Re: [HACKERS] [SQL] using constraint based paritioning to fix EAV type schemas? (view inheritance and constraints)
I've seen a few EAV designs in practice. They've all been problematic. I'd like to have a better way of dealing with them. Which is why I'm tentatively suggesting support for inheritance and constraints in views. If there's some other way to achieve constraint based exclusion across a UNION of heterogenous tables, I'd love to hear it. If you do your own rules anyway, why can't you use inheritance and create the rules on the parent table and the constraints on the child tables ? You can still use the child tables directly if you want. Andreas ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
Re: [HACKERS] [SQL] using constraint based paritioning to fix EAV type schemas? (view inheritance and constraints)
I've seen a few EAV designs in practice. They've all been problematic. I'd like to have a better way of dealing with them. Which is why I'm tentatively suggesting support for inheritance and constraints in views. If there's some other way to achieve constraint based exclusion across a UNION of heterogenous tables, I'd love to hear it. If you do your own rules anyway, why can't you use inheritance and create the rules on the parent table and the constraints on the child tables ? Ah, sorry, just saw that you want different column names in your subtables. Add me as another vote to extend the new constraint elimination to union all views :-) Andreas ---(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] [SQL] using constraint based paritioning to fix EAV type schemas? (view inheritance and constraints)
On 7/18/06, Aaron Bono [EMAIL PROTECTED] wrote: On 18 Jul 2006 09:07:08 -0700, Andrew Hammond [EMAIL PROTECTED] wrote: I have a client with the following EAV inspired schema.CREATE TABLE many_tables (table_id text primary key,-- defines which virtual table isencodedattribute1 text,attribute2 text, attribute3 text,attribute4 text,...);I'd like to use a mix of constraint based paritioning, rules_and_views_ to implement a real schema underneath this mess, like thefollowing. CREATE TABLE cat ( cat_id INTEGER PRIMARY KEY, cat_name TEXT NOT NULL, aloofness NUMERIC(1,3) DEFAULT 1.0 CHECK (0.0 = aloofness ANDaloofness = 1.0));CREATE RULE many_tables_cat_insert AS ON INSERT TO many_tables WHERE table_id = 'cat' DO INSTEADINSERT INTO cat (cat_id, cat_name, aloofness) VALUES ( CAST(attribute1 AS integer), attribute2, CAST(attribute3 AS numeric(1,3)) -- gleefully ignore the other attributes);-- etc for UPDATE, and DELETE rules-- This part doesn't workCREATE VIEW many_tables_a (CHECK (table_id = 'cat')) INHERITS(many_tables) ASSELECT 'cat' AS table_id, CAST(cat_id AS text) AS attribute1,cat_name AS attribute2,CAST(aloofness AS text) AS attribute3,null AS attribute4, ...FROM cat;So, I guess I'm stuck doing the UNION ALL approach in this instance. This won't get me the partitioning win, nor the flexibility andcleanliness of design that I'd get with inheritance.As far as I can see, supporting the above would it mean addinginheritance and constraint support to views. Does anyone have a better approach?If you don't mind having redundant data, you could change the ON INSERT trigger to copy the data into cat, add an ON UPDATE trigger (you should do this anyway) and revoke direct insert/update to cat. Then you don't need many_tables_a or a UNION. There's already a performance problem, I suspect that would just exacerbate it. Since I want to encourage developers to use the relational tables instead of the many_tables table, refusing DML wouldn't be a good idea. Of course I don't know if this achieves your intended result or not. What is your business requirement for this? The current virtual table design has performance (as well as maitenance) issues. Performance tuning is problematic. A major re-design of the application is not something that can be done until the next major release. However, if I can slide a proper relational schema underneath this hodge-podge table while retaining compatability for legacy apps then it becomes possible to fix parts of the application to use the relational tables incrementally on an as-needed basis. If I could get constraint based exclusioning to work with the partitioning, then I would be able to realize performance improvements immediately (which is always good for a consultant). Unfortunately I don't see any way to do this. Inheritance seems to fit backwards from what I'm actually trying to do. I've seen a few EAV designs in practice. They've all been problematic. I'd like to have a better way of dealing with them. Which is why I'm tentatively suggesting support for inheritance and constraints in views. If there's some other way to achieve constraint based exclusion across a UNION of heterogenous tables, I'd love to hear it. Drew
Re: [HACKERS] [SQL] using constraint based paritioning to fix EAV
Ühel kenal päeval, T, 2006-07-18 kell 16:44, kirjutas Andrew Hammond: On 7/18/06, Aaron Bono [EMAIL PROTECTED] wrote: On 18 Jul 2006 09:07:08 -0700, Andrew Hammond [EMAIL PROTECTED] wrote: I have a client with the following EAV inspired schema. CREATE TABLE many_tables ( table_id text primary key,-- defines which virtual table is encoded attribute1 text, attribute2 text, attribute3 text, attribute4 text, ... ); Maybe you can approach the problem from another end, and make the many_tables table the virtual one and all the others into real tables ? -- Hannu Krosing Database Architect Skype Technologies OÜ Akadeemia tee 21 F, Tallinn, 12618, Estonia Skype me: callto:hkrosing Get Skype for free: http://www.skype.com ---(end of broadcast)--- TIP 2: Don't 'kill -9' the postmaster
Re: [HACKERS] [SQL] using constraint based paritioning to fix EAV
Ühel kenal päeval, K, 2006-07-19 kell 00:20, kirjutas Hannu Krosing: Ühel kenal päeval, T, 2006-07-18 kell 16:44, kirjutas Andrew Hammond: On 7/18/06, Aaron Bono [EMAIL PROTECTED] wrote: On 18 Jul 2006 09:07:08 -0700, Andrew Hammond [EMAIL PROTECTED] wrote: I have a client with the following EAV inspired schema. CREATE TABLE many_tables ( table_id text primary key,-- defines which virtual table is encoded attribute1 text, attribute2 text, attribute3 text, attribute4 text, ... ); Maybe you can approach the problem from another end, and make the many_tables table the virtual one and all the others into real tables ? Oops, I see you kind of are :) Maybe you can solve some of the problems doing a VIEW over pl/SQL function ? And/or maybe using triggers instead of rules. -- Hannu Krosing Database Architect Skype Technologies OÜ Akadeemia tee 21 F, Tallinn, 12618, Estonia Skype me: callto:hkrosing Get Skype for free: http://www.skype.com ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
