, kirjutas Bruce Momjian: Hannu Krosing wrote: ?hel kenal p?eval, E, 2006-03-06 kell 12:12, kirjutas Bruce Momjian: Added to TODO: o Prevent parent tables from altering or dropping constraints like CHECK that are inherited by child tables Dropping constraints should only be possible with CASCADE. and we already have this in TODO: o %Prevent child tables from altering or dropping constraints like CHECK that were inherited from the parent table so I think we now have all the failure cases documented. If you want to be consistent, then ALTER TABLE ONLY ADD CONSTRAINT .. should also be forbidden, so you can't create non-inherited constraints I don't have a problem with creating ONLY constraints on parents and children. We just don't want them to be removed/modified if they are shared. Well, when you delete a constraint from child, the constraint becomes an ONLY constraint on parent. If you allow ONLY constraints on parents, then why disallow dropping them from childs ? IIRC the original complaint about being able to drop constraints from children was that inherited tables not being bound by constraints on parents was unexpected/broken. I.E when you have CREATE TABLE T(i int check (i0)); then you would be really surprised by getting -1 out from that table. --- Hannu ---(end of broadcast)--- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
Re: [HACKERS] [PATCHES] Inherited Constraints
On Wed, 8 Mar 2006, Hannu Krosing wrote: ??hel kenal p??eval, E, 2006-03-06 kell 17:25, kirjutas Bruce Momjian: Hannu Krosing wrote: ?hel kenal p?eval, E, 2006-03-06 kell 12:12, kirjutas Bruce Momjian: Added to TODO: o Prevent parent tables from altering or dropping constraints like CHECK that are inherited by child tables Dropping constraints should only be possible with CASCADE. and we already have this in TODO: o %Prevent child tables from altering or dropping constraints like CHECK that were inherited from the parent table so I think we now have all the failure cases documented. If you want to be consistent, then ALTER TABLE ONLY ADD CONSTRAINT .. should also be forbidden, so you can't create non-inherited constraints I don't have a problem with creating ONLY constraints on parents and children. We just don't want them to be removed/modified if they are shared. Well, when you delete a constraint from child, the constraint becomes an ONLY constraint on parent. Only if there's a single child, otherwise you have a partially-ONLY constraint unless you made it ONLY constraints on the parent and all other children (but then removing the parent constraint wouldn't remove it from the other children presumably). If you allow ONLY constraints on parents, then why disallow dropping them from childs ? I agree with this in any case. I think both are fairly broken. ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] [PATCHES] Inherited Constraints
Added to TODO: o Prevent parent tables from altering or dropping constraints like CHECK that are inherited by child tables Dropping constraints should only be possible with CASCADE. and we already have this in TODO: o %Prevent child tables from altering or dropping constraints like CHECK that were inherited from the parent table so I think we now have all the failure cases documented. --- Bruce Momjian wrote: Where are we on this patch? My testing shows it is still shows we have a problem: test= CREATE TABLE x(y INT CHECK(y 0)); CREATE TABLE test= CREATE TABLE z(a INT) inherits (x); CREATE TABLE test= ALTER TABLE z DROP CONSTRAINT x_y_check; ALTER TABLE test= ALTER TABLE x DROP CONSTRAINT x_y_check; ALTER TABLE Deleting the parent constraint first does not require CASCADE, as it should, I think: test= CREATE TABLE x(y INT CHECK(y 0)); CREATE TABLE test= CREATE TABLE z(a INT) inherits (x); CREATE TABLE test= ALTER TABLE x DROP CONSTRAINT x_y_check; ALTER TABLE test= ALTER TABLE z DROP CONSTRAINT x_y_check; ERROR: CONSTRAINT x_y_check does NOT exist --- Simon Riggs wrote: On Thu, 2005-12-08 at 11:10 +, Simon Riggs wrote: On Wed, 2005-12-07 at 21:24 +, Simon Riggs wrote: Following patch implements record of whether a constraint is inherited or not, and prevents dropping of inherited constraints. Patch posted to -patches list. What it doesn't do: It doesn't yet prevent dropping the parent constraint, which is wrong, clearly, but what to do about it? 1. make dropping a constraint drop all constraints dependent upon it (without any explicit cascade) 2. add a new clause to ALTER TABLE DROP CONSTRAINT CASCADE I prefer (1), since it is SQL Standard compliant, easier to remember and automatic de-inheritance is the natural opposite of the automatic inheritance process. Comments, please -hackers? Late night hacking again ALTER TABLE DROP CONSTRAINT CASCADE does of course already exist, so the following should cause dependency violation ERRORs: - omitting the CASCADE when attempting to delete parent constraint - attempting to drop the child constraint Best Regards, Simon Riggs ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org -- Bruce Momjian http://candle.pha.pa.us SRA OSS, Inc. http://www.sraoss.com + If your life is a hard drive, Christ can be your backup. + ---(end of broadcast)--- TIP 2: Don't 'kill -9' the postmaster -- Bruce Momjian http://candle.pha.pa.us SRA OSS, Inc. http://www.sraoss.com + If your life is a hard drive, Christ can be your backup. + ---(end of broadcast)--- TIP 1: 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: [HACKERS] [PATCHES] Inherited Constraints
Ühel kenal päeval, E, 2006-03-06 kell 12:12, kirjutas Bruce Momjian: Added to TODO: o Prevent parent tables from altering or dropping constraints like CHECK that are inherited by child tables Dropping constraints should only be possible with CASCADE. and we already have this in TODO: o %Prevent child tables from altering or dropping constraints like CHECK that were inherited from the parent table so I think we now have all the failure cases documented. If you want to be consistent, then ALTER TABLE ONLY ADD CONSTRAINT .. should also be forbidden, so you can't create non-inherited constraints --- Hannu ---(end of broadcast)--- TIP 1: 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: [HACKERS] [PATCHES] Inherited Constraints
Hannu Krosing wrote: ?hel kenal p?eval, E, 2006-03-06 kell 12:12, kirjutas Bruce Momjian: Added to TODO: o Prevent parent tables from altering or dropping constraints like CHECK that are inherited by child tables Dropping constraints should only be possible with CASCADE. and we already have this in TODO: o %Prevent child tables from altering or dropping constraints like CHECK that were inherited from the parent table so I think we now have all the failure cases documented. If you want to be consistent, then ALTER TABLE ONLY ADD CONSTRAINT .. should also be forbidden, so you can't create non-inherited constraints I don't have a problem with creating ONLY constraints on parents and children. We just don't want them to be removed/modified if they are shared. -- Bruce Momjian http://candle.pha.pa.us SRA OSS, Inc. http://www.sraoss.com + If your life is a hard drive, Christ can be your backup. + ---(end of broadcast)--- TIP 1: 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: [HACKERS] [PATCHES] Inherited Constraints
Where are we on this patch? My testing shows it is still shows we have a problem: test= CREATE TABLE x(y INT CHECK(y 0)); CREATE TABLE test= CREATE TABLE z(a INT) inherits (x); CREATE TABLE test= ALTER TABLE z DROP CONSTRAINT x_y_check; ALTER TABLE test= ALTER TABLE x DROP CONSTRAINT x_y_check; ALTER TABLE Deleting the parent constraint first does not require CASCADE, as it should, I think: test= CREATE TABLE x(y INT CHECK(y 0)); CREATE TABLE test= CREATE TABLE z(a INT) inherits (x); CREATE TABLE test= ALTER TABLE x DROP CONSTRAINT x_y_check; ALTER TABLE test= ALTER TABLE z DROP CONSTRAINT x_y_check; ERROR: CONSTRAINT x_y_check does NOT exist --- Simon Riggs wrote: On Thu, 2005-12-08 at 11:10 +, Simon Riggs wrote: On Wed, 2005-12-07 at 21:24 +, Simon Riggs wrote: Following patch implements record of whether a constraint is inherited or not, and prevents dropping of inherited constraints. Patch posted to -patches list. What it doesn't do: It doesn't yet prevent dropping the parent constraint, which is wrong, clearly, but what to do about it? 1. make dropping a constraint drop all constraints dependent upon it (without any explicit cascade) 2. add a new clause to ALTER TABLE DROP CONSTRAINT CASCADE I prefer (1), since it is SQL Standard compliant, easier to remember and automatic de-inheritance is the natural opposite of the automatic inheritance process. Comments, please -hackers? Late night hacking again ALTER TABLE DROP CONSTRAINT CASCADE does of course already exist, so the following should cause dependency violation ERRORs: - omitting the CASCADE when attempting to delete parent constraint - attempting to drop the child constraint Best Regards, Simon Riggs ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org -- Bruce Momjian http://candle.pha.pa.us SRA OSS, Inc. http://www.sraoss.com + If your life is a hard drive, Christ can be your backup. + ---(end of broadcast)--- TIP 2: Don't 'kill -9' the postmaster
Re: [HACKERS] [PATCHES] Inherited Constraints
On Wed, 2005-12-07 at 21:24 +, Simon Riggs wrote: Following patch implements record of whether a constraint is inherited or not, and prevents dropping of inherited constraints. Patch posted to -patches list. What it doesn't do: It doesn't yet prevent dropping the parent constraint, which is wrong, clearly, but what to do about it? 1. make dropping a constraint drop all constraints dependent upon it (without any explicit cascade) 2. add a new clause to ALTER TABLE DROP CONSTRAINT CASCADE I prefer (1), since it is SQL Standard compliant, easier to remember and automatic de-inheritance is the natural opposite of the automatic inheritance process. Comments, please -hackers? Which implementation should I pick (or another)? Further patch will utilise this new knowledge to reduce the number of tests made during constraint_exclusion. Best Regards, Simon Riggs ---(end of broadcast)--- TIP 1: 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: [HACKERS] [PATCHES] Inherited Constraints
Ühel kenal päeval, N, 2005-12-08 kell 11:10, kirjutas Simon Riggs: On Wed, 2005-12-07 at 21:24 +, Simon Riggs wrote: Following patch implements record of whether a constraint is inherited or not, and prevents dropping of inherited constraints. Patch posted to -patches list. What it doesn't do: It doesn't yet prevent dropping the parent constraint, which is wrong, clearly, but what to do about it? 1. make dropping a constraint drop all constraints dependent upon it (without any explicit cascade) 2. add a new clause to ALTER TABLE DROP CONSTRAINT CASCADE I prefer (1), since it is SQL Standard compliant, easier to remember and automatic de-inheritance is the natural opposite of the automatic inheritance process. Comments, please -hackers? It would be logical to do the same as DROP TABLE does, i.e (2). hannu=# create table parent(i int); CREATE TABLE hannu=# create table child() inherits(parent); CREATE TABLE hannu=# drop table parent; NOTICE: table child depends on table parent ERROR: cannot drop table parent because other objects depend on it HINT: Use DROP ... CASCADE to drop the dependent objects too. hannu=# Maybe there should be another option in addition to CASCADE, say DISINHERIT, which leaves all child constraints as heads of new ingeritance hierarchies. DROP CASCADE + ADD BACK ALL CHILD CONSTRAINTS may be prohibitively expensive for biggish tables. Another nice (but no doubt more complex) thing would be ability to add multiple constraints at once, needing only one seqscan to check for compliance with added constraints and/or making constraint checks smarter, so that for.ex. ADD CONSTRAINT CHECK i 0 could make use of index on i instead of doing a seqscan. Or if there is a constraint CHECK i 0 then adding another like CHECK i -1 would not need to check actual data either. Which implementation should I pick (or another)? Further patch will utilise this new knowledge to reduce the number of tests made during constraint_exclusion. So will hierarchical inheritance be the thing to do to take advantage of i then ? year +- month1 |+-day1 |+-day2 . |\-day31 +- month2 etc. btw, will your DROP patch support multiple inheritance ? --- Hannu ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
Re: [HACKERS] [PATCHES] Inherited Constraints
Another nice (but no doubt more complex) thing would be ability to add multiple constraints at once, needing only one seqscan to check for compliance with added constraints and/or making constraint checks smarter, so that for.ex. ADD CONSTRAINT CHECK i 0 could make use of index on i instead of doing a seqscan. Or if there is a constraint CHECK i 0 then adding another like CHECK i -1 would not need to check actual data either. Check out the comma in alter table. ALTER TABLE tab ADD COLUMN serial NOT NULL UNIQUE, ADD CHECK (foo 24), ADD CHECK (baz 18), ADD COLUMN integer NOT NULL DEFAULT 32; Table tab (and each of the tables that inherits from it) is scanned and rewritten once. I believe this was added for 8.0. -- ---(end of broadcast)--- TIP 2: Don't 'kill -9' the postmaster
Re: [HACKERS] [PATCHES] Inherited Constraints
On Thu, 2005-12-08 at 11:10 +, Simon Riggs wrote: On Wed, 2005-12-07 at 21:24 +, Simon Riggs wrote: Following patch implements record of whether a constraint is inherited or not, and prevents dropping of inherited constraints. Patch posted to -patches list. What it doesn't do: It doesn't yet prevent dropping the parent constraint, which is wrong, clearly, but what to do about it? 1. make dropping a constraint drop all constraints dependent upon it (without any explicit cascade) 2. add a new clause to ALTER TABLE DROP CONSTRAINT CASCADE I prefer (1), since it is SQL Standard compliant, easier to remember and automatic de-inheritance is the natural opposite of the automatic inheritance process. Comments, please -hackers? Late night hacking again ALTER TABLE DROP CONSTRAINT CASCADE does of course already exist, so the following should cause dependency violation ERRORs: - omitting the CASCADE when attempting to delete parent constraint - attempting to drop the child constraint Best Regards, Simon Riggs ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] [PATCHES] Inherited Constraints
On Thursday 2005-12-08 15:47, Simon Riggs wrote: does of course already exist, so the following should cause dependency violation ERRORs: - omitting the CASCADE when attempting to delete parent constraint - attempting to drop the child constraint Why should dropping the child constraint fail? Child tables are supposed to be able to over-ride parent constraints. Dropping a parent's constraint sounds like just a way to over-ride a constraint with no constraint at all. (Making the column unconstrained.) ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
