Index: doc/src/sgml/ddl.sgml
===================================================================
RCS file: /projects/cvsroot/pgsql/doc/src/sgml/ddl.sgml,v
retrieving revision 1.77
diff -c -r1.77 ddl.sgml
*** doc/src/sgml/ddl.sgml 28 Nov 2007 15:42:31 -0000 1.77
--- doc/src/sgml/ddl.sgml 1 Dec 2007 04:55:46 -0000
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*** 2510,2564 ****
If data will be added only to the latest partition, we can
! set up a very simple rule to insert data. We must
! redefine this each month so that it always points to the
! current partition:
!
!
! CREATE OR REPLACE RULE measurement_current_partition AS
! ON INSERT TO measurement
! DO INSTEAD
! INSERT INTO measurement_y2006m01 VALUES ( NEW.city_id,
! NEW.logdate,
! NEW.peaktemp,
! NEW.unitsales );
We might want to insert data and have the server automatically
locate the partition into which the row should be added. We
! could do this with a more complex set of rules as shown below:
! CREATE RULE measurement_insert_y2004m02 AS
! ON INSERT TO measurement WHERE
! ( logdate >= DATE '2004-02-01' AND logdate < DATE '2004-03-01' )
! DO INSTEAD
! INSERT INTO measurement_y2004m02 VALUES ( NEW.city_id,
! NEW.logdate,
! NEW.peaktemp,
! NEW.unitsales );
! ...
! CREATE RULE measurement_insert_y2005m12 AS
! ON INSERT TO measurement WHERE
! ( logdate >= DATE '2005-12-01' AND logdate < DATE '2006-01-01' )
! DO INSTEAD
! INSERT INTO measurement_y2005m12 VALUES ( NEW.city_id,
! NEW.logdate,
! NEW.peaktemp,
! NEW.unitsales );
! CREATE RULE measurement_insert_y2006m01 AS
! ON INSERT TO measurement WHERE
! ( logdate >= DATE '2006-01-01' AND logdate < DATE '2006-02-01' )
! DO INSTEAD
! INSERT INTO measurement_y2006m01 VALUES ( NEW.city_id,
! NEW.logdate,
! NEW.peaktemp,
! NEW.unitsales );
!
!
! Note that the WHERE clause in each rule
! exactly matches the CHECK
! constraint for its partition.
--- 2510,2589 ----
If data will be added only to the latest partition, we can
! set up a very simple trigger function to insert data. We must
! redefine this each month so that it always points to the current
! partition:
!
!
! CREATE OR REPLACE FUNCTION measurement_current_partition()
! RETURNS TRIGGER
! LANGUAGE plpgsql
! AS $$
! BEGIN
! INSERT INTO measurement_y2006m01
! VALUES (
! NEW.city_id,
! NEW.logdate,
! NEW.peaktemp,
! NEW.unitsales
! );
! RETURN NEW;
! END;
! $$;
!
!
! The first time we create the table, we create a trigger which
! calls the above trigger function. When we replace the trigger
! function, we don't need to replace the trigger.
!
!
! CREATE TRIGGER insert_measurement_current_partition
! BEFORE INSERT
! ON measurement
! EXECUTE PROCEDURE measurement_current_partition();
We might want to insert data and have the server automatically
locate the partition into which the row should be added. We
! could do this with a more complex trigger function as shown
! below:
! CREATE OR REPLACE FUNCTION measurement_insert()
! RETURNS TRIGGER
! LANGUAGE plpgsql
! AS $$
! BEGIN
! IF ( logdate >= DATE '2004-02-01' AND logdate < DATE '2004-03-01' ) THEN
!
! INSERT INTO measurement_y2004m02
! VALUES (
! NEW.city_id,
! NEW.logdate,
! NEW.peaktemp,
! NEW.unitsales
! );
! ELSIF ( logdate >= DATE '2005-12-01' AND logdate < DATE '2006-01-01' ) THEN
! ...
! ELSIF ( logdate >= DATE '2008-01-01' AND logdate < DATE '2006-02-01' ) THEN
! INSERT INTO measurement_y2008m01
! VALUES (
! NEW.city_id,
! NEW.logdate,
! NEW.peaktemp,
! NEW.unitsales
! );
! ELSE
! RAISE EXCEPTION 'In, measurement_insert(), the date out of range. Fix the trigger function!';
! END IF;
! RETURN NULL;
! END;
! $$;
!
!
! Note that the WHERE clause in each section
! of the trigger function exactly matches the
! CHECK constraint for its partition.
***************
*** 2568,2594 ****
As we can see, a complex partitioning scheme could require a
substantial amount of DDL. In the above example we would be
creating a new partition each month, so it might be wise to write a
! script that generates the required DDL automatically.
!
! Partitioning can also be arranged using a UNION ALL
! view:
! CREATE VIEW measurement AS
! SELECT * FROM measurement_y2004m02
! UNION ALL SELECT * FROM measurement_y2004m03
! ...
! UNION ALL SELECT * FROM measurement_y2005m11
! UNION ALL SELECT * FROM measurement_y2005m12
! UNION ALL SELECT * FROM measurement_y2006m01;
- However, the need to
- recreate the view adds an extra step to adding and dropping
- individual partitions of the data set.
-
--- 2593,2624 ----
As we can see, a complex partitioning scheme could require a
substantial amount of DDL. In the above example we would be
creating a new partition each month, so it might be wise to write a
! script that generates the required DDL automatically. You could
! also write a function to determine the partition dynamically
! before doing the INSERT.
!
! In the much rarer case where you only plan to do bulk
! inserts--batch INSERTs, but not COPY, of logs would be an
! example--you can use RULEs instead of TRIGGERs. Here is an
! example of a RULE you would change via a cron job at the end of
! each month:
! CREATE OR REPLACE RULE measurement_current_partition AS
! ON INSERT TO measurement
! DO INSTEAD
! INSERT INTO measurement_y2008m01
! VALUES (
! NEW.city_id,
! NEW.logdate,
! NEW.peaktemp,
! NEW.unitsales
! );
+
***************
*** 2751,2772 ****
There is currently no way to verify that all of the
CHECK constraints are mutually
! exclusive. Care is required by the database designer.
-
-
- There is currently no simple way to specify that rows must not be
- inserted into the master table. A CHECK (false)
- constraint on the master table would be inherited by all child
- tables, so that cannot be used for this purpose. One possibility is
- to set up an ON INSERT> trigger on the master table that
- always raises an error. (Alternatively, such a trigger could be
- used to redirect the data into the proper child table, instead of
- using a set of rules as suggested above.)
-
-
--- 2781,2792 ----
There is currently no way to verify that all of the
CHECK constraints are mutually
! exclusive. It is easier to create code which generates
! partitions and creates and/or modifies associated objects than
! to write each by hand.