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Update PL/pgSQL trigger example to be clearer about how to "merge" data 

into a table.

Jim C. Nasby
This commit is contained in:
Bruce Momjian 2006-02-05 02:47:53 +00:00
parent 3893127431
commit 354213c7f4
1 changed files with 27 additions and 21 deletions
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48
doc/src/sgml/plpgsql.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.83 2005/12/29 04:02:32 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.84 2006/02/05 02:47:53 momjian Exp $
-->
<chapter id="plpgsql">
@ -3007,16 +3007,17 @@ CREATE OR REPLACE FUNCTION maint_sales_summary_bytime() RETURNS TRIGGER AS $main
END IF;
-- Update the summary row with the new values.
UPDATE sales_summary_bytime
SET amount_sold = amount_sold + delta_amount_sold,
units_sold = units_sold + delta_units_sold,
amount_cost = amount_cost + delta_amount_cost
WHERE time_key = delta_time_key;
-- Insert or update the summary row with the new values.
&lt;&lt;insert_update&gt;&gt;
LOOP
UPDATE sales_summary_bytime
SET amount_sold = amount_sold + delta_amount_sold,
units_sold = units_sold + delta_units_sold,
amount_cost = amount_cost + delta_amount_cost
WHERE time_key = delta_time_key;
EXIT insert_update WHEN found;
-- There might have been no row with this time_key (e.g new data!).
IF (NOT FOUND) THEN
BEGIN
INSERT INTO sales_summary_bytime (
time_key,
@ -3029,20 +3030,15 @@ CREATE OR REPLACE FUNCTION maint_sales_summary_bytime() RETURNS TRIGGER AS $main
delta_units_sold,
delta_amount_cost
);
EXCEPTION
--
-- Catch race condition when two transactions are adding data
-- for a new time_key.
--
WHEN UNIQUE_VIOLATION THEN
UPDATE sales_summary_bytime
SET amount_sold = amount_sold + delta_amount_sold,
units_sold = units_sold + delta_units_sold,
amount_cost = amount_cost + delta_amount_cost
WHERE time_key = delta_time_key;
EXIT insert_update;
EXCEPTION
WHEN UNIQUE_VIOLATION THEN
-- do nothing
END;
END IF;
END LOOP insert_update;
RETURN NULL;
END;
@ -3051,6 +3047,16 @@ $maint_sales_summary_bytime$ LANGUAGE plpgsql;
CREATE TRIGGER maint_sales_summary_bytime
AFTER INSERT OR UPDATE OR DELETE ON sales_fact
FOR EACH ROW EXECUTE PROCEDURE maint_sales_summary_bytime();
INSERT INTO sales_fact VALUES(1,1,1,10,3,15);
INSERT INTO sales_fact VALUES(1,2,1,20,5,35);
INSERT INTO sales_fact VALUES(2,2,1,40,15,135);
INSERT INTO sales_fact VALUES(2,3,1,10,1,13);
SELECT * FROM sales_summary_bytime;
DELETE FROM sales_fact WHERE product_key = 1;
SELECT * FROM sales_summary_bytime;
UPDATE sales_fact SET units_sold = units_sold * 2;
SELECT * FROM sales_summary_bytime;
</programlisting>
</example>